Recent Developments in Applied Electrostatics Proceedings of the Fifth International Conference on Applied Electrostatics November 2~5, 2004, Shanghai, China Edited by Sun Keping and Yu Gefei
Elsevier
Recent Developments in Applied Electrostatics Proceedings of the Fifth International Conference on Applied Electrostatics November 2~5, 2004, Shanghai, China Edited by Sun Keping and Yu Gefei
Elsevier
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PREFACE This proceedings contains papers presented at the 5th International Conference on Applied Electrostatics held in Shanghai, China on November 2--5,2004. The ICAES 2004 Conference is of wide interest, as is shown by the contributions received from 11 countries and districts throughout the world. About 90 researchers attend the conference and more than 100 papers were submitted for presentation in the proceedings. The paper sessions covered following topics: 9 fundamentals and physics 9 applications (precipitation, pollution control, spray, separation, material, Ozone, etc. ) 9 hazards and problems 9 biology technology 9 electrets 9 measuring technology 9 electromagnetic compatibility and others These papers demonstrated recent research level and developing trends of the entire electrostatic field. The objective of the Conference is to provide an opportunity for researchers from all over the world to discuss various topics of electrostatic field at many levels, obtain more information, absorb rich scientific nutrition and pick up the advantages from varied researchers. New friends can be met and both the friendship and the cooperation can be enhanced during the Conference. The Conference is sponsored by the Commission on Electrostatics of Chinese Physical Society, Shanghai Physical Society and Shanghai Maritime University. We wish to thank all the authors for their cooperation and effort. We also thank Mr. Christopher Greenwell, Publishing Editor, Control, Electronic and Optical Engineering, Elsevier for his guide and assistance.
Prof. Sun Keping Dr. Yu Gefei November 1, 2004 Shanghai, China
The 5th International Conference on Applied Electrostatics International Technology Committee Prof. T.B.Jones, University of Rochester, U.S.A Prof. G.S.P.Castle, The University of Western Ontario, Canada Prof. Juliusz B.Gajewski, Technical University of Wrochaw, Poland Prof. T.Oda, The University of Tokyo, Japan Prof. J.D.Moon, Kyugpook Natl University, Korea Prof. T.S.Lee, University of Minnesota, U.S.A Prof. Akira Mizuno, Toyohashi University of Technology, Japan Prof. R.H.Amirov, Institute for High temperatures, Izhorskaya, Russia Prof. T.Yamamoto, Osaka Prefecture University, Japan Prof. J.O.Chae, INHA University, Korea Prof. Jen- Shih Chang, McMaster University, Canada Dr. Jaakko Paasi, VTT Technical Research center of Finland, Finland Prof. Keping Sun, Shanghai Maritime University, China Prof. Shanghe Liu, Shijiazhuang Mechanical Engineering College, China Prof. Yan Wu, Dalian University of Technology, China
Local Organizing Committee Prof. Keping Sun, Shanghai Maritime University, China (Chairman) Prof. Shanghe Liu,Shijiazhuang Mechanical Engineering College,China(Co-Chairman) Prof. Yan Wu, Dalian University of Technology, China Prof. Guanghui Wei, Shijiazhuang Mechanical Engineering College, China Dr. Yazhou Chen, Shijiazhuang Mechanical Engineering College, China Prof. Yanming Kang, Donghua University, China Prof. Zhiliang Ge, Tongji University, China Dr. Gefei Yu, Shanghai Maritime University, China Dr. Xuewen Li, Shanghai Maritime University, China
CONTENTS FUNDAMENTALS AND PHYSICS Charge behavior analysis in thin solid film by using simultaneous TSDC and LIPP measurements Tetsuji Oda, Koji Yamashita Induction Charging of Non-spherical Granular Materials" Size Analysis Wu Y., Castle GS.P., Inculet I.I On Disruption Onset for an Electrified Capillary Liquid Meniscus:Revisit of Zeleny's 1914 Experiments on the Phenomenon of Spraying T. S. Lee
10
Application of immune algorithm with searching diversity to arrangement problem of fictitious chareges and contour points for charge simulation method Nishimura R., Nishimori K.
21
Changes in Electrostatic Charges of Fine Panicles alter Addition to Gas-Solid Fluidized Beds Mehrani P., Bi H.T., Grace J.R.
5
Dynamics of EHD flow in pin-plate configuration generated by electric corona discharge in air Zhao L., Adamiak K.
29
Tribocharging characteristics of Nylon 12 and FEP byrubbing of carriers for copiers Ikezaki K., Jojima E.
33
Charge transport in flowing high resistivity liquids" periodic wire-channel configuration Adamiak K., Floryan J.M.
37
Comparative Studies between the New and Old Standard IEC61000-4-2 Xijun Zhang, Shiliang Yang, Lisi Fan, Zhancheng Wu
41
The Study of Irradiation Effects on Single-chip Microprocessor System under ESD EMP Xijun Zhang, Lisi Fan, Xiaofen Ruan, Zhancheng Wu
45
Study on Precise Movement Control of ESD Simulator Electrode Lei Lei, Shanghe Liu, Jie Yang
48
Electromagnetic Wave Propagation in collisional Plasma Ouyang J T, Zhang Z X, Miao J S, Zhang Q C, Gao B Q
52
Plasma Development in Dielectric Barrier Surface Discharge Cao J, Ouyang J T, Hui H X
55
Spectroscopic Investigation of Low-temperature Plasma Discharge Reactor Ma Ningsheng, Ge Ziliang
58
Investigation on Simultaneously Desulphurization and Denitrification from Flue Gas by Pulsed Corona Discharge Plasma and Additives Shang Kefeng, Wu Yan, Li Jie, Li Guofeng, Li Duan, Wang Ninghui, Zhu Jing
61
Discharge Characteristics of Magnet Enhancement Corona Discharges Dexuan Xu, Yinhao Sun, Haijun Wang, Mingfei Li
65
Study on emission specmma from high-voltage pulsed discharge in liquid-gas mixture and TiO2 photochemical catalysis Zhou zhigang, Li jie, Li guofeng, Wu yan
69
ii Automatic Design Of Insulation Structure In Power Transformer Yang Liu, Xiang Cui
73
Influences of Annealing Method on the Space Charge Properties in LDPE Wang NH, Zhou YX, Liu HB, Gao B, Liang XD, Guan ZC,Tatsuo Takada
77
Magnetic Field &Long Straight Current -Carrying Wires with Discrete Distribution Honglian Li, Lifei Li, Xiaoting Li, Zhonghua Zhang
81
The Research on Back Corona Physical Model on Deposited Dust Layer of collecting Electrode Sun Keping, Li Xuewen
84
The Physical Model of Dielectric Function and Radiofrequency for NaC1 Solution and Application of the Seawater Xu Yuan, Tang Shu Pian, Yan Chen Guang, Tang Xun
87
Theoretical and experimental study of the electromagnetic field generated by ESD Bi Zengjun, Liu Shanghe, Yang Jiangping
92
APPLICATION I (Precipitation, Pollution Control) Quadrupole Corona Discharge Ammonia Radical Shower Non-Thernmal Plasma System For Combustion Flue Gas Treatments And Conversion To Useful Products Chang J.S., Urashima K., Wang W., Hu H., Tong X.Y., Liu W.P., Itoh M., Obara S.
96
Electrohydrodynamic flow pattems in a wide spacing spike-plate electrostatic precipitators under negative coronas D. Brocilo, J. Podlinski, J. Dekowski, J. Mizeraczyk, K. Urashima, J.S. Chang
100
Synergy of Nonthermal Plasma and Catalysts in the Decomposition of Hydrofluorocarbons Futamura S., Annadurai G.
104
Modeling ofNOx, VOC, SO2 removal and ozone synthesis by streamer discharges Amirov R.H., Filimonova E.A.
108
Recent advances of power conditions for streamer corona plasma applications K. Yan, S.A. Nair, GJ.J. Winands, E. J .M. van Heesch, A.J.M.Pemen
112
Application of a plasma-catalytic system for removal organic pollutants Chae J.O., Demidiouk V.I., Yeulash N.M.
116
Plasma Assisted Selective Catalytic Reduction of Nitrogen Oxides Chae J. O., Demidiouk V. I., Ravi V., Yeulash N. M., Choi I. C.
120
Improvement of Energy Efficiency in the Dilute Trichloroethylene removal by Using Nonthermal Plasma Processing combined with Manganese Dioxide Sangbo Han, Tetsuji Oda
124
Micro-discharge in porous ceramics for exhaust gas cleaning J. Sawada, Y. Matsui, K. Hensel, I. Koyamoto, K. Takashima, S. Katsura, A. Mizuno
128
Decoloration of azo dye using active species formed by bipolar pulsed discharge in a three phase discharge reactor Zhang Ruobing, Li Guofeng, Wu Yan, Wang Ninghui
132
Theoretical Study on Electrode Configuration of Wire-plate Reactor with Pulse Streamer Discharge Dong Bingyan, Wu Yan, Li Guofeng, Li Jie
136
Removal of SO2 from Flue Gas by Water Vapor and NH3 Activated in Positive DC Corona Discharge Sun Ming, Wu Yan, Li Jie, Li Guofeng, Wang Ninghui, Shang Kefeng
141
, , ~
111
Theory and application of cyclone impulse electrostatic precipitation Li Jiwu, Cai Weijian
145
Development and application of high voltage pulse energization system in electrostatic precipitations Cai Weijian, Li Jiwu
150
Study on Trapping Inhalable Particles by Non-Thermal Plasma Zhu Y, Zhang M, Su P, Chen H, Huang L
154
Comparison of I-V Characteristics in Two Types of Wire-Plate Electrostatic Precipitators Kang Yanming, Chi Jinhua, Dang Xiaoqing, Zeng Hanhou
158
Analysis of the reason about the distribution of dust density and size in vertical electrostatic precipitator Qing Li, Fengming Wang ,Zhiqiang Liu
162
The statistic method and result of mobility of charged dust in electric field Zhiqiang Liu, Qing Li, Wenjie Zhou ,Qing'an Zhang
165
Effects of charged dust on dust-collecting electric field Zhiqiang Liu, Zengwei Peng, Qing Li, Dongxu Pang
167
The effect of discharge-electrode interval on corona current Qing Li, Zengwei Peng, Zhiqiang Liu, Zisheng Zhang
169
The analysis for even wind method of the vertical electric precipitator Qing'an Zhang ,Qing Li, Zhiqiang Liu
172
The high voltage electrostatic precipitator system based on fieldbus for the workshop of unloading coal Zisheng Zhang, Hongshui Li, Xiuming Zhao
176
Control system model of high voltage electrostatic precipitator based on foundation fieldbus Zisheng Zhang, Xiuming Zhao, Hongshui Li
179
The supervisory system of precipitator based on CAN bus Wenjie Zhou, Zisheng Zhang, Qing Li
182
The research of high temperature and high voltage electrostatic dust-collection technology Zisheng Zhang, Qing'an Zhang,Wenjie Zhou
185
Analysis on the characteristic of high voltage electric Field of different dust-collection electrode Zisheng Zhang, Wenjie Zhou, Qing'an Zhang
188
Fieldbus control system and electrostatic precipitator Zhiqiang Liu, Qing Li, Zisheng Zhang
192
APPLICATION ]] (Spray, Separation, Material, Ozone, Reprographics, etc.) Electrical Sterilization of Yakju By Discharged Oscillatory Decay Waveform Circuit Hee Kyu Lee, Myung Hwan So
195
Efficiency-Loss-Relations of Unipolar Nanoaerosol Chargers Marquard A., Bredin A., Meyer J., Kasper G.
199
Experimental Study On Optimum Of Low-Ozone Negative Ion Generator Liang Ping, Li Jie, Wu Yan, Lv Bin, Xu Minghua
203
Realization of the lower blade inclined spraying in electrostatic oiler Gao Quanjie, Wang Jiaqing
207
Biochemistry Effects Of Hydroxyl Radicals to Invasive Marine Species Xiyao Bai, Xiaohong Xue, Mindi Bai, Bo Yang, Zhitao Zhang
212
iv
Killing of Red Tide Organisms in Ocean Using Hydroxyl Radicals Mindong Bai, Bo Yang, Xiyao Bai, Zhitao Zhang, Mindi Bai
216
Treatment of 20t/h Ship's Ballast Water Using Strong Ionization Discharge Mindong Bai, Zhitao Zhang, Xiaohong Xue, Xingwang Liu, Xiyao Bai
220
Effect.of Hydroxyl Radicals on Photosynthesis Pigments of Phytoplankton of Ship's Ballast Water Mindi Bai, Xiyao Bai, Dongmei Zhang, Bo Yang, Keping Zhan
225
Study on Radiation of Microgap DBD Plasma at Atmospheric Pressure Zhitao Zhang, Xiaodong Wu, Jianlong Gu, Yang Xu, Xiyao Bai
230
The Influence of Grain Size on Electronic Properties of Pure Cubic AgC1 Emulsion Xiuhong Dai, Rongjuan Liu, Li Han, Guoyi Dong, Xiaoli Jiang, Shao-peng Yang, Xiaowei Li
234
The Influence of Electron Trap Capture Cross section on Carriers in Semiconductor Rongjuan Liu,Xiuhong Dai, Guangsheng Fu, Xiaowei Li, Shaopeng Yang, Rongxiang Zhang
237
Surface modification of metal material by N2-DBD Youping Hu, Yinduo Yang, Li Yan, Xinhe Zhu, Xiyao Bai, Shidong Fan
241
HAZARDS AND PROBLEMS
Research on the Security of Electro-igniting Device in Long-term Storage 'Condition towards ESD Guanghui Wei, Yazhou Chen, Lizhen Liu
244
Research on the Radiation Effects of FREMP towards Radio Fuse Guanghui Wei, Xing Zhou, Yazhou Chen
248
Research of Evolvable Hardware Technology in Improving the Reliability of VLSI Working in Extreme EMI Environment Huicong Wu, Shanghe Liu, Qiang Zhao, Guoqing Wang
252
Experimental Study on ESD Damage to 54 Series of Gate Circuits Haiguang Guo, Zhiliang Tan, Jie Yang
256
Experimental study on ESD sensitivity of 8212 chip Jie Yang, Zhiliang Tan, Haiguang Guo
259
The ESD Effect Experiment of the Integrated DC-DC Transformer Jie Yang, Zhancheng Wu, Shiliang Yang
263
The Analysis and measures of the Thunder Stroke Accident.of the Hefeng Gas Station in Gaozhou Li Zhaodong
267
Study on Electro-magnetic Shielded Packing Material Wang Wanlu, Liang Lihai, Yang Jianming, Yuan Zhongfu
270
Investigation on protection from ESD explosion of polyformaldehyde resin powder in pneumatic pipe Sun Keping, Yu Gefei
273
Research on Dielectric Oxide Film Breakdown Mechanism of IC Device in Human Body Model Sun Keping, Sun Zhiqiang
276
BIOLOGY TECHNOLOGY Effects of High Voltage Prickle Electrostatic Field on the Expressions of the Surface Molecules on the T Lymphoeytes and Antigen Presenting Ceils of Mice Sun YC, Liu XD, Yang XL, Ye S, Ma SM, Liu XC, Wang XL
280
Effects of High Voltage Prick Electrostatic Field on Lewis Zhang Y, Sun YC
287
High-quality Cucumber Production Improved by the High-tension Static Electricity Xiong Jianping, Hu Sume, Xie Sheng
291
Preliminary study on selecting the best treating dose of high static electric field by determining super-weak luminescence of germinating seed Hu Yucai, Bai Yaxiang
295
The transport character of water molecule on high voltage electric field in liquid bio-materials Ding C.J., Liang Y.Z, Yang J.
299
ELECTRETS Effect of ultraviolet radiation on charge storage stability of porous PTFE and non-porous PTFE electret Jiang Jian, Cui LiLi, Wang XiaoPing, Fang Ying, Song MaoHail, Li Ting
307
Charge Dynamic Characteristic in Hybrid Film Consisting of Porous PTFE and Teflon FEP with Negatively Corona-Charging Chen Gangjin, Jin Guangyuan, Li Qiaoling, Ye Feipeng
310
MEASURING TECHNIQUES The Reduction of Braking Torque under the DC Electric Field Gajewski Juliusz B., Glogowski Marek
314
Experimental comparison of probes for air discharge measurements Paasi J., Salmela H., Kalliohaka T., Fast L., Smallwood J.
318
Measuring the Size and Charge of Dust Particles in the Martian Atmosphere C.I. Calle, M.K. Mazumder, J.G Mantovani, C.R. Buhler, D. Saini, A.S. Biffs, A.W. Nowicki
322
Research on Electrostatic Discharge Test Standard and Theory Models Shanghe Liu, Ming Wei, Zhangcheng Wu, Qiang Zhao, Liang Yuan
323
An Electrostatic Approach for Aerial Moving Object Detecting and Locating Chen X., Cui ZZ., Xu LX., Bi JJ.
328
Research on Input Impedance of Measuring Circuit in Electrostatic Measurement System Bi JJ., Cui ZZ., Xu LX., Chen X.
333
Research on Vector Measurement Method of Electrostatic Field Xu LX., Bi JJ., Cui ZZ., Chen X.
338
Automation design of the ion stream generation device Qing Li, Wenjie Zhou, Zhiqiang Liu, Zisheng Zhang
342
The Development of ESD Radiated Field Measurement System Changqing Zhu, Shanghe Liu
345
vi
Research on 300kV Electrostatic Sensitivity Test for EED Qingmei Feng, Wei He, Tuan Zhao
350
EMC AND OTHERS
Test Method Study on Correlation of Electromagnetic Radiation and Injection for Microelectronic Devices Xing Zhou, Guanghui Wei, Shiliang Yang, Haiguang Guo
354
Investigation of the Antistatic Ability of Low-noise Microwave Device Shiliang Yang, Zhancheng Wu, Jie Yang, Xijun Zhang
358
Research on Electrostatic Discharge Radiation Field Simulating Technology Lizhen Liu, Guanghui Wei, Lisi Fan
361
The Influence of EUT to Characteristic Impedance in GTEM Cell Lisi Fan, Xijun Zhang, Lizhen Liu
365
Study on Mechanism and Protective Technology of Electromagnetic Harm to Micro-electronic Equipment Chaobin Tan, Jianzheng Yi
369
Analysis and Design of Electro-magnetic Compatibility (EMC) in Pulse Power System Dong Qi, Ninghui Wang
373
The TMR Fault-Tolerant based on EHW Under Single Event Upset Guoqing Wang, Qiang Zhao, Liang Yuan, Shanghe Liu, Huicong Wu
377
A Double Short Pulse High-Voltage Power-Supply Based On DSP 381 Xu Dapeng, Wu Yan, Liang Ping, Li Guofeng
381
Research on the Technology of Anti-electrostatic Interference for Radio Microwave FM Fuze Zhang Wanjun, Cui Zhanzhong, Li Wenying, Cheng Fang
385
Research on the Effect of Digital Circuit under the Influence of LEMP Yongwei Sun, Bihua Zhou, Guanghui Wei, Ming Wei
389
Computer System Disaster Recovery for Electromagnetic Interference Haitao Sun, Qiang Zhao, Guoqing Wang, Jianwei Zhang, Kaiyan Chen
393
AUTHOR INDEX
Author index
397
Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Charge behavior analysis in thin solid film by using simultaneous TSDC and LIPP measurements Tetsuji Oda, Koji Yamashita Department of Electrical Engineering, the University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan
Thermal Stimulated Discharge Currents (TSDC) analysis is very effective technique to understand the charge stability and space charge behavior in a charged thin film but the real position of those charges cannot be identified. For that, a novel charge analyzing system has been developed. During TSDC measurements, a Laser-Induced-Pressure Pulse (LIPP) method is applied to observe the charge in-depth profile of the corona charged film ni that new system. That system and new results obtained by that system are explained.
INTRODUCTIONS Recently various kinds of excellent dielectric materials have been developed which are very useful for us. However, such excellent dielectric materials are good insulators which may cause many unexpected electrostatic accidents (named as electrostatic discharge: ESD and electrostatic over stress: EOS); such as firing, explosion, device failure, computer misoperation etc. In order to prevent such trouble, the charge analysis of the stored charge on/in the dielectric material. For the charge stability analysis, relaxation process of the stored charge [ 1,2] in the dielectric material must be studied. Observation of the Thermally Stimulated Discharge Currents (TSDCs)[3] is one of analyzing methods of those relaxation processes. The authors also started to analyze the charge by the TSDC at first for the fly ash [4], for PTFE and High density Polyethylene (HDPE) films [5]. The TSDCs are very sensitive to the charge stability and it is easily to identify the different charge states. However, TSDCs cannot give us the information about the charge position in the film. Many researchers developed various space charge analyzing method. Thermal Pulse method [6] and that modified Laser Intensity Modulation Method (LIMM) [7] are charge analysis by using thermal conduction and expansion effects of the film. Pressure pulse traveling in the film can cause compression of the film and the displacement current can be detected [8]. Sessler groupe developed a very sensitive and high special resolution method by using a picosecond laser [9]. Other German group also developed the space charge detecting method by using high speed piezoelectric device [10].The author also developed a similar laser induced pressure pulse method [ 11 ]. Takada et al also developed a new system by using a piezoelectric device[12]. However, the reproducibility of TSDCs and LIPP methods is not so good and they must be observed at the same time for the same sample. For that purpose, we developed a novel device that can observe LIPP signal during TSDC analysis. That is, LIPP observation need only ten seconds or so and can be done during TSDC analysis. Therefore at some temperature during TSDC analysis, a weak DC current measurement is stopped about ten seconds and connected to LIPP measurement. EXPERIMENTAL TSDC and LIPP Observation A newly developed TSDC and !:!PP measuring cell is shown in Figs.1 and 2. Laser beam can enter the container from left side through a small window. The sample holder contains a charged sample film on
2 the detecting electrode (metal disk ) on right side and that electrode is connected to the BNC connector with a straight wire. On that electrode, the charged surface of the sample film is pressed with a contacting grease. A back side of the film is metalized by sputtering of aluminum before corona-charging and connected with another ground electrode plate (aluminum). All materials are wounded by the electrical heater and heated with a computer control. From that BNC connector, TSDC signal is transferred to picoammeter (pA) and amplified signal is digitalized and stored in a personal computer as TSDC signals. At some temperatures, Signal cable is switched to another low noise amplifier. The LIPP signal is amplified and digitalized by the high speed digital oscilloscope connected with a personal computer.
SampleHolder ,-......-----:BNCconnecter
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Fig.2 TSDC and LIPP measurement switching circuits. LIPP measurement and TSDC measurement (pA is measuring sample container)
Fig.1 Simultaneous TSDC and LIPP for TSDC and OSC is for LIPP)
Reproducibility of LIPP To improve the data reliability, reproducibility of LIPP measurement was examined as shown in Fig.3 where the first shot means a laser ablation for the first time. 100thshot means laser irradiation is repeated 100 times on the target surface and 100th means the data is obtained by the last laser irradiation. From Fig.3, about 20 % signal decrease from the 1st to 100thdata can be recognized. That degradation must be due to the increase of the surface roughness of laser irradiation target which coated with black special paint for better laser absorption. The impedance matching grease is not used because of heating. All peak values as shown X in Fig.3 are also shown in Fig.4 where the peak value gradually changes from -0.7 to 0.5 V during 100 laser irradiations. In Fig.4, 5 data are far from others indicating that the 5 % data are far from the real charge profile. In other word, if the data is far from the estimated value, LIPP measurement must be repeated. number of shots (times)
0.4 0.2
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. / Y ~
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....,~,-_,,...'--~,%.B 9 Lo
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Sample Preparation For our experiment now, 50 and 100 lxm PTFE Teflon sheet (Tomobo9001 supplied by Nichiasu ) and a polyethylene terephthalate (PET) sheet are used as the sample. They are corona-charged where the grid voltage is -5 kV where the corona voltage at the needle electrodes is about-30 kV at room temperature or high temperature (50, 100 and 150 ~ In this paper, all data shown here are charged at 100 ~ RESULTS AND DISCUSSIONS 100 gm PTFE Sheet Charged at 100 ~
3 A typical example of TSDC spectra of 100 ~tm thick PTFE Teflon sheet corona-charged at 100 ~ is shown in Fig.5. Two current peaks, b and g can be identified at about 250 ~ and 110 ~ Since the charging temperature is 100 ~ there is no current peak below 100 ~ LIPP signal for that sample before TSDC measurement (see Fig.5) is shown in Fig. 6 which is quite different from the TSDC spectra of corona-charged at the room temperature [13] as shown in Fig.7. At 345ns(that time is from the laser beam
Fig. 5 TSDC spectra of corona-charged 100
~tm thick PTFE thin film.
Fig.6 LIPP signal of 100 ].tm,thick PTFE film corona-charged at 100 ~ (before TSDC).
irradiation and means the vertical position of the charge), a large negative charge (peak C) is observed which may be negative charge in the sputtered aluminum back electrode and next peak B shows positive charge maybe injected from the back electrode but that is not so sure. There are two other mechanisms can be estimated. One is that the negative charges near the interface move from the PTFE to the back metal electrode and positive charges remains near the interface. Another model is that the strong negative electric field caused by the corona-charging induced the moving of the negative charge from the coronacharged film (fight side) to the left side and accumulate near the metal-PTFE boundary which is shown as peak C. That can well explained low negative charge peak A at the corona-charged surface. This model can well explain that a large surface charge peak (A) is observed in Fig.7 but becomes very small in Fig.8 because high temperature increases conductivity of PTFE. However, that explanation cannot explain why
Fig.7 LIPP signal for 100 mm thick PTFE film charged at room temperature (before TSDC)[ 13]
Fig.8 LIPP signals at 100, 125 and 150 ~ during TSDC measurement. Sample is charged at 100 ~
very sharp charge double layer as shown peaks B and C in Fig.6. More details will be discussed in near future. During TSDC measurement, LIPP measurements can be done at some temperature range which is shown in Fig. 8 and Fig. 9. By increasing the TSDC temperature, Peaks B and C are still very sharp but decrease with TSDC temperature. On the other hand, peak A is pretty stable and does not decrease at about 200 ~ Therefore those results suggested that Y peak in TSDC is strongly related with the charge peaks B and .C. TSDC current peak a should be related with charge peak A because both peaks are stable at 200 ~ and other apparent charge signal is not yet found. Off course, LIPP method is also not so highly sensitive for dipole
4 moment and there is a possibility that some new charges or dipoles are influenced TSDC a peak but not yet detected in LIPP method. That fact is an experimental result.
Fig. 9 LIPP signals at 175 and 200 ~ of PTFE charged at 100 ~ during TSDC measurement. 50 ~tm PTFE Sheet Charged at 100 ~ Similar experiments are done for 50 ~tm thick PTFE film. In this case, the electric field in the film must be double because the grid potential is the equal to -5kV which is the same for 100 ~tm PTFE film. The typical LIPP data before TSDC analysis is shown in Fig.10 and the TSDC data is shown in Fig. 11. LIPP signals at different temperatures during TSDC measurements are shown in Fig. 12 where the sample back
Fig. 10 LIPP signals of 50 ~tm thick PTFE corona charged at 100 ~ Before TSDC analysis.
Fig. 11 TSDC of 50 mm thick PTFE film corona-charged at 100 ~
electrode is at 305 ns and the corona-charged surface is at 400 ns, if the measuring temperature is 150 ~ When the measuring temperature increases, all peaks shift to larger time (fight side) in all data which is due to the change of sound velocity, film expansion and elastic coefficient. From Figs. 11 and 12, Y peak at TSDC corresponds the back electrode interface charge which disappear at 200 ~ for both in Figs. 11 and 12. 13 peak must .correspond surface charge (peak A). In other words, surface charge is trapped and stable if the sample is heated up to 100 ~ The double peaks A in Fig. 10 are not sure but maybe surface special configuration effect and will be disappear by heating. One LIPP example is measured for the 50 ~tm thick PTFE film corona-charged at 160 ~ as shown in Fig.13. A large amount of negative charge and counter positive charge are invaded inside the PTFE film. The negative charge at the boundary is assumed to the induced charge in the back electrode by the positive charge at the bottom of the film. That results suggest that various charge can move inside PTFE if the PTFE temperature is more than 160 ~ Those phenomena are well-know as large peaks at about 100 ~ by TSDC measurement, if the corona-charging temperature exceeds 180 ~
Fig. 12 LIPP sinals of 50 ~tm PTFE at 150, 175, 200, 225 and 250 ~ corona-charged at 100 ~
Fig. 13 LIPP signal of 50 mm PTFE charged at 160 ~ Before TSDC measurement.
CONCLUSIONS The simultaneous TSDC (thermally stimulated discharge current) and LIPP (laser-induced pressure pulse) measuring system is constructed for charge stability and charge position analysis. The position of charges which cause some TSDC peaks is identified and charge behavior in the PTFE film is visibly observed. Those results will explain various unknown electric current mechanisms near future by using that new device. ACKNOWLEDGEMENT This work is partially supported by the Grand-in-Aid for Science Research by the Ministry of Education, Culture, Sport, Science and Technology. The authors also thank Dr. Ono and Mr. Nakazawa for their advices and assist. REFERENCES [ 1] R.Chen and Y.Kirsh: Analysis of Thermally Stimulated Process," Pergamon Press, New York (1981) [2] P.P. Braeurich, ed.: "Thermally Stimulated Relaxation in Solids," Springer-Verlag, Berlin Heidelberg New York, (1979) [3] G.M.Sessler, ed.: "Electrets," Springer-Verlag, Berlin Heidelberg New York, (1980) [4] T.Oda, S.Masuda and T.Takahashi; "TSDC Measurements of Fly Ashes from Pulverized Coal Combustion," Proc.2nd Int.Conf. Electrost.Precip., pp.540-547 (1985) [5] T.Oda and S. Wang; "Charging on HDPE Films due to Surface Effects during Fabrication," J. Electrost., vol.35, pp.167177 (1995) [6] A.Migliori and J.D. Thompson, "A Nondestructive Acoustic Electric Field Probe," J.Appl.Phys., 51, pp.479-485(1980) [7] S.B.Lang and D.K.Das-Gupta, "Laser-Itensity Modulation Method: A Technique for Determination of Spatial Distribution of Polarization and Space Charge in Polymer Electrets," J.Appl.Phys., 59, 2151-2160(1986) [8] A.G.Rozno and V.V.Gromov, "Measurement of the Space-Charge Distribution in a Solid Dielectric," Sov.Tech.Phys.Lett., 5, pp.266-267(1979) [9] G.M.Sessler, J.E.West, R.Gerhard and H.von Seggem, "Nondestructive Laser Method for Measuring Charge Profiles in Irradiated Polymer Films," IEEE Trans. Nucl.Sci., NS-29, pp. 1644-1649(!982) [ 10] E.Eisenmenger and M.Haardt, "Observation of Compensated Polarization Zones in Polyvinylidenfluoride (PVDF) Films by Piezoelectric Acoustic Step-Wave Response," Solid St. Comm., 41, pp.2769-2775(1982) [ 11] R.Ono, and T.Oda, "Charge storage im a Corona-charged Polypropylene Film Analyzed by LIPP and TSC Method," Conf. Rec. 2002 IEEE-IAS Ann.Meeting, pp.585-588 (2002) [12] T.Takada and T.Sakai, "Measurement of Electric Field at a Dielectric/Electrode Interface Using Acoustic Transducwe Technique," IEEE Trans. Insul., EI-18, pp.619-628(1983) [13] T.Oda and K.Yamashita; "Charge Behavior Observation on/in Plasma Processed Thin Films by LIPP During Thermal Heating for TSDC Analysis," Conf.Rec.2004 IEEE/IAs Ann.Meeting, (2004) to be published
6 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Induction Charging of Non-spherical Granular Materials: Size Analysis Wu Y., Castle G.S.P. and Inculet I.I Dept. of Electrical and Computer Eng.,University of Western Ontario,London,Ontario,Canada N6A 5B9
The charge and forces on a particle strongly depend on the particle size and shape. In research studying induction charging of granular materials,, both the surface mean diameter (D~) and the volume mean diameter (Dv) are needed to predict the theoretical induction charge and determine the average charge per particle based on measured values of average charge-to-mass ratios (Q/M). This paper describes a suitable way to measure the particle size of irregularly shaped induction charged particles that normally have a sampled mass of approximately 10 mg. The results of charge per particle were found to be in good agreement with the theoretical predictions.
INTRODUCTION An accurate measurement of particle size and shape is vital for determining the average induction charge on each particle from the overall charge-to-mass ratio (Q/M) as measured in induction charging experiments. Although there are different techniques to measure particle size, each technique has its own limitations such as the required amount of the particle sample, the size range of the particles, the particle density, etc. There is no single sizing technique that is superior in all applications. [1] To achieve a reasonable result for the size of a group of particles, usually it is necessary to use several different methods to get meaningful measurements. Thus the relationship between the results from different methods needs to be considered. [2][3] Obviously particle shape takes a significant role in measuring particle size. [4][5] Quantitative analysis of the effect of shape on particle size has been less investigated. In this research efforts have been made to analyze particle size and shape and find a suitable way to measure the effective particle size in terms of surface mean diameter (D~) and volume mean diameter (Dv) of the collected induction charged samples which normally had a sampling mass of approximately 10 mg.
PARTICLE SIZE AND SHAPE Particle Size Particles can have many shapes such as a sphere, ellipsoid, wedge, irregular, etc. For a spherical particle it is straightforward and unambiguous to use diameter to describe its size. It is also possible and useful to define the size of a non-spherical particle in terms of an equivalent diameter as defined in terms of either a circle or a sphere. In practice different definitions of diameter are used for non-spherical particles depending upon the property for which the particle size is required. For example, the properties of a particle considered in the size definition include: surface area, volume, mass, sieve size, sedimentation rate, ete [1][4][5]. In the research reported here the surface diameter is used as the measure of particle size in induction charge analysis because the charge is dependent on the surface area of the particles. The volume diameter is used to calculate the mass of the particle to obtain the charge per particle from charge-to-mass measurements. When a particle is observed under a microscope, a number of diameters may be defined to characterize the particle based on its 2-Dimension projection [4]. The diameter of a circle which has the same property as the projected outline of the particle may be used such as the projected area, perimeter, maximum diameter, minimum diameter, etc.
7
Mean Size Almost all research deals with groups of particles instead of a single particle. Assuming that dsl, ds2,...dsn are the surface diameters and dv~, dv2, ...dvn the volume diameters for n particles, two definitions of means, surface mean diameter and volume mean diameter, are listed as follows [5]. /
~-7" D. -
av3~/n
(2)
Particle Shape The shape is an important property of the particle and is a critical factor in the correlation of size analysis. There are many descriptive terms that are applied to particle shape such as angular, flaky, irregular and spherical. It is necessary to incorporate a quantitatively defined shape factor into equations to analyze particle properties. Generally it is assumed that in a group of particles considered in particle size analysis each has approximately the same shape, which means that particle shape does not change significantly with particle size. The terms "shape factors" and "shape coefficients" are widely used in particle size analysis [4]. Shape Factors Particle shape can be represented by a variety of quantitative shape descriptors from image analysis. Particle shape factors primarily describe particle elongation, flakiness, roundness or angularity. Heywood [5] developed Heywood ratios based on three mutually perpendicular dimensions of a particle. Once the breadth (B), the length (L) and the thickness (T) are measured, the elongation ratio (RE) and flakiness ratio (RF) can be obtained as follows. R~ - L / B
(3)
RF - B / T
(4)
From the concept of elongation ratio a readily usable particle shape factor is the aspect ratio. Based on the measured maximum diameter and minimum diameter the aspect ratio (RA) is defined as follows. RA = Dmax/Dmin
(5)
In a similar manner one can define another useful ratio, the ratio of the mean surface diameter and mean volume diameter, as R~va. R,vd - D , / D v
(6)
To estimate the appropriate value for R~va, it is necessary to observe and measure the shape of the particle and find a similar geometric shape with the same aspect ratio and flakiness ratio. Shape Coefficients The other general method to indicate the particle shape is using shape coefficients. Shape coefficients are defined as the relationship between the measured size and the particle surface or volume diameter, for example, the volume shape coefficient, ~ , shows the relation between the volume mean diameter (Dv) and the mean projected area diameter (Da) [4]. g v - ~D3 / 6 D 312
(7)
PARTICLE SIZE MEASUREMENT METHODS Laser Diffraction Laser diffraction has become the preferred standard in many industries for characterization and quality control in particle size measurement [ 1]. Laser diffraction relies on the fact that the diffraction angle is inversely proportional to particle size [4]. A Malvem Mastersizer 2000 was used in this research. Samples ....
8 of 1-2 gram are necessary for accurate measurements. The results of laser diffraction give the size distribution in terms of surface area diameter.
Microscopy Microscopy is a method that allows the individual particles to be observed and measured. A digital camera with a fixed magnification lens is used to take a picture of a sparse layer of representative particles distributed on a microscope slide. An image analysis program is used to obtain measurements by analyzing the number and shade of individual pixels. Only a small quantity of representative particles are needed in the analysis. In this research an Olympus SZ-CTV microscope with a maximum magnification of 40 and an imaging software program, Image-Pro Plus, were used to measure the particle size. A Nikon digital camera DXM 1200 with a maximum magnification of 1,000 and a software program Automatic Camera Tamer-1 (ACT-l) were used to observe the particle shape. The aspect ratio, flakiness ratio and projected area diameter can be obtained from microscopic results. Size and shape Analysis in this Research In this research sieving was used to classify particles into fractions with a relatively narrow size range. All the particles used in the induction charging experiments were sieved and were labeled with their mean sieve diameters. These sieved particles were measured using laser diffraction and microscopy while the samples collected from the charging experiments were only measured using microscopy due to the small quantity collected. To illustrate the process of the measurements and calculations, an example of the determination of the charge per particle and saturation charge for A1203 particles with a mean sieve diameter (Dms) of 390 l.tm is given as follows. Step 1. Determination of Rsvd from Sieved Particles As described before, the aspect ratio and flakiness ratio for the particles can be measured using microscopy. Applying these ratios to corresponding similar shaped objects (wedge for A1203 or ellipsoid for aluminum particles), the ratio of the surface diameter and volume diameter, R~d, can be determined. For A1203 particles (Dms = 390 l.tm) it was found that RA = 1.6 and RF = 1.5, hence R,vd = 1.29. Note the projected area diameter (Da) can be also measured using microscopy. Here D~ = 559 l.tm. Step 2. Determination of Volume Shape Coefficient Laser diffraction results for sieved particles gave the surface diameter distribution. Based on these results and R~d, the volume diameter distribution can be determined. Then the volume mean diameter (Dv) and volume shape coefficient (tXv) can be determined.
D,, = ~ n,D 3 / N - 409 (l.tm) cr~ = ~ D 3/6D~3 = 0.2 Step 3. Determination of Size for Sampled Particles The measurement results for the samples from the induction charging experiments were measured using microscopy to give the mean projected area diameter, Da. Combining Da and the volume shape coefficient we can obtain the volume mean diameter. The corresponding surface mean diameter can be determined by multiplying D~ and R,vd for the samples. In the example of the sample, Da = 468 Ixm so: D~ - D~ 3~6ctv / lr = 341 (l.tm)
O, = DvR,,,d = 447 (l.tm) Step 4. Application of Dv and Ds Size in the Charge Analysis The above collected samples had an average charge-to-mass ratio of 39.0 (nC/g) in the induction charging experiments. So the average charge per particle is: a p = (Q / M ) . mp = (a / M) . ~D~p / 6 = 3.2 (pC) This may be compared to the saturation charge [8]: Q, = 1.18~0D~E ~ = 3.9 (pC) A summary of the calculation results is shown in Table 1 below along with a comparison if one simply assumes the mean sieve diameter as is normally used.
Table 1 Calculation results of charge per particle
Ds (~tm)
Rsvd
(~tm)
Q/M (nC/g)
Qp (pC)
Q$ (pC)
Qp/Qs
Dv
447
1.29
341
39.0
3.2
3.9
0.8
390
1
390
39.0
4.4
2.8
1.6
It is reasonable that the charge per particle is a little less than saturation charge in Table 1 when the above method is applied. If particle shapes were not considered, that is, mean sieve diameter is used to calculate the charge per particle and saturation charge, it can be seen that the calculated charge is 60% higher than the saturation charge, a result obviously in error. Similar errors occur when D~ or D~ is simply used. For different experimental conditions these potential errors could often exceed 100%. Analysis of results for the glass beads showed that the surface diameter and volume diameter were identical, confirming that the beads were close to spherical and the simple measurement method was adequate.
CONCLUSIONS It is known that particle shape takes a significant role in size analysis. The ratio of surface diameter and volume diameter can be obtained from shape analysis of similar geometries. A volume shape coefficient can be determined by combining the measurement results from laser diffraction and microscopy. The ratio of surface diameter and volume diameter can be used to determine the volume diameter from a known surface diameter or visa versa. The volume shape coefficient obtained from sieved particles can be used to determine the volume mean diameter for small samples measured with the microscope. Applying this method in the study of induction charging for irregular and spherical particles the results of charge per particle were found to be in good agreement with the theoretical predictions. Failure to properly account for the effect of shape in determining the particle size can lead to significant errors in interpreting results in induction charging experiments
ACKNOWLEDGEMENT The authors would like to thank Mr. J.G. Lusk, Mr. B. Verhagen, Mr. D. Yin, Mr. P. Belej and Mr. R. Harbottle, all of the Faculty of Engineering, UWO, for their help and advice. The authors would also like to acknowledge NSERC for the financial support for Mr. Wu and the research and Saint-Gobain Abrasives for the loan of equipment and provision of particle samples.
REFERENCES 1. Rawle, A., Basic Principles of Particle Size Analysis, Technical Report, Malvem Instruments Limited, Worcestershire, UK. 2. Seaver, A.E.,A Relationship between Mesh,Grit and Particle Diameter,Proceedings ESA Annual Meeting (2000).pp.168-179 3. Tan, S. Y., Microscopic Sizing Sugar Crystals Using Imaging Analysis, Bachelor of Engineering 4th Year Thesis, The University of Queensland, Brisbane (1998). 4. Allen, T., Particle size measurement, 4th Ed., London, England, Chapman and Hall Limited (1990). 5. Cadle, R. D., Particle Size Theory and Industrial Applications, Reinhold Publishing Corporation, New York, (1965). 6. Xu, R., Particle Characterization: Light Scattering Method, Dordrecht, Netherlands, Kluwer Academic Publishers, (2000). 7. Tuma, J.J., Engineering Mathematics Handbook, McGraw-Hill Book Company (1972). 8. Wu, Y., Castle, G.S.P., Inculet, I.I., Petigny, S., Swei, G., Induction Charge on Freely Levitating Particles, Powder Technology (2003), 135-136, pp. 59-64. 9. Wu, Y., Castle, G.S.P., Inculet, I.I., Petigny, S., Swei, G., The Effect of Electric Field Strength on the Induction Charge of Freely Levitating Particles, Proceedings ESA-IEEE Joint Meeting on Electrostatics (2003), Little Rock, Arkansas, June 2427, pp. 259-269.
10 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
On Disruption Onset for an Electrified Capillary Liquid Meniscus:Revisit of Zeleny's 1914 Experiments on the Phenomenon of Spraying T. S. Lee Electrical and Computer Engineering Department University of Minnesota, Minneapolis, MN 55455 USA
Tip behavior of a capillary liquid meniscus in a point-plane electrostatic field is examined. That liquid profile can deform in response to changes of electrical and mechanical forces is noted. By focusing on the local state of balance amongst effects of field, interior excess pressure, and surface tension, simple conditions of equilibrium and disruption are arrived at. Indications are (1) that profile equilibrium is not unique at lower applied voltage and pressure and (2) that, in consequence, tipgated jetting instability is triggered at high enough, but definite, values of the same, quite separate from the familiar and oftener- encountered dripping mechanism. These conditions of bifurcation and instability onset are formally independent of bulk material properties as long as the liquid is sufficiently conducting. Breakdown data from Zeleny's original experiments are compared.
I. INTRODUCTION Fine jets of slightly conducting viscous fluids and thicker jets or drops of less viscous ones can be drawn from capillary tubes by electric forces. University of Minnesota physicist Zeleny conducted pioneering work here ~3 following 1910. Since then, most of the experiments reported in the world literature 415 have been performed with an apparatus like his. As sketched in Fig. 1., a capillary tube opposite a metal plate at some distance supports a conducting fluid which is drawn out from the opening by a combination of external electric field force, internal back pressure force, and, wherever it is important, a body-distributed force field such as gravitation or centrifugal acceleration. The setup has been seen to suit studies of dripping and spraying. Wilson and Taylor 16 placed a soap bubble of measured volume on a horizontal wet aluminum plate. The half bubble thus formed was subjected to the influence of a uniform electric field by placing a second plate above it. They discovered that, when the potential difference reached a threshold, a thin thread of liquid would issue from the tip of the prolate-sphere form in a manner visually reminiscent of that of earlier analogous observations by Zeleny in his tube experiments 3. Dynamically speaking, their work was motivated by an interest in the disintegration of water drops in a strong electric field, a factor believed to play an important part in the formation of thunderstorms. Taylor later undertook to theoretically study the form deformation of an uncharged drop in a uniform field 17. Invoking mass (or volume) conservation, he found that, in a state of equilibrium, the altered shape closely resembled that of a spheroid and that a finite excess pressure in the interior would invariably accompany shape change. Under the spheroidal approximation, he showed that an elongated drop becomes unstable when its length is 1.9 times its equatorial diameter, a criterion which could not otherwise be arrived at without having the excess pressure taken into account 9. Rayleigh's original study 18 on the stability of a charged spherical drop revealed that, if and as the potential or charge first exceeds a certain critical level, the drop becomes unstable only for disturbance of the P2(cos0) kind for which it becomes slightly ellipsoidal while the displacement is small. In a later work 2, Zeleny assumed that the drop in his experiment became elongated approximately into the form of a prolate spheroid whence the field at the pole could be calculated. He attempted to adapt Rayleigh's
11 stability criterion for a charged sphere so as to be applicable to a spheroid by assuming that it applies at the polar end where the radius of Rayleigh's sphere is replaced by the polar radius of curvature of the spheroid and the mechanical stress due to the electric field is the same as that on the sphere when it becomes unstable. The particular P2(cos0)-mode invoked happens to be one with the property of zero excess pressure. Hence, as pointed out by Taylor 9, he had erroneously used this special property as the underlying assumption instead. Noting that this distinction explained why Zeleny had met with no theoretical success, Taylor proceeded to derive his well-known criterion of instability of a spheroid droplet in a uniform field based on retaining the attendant excess pressure as a fundamental premise. Significant differences separate the two problem types cited above: Droplet in uniform field: (1).Liquid mass or volume is finite. (2). Internal excess pressure follows elongation but is otherwise not subject to independent control. (3). Bipolar charge separation on a drop involves no external charge exchange. (4). Peak field enhancement on surface is limited. For illustration, in the limiting case of a sphere in a uniform field ~7, or, in the equivalent case of a plate-imbedded hemisphere in a parallel-plate field arrangement 16, the enhancement factor is merely three, a figure independent of size. Meniscus at capillary end: (1). Liquid is supplied from a reservoir. Meniscus mass or volume is not fixed. (2). Excess pressure is subject to external control. (3). Meniscus is in contact with a voltage source. Charge supply is not limited. (4). Peak field for a convex form occurs at tip. Take the case of a rigid hemisphere at tube end for example. As its radius decreases, the enhancement factor (over V/h) goes up without limit. Thus in contrast, the effect of this kind of field nonuniformity on a meniscus is far more significant than that of the corresponding kind of field nonuniformity on the elongated drop described above. In a way, this property accounts for the effectiveness of the narrow capillary tube as a popular device choice in experiment. Some theories of fluid breakup have been offered in the past ~9. Those which are strictly mechanicsbased are of two schools. The first considers the meniscus as an entity. With anticipated failure at the neck, it is related more to drop dripping, a phenomenon already familiar in a purely mechanical context. Taylor's work 9 is representative of this school. The second considers the meniscus liquid as a closed system and, by following and modifying Rayleigh's perturbation approach on charged drop 18, views instability by way of the time behavior of individual normal modes. Of this school, works by Hendricks et al. 7 and Schneider et al. 2~ are representative. In view of the observations elaborated on earlier, questions about modeling correspondence and appropriateness remain. A range of behavior is associated with the fluid issuing from the tube end as voltage is raised beyond a minimum necessary for first breakdown (cf. Drozin 5, Bailey 19and Cloupeau and Prunet-Foch2~). In this work, discussion will be restricted to conditions of impressed voltage and back pressure up to only values moderately beyond onset, pertinent to a range of practical interest encompassing meniscus equilibria ~ and first meniscus jetting (See Figs. 5 & 7 in Ref. 3 and Figs. 4-6 in Ref. 9) only. We begin by observing that, below onset, it is the dual features of the very special nonuniform field environment and the ability of the meniscus surface shape to self-adjust in response to changes in environment that distinguish the problem of Fig. 1. On a convex profile, the tip is the one region most affected and thus most vulnerable. We take the view that knowledge of the mechanical condition at the tip can be relied upon to give clue to the state of the entire meniscus. To this end, since the concept is surface-related rather than bulk-related, it is only necessary to collectively enlist the three effects of local capillarity, local excess pressure Ap (important as has been noted above), and local ambient field in a single consideration. While the first two are tractable, we can estimate the last only approximately. Van Dyke 22calculated the attractive force between a long cylinder and a perpendicular plane when a potential is established between them. His results show that the total force depends on length but its change is related to that of the part exerted at the far end only 23. Hence in an experimental situation like Zeleny's, they confirm the implicit assumption that attraction between the fluid and the plate does not depend on the field far from the end of the cylindrical tube with the inference that the peak field at fluid tip is by and large dependent primarily on the local surface curvature and the s h a n k effect of the long tube may be deemed secondary. In practice, this realization has been at the base of some theoretical approximations. For instance, in investigating the peak field at tip of a pendent drop hanging in equilibrium from a tube, Borzabadi and Bailey 24 invoked a paraboloidal approximation for the lowest part of the meniscus shape. To simulate the meniscus field at the tip in this work, we choose a particular model (Sec. II-1) using an asymmetrically deformed sphere. Convenient for evaluation by the method of
12 a single pair of image charges, such a model is judged to be closer to the thin-bodied reality behind the meniscus than the paraboloidal model whose dimension is, in principle, unlimited laterally. II. ANALYSIS 1. Tip field according to simulation by an asymmetrically deformed sphere. Consider in the y-z plane of Fig.2 a system of point charge Q and its image -Q located at (0, +D) respectively. The structure has rotational symmetry about the z-axis. The zero-potential ground is taken to be the z = 0 plane. Coulomb potential field is given by V(y,z) =
Q 4xs o
{ [(D-z)2+y2]" 1/2-[(D+z)2+y2]" 1/2 }.
(1)
For a given constant potential V, Eq.(1) traces out the shape of an asymmetrically deformed sphere in correspondence. If the shortest separation between the liquid and the plate is h, the lowest point (0,h) on this body simulates the meniscus tip. Here, we identify the liquid potential with V(0,h) such that 4x~ V
o
o
o
1_02
/
.
(2)
where a shape parameter 0 = h/D has been introduced for the range 1 > 0 > 0. We assume the peak surface curvature to occur at meniscus tip and denote the local radius of curvature by b. By selecting a shape sharing the same tip location and curvature, we have from Eq. (1),
id2 l
= dy 2 (Y=0,z=h) = '
h3o2+h2, D4_h4
With the normalized tip curvature defined as n = h~, this is equivalent to 02(3+02 ) n =
1-0 4
"
(
3
)
An quadratic algebraic equation in 02, Eq. (3) has the pertinent root 02= [2(n+l)]-l[-3+~9+4n(n+l) ] (4) It can be seen from either Eq. (3) or Eq. (4) that n and 0 are monotonically related. As shown in Fig. 3, the interval 1 > 0 > 0 has the range ~o > n > 0 in correspondence. The same Coulomb scheme also calculates the tip field, E(0,h), which is now aligned vertically with its z-component given by -Q [(D_h)-2+(D+h)-2]. Ez(0,h ) = 4XEo s
Thus, computed as -~q Ez2(0,h), the corresponding Maxwell's tensile stress is ~oV2.. 1+02 )2 Te= ( 2 h 2 )1"1__02
(5)
with the aid of Eq. (2). 2. Interface stress balance. For a meniscus at equilibrium, it is necessary that the three effects of capillarity, field, and excess pressure be in local balance throughout the profile. At the tip in particular, 2(Y (6) Te + Ap - b " By Eqs.(2),(4) and (5), this takes on the simple form of (7) Z=W, where we have introduced a dimensionless function
13 W(n,p) = 2(2n_P) f 2n+5-'~/9+4n(n+l) } 2n- l+~9+4n(n+l) in which
(8)
P = laAp denotes a normalized excess pressure, and t~
eo V2 z -
(9) oh ' a new dimensionless but largely physical parameter involving applied voltage and surface tension explicitly. 3. Behavior of the W(n,P) function. We view the behavior of W with interest. Figure 4 has sketched a few representative W vs. n curves at moderate P values (both + and-). For a convex meniscus, b or n is always +. The display is confined to the first quadrant of the n-W plane. Mostly, a curve ascends at small n, reaches a relative maximum Wo(P) at a position no(P), and descends uniformly thereafter. It can be shown that in the limit of large n the curve approaches 2(2n +l-P)/n 2 asymptotically. Let us take up the case of zero excess pressure first. The W(n,0) curve starts at the origin, climbs to Wo(0) = 1.2626 at no(0) = 1.049 and then subsides. Next, for the case of positive excess pressure for which P > 0, a curve starts at n = P/2 on the abscissa. While lying below W(n,0) with Wo(P)< Wo(0) and no(P)> no(0), it observes the said general pattern as n increases. When P becomes progressively more positive, no increases whereas Wo declines. Finally, at negative excess pressure for which P < 0, a complexity emerges. As P becomes progressively more negative, no decreases while Wo increases. Always, a curve will lie above W(n,0) but will intersect the ordinate at a point -2P above the origin. For small n, actually, linearized Eq.(8) yields W(n,P __--(-2P)[12
+~" ) n]. From this, certain features are discernible. If 0 > P > -3/2, for instance, intersecting takes
place on the upswing of the curve. A relative maximum exists with Wo(P) > Wo(0) and 0 < no(P) < no(0). If P <-3/2, on the other hand, it does so on the downswing and there will be no relative maximum for positive n. At P =-3/2, the relative maximum with Wo = 3 and no = 0 exists marginally. Figure 5 displays both no and Wo variations for the entire range of P >-3/2. At large P, the former increases and the latter decreases without limit.
III. BIFURCATED STATES OF EQILIBRIUM For sake of overall discussion, consider that all physical and structural parameters except the applied voltage have been prescribed. With P known, Wo is readily determined. It then follows that, if the voltage is low enough, the inequality Z < Wo obtains for those situations of Fig. 3 where a relative Wmaximum exists. Figure 6 shows such a typical characteristic selected from among those of Fig. 3. It is seen that the corresponding constant-Z line will make two distinct intersections. These dual possibilities are consistent with the equality of Eq. (2) and yet they point to the likelihood of two separate configurations for a convex meniscus with two different degrees of tip skew. The immediate discussion here will be restricted to cases of relatively great h, for which change in n in many realistic situations can be attributed to mainly that in b. Reinforcing scrutinies in supplement will be given in See. VI-4. 1. Ordinary mode (n < no). Intersection point A lies on a branch to the left of the maximum of the characteristic. As an equilibrium state, it suggests a meniscus shape having a character quite conventional. To illustrate, consider V the sole adjustable parameter in experiment. As it varies, Z follows. To maintain equilibrium, A moves up or down, toward a greater or smaller n value, as V increases or decreases. In the first instance, the shape adjusts itself in such a way that a more pronounced tip skewing accompanies the enhancement in field tensile stress in response to a voltage increase. In the second instance, an opposite tendency applies instead.
14 2. Extraordinary_ mode ( n > no_) For a state on the branch to the right, balance is again achieved. However, its mode behavior is rather unusual -- quite contrary to conventional expectation in fact. For the same illustration, for example, Z again varies alongside V. The corresponding state point B would migrate up (or down) likewise. Yet, movement would be now in a direction of reduction (or enhancement) in n instead. In situations where variation in n is attributed to mainly that in b, voltage increase and decrease actually cause weakening and augmentation in tip curvature, and thus in tip field strength, respectively. We label such behavior
extraordinary. IV. ONSET OF DYNAMIC RELEASE Suppose that V is allowed to be raised from low values, other conditions being equal. Continued maintenance of electrohydrostatic equilibrium entails self-adjustment of meniscus profile. There, the most important characterization concerns the changing condition at tip. The latter can be gauged through following the motion of the state point in Fig. 6. One sees that, with either A or B, i.e., with the meniscus already in one of the equilibrium modes, the migration is upward. Ultimately, the balance equality of Eq. (7) starts failing at Z~ - Wo(P) , ( 1 O) where, if h is fixed, the attendant critical voltage will be /(YhWo(P) Vc = ' ~ ~ f
~oo
"
(11)
Above this voltage level, we have Z > Wo(P). For an horizontal line associated with such a constant-Z value, no intersection with the W-curve is possible. In this regime, field disruption, aided by pressuredifferential effect, predominates at the tip, irrespective of the manner or extent of profile self-evolvement. In consequence, surface tension effect will be too weak to rein in the liquid. Material may be perceived to be flooding out in a jet-like manner from a gate or valve at the tip which has now been opened.
V. PHASE PLANE In the above, the behavior at the tip of a convex liquid meniscus has been formally examined. Essential features are summarized now in the P-Z plane of Fig. 7. Equilibrium bifurcation is recognized for P >-3/2. With positive P, the region is bounded from above by the Wo(P) curve. With P between -3/2 and 0, it is further bounded from below by Z = -2P. When Z <-2P at a negative P, the corresponding equilibrium can only be in an extraordinary mode. The region sharing Z >Wo(P) for P > -3/2 and Z > -2P for P < -3/2 represents the zone pointing to a state of tip liquid breakup.
VI. DISCUSSIONS ON EQUILIBRIUM 1. The two diametrically opposed modes of behavior having been detailed above, it would be timely to examine their respective characters in the vanishing-Z, or zero-V, limit. For the case of positive P, for example, the ordinary mode predicts n = P/2, a state of affair conceivably achievable by having a voltage vanishing at fixed h, in which case the surface tension effect exactly counterbalances the excess-pressure effect. On the other hand, the extraordinary mode predicts n = oo instead. Accordingly, Eq. (8) reduces to W = 2(2n+l-P)/n 2 as was pointed out earlier. In the limit, then, balance implies Z = 4/n, which, according to Eq. (5), is Te = 2cr/b. Thus, the field effect and the local curvature-induced surface tension effect are in mutual balance with the excess pressure playing an insignificant role by comparison. That such a peculiar picture can be deemed reasonable is attributed to the very special kind of field nonuniformity whereby, at a finite excess pressure, its disrupting effect and the stabilizing effect of surface tension at tip would both theoretically increase without limit as local curvature rises indefinitely, even for vanishingly small (but
15 finite) applied voltage. In the same connection, the reader might find it interesting to consider conditions theoretically attributed to a Taylor cone ~7.There, field and capillary effects are again in balance while the pressure differential plays no role. In this sense, a parallel is exact and treating Taylor's conical structure as the limiting model regime for the meniscus tip is in order. Yet, as n goes to infinity in the present context, the local radius of curvature would approach zero, violating the assumption that the stem be slender-bodied. In fact, with R denoting the radial dimension of the capillary tube, the ratio R/b would become unbounded. Thus in practice, individual W curves in Fig. 4 would become unreliable at n values far exceeding h/R. 2. The present analysis has assumed that the capillary tube is slender-bodied and that the meniscus shape is convex. There is some evidence ~5 from numerical work that, for strong enough negative excess pressure and under some conditions, the surface shape might even turn concave near tip. The peak field would then be found nearer the rim rather than at the tip, negating the very premise of the analysis. Relevant phenomena would then be those connected ultimately to rim instabilities of various kinds. In consequence, discussions on tip equilibrium and breakup in the above would cease to be meaningful. This would affect the use of Fig. 4, where caution in interpretation must be exercised whenever n is too small. 3. The evolving balance at tip during profile self-adjustment is insensitive to conditions in recessed regions of the profile. Therefore, tube size and other rim-wetting details might influence the profile details near tube opening but would by and large not be expected to affect the state at the tip materially. 4. With the meniscus extruding from the tube end, its shortest distance to the surface of the extracting electrode h does not vary greatly during profile evolution(in fraction) if it is large to begin with, as is true of many experimental situations and as has been assumed and examined in the above. In such cases, variation in n(=h/b) is traced to primarily that in b. However, if h is only moderately larger than the meniscus size, a different description could enter the picture. Imagine the meniscus being drawn out with increasing voltage accompanied by a reduction in h. The earlier interpretation of the ordinary mode was that the related increase in n is accompanied by a b decrease. For the extraordinary mode, by contrast, the related decrease in n was interpreted as being due to an increase in b. Obviously, these projections on b variation would continue to hold even when a moderate reduction in h is involved. On the other hand, in the new situation indicated where the effect of fractional h reduction could be severe, b might actually decrease, yet causing a net reduction in n still. With such a scenario, the previously labeled "extraordinary mode" would cease to be extraordinary in behavior. In fact, increase in applied voltage would accentuate curvature at the tip in the same way as in the case of the ordinary mode. Yet, even then, the basic bifurcation prescription for equilibrium still would stand. 5. Using a numerical method, Joffre et. al. have calculated some meniscus profiles from experimental specifications. Among them are those for silicon fluid at 2 mm excess pressure head over a range of V up to 2.6 Kv (See Fig. 4 of Ref. 15). It is interesting that on examination they show accentuation in tip curvature with increasing voltage, qualitatively consistent with a conventional-mode description. Here, the point-plane distance used, at 10 mm, is only moderate. In view of the discussion just undertaken, the possibility of having an extraordinary-mode description cannot be discounted. Unfortunately, the curves there presented are too rough for accurate enough b determinations to settle the question. 6. If P <-3/2, no would shift outside the domain of Fig. 4. There being no relative maximum on the positive-n side, -2P at n = 0 represents the absolute maximum for W. We incorporate this feature formally in Fig. 7, in which the Z =-2P line above (-3/2,3) separates the zone of extraordinary-mode equilibrium from the zone of breakup. 7. The possibility of equilibrium bifurcation according to our tip-related criterion points to the likelihood of two separate meniscus configurations in correspondence. They are distinguished by separate values of n or, indirectly, tip curvatures. Whether one or the other regime can be expected under a given set of moderate Ap, h, and V specifications depends on circumstances of experimental history. With reference to Fig.6, we deem the following experimental scheme plausible for bringing about state B, a meniscus in the extraordinary mode" Start with a moderate excess pressure but no applied field, in order to assure liquid protrusion with some finite tip curvature. Introduce the ground electrode at a good distance corresponding to a large n. Apply a small voltage and gradually increase it while reducing separation and concurrently adjusting the excess pressure needed until a desired state is finally achieved. To bring about a state in the ordinary mode like point A, on the other hand, a different scheme need be prescribed: Again, start with zero field. First, apply just enough excess pressure to give a small initial tip curvature in protrusion. Next, install the electrode close by (corresponding to a small n) and then apply a small
16 voltage. Increase both voltage and separation concurrently and gradually while adjusting the excess pressure as needed until the desired equilibrium state is finally arrived at.
VII. DISCUSSIONS ON LIQUID BREAKUP 1. We link the breakup condition (10) to the phenomenon of tip spraying at the end of a capillary tube. It is conceivable that, at high enough voltages, balance failure over a broader zone could occur around the tip which is the most vulnerable point on the profile. Therefore, Vr of Eq. (11) is regarded as the "minimum spraying voltage" as has been commonly known in the literature. Sensitive to conditions at tip, the mechanism hinges formally on local effects of surface tension, field, and excess pressure only. All other factors such as tube size and details of wetting and attachment on the mechanical side or liquid density, electric permittivity, viscosity, electric conductivity on the physical side do not enter consideration directly at all. 2. Following discussions of Sections IV and VI-2, the tip-jetting instability is unrelated to Taylor cone formation, contrarary to prevailing views (e.g. Ref. 19). This realization is consistent with findings of some recent numerical work 25. 3. Aside from the "tip-valve" breakup studied so far, the mechanism of "dripping" breakup could under some circumstances be at work separately. This is best understood in the context of a pendent drop. Liquid emerging from tube end is restrained by the force of surface tension acting around the base perimeter. The downward net force on the drop is due to the totality of all forces acting: (a). excess pressure force (integrated over the cross-section at neck), (b). downward electrostatic force (integrated over the drop surface), and (c). net gravitational force (force density integrated over the drop body). When it overpowers the restraint of surface tension at the neck, dripping would commence. Unfortunately, as the drop breaks away, there is always a 'necking in' effect which is difficult to assess in practice. In addition, the difficulty of solving the related Laplace:Young type of free-boundary problem for the drop profile (for evaluating (b). and (c).) is well known, even when we allow for the simplifying assumption of quasi-statics. Nevertheless, the mechanism of dripping is today considered physically understood, despite various difficulties encountered during quantitative determination. It is apparent that dripping and tip-jetting can be competing mechanisms. One or the other may take precedence in practice. There is evidence ~4'2~that in some experiments a working regime may even go through a sudden transition from a drop-dripping state into a tip-jetting state with the subsequent jetbreakup leading to spraying of greatly refined droplets. That the droplet-spraying frequency is typically orders of magnitude greater than the dripping frequency makes it appropriate to regard the dripping liquid to be in a state of quasi-static equilibrium prior to tip-jetting. It might not be too far-fetched then to associate the said transition with the valve onset mechanism considered in this work. 4. In Fig.7, a straight line issuing from the origin has a slope independent of If its reciprocal has a value above -1/2, the line intercepts the ~ curve at some value of always. It is then clear that, other things being equal, there exists a critical surface tension in correspondenc.e below which instability will occur. 5. As was emphasized earlier, the excess pressure plays a crucial role in the study of profile instability. It enters through the P = hAp/(y parameter whereby its influence becomes amplified at large h. Any experimental inaccuracy in Ap determination will result in a sizable scatter in P. Unfortunately, such determination has been either inferred indirectly or measured too roughly in most reported experiments. Real test for the present spraying theory need await more careful future experimentation. Nonetheless, it is revealing to selectively analyze some known results from Zeleny's original data. In one sequence, analyzed by Taylor9, a capillary tube was mounted in an inverted position. A pressure was applied until the meniscus rose to a definite height above the tube end and this height was maintained by reducing the pressure as electrical potential was increased until breakdown occurred and it was no longer possible to maintain steadiness. Tubes ranging in outer radius R from 0.0146 to 0.0543 cm were used and results of experiments for which the height of the meniscus was equal to the radius are given in Table I which is taken from measurements extracted from Fig. 6 of Zeleny's original paper ~ and displayed in Table 3 of Taylor's 1969 paper. Column 1 lists the tubes according to their approximate radii values. At a separation between tube end and ground of 1.5 cm, the corresponding h = 1.5-R in cms is given in column 2. To find Ap, it is necessary to take the values given in Zeleny's curves from the initial value which, when the meniscus was hemispherical, was 2cr/R. Using this method, Taylor 9 evaluated rtR2Ap and listed values in
17 column 5 of his Table 3. For water, we use his chosen nominal value of ~ - 74 dynes/cm. Values of P are then calculated and given in column 3, being found positive in all cases considered. By Eq. (8), then, Table I.Zeleny's measurements of critical voltage for instability when the meniscus was maintained at height one radius R above the top of tube. Calculations are based on ~ = 74 dyne/cm.
R (cm) 0.0543 0.0420 0.0340 0.0281 0.0231 0.0200 0.0166 0.0146
h (cm) 1.4457 1.458 1.466 1.4719 1.4769 1.48 1.4834 1.4854
P 6.961 9.9558 10.223 4.812 7.143 12.732 16.21 17.98
Wo 0.2474 0.1811 0.1768 0.3345 0.2420 0.1449 0.1158 0.1051
(Vc)calc(Kv) 5.467 4.697 4.654 6.415 5.465 4.233 3.790 3.731
(Vc)exp(Kv) 5.9 5.45 5 4.74 4.5 4.1 4.05 3.6
column 4 lists the corresponding values of Wo. From them, we arrive at the minimum voltages for tip spraying by Eq. (11). These values are listed in column 5. For comparison, results of experiments are given in column 6, which is taken from measurements displayed on p. 85 of Zeleny's paper in his Fig. 6. One notes that, for the tube with R = 0.034 cm, Taylor's transcribed record of 4.0 Kv was in error. It should have been close to 5.0 Kv according to Zeleny's original data. While agreement on critical voltage appears better for tubes of very small radii, it is best to test the overall theory by referring to the Z-P plot of Fig. 8. There, data points have been based on values found in columns 2, 3 and 6. Also shown is a segment of the theoretical Wo(P ) curve from Fig. 5. Organized and compared in this way, data appear to have some spread but otherwise consistently follow the prediction in general trend. Table II in Zeleny's 1914 paper also gave surface tension values for liquids used on tubes of a range of sizes. He had water slightly acidulated with hydrochloric acid to insure sufficient electrical conductivity. Although he did not specifically mention whether the same liquids were the ones actually used to obtain data of Table I, we shall assume it to have been the case. In Table II below, we have selectively listed those germane to experiments just described. Since he did not measure O for the R = 0.0281 cm tube, we leave it out accordingly. We have also assumed that the two tubes labeled R = 0.0229 cm and 0.0419 cm are the same ones as those labeled R = 0.0231 cm and 0.042 cm, respectively, in his Fig. 6 as well as in our Table I. Figure 9 portrays the phase-plane results in the manner of Fig. 8. Menisci for liquids of small viscosity are known to execute violent oscillations at the tip when conditions are nearing those of spraying onset, making precise voltage identification difficult z-3. In addition, for each capillary tube used, Zeleny maintained a meniscus height equal to the nominal tube radius by eye detection, always assuming that the initial shape was hemispherical with the tube end Table II.Zeleny's measurements of spraying onset under conditions identical to those of Table I, except that o values of acidulated water determined ~by him have been used.
R (cm)
o (dyne/cm)
P
Wo
0.0543 0.0419 0.034 0.0229 0.02 0.0166 0.0146
79 76 72.6 72.8 70.5 68.5 73.8
11.284 13.215 12.62 9.301 10.983 11.066 22
0.1618 0.1400 0.1461 0.1924 0.1658 0.16463 0.08676
(Ze)ex p 0.269 0.2373 0.208 0.1704 0.1392 0.1429 0.1046
perfectly and precisely wetted to the edge of the outer wall. The inherent difficulty in that task was actually stressed by him in relation to the scheme of deducing the true excess pressure (p. 89 of Ref. 1). In view of the fact that low-viscosity water was used and that his experiments were performed in preelectronic days, it is interesting to conduct comparisons in Figs. 8 and 9 and discern a level of agreement, while fully realizing that data scatter is not unexpected because the critical conditions discernible on Zeleny's original experimental curves (Fig. 6 of Ref. 1) show a sizable fluctuating spread. Zeleny also observed that, as voltage was raised toward its critical value, vigorous vibration of the tip region of the water meniscus would take place, ultimately ending up in a sudden local surface flattening (pp. 71-72 in Ref. 2). A!though sketchy, the report is noteworthy in that such behavior could be explained if it is assumed that, in the context of Fig. 6, the breakup point was reached as Z was increased
18
in his experiment through successive equilibrium states already in an extraordinary mode. There, we have dW/dn = 0 in the fiat-top limit whence the tip curvature would experience a drastic reduction. On the other hand, if the reported flattening followed tip release, a second explanation could be that, as the charged thin jet emerged, it would begin to shield the tip region from the high ambient field, thus causing a sharp retraction, as might be read into a related photograph of collapse (Fig. 7d of Ref. 17) obtained by Taylor. These two explanations are not mutually exclusive of course and could well be in collective effect for the same observed phenomenon.
VII. CONCLUDING SUMMARY Overall behavior of a liquid meniscus at the exit of a capillary tube in a point-plane electrostatic system has been examined. That liquid profile shape can deform in response to changes in electrical and mechanical conditions is recognized. By focusing on the local state of balance at the tip amongst effects of field, interior excess pressure, and surface tension as a necessary condition, a combined theory of equilibrium and spraying has been developed in which the field in question is determined through a method of simulation utilizing a single image-charge pair. Indications are (1)that the liquid profile for equilibrium is not unique at low values of applied voltage and pressure and (2) that, in consequence, a tip-gated jetting instability mechanism is triggered at high enough but definite values of the same, separate from the familiar and oftener-present mechanism of dripping. Criteria for both equilibrium bifurcation and instability onset are formally independent of bulk material properties as well as of the size and other details of the tube as long as the liquid has sufficient conductivity. While three different stresses contribute to balance at tip as is required of any meniscus in equilibrium, only the tip-field has seen need for approximate treatment in the model theory. It is judged that, while other more sophisticated types of approximation could be introduced and more refined quantitative results would then follow, the qualitative conclusions on equilibria and tip breakdown reached with the simple approximation used in this work would remain unaffected. It is wel~fo note that the phenomenon of free-stream thin jet spraying 4 is genetically akin to that of meniscus liquid spraying considered here. Breakdown data extracted from some of Zeleny's crude experiments have been examined. While comparison can be judged qualitatively reasonable, it is important that this and additional aspects of the theory be tested through more modem tests.
NOMENCLATURE: D E
Ez P +q R
T. V V~ W Wo
height of image charge [Fig. 2] Electric field vector z-component of electric field normalized excess pressure image charges outer radius of capillary tube Maxwell's tensile stress at tip of meniscus magnitude of applied voltage critical voltage [Eq. (11)] dimensionless function defined in Eq. (8) relative maximum value of W
REFERENCES 1. J. Zeleny,Phys. Rev. 3, 69 (1914). 2. J. Zeleny,Proc. Camb. Phil Soc. 18, 71 (1915). 3. J. Zeleny,Phys. Rev.. 10,1 (1917). 4. B. Vonnegutand R. L. Neubauer, J. Coll. Sci. 7, 616 (1952).
Z Zr b h n no Ap eo 0
dimensionless parameter defined in Eq. (9) critical value of Z radius of curvature at meniscus tip separation between meniscus and ground normalized tip curvature value of n where W peak occurs excess pressure at tip vacuum electric permittivity = h/D, a normalized parameter of geometry surface tension
19 5. V. G. Drozin,./. Coll. Sci. 10, 158 (1955). 6. C. D. Hendricks, ,I. Coll. Sci. 17,249 (1962). 7. C. D. Hendricks, R. L. Carson, J. J. Hogan and J. M. Sneider, AIAA J. 2, 733 (1964). 8. J. J. Hogan and C. D. Hendricks, AIAA J. 3,296 (1965). 9. G. I. Taylor, Proc. Roy. Soc. A313,453 (1969). 10. S. B. Sample and R. Bollini, J. Coll. and Interface Sci. 41, 2 (1972) 11. A. G. Bailey and E. Borzabadi, IEEE Trans. on Ind. Appl. IA-14,2,162 (1978). 12. A. R. Jones and K. C. Thong, J. Phys. D: Appl. Phys., 4, 1159 (1971). 13. B. Raghupathy and S. B. Sample, Rev. Sci. Instruments 41,645(1970). 14. T. Agui and M. Nakajima, IEEE Trans. on Electron Devices ED-24,262 (1977). 15. G. Joffre, B. Prunet-Foch, S. Berthomme and M. Cloupeau, J. Eltrostatics.,13, 151 (1982). 16. C. T. R. Wilson and G. I. Taylor, Proc. Camb. Phil. Soc. 22, 728 (1925). 17. G. I. Taylor, Proc. Roy. Soc. A280, 383 (1964). 18. Lord Rayleigh, Phil. Mag. 34, 184 (1882). 19. A. G. Bailey, Sci. Prog, Oxf 61,555-581(1974). 20. J. M. Schneider, N. R. Linblad, C. D. Hendricks, & J. M. Crowley, J. appl. Phys. 38, 2599 (1967). 21. M. Cloupeau and B. Prunet-Foch, Jr. Eltrostatics.,25,165-184 (1990). 22. M. D. Van Dyke, Appendix to G. I. Taylor, Proc. Roy. Soc. A313,453 (1969). 23. G. I. Taylor, ibid. (1969) p.456. 24. E. Borzabadi and A. G. Bailey, J. Electrostatics. 5,369 (1978). 25. e.g.K. Adamiak, Conf. Record, IEEE IAS Annual Meeting (1993) pp. 1805-1810. z
f +(
4
~,_ tip.curvature -lib ~tlp
curvature t l ~
I:
(a} Zeleny,s experiment
......) .......
t ..................... ,
,,
...... ,.....
o
:
-0
(b) enlarged tlp region
Fig. 1. Experimental setup on electrically driven liquid meniscus at end of capillary tube in a point-plane field arrangement.
. ~ ,
Fig. 2.Image-method simulation of field at meniscus tip according to the model of an asymmetrically deformed sphere.
4": !: .P=-2
: 1:5 ;
W
0,I)
. 8-
-. . . . . .
0;
9 10
2i
~0
0.0
2,0
4.0
6.0
n
Fig. 3. Parametric relationship between n and 0.
Fig. 4. Behavior of W versus n according to P = -2,-3/2,- 1,0,2,and 4.
20 I
. . . . .
"='
"'"
""
, ,u|
i
i
w.
l -1.$
0.0
~1,5
~.0
4,5
i
6,0
'k
!
ri o
P
OOO
It
Fig. 6. Meniscus equilibrium in bifurcation: an ordinary mode with state point A on the branch lying to the left of no and an extraordinary mode with a state point B on the branch lying to the fight of no.
Fig. 5.Variations of Wo and no with P.
----
.
-
LO'
Zc O.S"
m,.~,.-.+r:,n+t~
,,+:,t"m_,+,-
'I,
o
-'......_
\
D
-~.ILY O.D .
.
.
.
.
.
; ....
+
---
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
9
,,,
,J
1,0"
Zc
O
0
.
.
.
.
.
.
1~)
.
"::
....
~0
Fig. 8.Comparison between data from some of Zeleny's experiments and the present theory according to o = 74 dynes/cm (Table I). Solid curve represents the theoretical prediction.Outer tube radii range from 0.0146 to 0.0543 cm.
Fig. 7. P-Z phase plane.
0.0
0
+- ' 10
2 "O
Fig. 9. Comparison between data from some of Zeleny's experiments and the present theory according to surface tension individually measured for the acidulated fluid used for each tube (Table II). Outer tube radii range from 0.0146 to 0.0543 cm.
21 Paper Presented at the 5th International Conference on Appfied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Application of immune algorithm with searching diversity to arrangement problem of fictitious chareges and contour points for charge simulation method Nishimura R., Nishimori K. Electrical and Electronic Engineering, Tottori University, Koyama-minami, Tottori 680-8552, Japan
When the charge simulation method is used for electric field analyses, an appropriate arrangement of both fictitious charges and contour points is indispensable to obtain an accurate solution. However, when they are placed three dimensionally (3D), it is very difficult to obtain such an arrangement even if a conventional searching method, such as Genetic Algorithm, is adopted because the searching area for 3-D case is remarkably wide. In this paper, we adopt Immune Algorithm (IA) with a high searching performance to this 3-D arrangement problem. By using IA, an accurate 3-D potential distribution around the electrodes is automatically obtained in high probability.
INTRODUCTION The charge simulation method (CSM) is often used for electric field analyses. However, appropriate arrangements of fictitious charges and contour points are indispensable to obtain accurate solutions. When large numbers of the charges and the contour points are placed three dimensionally, it is quite difficult to comprehend these arrangements correctly. In this case, it is not easy to correct the error of electrode surface potentials by try-and-error method. This inconvenience is obvious when electrodes with complicated shapes are assumed. Because of this, it is desirable that the appropriate arrangements are obtained automatically.
PURPOSE OF STUDY When fictitious charges and contour points are placed two dimensionally (2-D), appropriate arrangements, which give accurate potential distributions around the electrodes, are likely to be obtained by using Genetic Algorithm (GA) [1 ]. However, when they are placed three dimensionally (3-D), the probability that appropriate arrangements are obtained goes down. The search domain for the 3-D case is remarkably wider than that for the 2-D case because the components of both the charge- and the contour-pointpositions are described in a bit sequence which is longer than that for the 2-D case. So, it is difficult to obtain an appropriate arrangement by a single computing run for the 3-D case using GA. A new searching method, that can find out an appropriate solution in a wide search domain more efficiently than GA, is required for such problems. Recently, immune system mechanisms of a living body are applied to various engineering problems[2]. In this paper, we adopt Immune Algorithm (IA) with searching diversity to the 3-D arrangement problem of the charges and the contour points so that the appropriate arrangements are likely to be obtained efficiently.
IMMUNE ALGORITHM The principles of Immune algorithm (IA) used in this research were proposed by Mori et al [3]
22 spotlighting on the antibody-production mechanism of the immune system. IA is an algorithm imitating the immune system that is based on the somatic theory and the network hypothesis. The biological immune system is a basic defence system against disease-causing organisms such as bacteria and viruses. When an antigen invades a living body, lymphocytes recognize it and produce the antibodies that cope with and exclude the antigene. Furthermore, the immune system has immunity to its own body. It suppresses the excessive production of antibodies and has the characteristics returning to the normal state. The immune system has the ability to cope with almost infinite antigenes by this mechanism. IA can produce the required diversity of antibodies and regulate the proliferation of clones as in a real immune system[3]. The outline of how to solve the problems using IA is described in Refs. [3,4].
CALCULATIONS Numerical model In order to show the difference between the results obtained by GA[5] and IA clearly, we adopt the same numerical model used in Ref. [5]. Figure 1 shows the two-electrode system that consists of two spherical electrodes placed above a grounded plate electrode. The centers of both electrodes are on z-axis. As shown in this figure, a point P belonging an each electrode is expressed by using spherical coordinate system whose origin o' is set at the center of each electrode as P(r,O,~o). The local axes x ', y', and z' are parallel to the global axes x , y, and z, respectively. For IA calculaions, the positions of both the fictitious charges and the contour points are described as a "chromosome" as for GA calculations. The r-,0-and ~o-components of an each charge position and the 0and ~0-components of an each contour point position are described as sequences of binary digits. All of the bit sequences are connected into a single chromosome that contains the information of the positions of all the charges and the contour points. In this arrangement research, we use a chromosome with the same structure described in Ref. [5]. The positions of the charges and the contour points are calculated by decoding the chromosome. The decoding procedure is also described in Ref. [5]. Table 1 shows the numerical conditions used for the calculation. Table 1 Parameters used for calculation Numbers of fictitious charges and contour 12, 10 points of an each electrode N,, N 2 Radius of an electrode R ], R 2 10 cm, 10 cm Electrode potential r ,, ~ 2 5000 V, 30V Distance between the center of an 30 cm, 70 cm electrode and grounded plate h 1, h 2 Bit length of the r -component of a charge 14 bit/charge position Bit length of the 0-component of a charge 14 bit/charge position Bit length of the tp-component of a 14 bit/charge charge position Bit length of the 0-component of a 14 biiJcharge contour point position Bit length of the tp-component of a 14 bit/charge contour point position Crossover rate at each locus (bit location) 5% of a chromosome Mutation rate at each locus of a 0.50% chromosome Capacity of the database (memory cells) 20 antibodies 1 cm Threshold s Iteration number 150 ,,. I
z'
~y'
I
h2
~
Electrode 2 Potential ~2 t
o': The center of each spherical Electrode 1 electrode Potential ~1
X ._
Figure 1 3-D electrode system
II
I
II
Procedure for decision of arrangements of fictitious charges and contour points using IA The decision of arrangements of the charges and the contour points is carried out as follows. (I) Recognition of antigenes" The computing program reads the arrangement of the electrodes and the
23 electrode surface potentials listed in Table 1 as an "antigene". This step corresponds to the situation that the immune system recognizes the invasion of an antigene. (II) Production of antibody population: One hundred of bit streams are produced by using random numbers and stored into the database (DB) that corresponds to memory cells of the biological immune system. They are the chromosomes of the initial antibodies. (III) Calculation of "affinities": Each chromosome is decoded into an antibody (arrangement of charges and contour points). The affinity axi E (0,1) for the i-th antibody is calculated by the following equation: axi-- 1/(1+~ ) (1) where oq >0 is the absolute value of the maximum relative error of the electrode surface potentials. The affinities are calculated for all produced antibodies. The high affinity corresponds to the high ability to cope with the antigene. If ax i =1, the antigene is successfully excluded by the i-th antibody. Then, the antibody AB h with the highest value of ax (aXma x ) is selected. (IV) Differentiation of memory cell: Simialrity parameter aij, which will be described later, between AB hand an each antibody in DB is calculated. Then, the antibody ABDB in the DB with the highest value of a (amax) is selected. The affinity aXDBbetween ABDB and the antigene is calculated. If aXma x is greater than aXDB, ABDB is deleted from DB and AB h is added. This procedure allows the diversity of the antibodies stored in the memory cells. (V) Promotion and suppression of antibody: Fifty of the produced antibody with low ax are deleted. For the i-th antibody in the rest of 50 antibodies, the similarity parameters a~j between the i-th and the j-th (/= 1.... 50, j#i) antibodies are calculated. The concentration parameter c i for i-th antibody is determined by counting the number of a.j with the value smaller than the given threshold s. This parameter c, corresponds to the number density of the antibodies that are "similar" to the i-th antibody. The i-th antibody's viability p~is calculated by Pi-- ax/ci" Then, 10 antibodies are selected by roulette selection [6]. In this selection, the probability that antibody i is selected is p~. This procedure corresponds to the control mechanism of the diversity of the immune system. The antibodies with high affinities are promoted and the antibodies with high number density are suppressed. (VI) Proliferation of antibodies: The selected antibodies make breeding pairs in round-robin system. Two new antibodies are produced from a single pair by using the crossover and mutation procedures [6]. A chromosome (bit stream) for new antibodies is produced by using random numbers. This new one also makes breeding pairs with 5 of the selected antibodies one after another. The each pair also produces two new antibodies. Thus, the 100 new antibodies are produced. (VII) Precedures (III)-(VI) are repeated until the iteration number reaches the specified value. When the calculation is terminated, the antibody in the DB with the highest value of ax corresponds to the quasioptimal arrangement of the fictitious charges and the contour points. The similarity parameter a mentioned in the steps (IV) and (V) between two antibodies are defined as follows; (i) Distances between charge 1 of antibody i (C/,l) and each of the charges belonging to antibody j (C;k, k=-l,...,N) is calculated one after another where N is the total number of the charges of an antibody. The distance d between C~,~and Cj,k is calculated by d=[ri,/--~/,k] (2) where r~,~and r:k are the position vectors of the charge positions from the origin o in Fig. 1. The charge m (C:=) that gives the shortest distance d, to C~,, is found. Then, the distances between C~,2 and the each of the remaining charges (C:k, k =l,...,m-l,m+l,...,N) are calculated and the charge C,, (n:/:m) that gives the shortest distance d 2 to C/,2 is found. Thus, all of the charges belonging to antibody i and those to antibodyj make pairs one to one. These pairs are selected minimizing the sum of the distances. The sum of the distances between the fictitious charges Sec is calculated by the following definition; N
SFd=s i=1
(ii) The sum of the distances between the contour points ScP is also calculated as described in (i).
(3)
24 (iii) We defilie the similarity parameter a between two antibodies by the equation; SFc + Scv t r - 2 ( N - 1)
(4)
RESULTS AND DISCUSSIONS We carried out 10 runs using different initial values of random numbers. The calculations are carried out not only for IA optimization but also for GA for a reference. Figure 2 shows the maximum values of the relative errors of the surface potential of the electrode system at 150th iteration. By using IA, the accuracy of the potential distribution around the 3-D electrodes is improved to reduce the error by more than one tenth on an average in comparison with the result obtained GA optimization and the accurate solutions are likely to be obtained. Figure 3 shows the changes of the errors of the electrode surface potentials for the best cases of both IA and GA optimizations. The error in IA optimization converges smoothly. The error convergence in GA optimization, on the other hand, rests once at around 40th iteration. This means that the improvement is trapped into a local solution and the accurate potential distribution cannot be obtained unless the improvement succeeds by escaping some local solutions. We can obtain the accurate potential distribution around 3-D electrode system by using IA-aided CSM proposed by this paper. 0~' 10000 .
.
.
.
.
.
t_.._J
1000
GA
0 ~ 0 0
IA
OIl i
0.1
!
i
i
m
9
j
00
9
A
i
i
9
9 I l l
9
9
w
I
I
I l l
~9
100
~
l0
~
9
10 100 Maximum surface potential error [%] 1
Fig. 2 Maximum relative errors of the electrode potentials
0.1 0
IA ................ 50 100 Iterations
GA 150
Fig. 3 Changes of electrode potential errors with iteration
REFERENCES 1. Nishimura, R., Nishimori, K. and Ishihara, N., Automatic arrangement of fictitious charges and contour points in chargesimulation method for polar cordicate system, J. Electrostatics (2001), 51-52, 618-624 2. e.g, Castro, L. N. and Zuben, F. J., Leaning and Optimization Using the Clonal Selection Principle, IEEE trans, on Evolutionary Computation (2002), Vol. 6, No. 3,239-251 3. Moil, K., Tsukiyama, M. and Fukuda, T., Immue Algorithm with Searching Diversity and its Application to Resource Alloca-tion Problem (in Japanese), T. IEE Japan (1993), Vol. 113-C, No.10, 872-878 4. Chun, J., Kim, i . , Jung, H. and Hong, S., Shape Optimization of Electromagnetic Devises Using Immune Algorithm, IEEE trans, on Magnetics (1997), Vol. 33, No. 2, 1876-1879 5. Nishimura, R., Nishihara, M., Nishimori, K. and Ishihara, N., Automatic arrangement of fictitious charges and contour pointsin charge simulation method for two spherical electrodes, J. Electrostatics (2003), 57, 337-346 6. Nishimura, R., Nishimori, K. and Ishihara, N., Determining the arrangement of fictitious charges in charge simulation methodusing genetic algorithms, J. Electrostatics (2000), 49, 95-105
25 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Changes in Electrostatic Charges of Fine Particles after Addition to Gas-Solid Fluidized Beds Mehrani P., Bi H.T., Grace J.R. Department of Chemical and Biological Engineering, The University of British Columbia, 2216 Main Mall, Vancouver, BC, Canada V6T 1Z4
Experiments were performed to determine the changes in the electrostatic charges of various free particles atter addition to gas-solid fluidized beds to better understand their role in influencing electrostatic charge generation/dissipation. Electrostatic charge measurements, were performed by an on-line Faraday cup employing the fluidization column as the inner Faraday cup, located symmetrically inside a second copper column forming the outer cup. Preliminary results show that the entrained fines leaving the top of the fluidization column carry charges, resulting in a net charge inside the bed. The charges carried by different frees (Larostat 519 antistatic agent, glass beads and silver-coated glass bead particles) were determined for a range of operating conditions and relative humidities.
INTRODUCTION Electrostatic charges are almost unavoidable in gas-solid fluidization. They are generated due to repeated particle contacts and separation, supplemented by the friction of particles rubbing against each other and the column wall. Electrostatics has often been observed to affect fluidized bed behaviour [1]. Some previous research has been performed to determine ways to prevent or reduce electrostatic charges in gassolid fluidized beds. One of the methods investigated is addition of antistatic agents or fines, but efforts have generally been confined to minimizing the influence of electrostatics, rather than to understanding the phenomena involved. Wolny et al. [2] performed experiments by adding conductive, semi-conductive and dielectric free materials to the bed and concluded that the addition of fines decreases the electrostatic effects independent of the electrical nature of the frees. They determined the effect of addition of frees by measuring the charge on single particles removed from the bed during the experiments and poured in a Faraday cage. Wolny et al [3] studied the effect of adding fines such as aluminum powder on bed behavior due to electrostatic charge generation by withdrawing particles from the bed and placing them in an electric field. By measuring the electric field inside the bed by using a wall mounted ball probe, Park et al. [4] found that the addition of Larostat 519 reduces the electrostatic charge build-up in the bed. Goode et al. .[5] and Song et al. [6] used a spherical electrode to monitor the bed voltage change due to the addition of different chemical additives to reduce sheeting in polymerization processes. Previous works have all focused on measuring the change in the bed charge due to the addition of fines. However, in order to gain a better understanding of the effect of addition of fines on electrostatic charge generation/dissipation inside the bed and especially its mechanism, it is also necessary to study the changes of the frees electrostatic behavior after their addition to the bed. In the present work, a gas-solid fluidized bed Faraday cup system is used to investigate the charges transported by different fines from the fluidization column after their injection into an initially charged bed of large mono-sized particles. EXPERIMENTAL APPARATUS AND PROCEDURE The experiments were performed in the three-dimensional Faraday cup gas-solid fluidized bed system shown in Figure 1, with details presented in Mehrani et al. [7]. The main unit is a fluidization column
26 consisting of two concentric vessels. The outer copper shell, 0.2 m in diameter and 1.7 m high, is grounded to eliminate external electrical interference. The inner column, 0.1 m in diameter and 2.1 m high consists of three sections of different materials. As shown in Figure 1, the middle section is made of copper connected at both ends with Teflon sections and connected directly to a Keithley Model 6514 Digital Electrometer. In the present work, the top section of the apparatus consists of a filter bag contained in a box connected to a vacuum machine. The gas distributor at the bottom consists of two Teflon perforated plates. Nine pressure taps are located at various heights in the column and connected to differential pressure transducers in order to measure pressure gradients and overall pressure drops. A packed water column (humidifier) was used to humidify the gas to the desired relative humidity by adjusting the gas flow rate to the humidifier. The relative humidity and the temperature of the gas were monitored by a Vaisala Model HMP238 Humidity Transmitter.
Figure 1 Schematic diagram of experimental apparatus. The experiments employed extra dry air from gas cylinders as the fluidizing gas and 500-600 gm glass beads of density 2460 kg/m 3 as the solid particles. The fine particles were Larostat 519 (antistatic agent), glass beads (non-conductive) and silver-coated glass beads (conductive), with properties as shown in Table 1. Table 1 Fine particles used in experiments and their properties Particles
Glass beads I
Density (kg/m3) Mean diameter (gm) Size range (gm)
2500 30 10-80
Silver-coated glass beads I 2700 32 18-49
Larostat 519 520 13 6-20
Glass beads II 1100 11 8-25
Silver-coated glass beads II 1700 14 8-20
The large particles were washed with water and alcohol and then dried to clean any dirt from the surfaces and to eliminate some of the fines. The static bed height was maintained at 0.2 m for all experiments. All experiments were performed at room temperature by first fluidizing the mono-sized 500600 gm glass beads with extra dry air at a superficial gas velocity of 0.21 m/s while charges were measured on the inner column. The mono-sized particles were fluidized to generate some charges inside the bed before the addition of fines. Even though the large mono-sized particles were washed to eliminate fines, there could still be some residual fines. Therefore, the charges were measured during the
27 fluidization to determine if any fines remained in the system so that they would not affect the charge measurement when different fines were added to the column. Fine particles (0.2 wt%) were then injected into the fluidization column close to the distributor. A filter bag was then placed at the top of the column connected to a vacuum machine to capture all the entrained fines. The binary mixtures of the particles were then fluidized under the same operating conditions as for the mono-sized system. As the fluidization continued, since the operating gas velocity was much higher than the terminal velocity of the fines, the fines were entrained from the bed and they induced charges on the inner column measured by the electrometer. The mass of fine particles entrained was determined by measuring the weight of the filter before and after each run.
RESULTS AND DISCUSSION Experiments were performed at various relative humidities (RH) of the fluidizing gas (0%, 15%, 35% and 60%). The charge to mass ratio, Q/m, was determined for different added fines. The results are presented in Table 2. Table 2 Charge/mass ratio, Q/m [gC/kg], for different fines and different gas relative humidities Particles
Glass beads I
RH = 0% RH = 15% RH = 35% RH = 60%
58 17 6.7 6.7
Silver-coated Glass beads I 9.1 3.1 2.6 4.6
Larostat 519 42 47 32 25
Glass beads II 700 430 270 300
Silver-coated glass beads II 120 130 120 23
Overall, the results show that all the different added fines carry positive charges out of the bed. Therefore the same quantity of charges, but negative, must have been left behind in the bed which then could have resulted in a reduction or neutralization of the original bed net charge. Comparison of Q/m for glass beads and silver-coated glass beads of different sizes shows that the finer the particles, the higher the charges they carry out. This occurs because smaller particles have higher surface areas per unit mass and therefore are able to hold/generate more charges. The results show that Larostat 519 carries less Q/m compared to glass beads II and silver-coated glass beads II, even though they had very similar average particle sizes. This could be due to their physical surface structure as shown in Figure 2.
Figure 2 SEM images of the fines in this study. (a) Larostat 519, (b) Glass beads II, (c) Silver-coated glass beads II Scanning Electron Microscope (SEM) images of added fines show that Larostat particles are non-spherical and have rough surfaces, whereas both glass beads II and silver-coated glass beads II are spherical and have smooth to relatively smooth surfaces respectively. Since the bed materials (500-600 grn glass beads) are smooth and spherical, there will be fewer contacts between the large glass beads and Larostat 519 than for the fine glass beads II and the silver-coated glass beads II. On the other hand, the SEM images of samples taken after each binary mixture run (Fig. 3) show that Larostat 519 particles tend to attach to thesurfaces of the large glass beads, whereas glass beads II and silver-coated glass beads II fines do not. This shows that Larostat 519 particles remained in the bed may helped the dissipation of the initial bed charges leading to lower measured Q/m values.
28
Figure 3 SEM images samples taken after the binary mixture runs. (a) Bed material with Larostat 519, (b) Bed material with glass beads II, (c) Bed material with silver coated glass beads For the same size of fine particles, silver-coated glass beads carried less charge than the pure glass beads. This could be because the silver-coated glass beads are highly conductive and, therefore, they can easily lose their charges to the column walls and they can also help dissipate initial bed charges. The charge-to-mass ratios are highest for the runs with extra dry air (RH=0%), and as the relative humidity increases the ratios decrease. This is obvious since it has been long proven that increasing the relative humidity of the fluidizing gas helps dissipate charges and also reduces generation of electrostatic charges inside the bed. The results show that for most fines, except for the silver-coated glass beads II, the measured Q/m values are very similar for relative humidities above 35%. In conclusion, fines added to an initially charged fluidized bed carry significant but different amount of charges out of the column depending on their sizes and surface physical structure, therefore leaving a net charge behind. Experiments are currently being performed to find the initial bed charges in order to determine the charging mechanisms due to the addition of fines.
ACKNOWLEDGEMENT Financial assistance from the Natural Sciences and Engineering Research Council of Canada (NSERC) and NOVA Chemicals Ltd. is acknowledged with gratitude.
REFERENCES 1. Cross, J.A., Electrostatics: Principles, Problems and Applications, Adam Higler, Bristol, England (1987) 2. Wolny, A., Opalinski, I., Electric charge neutralization by addition of fines to a fluidized bed composed of coarse dielectric particles, Journal of Electrostatics (1983) 14 279-289 3. Wolny, A., Kazmierczak, W., Triboelectrification in fluidized bed of polystyrene, Chem. Eng. Sci. (1989) 44 2607-2610 4. Park, A., Bi, H.T., Grace, J.R., Reduction of electrostatic charges in gas-solid fluidized beds, Chem. Eng. Sci. (2002) 57 153-162 5. Goode, M.G., Hasenberg, D.M., McNeil, T.J., Spriggs, T.E., Method for reducing sheeting during polymerization of alphaolefins, U.S. Patent, 4803251, (1989) 6. Song, G.H., Rhee, A.S., Lowder, G.R., Method for reducing sheeting and static charges during polymerization of ethylene polymers, U.S. Patent, 5391657, (1995) 7. Mehrani, P., Bi, H.T., Grace, J.R., Electrostatic charge generation in gas-solid fluidized beds, To be published in Joumal of Electrostatics
29 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Dynamics of EHD flow in pin-plate configuration generated by electric corona discharge in air Zhao L., Adamiak K. Dept. of Electr. and Comp. Eng., University of Western Ontario, London, Ontario, Canada N6A 5B9
The characteristics of the electrohydrodynamic flow in air produced by the electric corona discharge in a pin-plate configuration have been investigated numerically in this paper. The numerical algorithm based on the Boundary and Finite Element Methods and the Method of Characteristics was employed to simulate the electric field. The FLUENT software was used to calculate the airflow parameters. The EHD flow patterns and the velocity distributions at different instants of time were predicted. The simulation results indicate that the applied voltage level greatly affects the transient dynamics of the process.
INTRODUCTION In the electric corona discharge, a high electric field in the area close to a sharp electrode causes gas ionization and its partial breakdown [ 1,2]. While the whole process is rather complicated, the net effect is that ions, of the same polarity as that of the corona electrode, are drifting towards the ground electrode. Therefore, a space charge is formed and an electric current flows between both electrodes [2]. The moving ions collide with the electrically neutral air molecules so frequently that the complete momentum transfer from the ionic space charge to the air bulk can be assumed to take place. Therefore, the Coulomb force acting on the ions becomes an electric body force on the air. This force gives rise to the electrohydrodynamic (EHD) flow that was firstly reported by Hauksbee in 1709 [3]. During the last several decades some efforts have been made to analyses and visualize this flow [3-7], but a reliable numerical model has not yet been established. MATHEMATICAL MODEL The configuration under investigation in this paper consists of an infinitely large metal plate as the ground electrode and a hyperboloidal needle with the tip curvature radius R as the corona electrode, supplied with a high positive DC voltage and perpendicular to the ground electrode at a distance D. The ambient gas is air at room temperature and atmospheric pressure. ~."
,. ......
: {
;I
~,
--
!
i
!
ix i
I ..... -.. ; ""...
i
i
!
/
r.
~met~ Wall
(a) (b) Figure 1. Pin-plane corona model and the boundary conditions for airflow
30 Taking into account the axial symmetry of the problem, a two dimension computational model in the cylindrical coordinates can be assumed as shown in Figure 1(a). Figure 1(b) shows the simulation domain for airflow; both electrodes are defined as stationary walls, and the sidewall as the pressure outlet. The electric field in the corona discharge is governed by the Poisson equation: V:~ - -q
(1) E
and the charge conservation equation has to be satisfied: V 9y ' - 0 (2) where ~ is the scalar electric potential, q - the space charge density and e- the permittivity of the ambient gas, y'= Kq~,- the current density, K - the mobility of ions and if- the electric field. Under the assumption that the air is incompressible, has constant density and viscosity, and the flow is unsteady and laminar, the airflow has to satisfy the continuity equation: ~P+v.~=0
8t and the Navier-Stokes equation: tpv) + V . (pvv) = -VP + V . (r) + F 3t
(3)
(4)
where p is the gas density, P - the static pressure, ~'- the gas velocity vector, F - the stress tensor and F-the external body force, in this case equal to the Coulomb force q V ~ . SIMULATION RESULTS The algorithm for simulation of the corona discharge is based on three different numerical techniques" the Boundary Element Method (BEM), the Finite Element Method (FEM) and the Method of Characteristics (MOC) [5]. The BEM is used to obtain the solution for the Laplacian electric field where space charge is assumed to be zero and only the applied voltage between the two electrodes is considered. The electric potential gradient is very high in the vicinity of the corona electrode tip and the BEM can provide very accurate and smooth solution in this area without creating too large algebraic system. The BEM solution is also used to generate the FEM mesh. In the next step, the conventional FEM procedure is employed to obtain the Poissonian component of the electric potential where the space charge is considered and both electrodes are at ground potential. The final solution for 4~ is a superposition of the BEM and the FEM components. The electric field can be easily calculated by differentiating the potential distribution. The last step is to solve the space charge density by the MOC [4]. The numerical algorithm is arranged in two coupled iterative loops [4,5]: the inner loop starts from some initial guess of the space charge density, then Equations (1) and (2) are solved iteratively for ~ and q; the outer loop is added to update the charge density on the corona electrode surface until the electric field values there are sufficiently close to Peek's value [8]. The space charge density, the current density, the electric field and the potential for every point in the simulation domain can be obtained. The FLUENT commercial software is used to simulate the airflow. After the Coulomb force has been calculated, the user-defined functions (UDF) allow us to input it into every single volume cell of the discretized FLUENT model. The partial differential equations (3) and (4) are solved by using the Finite Volume Method: a control-volume-based technique is used to convert the governing equations into a set of algebraic equations that can be solved numerically. This control volume technique consists of integrating the governing equations over each control volume, yielding discrete equations that conserve each quantity on a control-volume basis. For an unsteady airflow, a fixed time step is set and at each instant of time both the radial and axial velocities have to converge before continuing to the next time step. It usually takes about a hundred of iterations to reach the convergence. Figures 2 and 3 show the airflow velocity magnitude contours and the velocity streamlines at some instants of time when the applied voltage is 10kV. The maximum values are indicated in the figures, and every figure shows 20 contour lines between the maximum value and 0. It can be seen from Figures 2(a) and 3(a) that the airflow starts in the vicinity of the tip of the corona electrode where the Coulomb force reaches the maximum value. At the beginning, the flow velocity is small, and the air movement is concentrated in a very small area near the tip. The air is accelerated by the Coulomb force
31 and quickly spreads out both in axial and radial directions; the maximum velocity increases and so does the maximum mass flow, what can be seen from Figures 2(b) and 3(b). After several milliseconds (Figures 2(c) and 3(c)) the airflow almost reaches the steady state in which the axial velocity dominates along the axis of the symmetry and the radial one along the plate as shown in Figures 2(d) and 3(d).
Figure 2. Velocity contours at 10kV at different instants of time.
Figure 3. Velocity streamlines (mass flow contours) at different instants of time at 10kV The dynamics of the airflow can also be seen from the time-dependent air velocity profiles along the axis of the symmetry at 10kV, as shown in Figure 4. The velocity profile first quickly increases at points close to the tip and after about 0.5ms it practically reaches the steady state value in this area; then the profile extends towards the ground plate. It takes about 4ms to reach the steady state at all points along the axis. Figure 5 shows the air velocity plot at different points on the axis of symmetry versus time for 7kV(a) and 10kV(b), respectively. At all points the velocity seems to follow a similar pattern with values increasing nearly linearly with time, reaching the steady state in a few milliseconds. However, the voltage levels have a significant effect on the airflow transient time. For example at the point x=0.002m, the air velocity reaches 9.3m/s after one millisecond at 7kV comparing to 13.0m/s at 10kV. For the same position of a point and the same time the higher the applied voltage, the larger the velocity. It can be noticed that at the point x=0.004 m it takes 10ms to reach the steady state velocity, what compares to 4ms at 10kV. Also, the conclusion from Figure 4 is confirmed that at the points closer to the tip the steady state velocity is reached faster.
32
Figure 4. Axial velocity along the axis versus time at 10kV
Figure 5. Velocities at different points on the axis versus time. CONCLUSIONS This paper presents the results of numerical simulation of the EHD flow produced by the electrical corona discharge in air. The numerical algorithm, which can be used to simulate the EHD flow in both steady and unsteady states, has been presented. The electric field is calculated by means of the BEM, FEM and MOC. The FLUENT software package is employed to simulate the airflow. The electric corona discharge produces the EHD flow with the velocity distribution pattern affected not only by the air gap geometry but also by the applied voltage; the length of time that it takes to reach the steady state axial velocity is greatly affected by the applied voltage. Usually, it takes several milliseconds to reach the steady state, and the higher the applied voltage, the shorter the time it takes to produce the steady EHD airflow. REFERENCES 1. Loeb L.B., Electrical Coronas, University of Califomia Press, London, 1965 2. Cobine J.D., Gaseous Conductors, Dover, New York, 1958 3. Batian J., NoEl F., Lachaud S., Peyrous R. and Loiseau J.F., Hydrodynamical simulation of the electric wind in a cylindrical vessel with positive point-to-plane device, J.Phys.D:Appl.Phys., (2001) 34 1510-1524 4.A~amiak K. and Atten P., Simulation of corona discharge in point-plane configuration, ESA-IEEE Joint Meeting on Electrostatics, Little Rock, Arkansas (2003) 104-118. 5. Adamiak K., Zhang J. and Zhao L., Finite element versus hybrid BEM-FEM techniques for the electric corona simulation, The Electrotechnical Review, (2003) 10 753-756 6. Fukumoto M. and Ohyama R., Image analysis of gas-phase EHD flow field for needle-plane electrode system, IEEE Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Albuquerque, New Mexico, (2003) 694-697 7. Feng J.Q., Electrohydrodynamic flow associated with unipolar charge current due to corona discharge from a wire enclosed in a rectangular shield, J.Appl.Phys., (1999) 86 2412-2418. 8. Meroth A.M., Gerber T., Munz C.D., Levin P.L. and Schwab A.J., Numerical solution of nonstationary charge coupled problems, J.Electrostatics, (1999) 45 177-198.
33 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Tribocharging characteristics of Nylon 12 and FEP by rubbing of carriers for copiers Ikezaki K., Jojima E.,* Keio University, Tokyo 108-8345 Japan *Jissen women' s University, Tokyo 191-8510 Japan
Triboelectrification was examined for films of Nylon 12 and FEP by rubbing with a brush of carriers for copiers under different electrical conditions: the cartier brush was grounded directly or through a capacitor of C in series, and electrically isolated by floating it. Observed tribocharges strongly depended on the electrical conditions of the brush. Temperature dependence of the tribocharges was also examined and conductive diffusion of them was found to be operative for observed singularly large amount of tribocharges.
INTRODUCTION Electrification in the atomic scale and its detection and control were successfully made using electrostatic force microscopes [1-3]. Moreover, microplasma was recently observed in rubbed surfaces of insulators [4]. In spite of these recent modem approaches to the basic study in electrostatics adding to numerous amounts of traditional study, "classic" approaches are also necessary for practical application of electrostatics or preventing electrostatic hazards, because some problems are still left unsolved. For example, electrical condition of triboelectrification systems does not seem to attract interest of researchers. In tribocharging or contact charging between metal and insulator, charges on the insulator are measured in some cases [6] under the electrical condition that the metal is grounded. In other cases, metal electrode is connected to an electrometer to measure electrification current [7] or voltage [8]. In these cases, a resistor equivalent to an electrometer or appropriate capacitor is connected from the metal electrode to ground. In the cascade method [9], which is frequently used recently, metallic beads sliding down on a surface of sample materials are electrically isolated. Previously, one of the authors reported contact charges between carriers for copiers and compacted quasi-toners under different electrical conditions [10]. In this charging system, surface voltages of samples were measured instead of tribocharges as a function of the number of contacts. Further, the sample should be replaced from a charging position to a measuring position for every contact. We improved these drawbacks of the former system and developed a fully automated slide electrification system in which tribocharges can be measured. In this paper, we report tribocharging characteristics between Nylon 12 or FEP and a brush of carriers for copiers under different electrical conditions.
EXPERIMENTAL Sample polymers used in this study are 40 I~ m thick Nylon 12 and 25 I~ m thick FEP films. Before charging, residual charges on both of the front and the rear surfaces of every FEP film were neutralized using a scorotron till the absolute surface voltage decreased below 10 V, typically 2-8 V. For Nylon 12 sample, no pretreatment of neutralization was done because of its low resistivity. Uncoated magnetic powder KBN-200, a product of Hitachi Metals, Ltd., was used for a rubbing brush. The newly developed triboelectrification system is schematically illustrated in Figure 1. The weight of the carrier brush was about 17gr including 0.3gr of the carriers. In this system, linear sliding of the carrier brush was performed
34 by transferring of rotational motion of a motor using a crank. Therefore, the sliding velocity of the brush on the effective surface of the samples sinusoidally varies from 9.4 to 7.0 cm/s. The data of tribocharges after nth rubbing Q(n) were automatically stored in a digital voltage recorder every 2 seconds as a function of the number of rubbings. 1:Teflon block, 2:Magnet, 3: 0.1mm thick stainless steel sleeve, 4: Brush of carrier for copiers, 5: Sample film, 6: 0.1mm thick copper square electrode (10xl0 mm2), 7: 3mm thick fused quartz plate, 8:10 mm thick aluminum plate, 9" sheet heater, S l" Carrier brush is connected to a capacitor C, $2: Carrier brush is directly grounded, $3" Carrier brush is electrically floated, CO" 0.104 F, V: Vibrating reed electrometer
Fig. 1 Schematic illustration of triboelectrification apparatus
RESULS AND DISCUSSIONS The values of Q(n) were observed at about 20 ~ and 65 %RH for FEP and Nylon 12 as a function of the number of rubbings of the carrier brush under various electrical conditions. The observed results were shown in Figure 2 (a) for FEP and 2 (b) for Nylon 12, respectively. As clearly shown in these figures,
Figure 2 Tribocharging curves (a) for FEP and (b) for Nylon 12 the electrical condition of the charging brush drastically affects the tribocharges. For FEP, the amount of tribocharges saturated only after few rubbings when the carrier brush was electrically isolated. Moreover, back-flow of the tribocharges [5] was clearly observed. In the meanwhile, for Nylon 12 the amount of tribocharges seems to increase continuously with the number of rubbings even when the brush was electrically isolated, though it was very small. The values of Q(50) are plotted in Figure 3 against the capacitance of the capacitor connected between the brush and ground. The effect of connecting a capacitor on tribocharging is relatively large for capacitors of smaller capacitance. Dependence of the electrical condition of the rubbing brush on charging characteristics of FEP is best demonstrated by Figure 4. In this experiment, nothing was changed during the tribocharging process except electrical condition of the rubbing brush: at 19th rubbings, the brush was switched from the grounded state to the electrically isolated one and at 53th rubbings from the isolated state to the grounded one. In consistence with switching the electrical condition of the rubbing brush, tribocharges
35
Figure 3 Relation between Q(50) and capacitance C for FEP and Nylon 12
Figure 4 Effect of the electrical state of the rubbing brush on FEP triboelectrification
of FEP increase or saturate. When the brush is electrically isolated, even small charges increases the electric potential of the brush. As a result, difference in electrochemical potential between the carrier brush and FEP disappears and triboelectrification between them ceases. Temperature dependence of triboelectrification was also examined for FEP and Nylon 12 under the electrical condition that the brush was grounded. Obtained results are expressed in Figure 5 for FEP.
Figure 5 Temperature dependence of (a) tribocharging curves and (b) Q(n) for FEP As shown in Figure 5 (b), it is roughly concluded that the values of Q(n) are almost same irrespective of temperature for n smaller than about 10, though the plots fairy scattered. Results for Nylon 12 are shown in Figure 6. Comparing results for Nylon 12 with those for FEP, temperature dependence of triboelectrification is larger than that for FEP. Further, the values of Q(300) at temperatures higher than 80DC exceeded 10-2C/m2. This singularly large amount of tribocharges is much more than the reported values of the order of 10-3C/m2 for Nylon 66 observed in vacuum [11] and also exceeds the limit of charge density, 5x10-5C/m2, that corresponds to air break down field at atmospheric pressure when the charged body is isolated [5]. To know the origin of the observed singularly large tribocharges, triboelectrification was monitored for a Nylon sample at 60 V]C under the condition that the brush was grounded and a 25 Ix m thick FEP film was inserted between the sample Nylon film and the copper electrode. Observed tribocharges drastically decreased (not shown). From this result, it was concluded that the singularly large tribocharges were caused by conductive diffusion of tribocharges passing through the sample into the capacitor C0which was connected to measure tribocharges as shown in Figure 1.
36
Figure 6 Temperature dependence of (a) tribocharging curves and (b) Q(n) for Nylon 12
CONCLUSIONS From the above experimental results, it can be concluded that triboelectrification between metal and polymer strongly depends on the electrical condition of the metal: when the metal is electrically isolated like the case of the cascade method, observed tribocharges will be smallest and when the metal is grounded directly or through a resistor like the case of a current measurement mode, they will be largest. When the metal is connected to an electrometer in a voltage measurement mode, values of tribocharges will fall in those between the above two cases depending on the capacitance of the electrometer and an additional capacitor. It is also concluded that the singularly large tfibocharges observed in our experiment is due to conductive diffusion of tribocharges.
REFERECES 1. Terris B.D, Stem J.E., Rugar D., Mamin H.J., Contact electrification using force microscopy, Phys.Rev.Letters (1989), 63 2669-2672 2. Schonenberger C., Alvarado F.A., Observation of single charge carriers by force microscopy, Phys. Rev. Letters (1990), 65 3162-3164 3. Morita S., Fukano Y., Uchihashi T., Okusako T., Sugagwara Y., Yamanishi Y., Oasa T., Reproducible and controllable contactelectrification on thin insulator, Jpn. J. Appl. Phys. (1993), 32 L1701-L1703 4. Nakayama K., Nevshupa R.,Plasma generation in a gap around a sliding contact, J.Phys. D (2002), 35 L53-L56 5. Lowell J., Rose-Innes A. C., Contact electrification, Advances in Phys. (1980), 29 947-1023 6. Lowell J., The electrification of polymers by metals, J. Phys. D, (1976), 9 1571-1585 7. Wahlin A., Backstrom G., Sliding electrification of Teflon by metals, J. Appl. Phys. (1974), 45 2058-2064 8. Haenen H. T. M., Experimental investigation of the relationship between generation and decay of charges on dielectrics, J. Electrostatics (1976), 2 151-173 9. Gibson H. W., Linear free energy relationships. V. Triboelectric charging of organic solids, J.Am Chem.Soc.(1975), 97 3832-3833 10. Ishikawa T., Ikezaki K., Charging characteristics of two-component developers for copiers in electrically isolated and nonisolated systems, Proceedings of the forth international conference of applied electrostatics-Dalian, China (2001) 420-424 11. Davis D. K., Charge generation on dielectric surfaces, Brit. J. Appl. Phys. (1969), 2 1533-1537
37 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Charge transport in flowing high resistivity liquids: periodic wire-channel configuration Adamiak K.*, Floryan J.M.** *Department of Electrical and Computer Engineering **Department of Mechanical and Materials Engineering The University of Western Ontario, London, Ontario, Canada N6A 5B9
The charge transport in moving weakly conducting fluids is studied numerically for a periodic structure of infinitely long cylinders between two parallel planes. An external electric field results in dissociation of impurities and generating of the electric charge. The numerical algorithm used for simulation is based on the Finite Element Method for the electric field, the Method of Characteristics for the charge transport and the Finite Volume Method for the fluid flow. The results of simulation show an effect of the fluid flow on the charge transport, and also modification of the flow characteristics caused by the electric force.
INTRODUCTION Impurities present in dielectric liquids can cause spontaneous dissociation - generated ions drift through the liquid creating an electric current. This is the source of a weak electrical conductivity of dielectric liquids: heterocharge layers are formed close to electrodes, with majority of the liquid volume practically neutral, what happens for example for mildly polar liquids and results in an ohmic behavior of liquids. Due to this effect a DC voltage applied across a thermally stabilized plane layer of dielectric liquid can induce instabilities significantly increasing heat transfer. The effect of dissociation and recombination of ions on the liquid instabilities was investigated in [1]. In asymmetrical configurations of electrodes interaction of the space charge and an electric field produces the net volume force and results in the fluid motion. In the case of point-plane configuration the fluid motion towards the point electrode has been predicted [2]. Such a phenomenon is of practical importance in designing of EHD pumps [3]. Many authors have attempted to simulate this process. One-dimensional model of the charge transport in a stationary layer of liquid was investigated in [4]. Current oscillations in one-dimensional plane, cylindrical or spherical configurations were also studied [5]. Pontiga and Castellanos correlated the V-I characteristics with two parameters defining the model: the ohmic conductivity and the ratio of the emitted and bulk ion densities [6]. First two-dimensional model of the charge transport in the point-plane geometry has been given in [3], where the Finite Volume Method was used. A different approach was suggested in [7] with a hybrid algorithm based on the Finite Element Method and the Method of Characteristics.
MATHEMATICAL MODEL The stationary charge transport between a periodic row of identical parallel cylinders of a diameter D and two infinite conducting plates at distance 2L is studied in this paper. The cylinders are conducting, positioned symmetrically and supplied with a DC voltage V, while the plates are grounded. A non-polar, or mildly polar, dielectric fluid of density p and kinematic viscosity r/flows in the formed channel. It is assumed that the fluid is electrically neutral, but a ionophore salt is dissolved in it, which molecules can
38 dissociate into positive and negative ions [3]. A constant dissociation rate ko has been assumed and both ionic species can recombine with the constant rate kR. There is no injection of charge from the electrodes. The densities of ions can be determined from the charge conservation equations for both species [1 ]"
Op bt t)n
+ V.Jp
= k o c - kRpn
(1)
+V.J,
=koc-kRpn
(2)
Ot
where p and n are charge densities for positive and negative ions, respectively, c - density of ionic pairs. and J, are current densities due to positive and negative ions, and can be calculated as:
Jp
Jp = KpE + pu-OVp
(3)
Jn = - K n E + nu - D V n
(4)
where K is the ion mobility and D - the ion diffusivity, both equal for the positive and negative ions. The electric field distribution can be calculated from the Poisson equation: - eVEV - p-
(5)
n
The fluid flow is governed by the Navier-Stokes equation:
bu
p ( - - ~ + u 9V u ) = - r e
(6)
+ 71v 2 u + ( p - n ) E
where u is the velocity of liquid, P - the pressure and E= VV- the electric field intensity. Equations (1-6) form a mathematical model of the problem and must be supplemented with appropriate boundary conditions. For the potential V they result from the fact that the cylinder surfaces and the ground plates are equipotential. When diffusion is neglected only one boundary condition is required for p and n" p = O on the wire surface and n=O on the ground plane. Both components of the velocity vector are equal to zero on the cylinder and plate surfaces. After substitution of (3) and (4) into the charge conservation equations and neglecting the ion diffusion, the following equations for the transport of positive and negative ions can be derived: "r + KVp. E + Kp i)t
P
I
n
(7)
= koc - kRpn
e
~9._nn_ K V n . E - Kn p - n = kD c _ kR p n i)t e
(8)
The number of different parameters affecting the solution can be substantially reduced, if these equations are expressed in the dimensionless form. Introducing the following non-dimensional quantities lit
lit
x* = x / D , V* - V / V o, E* = E d / V o, p
= pD2 /(eoVo), n
lit
= nDE / ( e o V o ) , t
= t K V o / d 2, u
=uD/kV o
the following non-dimensional equations can be derived [8]" VZv, _- ~Ehd (n* - p * )
(9)
Md ___~"
.
Ehd
* 9
--~)P f - V p ' . ( E ' + U ) = m d ( 2 - p n bt
bn
o~t +Vn . ( - E ' + u
8u "
~t
Ehd
)= M d
+u , e V u * = - V P * +
1
Re
(2
-P .
V2u +
n
.2
-p ) -
(10)
n )
Ehd
Re 2
(1 1) (12)
(p-n)E
The process is governed by four non-dimensional parameters" E h d = P~176 2 pr/
, Md=
e~176
(Masuda)
pr/2
and Re = kV~ (Reynolds) numbers, and a non-dimensional velocity of the fluid motion. The ratio of the r/ Ehd and Masuda numbers is a measure of the volume charge density in the fluid, while the electric force
39 is normalized with respect of the ratio of the Masuda and square of the Reynolds numbers. Therefore, for convenience the following two parameters will be used: C O - Ehd and F o - M d Md Re
2
"
Figure 1 Space charge density in a stationary liquid for C0=l.0 (left) and Co=l0.0 (right) RESULTS Numerical calculations have been performed for a*=l (distance between two adjacent cylinders equal to the distance between both plates), D*=0.1 and different values of four non-dimensional parameters" Re, Co, Fo and u*o. The results of calculations for the space charge density at different Co (Figure 1) prove that only close to the cylinder, supplied with the positive voltage, there is a layer with a net negative charge. Similarly, a layer with positive ions is formed close to the ground plate. Thickness of both layers is approximately equal to 1/Co [2]. Effect of the fluid flow, and the Reynolds number, on this distribution is practically negligible. The positive and negative ions flow between both electrodes and form an electric current with the densities given by Equations (3) and (4). The results of calculations show that only for small Co there is a visible effect of the flow on the total electric current (Figure 2). For larger Co and at varying Reynolds numbers the fluid velocity doesn't affect the value of the current. The Coulomb force produced by the electric field acting on the space charge is a volume force for the fluid flow, so it modifies the flow characteristics. This phenomenon has been studied for Re=250, C0=0.2 and u0=0.1. Varying Fo, different components of the force in the direction of the flow were calculated: the viscous and pressure component of force acting on the cylinder, and the viscous force on the plate. For small Fo the electric force has a negligible effect on the fluid flow (Figure 3). With the increased value ofF0 both components of the cylinder force start to decrease, while the plate
Figure 2 Non-dimensional current between cylinder and Figure 3 Values of dii.'ferent components of the ground plate as a function of C0 (F~r=0.0,Re=250) non-dimensional force versus/~)j (Co=0.2,Re=250)
40 force slightly increases. However, the increase of the plate force is much weaker than the decrease of the cylinder force, so the total force is decreasing.
CONCLUSIONS The electric charge transport in weakly conducting liquid has been studied numerically for the cylinderplate geometry. The used iterative numerical algorithm was based on three techniques: the Finite Element Method for the electric field, the Method of Characteristics for the charge transport and the Finite Volume Method for the fluid flow. When an electric potential difference is applied between the electrodes two layers of charges are created. The electric current is formed with the value strongly affected by Co and only slightly by the fluid velocity. The electric force can modify the flow parameters, reducing in some cases the total force acting on the cylinder.
ACKNOWLEDGMENTS This work was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada.
REFERENCES 1.Pontiga, F. and Castellanos, A., The onset of electrothermal convection in nonpolar liquids on the basis of a dissociationinjection conductivity model, IEEE Trans. on Industry Appl. (1992) 28520-527 2.Atten, P. and Seyed-Yagoobi, J., Electrohydrodynamically induced dielectric liquid flow through pure conduction in poin/plane geometry, IEEE Trans. on Dielectr. and Electr.insul. (2003) 1027-36 3.Jeong, S.-I., Seyed-Yagoobi, J. and Atten, P., Theoretical/numerical study of Electrohydrodynamic pumping through conduction phenomenon, IEEE Trans. on Industry Appl. (2003) 39355-361 4.Vartanyan, A.A., Gogosov, V.V., Polyansky, V.A and Shaposhnikova, G.A., A numerical simulation of non-stationary electrohydrodynamic process in weakly conducting liquids, J. of Electrostat. (1989) 23431-439 5.Polyansky, V.A. and Pankratieva, I.L., Electric current oscillations in low-conducting liquids, J. of Electrostat. (1999) 482741 6. Pontiga, F. and Castellanos, A., Electrical conduction of electrolyte solutions in nonpolar liquids, IEEE Trans. on Industry Appl. (1996) 32816-824 7.Adamiak, K., Charge transport in weakly conducting liquids; wire-plane configuration, 2003 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Albuquerque, New Mexico, 2003, 678-681 8.IEEE-DEIS-EHD Technical Committee, Recommended international standard for dimensionless parameters used in electrohydrodynamics, IEEE Trans. on Dielectr. and Electr. Insul. (2003) 1___003-6
41 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Comparative Studies between the New and Old Standard IEC61000-4-2" Xijun Zhang, Shiliang Yang, Lisi Fan, Zhancheng Wu Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College,97 Heping West Road, Shijiazhuang, 050003, P.R. China
Abstract: IEC 61000-4-2:2001 is modified on the foundation of the IEC 61000-42:1995, there are seven modifications. In this paper, using two different models of generators, the radiation effect experiment of ESD to the single chip microprocessor (SCM) system have been carried out based on the two old and new different standards. Research result shows: The test result is not consistent through the two types of generators accorded with the same standard IEC61000-42, and it really reduces the discrepancy between different generators according as the new standard. But it is necessary to normalize the radiation field of generator in order to solve the problem in root. Key words: IEC standard, ESD simulator, radiation effects
INTRODUCTION The IEC61000-4-2 standard [1] is a representative intemational standard on EMC (electromagnetic compatibility) testing of electric and electronic equipment, which has stipulated the ability against ESD of electronic product and relevant testing method. IEC 61000-4-2:2001 is modified on the foundation of the IEC 61000-4-2:1999, there are seven modifications. In this paper, using two different models of generators, the radiation effect experiment of ESD to the single chip microprocessor (SCM) system have been carried out based on the two old and new different standards. There is also discussing the difference on the edition 1.2:2001 and edition 1" 1995.
TEST SET-UP AND SCM SYSTEM International Standard IEC 61000-4-2 (edition 1.2:2001) has been modified mostly compared with the first edition (1995). It is the method of ESD discharge to horizontal coupling plane (HCP) relating to the experiment. The new standard (edition 1.2:2001) specifies that discharge to the HCP shall be made horizontally to the edge of the HCP, and the discharge electrode shall be in contact with the edge of the HCP (see figure 1). However the old standard (edition 1" 1995) requires that discharge to HCP shall be made vertically on the HCP. The equipment under test (EUT) is the SCM system being used to EMP effects experiment, which has the functions of failure reappearance and automatic detection
[2]. Project supportedby the NSFC No. 50077024 and 50237040
Fig. 1 test set-up for table-top equipment
42 The ESS-200AX generator and the NSG435 generator are adopted in experiment. The ESS-200AX is made in Noiseken, and the output voltage is 0.2kV to 30kV. The discharge voltage of the NSG-435 is up to 16.5kV for air-discharge and up to 9kV for contact discharge.
VERIFICATION OF ESD CURRENT WAVEFORM OF THE GENERATORS In order to compare the test results obtained from different test generators, the ESD current waveform and its waveform parameters have been verified using the calibration setup [3] of ESD current waveform. The ESD current waveforms of 2kV, 4kV, 6kV, and 8kV are measured in this experiment. To measure the waveform parameters accurately, the number of discharge per voltage test level is 10. ESD current waveform IEC61000-4-2 standard stipulates that the current waveform of hand-metal model discharge is the calibration current waveform of an ESD generator. Fig. 2 and Fig. 3 are the waveforms of the output current of the generators during the verification procedure. It can be seen that they are all consistent with the standard waveform [ 1].
7: 6:
7 6
5:
5,
<"
4 3: 2: i: o:
4. <
A v
-1 -20
6 2'04'0 t(ns)
3.
-1 -20
8'o16o
96
2'oio4o
/o16o
t(ns) Fig.3 2kV contact discharge current waveform of NSG435
Fig.2 2kV contact discharge current waveform of ESS-200AX
Waveform parameters The values of the waveform parameter of the discharge current are given in Table 1. These data are all meet with the standard. Table 1 waveform parameter of generator ESD NSG435
ESS-200AX ESD vtg.
tr (ps)
/p(A)
t~(ps)
&(A)
2 kV
883
7.05
769
6.74
4 kV
923
14.35
734
13.38
6 kV
896
21.66
743
20.00
8 kV
907
29.33
733
26.94
ESD repeatability Table 2 gives the coefficients of each waveform characteristics parameter. As shown, they have satisfying repeatability. The two generators both comply with IEC61000-4-2 standard.
43 Table 2 Coefficient of variation of tr & Ip ESD Generator
ESS-200AX
NSG435
ESD vtg.
Coefficient of tr (ps)
Coefficient oflp (A)
2 kV 4 kV 6kV 8 kV 2 kV
1.4 % 4.6 % 1.8 % 1.6 % 2.4 %
0.8 %
1.8 % 1.1% 0.7 % 1.6 %
4 kV
2.5 %
0.8 %
6 kV 8 kV
4.2 % 3.3 %
1.5 % 0.6%
ESD IMMUNITY EXPERIMENT Using the two different models of generators, the radiation effect experiment of ESD to the single chip microprocessor (SCM) system has been carried out based on the two old and new different standards. Experiment method The experiment set-up for table-top equipment is given in figure 1.The SCM system under test (EUT) is located on the HCP, which is isolated from the EUT by insulation foil 0.5mm thick. The generator discharges to HCP at the distance of 10cm from the front of the EUT, and the EM-field produced by ESD irradiates the EUT indirectly. Then the EUT will automatically display the failure phenomena. The experiment consists of two portions due to the method of ESD discharge to HCP: (1) Discharge to the HCP has been made horizontally to the front edge of the HCP, and the discharge electrode shall be in contact with the edge of the HCP (see figure 1). (2) Discharge to the HCP has been made vertically on the HCP (the old standard, edition 1:1995). Experiment results and analysis With ESS-200AX generator and NSG435 generator, the number of one single contact discharge to HCP is 100. We record the minimum discharge voltage when SCM appears failure phenomena. The results are given in Table 3. Table 3 Comparisons of the two standards Failure phenomena Exterior interrupt disoperation Exterior RAM overwritten
Generator ESS-200AX NSG435 ESS-200AX NSG435
ESD vt~ kV New standard 5.00-5.50 -2.50~ 3.00 5.0-~5.5 -3.0~ -3.5 8.00~8.50 -2.50~ -3.00 >8.0 -3.0~ -3.5
Old standard 3.50~4.00 -2.00~ -2.50 4.5~5.0 -3.0~ -3.5 7.00~7.50 -2.00~ -2.50 >8.0 -3.0~ -3.5
The data of Table 3 show that, the experiment results of the NSG435 on the new and old standard are basic conformity. The ESS-200AX generator, the sensitive discharge voltages obtained by the new standard are larger than by the old standard; however the result is consistent with the NSG435's basically. S.Frei discussed the question [4], who considered that the discrepancy of ESD radiation field between different generators may reduce when the generator discharges on the edge of the HCP and the long axis of the discharge electrode is in the plane of the HCP. Experiment results show that it really reduces the discrepancy between different generators according as the new standard. But it is necessary to normalize the radiation field of generator in order to solve the problem in root.
44 CONCLUSION The experiment results show that the test results obtained from different test generators are inconsistent though they both comply with International Standard IEC61000-4-2, and it really reduces the discrepancy betweer~ different generators according as the new standard. But it is necessary to normalize the radiation EM-field of generator in order to solve the problem in root.
REFERENCES 1. IEC, Std. 61000-4-2, Electromagnetic Compatibility (EMC) part 4, Testing and Measurement Techniques-Section 2: Electrostatic Discharge Immunity Test (2002) 2. Hou Mingsheng, Chen Yazhou, The Design for Single Chip Computer System on Intensive Electromagnetic Pulse Effect Experiments, Journal of Electrician Technology (2001) 8 8-10 3. Wu Zhancheng, Liu Shanghe, Wei Ming, Chen Yazhou, The Verification of the Current Waveform of ESD Generator, Journal of Hebei Normal University (Natural Science) (1999) 23 4. Frei, S., Pommerenke, D., An Analysis of the Fields on the Horizontal Coupling Plane in ESD Testing, EOS/ESD symp. (1997) 99-106.
45 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Study of Irradiation Effects on Single-chip Microprocessor System under ESD EMP* Xijun Zhang, Lisi Fan, Xiaofen Ruan, Zhancheng Wu Electrostatic and Electromagnetic Protection Research Institute, Mechanical Engineering College 97Heping West Road, Shijiazhuang, Hebei, 050003,P.R.China
Abstract: In this paper, a typical single-chip circuit is designed to simulate serial communication interface in order to study the effect of ESD EMP to single-chip microprocessor (SCM) system. Using the ESD generator, the radiation effect experiments of ESD to the single chip microprocessor (SCM) system have been carried out. By analyzing the experiment data, some rules of the typical serial single-chip circuit under ESD are presented. Key words" electrostatic discharge (ESD), radiation, single-chip microprocessor
INTRODUCTION Peak value of the current pulse being induced at a ESD event is much higher, and the rise time is much quicker, which yields severe electromagnetic interference (EMI) or even damage to the surrounding electronic equipments or electronic system. Thereby determining theirs ESD sensibility is very significant, which offers reference and guidance to designing circuit or selecting chip. In this paper, a typical single-chip circuit is designed to simulate serial communication interface in order to study the effect of ESD EMP to single-chip microprocessor (SCM) system. Putting it into ESD radiated field, the radiation effect experiment of ESD to the single chip microprocessor (SCM) system has been carried out. The experiment data have been given out and analyzed and discussed, which offers gist to studying the measures of protection about SCM system against ESD. Let us first describe the experiment set-up and the SCM system.
EXPERIMENT SET-UP AND SCM SYSTEM The experiment set-up is given in figure 1. Communication cable (total length: lm) is connected the TXD of one SCM system to the RXD of another SCM system, performing data transfer between the two SCM systems. In order to prevent the printed circuit board (PCB) and electronic components on the PCB from pulse field irradiation directly, the two SCM systems have been shielded with grounded metal boxes, only the communication cable is exposed itself to ESD pulse field (see fig.l). The induced current of communication cable is measuring by a current probe (conversion ration of I AJ: 1:5).
Project supportedby the NSFC No. 50077024 and 50237040
Fig. 1 SIO's experiment set-up
46 The transmitting system transmits control signal and serial data to the receiving system, while the receiving system transmits response signal to the transmitting system under ESD. The receiving system has been configured 4 nixie display, which determinate that the communication of SCM system is proper or not by checking the transmission data. At last, the two SCM systems have been programmed in assembly language, and the programs are written in the MCS-51. Communication cable
ESD EFFECT EXPERIMENT
D
I
HCP I
C
According to the electromagnetic field theory, the induced current of communication cable is quite different as varied angle between the cable and the direction of electric field (direction of polarization is different). At first, the cable is ~ertical Parallel mode parallel to the direction of the electric field, i.e. the ESD mode generator discharges to the edge BC of the HCP (see fig.2). In the experiment, the operating program module of Fig.2 Schematic of discharge mode SCM system is serial interface circuit, and observing the nixie display during the ESD process. After that, the cable is vertical to the direction of the E-field (see fig.2), reduplicating above experiment, and recording sensitive discharge voltage of SIO's failure. The results are given in Table I. The grounding methods of the shielded cable are (1) single-end grounding and (2) double-end grounding. Table 1 Sensitive discharge voltage of SIO's failure Discharge to the HCP
Vertical mode Parallel mode
ESD v t g . / k V
Single-end grounding 4.50~5.00 4.00~4.50
Double-end grounding 4.00--4.50 4.00~4.50
For current measurement at the cable, the Tektronix Tek P6041 (5mV/mA,25kHz~ 1GHz) is used in order to obtain the real current. In this paper, some typical induced current waveforms at the cable are shown in fig.3 to fig.6(ESD voltage" +5kV).
Fig.3 The induced current at the cable, single-end grounding, vertical mode, +5Kv
Fig.5 The induced current at the cable, single-end grounding, parallel mode,+5kV
Fig.4 The induced current at the cable, double-end grounding, vertical mode,+5kV
Fig6 The induced current at the cable, double-end grounding, parallel mode,+5kV
47 EXPERIMENTAL RESULTS ANALYSIS The grounding model- induced current As shown in figures 3 and 4 peak value of the induced current when the communication cable is singleend grounding is much larger than that of double-end grounding. Comparing fig.5 with fig.6 Similarly, the result is consistent with the above overcom. To study this phenomenon, the loop area between the cable shielding layer and the earth is reduced when the cable is double-end grounding, and the induced current is also decrease. The result shows that the EM-energy is coupling into the shielding layer along the loop between the shielding layer and the earth, and further influence the communication line in it. The conclusion is consistent with the effect experiment (see Table 1). For this reason, the communication cable should be single-end grounding in practical application. Direction of polarization- induced current Comparing figure 3 with figure 5, and figure 4 with figure 6, we observe the peak value of the induced current pulse is a little high when the cable is parallel to the direction of the electric field, but the difference is very finite. The result is consistent with the effect experiment (see Table 1). However, according to the electromagnetic field theory, the induced current of communication cable is quite different as varied angle between the cable and the direction of electric field (direction of polarization is different), and the induced current increase with increment of Brewster angle [ 1]. If the induced current is decided by the coupling of ESD EMP to the cable, the induced current is almost zero when Brewster angle is zero. However, the experimental results show that there is very large induced current at the cable when the ESD generator discharges to the edge BC of the HCP (see fig.2). The reasons for this result are believed to (1) ESD pulse field, which is belong to near field, and the distribution of near field is very complex, and its direction of polarization is not complete decided by discharge model [2],[3]. (2) Orifices, gaps and some penetration conducting wires, which is formed a complex EM-energy cavity coupling system with the shielding box together.
CONCLUSION ESD EMP can couple into SCM circuit along the communication cable, and disturb or even damage the surrounding electronic equipment. The experimental results show that the induced current at the cable is relation to the grounding model of cable, and single-end grounding in practical application. In addition, the induced current is identical magnitude when the angle between the communication cable and direction of electric field is different, and the induced current isn't zero when the cable is vertical to the direction of Efield.
REFERENCES 1. Si'an Fan, Testing Study on Coupling Rules of Cables to EMP, .6thRadiation Resistance and EMP Comp. (1999) 355-360 2. Pommerenke, D., Aidam, M., ESD: waveform calculation, field and current of human and simulator ESD, Journal of Electrostatics (1996) 38 33-51 3. Leuchtmann, P., Sroka, J., Transient field simulation of electrostatic discharge (ESD) in the calibration setup (acc. IEC 61000-4-2), IEEE International Symposiumon Electromagnetic Compatibility(2000) 443-448
48 Paper Presented at the 5th International Conference on Appfied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on Precise Movement Control of ESD Simulator Electrode* Lei Lei, Shanghe Liu, Jie Yang Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003,P.R.China Abstract: To reduce the uncertain factor and artificial interference during the process of the air discharge, this paper puts forward an idea about motion controlling the discharge electrode of simulator, establishing electrostatic discharge (ESD) simulator controlling system, controlling the electrode speed approaching to current target, replacing the commonly-used way of hand holding electrode, offering condition to study further the air discharge characteristic of ESD simulator. Key words: ESD, Air discharge, Controlling system
INTRODUCTION ESD simulator is presently the most commonly-used simulated source of electrostatic electromagnetic pulse (ESD EMP). Its discharge ways can be divided into air discharge method and contact discharge method. The air discharge is a method of testing, in which the charged electrode of the simulator brought close to the EUT(equipment under test), and the discharge actuated by a spark to the EUT[1 ]. It can be accurately to imitate the actual ESD course. But air discharge is complex and its repeatability is very poor, which can be caused to change significantly by the factors including temperature, humidity, electrode approaching speed and artificial interference[2,3]. To reduce the influence of those factors and improve the repeatability of air discharge, a kind of ESD simulator controlling system is designed and implemented, which creates the environments of making further study on the characteristic and regularity of air discharge. ESD MEASUREMENT SYSTEM As Figure 1 shows, ESD measurement system is a verifying unit for current waveform that satisfies IEC61000-4-2, which can both measure the waveform of time domain of ESD current and ESD electromagnetic field at the same time. The system includes primarily: Faraday cage, current target, magnetic annulet antenna, ESS-200AX ESD simulator and digital storage oscillograph with high performance, etc. Measurement instrument adopts the Agilent infiniium oscillograph, with 8 GS/s samplingrate and 1.5 GHz measuring bandwidth. Two channels of the bscillograph connect the target and antenna with coaxial cable to measure respectively the waveform of ESD current and ESD electromagnetic field. The oscillograph and coaxial cable are both located in the Faraday cage, shielded well and isolated effectively. By this system, the air discharge method of the simulator can be controlled, including discharge distance between electrode and the target and the speed approaching of electrode.In this way, study on the air discharge is carried out. REALIZATION AND DESIGN OF THE CONTROLLING SYSTEM The principle and structure of system "Project supportedby the NSFC No. 50077024and 50237040
Faraday cage
ttor
m m
Figure 1Measurementsystemof ESD currentand field
49 Figure 2 shows the stxucture diagram of the ESD simulator controlling system. Step motor is used in order to supply the I Transmissive precisely moving power. The displacement Stepper] > PLC D)river Motor[ Mechanism [ and rotational speed are respectively in Unit proportional to the number and frequency B of the received step pulse [4]. The motor can be controlled well and started, braked N Power Supply v/ and inverted quickly, without too much De 24V difficulty in the using. It offers accurately Power Supply displacement and speed of the electrode by AC IOOV driving the transmissive mechanism. The driver unit is a integrated module which Electrodeof Position drives the motor. Its pulse signal controls Simulator Detect displacement and rotational speed of the motor, the direction signal controls the Figure 2 The structure of ESD simulatorcontrollingsystem rotational direction. Programmable logical controller(PLC) with instruction memory and digital or analog interface I/0 can 0+5/24V complete the function of logic and sequence, timing , count and arithmetic operation, FPO SHwhich has advantages of simple programming, series of 21006C Start PLC lommon high reliability, versatility, strong function, epper nd 9 S tmotor - ~ L x0 pc being used conveniently, short period of driver Speed Pulse design and debug, etc[5].Under the ignal 9 setting i I YO controlling program, the direction and step 86BYG250B A§ rection pulse signal received by the driver, working Inal 9 A-(C) X5 Y2 S t p p e r motor StoR B+(B) state of the motor is controlled. Controlling B-(D) X6. X7 box is designed mainly for the circuit of controlled switch and working state Self-~ check Y4 indication systematic route switch.
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Circuit structure and working process" The controlling system adopts two-phase ,oov^~ compound step motor of 86 series, SHso.. 21006C two-phase compound step motor driver and FP0 series of PLC. The controlling system wiring diagram is shown in Figure3. Through program, the input ends X of PLC are set as control switch of the system: X0 is iring diagram "start" switch to go forward and retreat; X0 closes, system retreats; Otherwise, system goes forward. X1 to X5 is a mutual lock switch, which can select and set five different speed. X6 and X7 are both "stop" switch, which stops system from running at any time. The output end Y0 and Y2 are step pulse and direction signal respectively, which are delivered to the driver to drive the motor to rotate back and forth. The ends Y4, Y5, Y6 and Y7 are in sequence representative of four working state: self-check, go forward, retreat, shutoff, which are displayed by the responding lamps. PLC adopts the logical language towards control process, which is expressed as relay logic ladder diagram. Programming operation is simple and easy to realize. System work flowchart is shown in Figure 4.
50 System characteristic: For PLC controlling step motor is adopted, system has its own characteristics as follows" (~ PLC is essentially a kind of microcomputer system and its input ports connect directly the signal lines, output ports have enough power to drive the system without other peripheral equipments. The PLC is simple and convenient to operate and use. (~ PLC adopts ladder diagram as programming language, which is simple and flexible and changing only the corresponding parameter in program can realize controlling the system.@ There is strong interference rejection capability in PLC itself and the power supply is multiplefiltered and the input and output adopt photoelectric isolation technique, with which PLC has strong interference rejection capability, and the reliability of the entire system can be impoved. PRELIMINARY EXPERIMENT Applying the ESD measurement system and the ESD simulator controlling system, the test experiment of ESD current waveform of time domain is carried out. The input impedance of 6scillograph is 50 f2.
Figure5.1 the discharge
FigureS.3tlledischarge
current waveform of 6 kV for the first time
current w'avetbrm o f 6 kV for tile third time
Ftgure5.5 tile discharge current wavefornl of 16 kV for the first time
Figure5.7 the discharge current waveform of 16 kV for the third time
Figure5.2 the discharge
Figure5.4 the discharge
current waveform of 6 kV for the second time
current waveform of 6 kV for the fourth time
Figure5.6 the discharge current waveform of 16 kV for the second time
Figure5.8 the discharge current waveform of 16 kV for the fourth time
51 Current input channel connects an attenuator of 20 dB, which gets that the proportion of voltage amplitude on oscillograph to actual current amplitude is l'10.The following figures are ESD current waveforms of air discharge, which are got under the condition of temperature 25.6 ~ humidity 58.7%, and electrode with t h e same speed of 6 cm/s . Figure5.1 to Figure5.4 are four times of discharge currentwaveform of 6 kV respectively; Figure5.5 to Figure5.8 are four times of discharge current waveform of 16 kV respectively. From the figures, it can be seen that at the same voltage, the current waveform of each discharge are consistent and air discharge can also get better repeatability, which offers better experiment method to make further study on ESD regularity and the influence on electronic equipment of ESD.
CONCLUSION To resolve the problem of air discharge being influenced by the moving speed of electrode and its poor repeatability, this paper puts forward the idea of controlling the electrode of the simulator, and ESD simulator controlling system is designed, which makes the electrode approaching to target to discharge at a constant speed and reduces artificial interference. On the basis, preliminary experiment is carried out. The result shows that although the process of air discharge is very complex, its repeatability can be guaranteed to a certain extent. It is feasible to control the approaching speed of discharge electrode to improve the repeatability of air discharge. Additionally, the controlling system realizing choosing and setting the approaching speed of electrode, comparative experiment of ESD test at the same voltage and different speed or at the same speed and different voltage can be carried out respectively, which offers condition to make further study on the characteristic of air discharge.
REFERENCES 1. ElectromagneticCompatibility(EMC)-Part4-2: Testing and MeasurementTechniques- Electrostatic Discharges Immunity Test,IEC61000-4-2(2001) 2. Shanghe Liu, Guanghui Wei and Zhicheng Liu, ElectrostaticTheory and Protection ,Weapon Industrial Press,Beijing, China(1999)180-198 3.Hongjian Li, Research on Experiment of Strong ElectromagnetismPulse Effect on Typical Electricity detonator, Mechanical Engineering College, Shjiazhuang,China( 1998)45-53 4. Weishan Chen, Electromechanical System Computer controlling, Harbin Industrial Universitypress, Harbin, Chian(1999) 5. Zhansong Gu, Tienian Chen, Principle and Application of Programmable Logic Controller, National Defence Industrial press, Beijing, China(1994)
52 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Electromagnetic Wave Propagation in conisional Plasma Ouyang J T I'*, Zhang Z X 1, Miao J S l, Zhang Q Ca, Gao B Q2 ~Physics Department, Beijing Institute of Technology, Beijing 100081, China 2 Department of Electronics Engineering, Beijing Institute of Technology, Beijing 100081, China Emall: j
[email protected]
In this paper, the propagation characteristics of electromagnetic wave (EMW) in collisional (dispersive) plasma were studied. The attenuation and distortion coefficients of EMW in the plasma were calculated based on the Maxwell's equations. The results show that the plasma density (frequency), the electronneutral collision and signal duration play important roles on the EMW transfer characteristics. The dense, collisional plasma can be used as controllable medium for transmitting and obstructing EMW.
INTRODUCTION Non-equilibrium, weakly ionized plasma has a special property that exploited for a wide variety of scientific applications. The response of a weakly ionized plasma to the incident electromagnetic wave (EMW) depends on the angular frequency co of the wave and the plasma frequency COpe,as well as the electron-molecular collision frequency v~. There are 3 modes for the EMW interacts with plasma: 1) reflection, occurring at the surface when co < ~ , 2) transmission, passing through the plasma if co > ~ , and 3) surface mode, propagating along the boundary of the plasma and the dielectric. Therefore the gas discharge induced plasma is a special medium which has the ability to reflect EMW below the plasma frequency, while transfer EMW above the plasma frequency. Another property is the plasma may decay rapidly once the ionization source is removed. A thin sheet plasma could thus serve as an agile mirror used to direct a radar beam, [1 ] and a plasma column could be attempted to use as radio frequency (RF) antenna. [2,3] The purpose is that the gas discharge induced plasma has many advantages comparing with a metal, such as stealth due to non-metal elements, re-configurable characteristics for bandwidth, frequency, gain, directivity, etc. On the other hand, the ionized plasma is usually dispersive (collisional). This causes two effects on the EMW transmission: attenuation of amplitude and distortion of waveform. This property makes the plasma be able to attenuate or block the un-expected EMW from outside, while let the useful signal pass through. This paper focuses on the feasibility of the controllable plasma as EMP defense medium. The propagation characteristics of EMW in the dispersive plasma were investigated. The plasma requirements for EMW passing or obstructing were discussed. TRANSFER CHARACTERISTICS OF EMW Propagation constant The dispersion relation which specifies the propagation constant k in terms of frequency m is given from Maxwell's equations as follows: [4] k2c2
-
(1)2
_
O)pe2
l + (v~ / w) z
+ j
COpe2 (V c / CO)
l + (Vc / CO)2
where c is the light speed in vacuum. Let k = fl + j a , o~ and 13 are real and correspond to the attenuation and phase-distortion constant, respectively. Then one can get:
53 co[- B + 4B ~+ A' ],/~ and fl co[B +-,/B 2 + A 2 c 2 c 2 where A - ((Ope / (-0) 2 "(V c / co)/(1 +(v~ / o) 2) andB = l--(O)pe / (.0) 2/(1 +(v C/ o9)2). 200
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0.2 0.4 0.6 0.8 4 6 8 10 f(GHz) f(GHz) Figure 1 Attenuation and phase constant of EMW in plasma
1.0
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The attenuation and distortion constants of the EMW in plasma are shown in figure 1 (with Vc= 5• It is clear that both cz and 13 depend strongly on the EMW frequency. In low frequency limit (co < COpe),the attenuation and the phase distortion of EMW in the plasma are significant, and increase steeply at low frequency, while are small in high frequency limit (co>COpe). Meanwhile, the attenuation and the distortion for a given EMW depend strongly upon the plasma density, decreasing sharply as the electron density reducing.
Figure 2 Effect of electron-neutral collision on attenuation The effect of the electron-neutral collision on the attenuation coefficient is shown in figure 2 (with ne = 1012/cm3). One sees that the behavior of electron collision is different for high and / or low EMW frequency limit. Below the plasma frequency (co
COpe),the EMW may transfer through the plasma. The attenuation increases with the collision frequency. Thus high transmission of EMW requires low absorption (small collision frequency) and low plasma frequency (low electron density) in the plasma. Transmission of EMW signal When a plane wave E ( z , t ) - Eo ej(kz-~ transmit into the medium at z=O, the change of the output signal at z=L
is characterized simply given by transfer function H(co), H ( c o ) - e -~(~
e -jr176
54 where e-a(~L and e 4p(~L are the attenuation and phase-distortion factors, respectively. The output signal may be determined by Fourier transfer. The output waveform of electromagnetic pulse (EMP) with duration of 10-9s and 10-6s are shown in figure 3(a) and (b), respectively (with L = 5cm, ne= 1012/cm3, ve = 5x 10S/s). It is seen that a short EMP will attenuate greatly due to the amplitude reduction (~28dB) and waveform oscillation (see fig 3(a)), while a suitable pulse (duration of 106s) can pass the plasma without significant distortion (see fig 3(b)) with amplitude decreasing to --40%. Therefore, one can control the electromagnetic signal transmitting or blocking in the plasma by choosing the plasma parameters and the signal duration. 0.04
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PLASMA REQUIREMENTS AND FEASIBILITY FOR EMP DEFENCE From above, we see that the higher the plasma density and the larger the electron-neutral collision are, the stronger the EMW attenuation and absorption in the plasma. For most gases, the electron-neutral collision rate v~= 10Tn0 ( where no is the neutral density, e.g. v~=3.5x 109/s for p = 1tort = 13 3 Pa ). To defense EMP at X-bandwidth (f=100MHz to 10GHz ), a dense plasma with electron density ranged from 109~1013cm"3 and p >ltorr (to ensure significant electron-neutral collision) is needed. However, for the use of plasma as radar reflector, the pressure should be low enough to reduce the absorption.[1 ] Moreover, the plasma should be produced when needed, and disappear immediately after the discharge "turn-off'. As we knew, the rising time of gas breakdown and decay time of the plasma are on order of 10-s'9s, depending on the gas property. The plasma may therefore be generated simply by laserguided or surface wave induced glow discharge at a few torrs The electron density may be controlled by the discharge current. To choose the gas mixture and pressure, the plasma can be generated efficiently and with high control to be used as EMW-defense medium. CONCLUSIONS It has been shown that a dense, collisional plasma can be used as EMP-defense medium. The electronneutral collision and the electron density play very important roles on the EMW transfer characteristics in the plasma. The attenuation and phase distortion are strong in low frequency regime (co < rope) and increase with the plasma density but decrease with the collision frequency. While in high frequency limit (co > O~e), the attenuation increases with the electron collisions. The EMW propagation in the collisional plasma can be controlled by adjusting the plasma parameters, such as gas mixture and pressure, the discharge current etc and the signal duration, to make the electromagnetic signal transmitting through or blocking in plasma. REFERENCES 1. Robin A E, "Demonstration of a plasma mirror for microwaves", IEEE Trans Plasma Sci. (1992) 20 1036-1040. 2. DwyerT.J., Greig J.R., Murphy D.P., etal., "On the Feasibilityof Using an Atmospheric Discharge plasma as RF Antenna", IEEE Trans on Antenna and Propagation (1984) 32 141-146. 3. BorgG.G. and HarrisJ.H., "Applicationof PlasmaColumnsto RadiofrequencyAntennas",Appl PhysLett (1999)74 3272-3274. 4. TanenbaumB. S., in: Plasma Physics, McGraw-Hill,NY, USA (1967).
55 Paper Presented at the 5th International Conference on Appfied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Plasn/a Development in Dielectric Barrier Surface Discharge Cao J, Ouyang J T § Hui H X Physics Department, Beijing Institute of Technology, Beijing 100081, China +Email" j [email protected]
The plasma development along the dielectric surface in the dielectric barrier discharge has been investigated experimentally by using a high speed CCD camera. The spreading velocity of plasma on the anode and cathode were obtained for different sustaining voltages and frequency. The electron energy and surface electric field have been discussed in this paper.
INTRODUCTION The dielectric barrier discharge (DBD) is a highly transient, low-temperature non- equilibrium discharge formed from electrons of high mean energy which exists in a broad range of pressures. Recently, more and more researches have been attempted to produce uniform glow discharge at atmospheric pressure (GDAP), for the reason that it offers a wide field of applications, e.g. treatment of surfaces, radiation sources without any vacuum system. [1 ] One of the common configurations for generating GDAP is the 'surface discharge' (SD) arrangement, in which a plane dielectric with an electrode locate on one surface and a metallic cover on its reverse side. The gas gap is relative narrow, on order of 0.1mm to lmm to ensure a low pd production. Nowadays, SD under high pressure has been widely used in industry, e.g. plasma display panel and surface modification, etc. However, the physical process of discharge along the dielectric surface is still not very clear. One of the problems is the propagation of plasma on the surface and the electron energy. In SD arrangements, successive discharge steps develop on the dielectric surface at field strength distribution which is substantially influenced by the surface charges. The evolution of plasma and the electron energy relates to the surface states. Generally, the plasma propagation on cathode is mainly determined by the sheath motion along the surface, which is controlled by: 1) ionization in gas, 2) ion velocity, since the ions created in the cell volume must go back to the cathode surface to generate secondary electrons, and 3) secondary electron emission on cathode surface. The plasma development on anode, however, is mainly determined by the electron motion, which is induced by the electric field along the surface. In this paper, we investigate the plasma propagation in SD experimentally. The spreading velocity of plasma has been measured with high-speed ICCD camera. The electron energy and the electric field are obtained from the experiments.
EXPERIMENTAL SET-UP The SD macro-cell we used is a macro-cell (which operates in 100 lower pressure and size of 10cmx3cmxl cm according to the "scaling laws" of glow discharge) instead of micro-system, in this way, the parameters are measured more conveniently. (see Ref [2]) The macro-cell is a glass vessel with internal dimensions 9 cm x 3 cm x 1 cm, filled with a gas mixture of 4% Xe in Ne-He at 5 tort, corresponding to 900gmx300gmx100gm of microcell. The electrodes are placed outside the vessel. The glass sides of the vessel between the two plates is polished so that optical measurements are possible from the front and from the side of the discharge cell. The coplanar electrode dimensions are of 2 cm x 2 cm
56 with gap of d = 0.8 cm. A square-wave voltage is applied between the two coplanar electrodes. The discharge current was measured by using a digital Osciliscope. An intensified CCD camera with filters (infrared emission around 823 nm or visible emission around 640nm) has been used to measure the time evolution of the xenon and neon emission from the discharge. For the details of the experiments, please refer to Ref. [2].
RESULTS AND DISCUSSIONS Propagation of plasma Fig. 1 shows the position of plasma boundary changing with time and the discharge current for voltage/Is = 200V and frequency f = 50Hz. It is seen that the plasma forms firstly above the anode and then develops towards both sides. The plasma stops developing after reaching the outer edge of cathode at the current peak, and then fades out gradually. Usually, the plasma reaches anode boundary earlier than cathode. 0.2
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plasma spreading velocity The plasma developing velocity can be deduced form the change of the plasma position. Fig.2 shows the spreading velocity on anode V~ and cathode Vr for different applied voltages. One can see that the spreading speed increases with the voltage. The velocity is not very different on cathode and anode, on order of a few cm/gs. The frequency (if not very high) has not great influence on the plasma spreading. But, at higher frequency (/'= 500Hz), the velocity is larger and, it is difficult to determine the velocity on anode, due to the reason that discharge mode is different. [3] Electric field and electron ener~'r Because the plasma propagation on anode is caused by electron motion along the surface electric, which can be expressed by v e = f i e E , where/re is the electron mobility. In glow discharge regime, /tep is .
.
.
.
.
supposed to be constant and the value is ~l.4xl 06 cm 2 torr/Vs. Thus the surface field on anode is about E / p = 0.2-2 V/cm torr. The electron energy balance in a weak ionized plasma is controlled by the inelastic collision, which is given by ~e --e2eE, where ~Leis the mean free path due to inelastic process.J4] In mixture of Ne-Xe4%, the inelastic collision section is ~5x10 "16 cm 2, ~Lo~0.3cm at 5torr. Therefore, Ee - 0.3 ~3eV on anode range. Both the field and electron energy increase slightly with the voltage. This is in good agreement with the previous measurements. [5]
57
Figure 2 Plasma spreading velocity for different applied voltages and frequency
CONCLUSION The development of the plasma on the anode and cathode in dielectric barrier surface discharge has been investigated experimentally and the spreading velocity on both anode and cathode were measured for different sustaining voltage and frequency. The velocity, on order of ~ 0.2-3 cm/l.ts, increases with the applied voltage. The propagation of the plasma is not synchronal on both sides, reaching outer side of anode faster. The energy and electric field on anode can be deduced form the electron motion on anode, which are about 0.3 ~3eV and 0.2 ~2V/cm torr, respectively.
REFERENCES 1. Kogelschatz U., "Dielectric-barrier discharges: their history, discharge physics and industrial applications", Plasma Chem. Plasma Proc. (2003) 23 1-46. 2. Ouyang J., Callegari Th., Caillier B., Boeuf J.P., "Large-gap AC coplanar plasma display cells: macro-cell experiments and 3D simulations", IEEE trans-PS (2003) 31 422-428. 3. Ouyang JT, Cao J, Callegari Th and Boeuf JP, "Discharge characteristics in plasma display cell at high frequency", Chin. Phys. (2004) to be published 4. Raizer Y P., in: Gas Discharge Physics, Springer-Verlag, Berlin, Germany (1991). 5. Noguchi Y., Matsuoka A, Uchino K, Muraoka K, "Direct measurement of electron density and temperature distributions in a micro-discharge plasma for a plasma display panel", J. Appl. Phys. (2002) 91 613-616.
58 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Spectroscopic Investigation of Low-temperature Plasma Discharge Reactor Ma Ningsheng, Ge Ziliang Department of Physics, Tongji University, Shanghai 200092, China
Abstract: Low-temperature plasma discharge reactor has been found widely use in environmental engineering. For cutting down power consumption and raising productivity, it is essential to optimize discharge reactors. Discharge reactor supplies low-temperature plasma in which energy of electron is far higher than energy of other particles, and brings about chemical reaction. Discharge light transmits these messages, thus a low-temperature plasma discharge reactor has been chosen as the subject of the study. The spectrum of discharges in air at atmospheric pressure has been measured in the near-ultraviolet region. Having made an investigation on the spectrum, has found out the reacting process and has detected energy of electron. So that can make an evaluation to the lowtemperature plasma discharge reactor. This paper presents an evaluating method by spectral analysis to low-temperature plasma discharge reactor. Key words: low-temperature plasma; discharge reactor; spectrum
In recently years, the technology of the plasma discharge is already used to ozone compose, sulfur or NOx removal from exhaust gas, VOC decomposition etc. industrial processes, but the mechanism of reaction in plasma discharge is not understood completely. Because the variable parameters are much more and the control method is short, it is result in low produce efficiency. The process parameter should be optimized, that is, how to choose the mix gas and volume of flow, how to choose discharge reactor and the low-temperature plasma discharge condition(discharge voltage, power, frequency, etc.). The characteristic of the discharge plasma in chemical reaction is that the electrons of high mobility obtain to speed up in electric field and obtain high energy that is much more than molecular energy. When the hard electron collides with neutral molecules, they will be stimulated, ionized, dissociated, high speed action will be realized. Discharge light transmits these messages. Analyzing the emission in pulse transient corona discharge, has got the relation of the flow-light and energy distribution [ 1], thus can also design electric power and reactor. In this paper, we have analyzed the spectrum, have found out the reacting channels and detect the energy of electron, so that we can make an evaluation to the low-temperature plasma discharge reactor.
EXPERIMENTAL The discharge reactor is shown in Fig. 1. It is make up two parts. The first is the glass tube with length of 23 lmm, and outside diameter of 30mm. A stainless coil of 30 turns was pressed close to the glass tube as an electrode. Diameter of the wire is 0.5mm. The other is the quartz tube with length of 259mm and outside diameter of 42mm. A stainless wire mesh with a diameter of 0.2mm was pressed close to the quartz tube as other electrode. The glass tube and the quartz tube is coaxial, there are two holes on the two sides of the discharge reactor respectively. A luminous tube transformer was used as a power supply, can supply 50Hz, 15kV high voltage alternating current.
59 Quartz tube Stainless wire mesh (outer electrode) ------ Glass tube
Stainless coil
Fig. 1. Discharge reactor.
When 15kV voltage was applied on the discharge reactor, the gap between the quartz tube and the glass tube produce silent discharge was produced and generated purplish light, the light massage was detected by the monochrometer in Fig.2. DC high voltage
I
Monochrometer
PM I
Discharge reactor
I
High-voltage power supply Sampling unit
Computer
Fig.2. Experimental setup.
EXPERIMENTAL RESULTS AND DISCUSSIONS Under the action of electric field in the discharge reactor, electrons gained energy from it, and collided with atoms and molecules, electrons transferred energy to them, led to their stimulation and ionization, produced the electron avalanche, so that the air was broken down. There was a lot of conductive path by 30000 25000 "~
20000 15000
~. lOOOO
,
5000 0
200
l
i
i
220
240
2BO
280
, ._..,x,_~ 300
320
340
t, 360
380
400
420
440
/nm
Fig.3. The spectrum of discharges electronic current in the air. When high electrons went through the conductive path, the some atoms and molecules in excited state would emit ultraviolet light spontaneously. For one thing these ultraviolet photons could increase electron emission at cathode, and for another could ionize atoms and molecules strenuously, and formed the new avalanche. Thus we measured the spectrum of discharges in the nearultraviolet region, could find out formed process of discharge plasma. The spectrum of discharge is shown in Figure 3, measured multiplets of the atomic oxygen are shown Table. 1.
60 Tab. 1. Measured multiplets of the atomic oxygen in the spectrum of discharges Wave length(m)
369.2 5p3p
382.3 395.2 423.3 3 p " 3 D 3s,,3p~ 3d,3p o
436.8 4p3p
Transition Upper-state energy (eV)
3s3S~
3s,3D~
12.88
15.78
3p3p
4p3p
14.12
15.29
3s3S~ 12.36
The bond energy of the 02 molecule is 5.08eV, the inelastic collision of electron led to its dissociation, could occur a number of processes [2]" ( 02 (A 3 Z +u) + e ~ 2 0 ( 3p ) + e (1) e+O2 (X 3 Z g ) -~ ~ O2 (B 3 2 : u ) + e ~ O ( 3 p ) + O ( I D ) + e (2) O2" (A 2II u) --" O ( 3p )+ O ' ( 2p ) (3) Detecting the spectrum in the discharge reactor, really occurred process of dissociation of the 02 molecule was only a process 1, that is, the electron which energy was greater than or equal to 4.340eV excited the ground state O2(X3 2: g)to A32 +u state. At the A32 +u state, the radiation lifetime of the 02 molecule was 103s, then was collided by the electron which energy was greater than or equal to 6.1eV, and was dissociated into the ground state O(3p) atom. The process of the dissociation is decided by the transition cross section of atomic spectrum (the process 1, 2) or the attached cross section of electron (the process 3) when its energy level transits. When the transition cross section is 5.6 • 1021m 2, the dissociation of 02 molecule is going by the process 1. Of cause, the transition cross section or attached cross section relates to the electronic energy before the electron collides with others. In other words, the section relate to the drift velocity of the electron and the intensity of the referred field E/N (the ratio electric field intensity to number density of the 02 molecule). A low-temperature plasma discharge reactor is intended to supply a strong electric field. Investigating the spectrum of discharges, we did not detect the transition spectrum in the first excited state O(~D), that meant the electron which energy was greater than or equal to 8.4eV had not collide with B3~; u state of the 02 molecule, and did not dissociate it into the ground state O(3p) and the first excited state O(1D). We had not survey the spectrum of O (2p) either, it indicated that the process of the dissociation by 2 or 3 did not happen. Oxygen is electronegative gas. Until the energy of electron was between 6.7 and 10eV, the 02 molecule could not seize the electron in large number, could not form O (2p). Thus, the discharge reactor supplied the energy of the electron principally less than 6.7eV. It means there is room for improvement in the discharge reactor. For example, the width of its discharge gap is 4.2mm. If we decrease the discharge gap, the value of E/N will increase.
CONCLUSIONS As the low-temperature plasma, the electrons of high mobility are accelerated enough, and form nonequilibrium state of energy, namely the energy of electron is higher than molecular or ionic, and can realize some chemical reactions which is hard to accomplish in general. Therefore, it can supply the high-energy electron whether or not, we can make an evaluation to the discharge reactor by spectroscopic investigation.
REFERENCES 1. Massimo Rea. Evaluation of pulse voltage generators. IEEE Tran. Ind. Appl., 1.995,31(311):507-512 2. Christophorou L G. Electron-Molecule Interaction and their Applications. Vol.1, New York: AcademicPress, 1984
61 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Investigation on Simultaneously Desulphurization and Denitrification from Flue Gas by Pulsed Corona Discharge Plasma and Additives Shang Kefeng, Wu Yan, Li Jie, Li Guofeng, Li Duan, Wang Ninghui, Zhu Jing Institute of Electrostatics & Special Power, Dalian University of Technology, China, 116024
In this paper, simultaneous removal of $02 and NOx from flue gas by combining pulsed discharge plasma with activated additives has been studied. The factors influencing NOx and SO2 removal such as activated additives, humidity and flow rate of flue gas, pulse discharge frequency etc are investigated. The experiments demonstrate that NOx and SO2 can be more effectively removed using hybrid process of activated additives combined with pulsed corona discharge, and higher NOx removal efficiency can be obtained when SO2 is present in flue gas.
INTRODUCTION Early in the 1970's, Palumbo et al Eli had utilized electric discharge technology to destroy $02. But the process had not been under intensive investigations until the 1980's when researchers found that simultaneous removal of NOx and SO2 from flue gas could be realized with the pulsed corona discharge plasma technology [2-31. The NOx and SO2 removal process by pulsed corona discharge has many advantages over conventional wet scrubber and catalytic converter for flue gas such as no additional waste water treatment and expensive construction cost, but the energy cost had been high as more than ten watt-hours per standard cubic meters [4]. In order to reduce energy cost and increase pollutants' removal efficiency, many researchers studied to combine catalysts, additives and electric discharge plasmas for removal of NOx and SO2 from flue gas E5-81.For large-scale industrial de-NOx and de-SO2 operation, the de-NOx and de-SO2 process combining electric discharge plasma and catalysts is not practical because the easy deactivation and inaccessible operation conditions of catalysts. So in this paper, the process of combining activated additives (ammonia, propylene, etc) with pulsed corona plasma is studied for simultaneously removing SO2 and NOx from flue gas.
EXPERIMENTAL SETUP Fig.1 shows the simultaneous removal process of NOx and SO2 using pulsed corona discharge. Air is introduced into air heater by an induced fan and is heated to experimental temperature, and NOx and SO2 infused from the fore pipeline of deSO2 reactor are blended with heated air to form the simulated flue gas. Synthetic flue gas is treated by a wire-plate pulse discharge reactor and the byproducts are collected by a bag filter. The concentrations of NOx and SO2 are monitored online by NOA-305A portable NOx Analyzer (Shimadzu, Japan) and IRA-107 continuous Gas Analyzer (Shimadzu, Japan) respectively; the velocity, the humidity and the temperature of flue gas are measured by Hygropalm 3 gas parameter testing apparatus (Rotronic, Swiss). The wire-plate reactor for de-NOx and de-SO2 is composed of nine nozzle electrodes in the fore section (a) and twenty-two wire electrodes in the hind section (b). According
62
~
.~.
~r~]
~
\-
to experimental arrangements, nine nozzle electrodes are equally separated into three groups; ammonia, propylene ete injected into reactor from different groups are activated by pulse electric discharge to produce more radicals for increasing contaminants' removal efficiency; and then flue gas is further treated by pulse electric discharge section (b). In experiments, rectangular stainless steel wires of 4 • 4 • 850mm are used as corona wires. The distance between corona wires and the wire-to-plate spacing are 90mm and 150mm. Nozzle electrodes are made up of pipes of 10mm (ID) and 12mm (OD) and nozzles of lmm (ID) and 2mm(OD); the lengths of pipes and nozzles are 740mm and 25mm respectively, and the distance between nozzle electrodes is 200mm.
-
H
6
2345
1.Air Heater, 2.SO~_Cylinder, 3.NO Cylinder, 4.NH3 Cylinder, 5.C3H6Cylinder, 6.water vapor Generator, 7.Reactor, 8.NOx Analyzer, 9.SO2 Analyzer, 10.Pulse Generator, 11.Pocket-type Precipitator, 12.Induced Fan, 13.Stack a: Nozzle-type Electrode, b: Rectangular corona wire Electrode Fig.1 Schematics of the SOz and NOx removal process
RESULTS AND DISCUSSION NOx and SO2 Removal by Nozzle Electrodes In different NOx removal processes, there are different dominating reaction paths for NOx removal. When no additives are added, NOx is directly removed by discharge plasma, and the byproducts are mainly NO2 and HNO3; when ammonia is added, the byproducts such as NH4NO3, N2, etc should also be included [9-10]. The information in Fig.2 demonstrates that when ammonia is present, the reaction path of generating NO2 is not dominating. 55
36
50
32
45
28 24
o Z
~, 20
76 0 ~ fJ )
40
8
72
30
9 NO conversion to N2 and NH4NO3 9 Total conversion of NO A NO conversion to NO2
12
25
68
20
4
40
x
o~ 35
~" 16
0
80
- - " - - H=2.82% - - i - - H=1.44%
a
50
n
60
i
70 f/HZ
l
|
80 "
90
a
NO and SO2 initial concentration: 104ppm and 1500ppm Cp: 800pF, T: 330-356K, H: 1.4%, [~#([NOI+2[SO2]): 1"1, Q: 100Nm3/h. Fig.2 Relation between NO removal and pulse discharge frequency
15 40
n
f2Oz I
l
8'o
i
9'o
i
NOx and S O 2 initial concentration: 90ppm and 1500ppm, [CaH6]/[NO]: 1"1, [NH3]/([NO]+[SO2]): 1"1, Q: 100Nm3/h,Cp: 800pF, T: 326K-354K.
Fig.3 Relationbetween NOx and SO2removal and pulse dischargefrequency
The lines with symbols and the scatters in Fig.3 show the SO2 and the NOx removal efficiency respectively when ammonia and propylene are infused from the fore pipeline of reactor (Activated). Fig.3 shows the NOx removal efficiency when the humidity of flue gas (H) being l.44% is higher than that when the humidity of flue gas being 2.82%, and the influence of humidity on NOx removal is greater when the pulse discharge frequency is lower (the electric discharge energy is less). The reason may be that the generated ozone, which is very important for NOx removal, is destroyed when humidity of flue gas increases. But the lines in Fig. 3 shows the SO2 removal efficiency is higher when the humidity of
63 flue gas is greater because of the important role played by water vapor and OH radicals in the SO2 [6,11] removal process NOx and SO2 removal efficiency by pulse discharge electric field Fig.4 and Fig.5 show the NOx and SO2 removal when the pulse electric discharge unit (b) is utilized. The curves in Fig.4 show the NOx can be more effectively removed when both ammonia and propylene are present, and the scatters in Fig.5 show SO2 removal efficiency is just slightly improved when C3H6 is infused. The two figures show that C3H6 is more important for NOx removal than SO2 removal. When hydrocarbon such as propylene is injected, alkyl or alkoxy radicals such as RO2, R, RO, etc will be produced in electric discharge, and NOx was mainly removed by chain reaction between these radicals and NOx [12-131. But for SO2 removal, hydroxyl radicals are the most effective species. -,-
NOx - v - NO - o - NOx - v - NO
110 100 E 90
74
NH3 exists NH3 exists NH3 and C3H6 exists NH3 and C3H6 exists
72 70
(D. (D.
r 80
oO~
o~
70
~
66
tO tO
68
60
9 NH3 exists 9NH3 and 03H6 exists
64
50
62
40 I
=
I
0
=
20
I
=
I
40
=
/
60
=
80
100
5'0
'
6'0
'
70
'
8'0
'
9'0
f/HZ [NH3]/([NO]+[SO2]): 1"1, Q: 77Nm3/h, Cp: 1.33nF, T:
[C3H6]/[NO]: 1"1, [NH3]/([NO]+[SO2]): I:1, Q: 77Nm3/h, Cp: 1.33nF, T: 326K-360K.
326K-360K, SO2 initial concentration: 1600ppm.
Fig.4 Relation between NOx concentration and pulse discharge frequency
Fig.5 Relation between SO2 removal and pulse discharge frequency
NOx and SO2 removal efficiency by combining activated additives and pulse corona discharge 70 65
84
9Cp=2nF 9Cp=1.33nF 9Cp=1.33nF
60 55
80
50
o~
~45
~6
72
40 :30 25
- , - N H 3 and C3H6 Activated
68
35
- - - N H 3 and Call 6
64 6
0
'
/
80
=
I
100
=
I
120
i
I
140
i
I
160
C0/ppm Activated NH3 and C3H6 (i, O), NH 3 and C3H6(A), [C3H6]/[NO]: 1"1, [NI--I3]/([NO]+[SO2]):1"1 SO2 initial concentration: 1750-1800ppm T: 330K-360K, Q=100Nm3/h Power: 2Wh~m 3(Cp=2nF), 1.5Wh~m 3 (Cv=I.33nF).
Fig.6 Relation between NOx concentration and its removal efficiency
' 70
8 ' o ' 9 ' o '
' 100
'
' 110
'
' 120
Q/(Nm3/h~
'
' 130
' 140
150
Activated NH3 and C3H6 (m), NI-I3 and C3H6(A), T: 330K360K, [C3H6]/[NO]: 1:1, [NH3]/([NO]+[SO2]): 1:1, SO2 and NOx initial concentration: 1750-1800ppm and 100ppm,Cp= 1.33nF, power= 1.5Wh/Nm3.
Fig.7 Relation between SO2 removal and flow rate of flue gas
Fig. 6 and Fig.7show the NOx and 802 removal efficiency by combining pulse electric discharge and activated additives. The scatters in Fig.6 show the NOx removal efficiency is higher when ammonia and propylene are injected from nozzles and the pulse forming capacitance (Cp) is 2nF. The reason is the pulse forming capacitance increases, more energy will be infused into reactor; if additives are infused from nozzles, more radicals will be produced, both are advantageous to NOx and SO2 removal.
64 CONCLUSIONS In our experiments, simultaneous removal of NOx and SO2 is realized by combining activated additives and pulsed corona discharge, and the influence of different additives on N O x and SO2 removal is preliminarily clarified. 1) The NH3 and C3H6 activated by pulsed corona discharge can improve N O x removal efficiency, and C3H6plays a greater role in NOx removal. 2) The NH3 and C3H6 activated by pulsed corona discharge can improve SO2 removal efficiency, and C3H6 plays a less role in SO2 removal than NOx removal. For SO2 removal, water vapor plays a more important role. 3) The hybrid process of activated additives and pulsed corona discharge is effective for NOx and SO2 removal, at an energy density of 2 W h ~ m 3, NOx and SO2 removal efficiency can reach 60% and 84% respectively.
REFERENCES [ 1] F. J. Palumbo, F. Lraas. The Removal of Sulfur from Stack Gases by an Electric Discharge. J. Air pollution Contr. Assoc. (1971) 21 143-144 [2] S. Masuda and H. Nakao. Control of NOx by positive and negative pulsed corona discharge. IEEE/IAS Annual Meeting21, Denver, CO, USA (1986) 1173-1182 [3] J. S. Clements, A. Mizuno, W. C. Finney, R. H. Davis. Combined Removal of SO2, NOx, and Fly Ash From Flue Gas Using Pulsed Streamer Corona. IEEE/IAS Annual Meeting- 21, Denver, CO, USA (1986) 1183-1190 [4] G. Dinelli, L. Civitano, M. Rea. Industrial experiments on pulse corona simultaneous removal of NOx and SO2 from flue gas. IEEE/IAS Annual Meeting-23, Pittsburgh, PA, USA (1988) 3__551620- 1627 [5] J. S. Chang, P. C. Looy, J. Pevler, J. Yoshioka, K. Nagai. Reduction of NOx from a combustion flue gas by a corona radical injection method. IEEE/IAS Annual Meeting-28, Toronto, Ont, Canada (1993)3 1969-1976 [6] Wu Yan, Li Jie, Wang Ninghui, Zhang Yanbin, Liu Zhougyang, Yang Liming. Experimental research about the role of activating water-vapor in the DeSO2 technology from flue gas with PPCP. IEEE/IAS Annul Meeting, (2000) 1 704-708 [7] H. H. Kim, K. Takashima, S. Katsura and A. Mizuno. Low-temperature NOx reduction processes using combined systems of pulsed corona discharge and catalysts. J. Phys. D: Appl. Phys. (2004) 3__44604-613 [8] H. H. Kim, K. Tsunoda, S. Katsura, and A. Mizunol. Novel plasma reactor for NOx control using photocatalyst and hydrogen peroxide injection. IEEE Trans. Ind. Appl. (1999) 35 1306-1310 [9] I. Orlandini, U. Riedel. Chemical kinetics of NO removal by pulsed corona discharges. J. Phys. D: Appl. Phys. (2000) 33 2467-2474 [10] J.Y. Park, I. Tomicic, G.F. Round, J.S. Chang. Simultaneous removal of NOx and SO2 from NO-SO2-CO2-N2-O2 gas mixtures by corona radical shower systems. J. Phys. D: Appl. Phys. (1999) 32 1006-1011 [11] J. J. Lowke, R. Morrow. Theoretical analysis of removal of oxides of sulphur and nitrogen in pulsed operation of electrostatic precipitators. IEEE Trans. Plasma Sci. (1995) 2__33661 -671 [12] M. Dors, J. Mizeraczyk. NOx removal from a flue gas in a corona discharge-catalyst hybrid system. Catalysis Today (2004) 89 127-133 [ 13] A. R. Martin, J. T. Shawcross, J. C. Whitehead. Modelling of non-thermal plasma after treatment of exhaust gas streams. J_ Phys. D: Appl. Phys. (2004) 3__7_42-49 7
65 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, 'ISBN0-08-044584-5
Discharge Characteristics of Magnet Enhancement Corona Discharges* Dexuan Xu, Yinhao Sun, Haijun Wang and Mingfei Li Department of Environmental Science and Engineering, Northeast Normal University, Changchun 130024, China
In this paper, the experimental researches on the discharge characteristics of the magnet enhancement corona discharge were carried out, and the discharge mechanism was theoretically analyzed. The magnet enhancement functions between positive and negative corona discharges were experimentally compared. The magnet enhancement effects in different interelectrode regions were researched. The researches demonstrated that magnet field can efficiently increase the concentrations of ions and free electrons. The dominant mechanism of magnet enhancement in corona discharges is that the Larmor movements of free electrons enhance the nonthermal plasma in ionization region near discharge electrode. A reasonable configuration for magnet enhancement can be formed by permanent magnets with a local strong magnet field near the discharge electrode.
INTRODUCTION In recent years, more and more countries begin limit the emissions of micrometer and sub-micrometer particles. The process of electrostatic precipitation depends on the force acting on charged particles in an electric field. The more the charges on a particle are, the greater the force is. It is important to increase the charges on the fine particles, in order to improve the capture of the particles. The most effective approach for increasing charges on fine particles in negative corona discharges is to enhance the ion diffusion charging mechanism and the electron charging mechanism. When the density of free electrons is increasing in ionization region, the concentration of both the electrons and negative ions enhance in the whole interelectrode region. Therefore, not only the charging mechanism of free electrons is enhanced, but also the ion diffusion charging mechanism is increased. In recent years, we did some researchers on the magnet enhancement corona discharges and the function for changing particles [ 1]. In our researches, free electrons were deflected in a magnetic field and traveling lengths of the free electrons was greatly increased. The density of both the electrons and negative ions were increased. Moreover, a simple DC HV power supply was employed and the charging time on particles was continued. Therefore, the magnet enhancement corona discharges can serve as an advanced charging technique and will be promising in the applications. The experiments on removal of harmful gases in the corona discharges with a crossed magnetic field were also reported [2], in which an external cylindrical electromagnet was adopted.
DISCHARGE CHARACTERISTICS OF MAGNETIC ENHANCEMENT CORONA DISCHARGES Experimental apparatus The electrodes configuration of the experimental apparatus for the magnet enhancement corona discharges is shown in Figure 1.
* Project 50277004 supported by National Natural Science Foundation of China
66 The effective discharging length of a stainless steel wire electrode 4 was 40 mm and the diameter of the wire was 0.5 mm. Two strings of the permanent magnets 5 had a cylinder shape and 10 mm diameter. The strings of magnets were respectively assembled at each end of the wire electrode. The magnetic flux density near the wire electrode could be changed by increasing or decreasing the length of the magnet strings. The spacing between two magnet strings was 50 mm. The joint between the magnet strings and the wire electrode formed an arc shape, in order to prevent the discharges of the magnet string edge. The wire electrode was settled in the symmetric center of the two stainless plate electrodes 3, which were 265 mm in width and 200 mm in height. The spacing between two plate electrodes was adjusted as 70 mm. The directions of the magnetic force lines were perpendicular to the directions of the electric force lines near the wire electrode. High-voltage power supply 1 could provide 0-40 kV positive or negative DC high voltages. Between the plate electrodes and grounding wire there was two ampere-meters, which had different measurement ranges. One ampere-meter was to measure the corona onset voltage and another was to measure the discharge currents. We could read the HV value of the power supply using a HV divider. Between the ampere-meters and the plate electrodes there was a shielding line, which could avoid the interference of the high-voltage electromagnetic noise to the corona currents. The water bottle 2 was just used in the last experiment, in order to research the influence of magnetic field on the agglomeration of spraying droplets.
Figure 1 Schematic of experimental apparatus for the magnet enhancement corona discharges 1. H.V. power supply; 2. Water bottle; 3. Plate electrode 4. Wire electrode; 5. Magnet string; 6. Valve
Figure 2 Interelectrode distribution of magnetic flux density (T)
Figure 2 shows the magnetic field distribution between wire and plate electrodes, when the mean magnetic flux density is 0.0372 T. In the line connecting the centers on the circle surfaces between two magnet strings, we take 4 points with an equal spacing and respectively measure their magnetic flux densities. The average value of the 4 values is defined as the mean magnetic flux density of the whole magnet field. Influence of magnetic fields on currents of negative corona discharges The circuit diagram for negative corona discharge is shown in Fig. 1. The I-V characteristics curves of the negative corona discharges in different magnetic fields are shown in Fig. 3. The Influence of magnetic fields on currents of negative corona discharges under two different HV was shown in Fig. 4. It is obvious in Figure 3 and Figure 4 that the discharge currents were greatly increased, when the magnetic field was increasing. When the average magnetic flux density increased from 0 to 0.0372 T, the current in the negative corona discharges could reach to 300% or so. When an external cylindrical magnet was employed in the previous experiment, a more uniform magnet field was formed in the whole interelectrode region and the discharge current increased to only 110-125%. It can be demonstrated that the enhancement of the magnetic field near the wire discharge electrode has a significant influence on the discharge currents in negative corona discharges.
67 In the traditional negative corona discharges, free electrons are obliged to move along the electric force lines because of the Coulomb force in the electric field. When a magnetic field applies on the electric field in above experiments, the magnetic force lines are perpendicular to the electric force lines near the wire discharge electrode. The free electrons would receive both Lorenz force and Coulomb force and the Larmor movements are formed. A motion component of the electrons is surrounding the magnetic lines of force and another motion component is along the electric lines of force. If the moving velocity of the electrons is taken as 2.0xl 05 m/s in the ionization region, the circle radius of Larmor motion are 150 ~t m in the middle part of the region and 15 ~t m in both end parts. The motion length of the electrons can greatly increase in the ionization region. The numbers of ionization collisions for electrons also obviously increase in each electron avalanche and the concentrations of both ions and electrons in the region greatly rise. The non-thermal plasma in ionization region near discharge electrode is enhanced. Therefore, the current of corona discharges increase because of the influence of magnet field.
Figure 3 l-V characteristics curves of negative c o r o n a discharges in different magnetic fields
Figure 4 Influence of magnetic fields on currents of negative corona.discharges
Although the electrons and ions can increase their motion length outside the ionization region, the total concentration of charged particles could not change, because the new ionizations could not occur in the low electric field region. The increase of motion lengths for the charged particles means lowering the drift velocity, which could not produce the increase of the current. Therefore, the increase of corona discharge current should attribute to the Larmor motions of electrons under the action of both Lorenz force and Coulomb force in the ionization region. Influence of magnetic field on positive corona discharges
Figure 5 I-V characteristics curves of positive c o r o n a discharges in different magnetic fields
Figure 6 Comparison of currents between negative and positive coronas in magnetic fields
When positive HV connected with wire electrode and plate electrodes were grounded through amperemiters in Figure 1, the positive corona discharges occurred. The I-V characteristics curves of the positive corona discharges in different magnetic fields are shown in Figure 5. The star symbols indicated the points of spark discharges in the Figure. The influence of magnetic fields on the discharge currents of the positive corona discharges and ce~parison of currents between negative and positive corona discharges in magnetic fields are shown in Figure 6.
68 It can be seen from Figure 5 and Figure 6 that the discharge currents were slightly increased with increase of magnetic field, unlike steeply increase in negative corona discharges. The original electrons of electron avalanches produced on the surface of discharge electrode in negative corona discharges. But in positive corona discharges, the original electrons frequently produce from the inner of ionization region and greatly decrease the influence of magnetic field on electron motion. Another obvious influence is the decrease of the spark voltage in positive corona discharges. The spark discharges always produce from the side surface of magnet cylinder. Influence of magnetic field on the a~lomeration of negative spraying droplets The water bottle 2 was employed in Figure 1 and supplied water to wire electrode through the syringe. The water flow rate could be controlled by a valve 6. When enough negative HV was applied on the wire electrode the spraying corona discharges occurred [3]. The sampling of droplets was realized by a sheet glass, which is covered with silicon oil. The droplet sizes were measured by a microscope. The influence of magnetic fields on size distribution of droplets in negative spraying corona discharges is shown in Figure 7. After employment of a magnetic field, the numbers of droplets decrease under 50 la m and the numbers increase above 50 ~t m. The spraying droplets ejected from the discharge electrode and charged by electrons and negative ions. The droplets with different sizes could reach different rate of charge/mass and produce different moving velocity. The difference of the velocity can increase the possibility of collide and agglomeration for different droplets. When a magnetic field was applied on the negative spraying corona discharges, the concentration of electrons and negative ions greatly increased. The difference of both charge/mass and velocity for different Figure7 Influence ofmagneticfieldsonsizedistribution droplets obviously enlarged. The agglomeration of of droplets in negative spraying corona discharges different droplets significantly enhanced.
CONCLUSION (1) The dominant mechanism of magnet enhancement in corona discharges is that the Larmor movements of free electrons enhance the non-thermal plasma in corona region near discharge electrode. (2) The magnet enhancement is more effective for the negative corona discharges than the positive. (3) A reasonable configuration for magnet enhancement can be formed by permanent magnets with a local strong magnet field near the discharge electrode. (4) An experiment of the spraying corona discharges shown that magnet enhancement corona discharge may promising in the charging and the agglomeration of fine particles.
REFERENCES [ 1] Dexuan Xu,Jie Li,Yan Wu,Linhui Wang,Dawei Sun,Zhongyang Liu,YanbinZhang.Discharge characteristics & applications for electrostatic precipitation of DC corona with spraying discharge electrodes, J. of Electrostatics 57 (2003): 217-224 [2] Jae-Duk Moon, Geun-Taek, Suk-Hwan Chtmg "SO2 and CO Gas Removal and Discharge Characteristics of a Non-thermal Plasma Reactor in a Crossed DC Magnetic Field" IEEE Transactions Vol.35, No.5, (1999) [3] Xu Dexuan, Zhao Jianwei, Ding Ytmzheng, Ge Weili. Removal of adhesive dusts from flue gas using corona discharges with spraying water, J. of Environmental Science 15 (2003): 561-568
69 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on emission spectrum from high-voltage pulsed discharge in liquid-gas mixture and TiO2 photochemical catalysis Zhou zhigang, Li jie, Li guofeng, Wu yan Institute of Electrostatics & Special Power, Dalian University of Technology, Dalian 116023
Ultraviolet radiation is one of the main ways of energy release in the highvoltage discharging process in liquid-gas mixture. In the paper, we investigated the relationship between characteristics of emission spectrum of discharging in liquid-gas mixture and its influence factors, such as pulse peak voltage, pulse forming capacitance and repeated rate. Then, we discussed the feasibility of combining the discharge process with photochemical catalysis to decolorate Acid Orange II wastewater.
INTRODUCTION High-voltage pulsed discharge technology [1] (non-thermal plasma technology) is one of the most promising electrical discharge processes in advanced oxidation processes (AOPs). Such discharge in liquid-gas mixture can lead to chemical and physical process. The chemical processes are the formation of active species and the physical processes are mainly light emission and intense shock waves. The spectral characteristics of an underwater discharge as reported approximate to that of a black body radiator at 20000 to 30000K. From Planck's laws, for a black body at 20000K, 75% of the continuous light emission occurs at wavelengths less than 300nm[2]. Light emission is a main way of energy release in discharge process and the maximum of emission is in the ultraviolet region. In order to use such ultraviolet emission efficiently, we try to combine high-voltage pulsed discharge technology with photocatalytic technology together, that is, adding catalyzer to the discharge reactor, using UV light emitting from discharge to trigger TiO2 and get more active free radicals, finally reaching the target of improving the efficiency. This paper investigated the characteristics of UV light emission of discharging in liquid-gas mixture and referred basic information for the combination of high-voltage pulsed discharge and photocatalysts.
EXPERIMENTAL SYSTEM The schematic diagram of experimental system is shown in Fig. 1. The system mainly included highvoltage pulsed power supply and reactor. The power supply with a rotating spark-gap switch was used to generate high-voltage pulse. A digital spectrometer(HP54810A), a HV probe(Tektronix P6015A), and a current probe(Tektronix TM501A) were used to measure the peak voltage and peak current. The pulsed electric discharge was generated in the electrode system of the muti-needle to plane electrode geometry located in the centre of Plexiglas cylinder (100mm inner diameter) reactor. The stainless steel needle electrode was discharge electrode and the number was 7(1.5mm tip diameter). The stainless steel plane electrode (50mm diameter) was ground electrode. They were placed on axis of the reactor and the distance between them can be adjusted according experimental need. A bubbling apparatus was fixed at the bottom of the reactor and air was used as the gas source in the experiment.
70 In the diagnostic experiment of emission spectral characteristics, we used distilled water as medium and the conductivity of liquid was adjusted by KC1. Emission spectrum was measured using SPHV 300iCCD(Acton). Acid orange II (AO7)was used in the o~C r __L obe decoloration experiment and the catalyzer was TiO2 IS ce]----q--Ce [ Bubble_Needle ~ o~176 ~10sc[ll(liJ graph [ which was rounded particles of 10nm diameter. Spectrophotometer (UVVS 2100C) was utilized for Spectrometer ] [_~_oQo~ ,3] Probe measuring dye absorption. Fig.1. Experimental System
RESULTS AND DISSCUSSION In the experiment, the gap between positive and ground electrode was 15mm. The pulse peak voltage, pulse-forming capacitance, repeated rate were investigated as influence factors to emission spectn~. Fig.2 shows the emission spectrum between 250nm and 550nm from discharge in distilled water and gas mixture. 22000
24000
20000
22000
18000
~"
337.1nm
.,0 0
"~ 14000
357.7nm
~o loooo n,
,
.[ ~
"~ 18000
iI
~ ,4000
20000
.
.
8000
6000
6000
9 250
, 300
, 350
= 400
v' AI 26k
N
8000
4000
29kV
450
Wavelen.clth/nm
I
i
500
550
,
Fig.2. Emission spectrum from discharge in liquid-gas mixture (26kV, 2.0nF, 50Hz, 100 ~t s/cm KCI, 0.8 m3/hair)
4000 300
,
i 310
,
i 320
,
i
,
i
,
i
330 340 350 Wavelength/nm
,
I 360
,
i
,
370
Fig.3 Effect of pulse peak voltage on emission spectrum (2.0nF,50Hz, 100 Lt s/cm KCI, 0.8 m3/hair)
From Fig.2, it can be seen that the light emitting from a discharge included a broad spectrum, the distribution was similar to that of sunlight and the relative intensity was high between 275nm and 380nm. The peaks in these regions are due to N2 active radicals. The main transitions of the N2 radicals generated in the discharge are: A 2~2+~ X 21-I.The A 2~ § ~ X 21-I(v= 1) transition is at 313.6nm, A 2Z +(v=0)~ X2I-I(v=0) transition at 337.1nm, and A2 ~ § transition at 357.7nm[3]. As we know, the maximum wavelength triggering TiO2 is 387nm, so this article mainly studied the relationship between characteristics of emission spectrum below 380nm and its influence factors. Effect of pulse peak voltage Fig.3 shows the emission spectrum from discharge in liquid-gas mixture when the pulse peak voltage was 23kV, 26kV and 29kV respectively. As shown in Fig.3, the relative intensity of emission spectnml became stronger with increase of the pulse peak voltage. With the voltage increasing, the average intensity of electric field also increases and then more energy is injected into the reactor. Subsequently, the number of high-energy electrons excited by electric field increases, and the probability of collision between N2 and high-energy aggrandizes. Such collisions can make more N2 transit from ground state to excitated state. Finally, when N2 transits back from excitated state to ground state, more intensity light emits from the process. This is the possible reason that the increasing of pulse peak voltage makes relative intensity of emission spectatm rise.
71 Effect of pulse forming capacitance The pulse forming capacitances selected in the experiment was 2nF, 3nF and 4nF. Fig.4 presents the results. 24000 -
26000 240O0
22000 20000
7
::J 18000
22000
4nF t~
3nF
"
70Hz
20000
50Hz
~16000 r
_r
ID
14000
~ 14000
~) 12000 _.
12000
"~9 10000 iv' 8000
8000 6000 4000
6000 4000 ,
300
I
310
=
I
320
t
I
.
I
.
330 ~ 340 Wavelength/nm
I
350
.
I
360
.
I
.
30Hz~
,
I
,
I
,
I
,
I
,
I
,
I
,
I
370
Fig.3 Effect of pulse forming capacitance on emission spectrum (26kV, 50Hz, 100 g s/cm KCI, 0.8 m3/h air)
Fig.4 Effect of repeated rate on emission spectrum (26kV, 2.0nF, 100 la s/cm KCI, 0.8 m3/h air)
The energy injected into reactor can be calculated by formula (1): W= 1/2CpfVp2
(1)
W is the total energy injected into the reactor. Cp represents the pulse forming capacitance, f is the repeated rate and Vp is the pulse peak voltage. As shown in Fig.4, the relative intensity increases with an increase of pulse forming capacitance. Formula (1) shows, when pulse peak voltage and repeated rate are invariable, the alteration of pulse forming capacitance makes input energy change. In the experiment, pulse peak voltage was 26kV, repeated rate was 50Hz and pulse forming capacitance were 2nF, 3nF and 4nF respectively, we can calculate the energy injected into reactor were 33.8W, 50.7 W and 67.6. The increasing of input energy leads to the rising of the number of high-energy electrons, and then more nitrogen molecules in excitated state were produced, finally when nitrogen molecules transit back from excitated state to ground state, more intensity light emits from reactor. Effect of repeated rate The emission spectrum from discharge in liquid-gas mixture when the repeated rate were 30Hz, 50Hz and 70Hz respectively are shown in Fig.4. The relative intensity increases with an increase of the repeated rate. As shown in Formula (1), if pulse peak voltage and pulse forming capacitance are invariable, the energy injected into reactor by one pulse is same. The change of the repeated rate just alters input energy of per second. When pulse peak voltage was 26kV, pulse forming capacitance was 2.0nF and the repeated rate were 30Hz, 50Hz and 70Hz respectively, we can calculate the energy injected into reactor were 20.8W, 33.8W, 47.3W. The increasing of injected energy finally leads to the rising intensity of emission spectnnn from discharge. Result of decoloration and discussion In order to confirm the cooperation of high-voltage pulsed discharge and photocatalysts, we designed a decoloration experiment. The dye in the experiment was Acid Orange II (AO7) and the catalyzer was TiO2 powder. The maximum absorption wavelength of AO7 solution that we got by scanning the dye solution with spectrophotometer (UVVS 2100C) was 485 nm. Spectrophotometer was used for measuring dye absorbency. The decoloration efficiency was calculated by the following formula.
l~~
X 1O0
(2)
q% is decoloration efficiency. Co and Ct represent initial absorbency and absorbency of t minute later respectively.
72 We compared the decoloration efficiencies of three kinds of processes. The three kinds of processes respectively were (~ adsorption by catalyzer, (~ high-voltage pulsed discharge, and (~ combination of discharge and photochemical catalysis. The quantity of catalyzer added into (~ and (~ was l g/L. TiO2 powder was added into the wastewater directly and the discharge started after the wastewater mixed up uniformly. And the experimental conditions in (~ were same to those in (~ except the catalyzer. Those conditions were the following: pulse voltage was 29kV, repeated rate was 70 Hz, pulse forming capacitance was 2nF, quantity of bubbling was 0.8 m3/h ,the initial conductivity of solution was 50 la s/cm, and gap between positive electrode and ground electrode was 15mm. As shown in Figure 5, the decoloration 100 efficiency was 2.0% by adsorption, 72.5% was the - - " - - catalyzer adsorption --e--discharge cooperate with catalyse final result by high-voltage pulsed discharge and - - A - - only discharge 80 91.0% was degraded by combination of discharge and photochemical catalysis. Apparently, the decoloration efficiency was improved 18.5% by 60 comparing the results of (~ and Q . The result proved that it was feasible to combine the discharge process ~9, 40 and photochemical catalysis together. The mechanism of cooperation of discharge and 20 photochemical catalysis is so complex that we will analyze and present it in other papers. I
,
0
I
10
,
I
20
,
I
30
=
I
40
=
I
50
,
I
,
60
t/rain Fig.5 Results of decoloration of three processes
CONCLUSION The experimental results were summarized as follows" 1. Pulse peak voltage, pulse-forming capacitance and repeated rate have great effect on relative intensity of emission spectrum. And the intensity increases with the rising of voltage, capacitance and repeated rate. 2. In the experiment of decoloration, cooperation of discharge and photochemical catalysis improve the efficiency from 72.5% to 91.0% by comparing with high-voltage pulsed discharge process. The absorption by catalyzer is little, only 2.0%.
REFERENCE [1] Anto Tri Sugianto, MasayukiSato. Advanced oxidation processes using pulsed streamer corona discharge in water. Thin Solid Films(2002) 407 174-178 [2] M G Stewart,LC Campbell. Application of pulsed plasma discharge to the sterilization of contaminated water. IEEETrans. Ind. Appl (1998) 2_44387-394 [3] L.J.Galance,M.Selby,D.R.Luffer,Anal.Chem (1988) 60 1370
73 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Automatic Design Of Insulation Structure In Power Transformer Yang Liu, Xiang Cui, Senior Member, 1EEE. Department of Applied Physics, North China Electric Power University, Baoding, Hebei, 071003, China E-mail: [email protected], [email protected]
Based on the finite element method, a new algorithm for evaluating the sensitivity of electric field intensity to geometric parameters is presented in this paper. By means of this algorithm, the sensitivity can be evaluated as like the nodal potential solution. Adopting the Hermite polynomial instead of the Taylor polynomial greatly decreased order number of the high-order cross sensitivity. Numerical results show that this procedure is very effective and can be used in the automatic design of the insulation structure in high voltage and big volume power transformer.
INTRODUCTION In the automatic design of electromagnetic apparatus, the optimization technique, based on derivatives, i.e., sensitivity, of the objective function, is often selected as a numerical tool. it is often hoped that an approximation function instead of calculation of the objective function and its derivatives is built in order to reduce very high computational cost due to a lot of finite element meshing and finite element equation solution. Dr. Coulomb etc. proposed a Taylor polynomial approximation of the objective function with respect to both physical and geometric parameters for the magnetic field problem. In their approximation, based on the finite element meshing only once, through calculation of the first-order and high-order derivatives of the objective function at center point, the objective fimction is expressed as a Taylor polynomial and it is used into optimization of the objective function for electromagnetic apparatus [1 ]. Obviously, in this algorithm, once the Taylor polynomial is built, there is no need to do repeated finite element meshing and solving in the optimization. Differing to the Taylor polynomial approximation, in this paper, the multidimensional Hermite polynomial is used to approximate the objective function in order to replace the finite element computation in optimization.
HERMITE POLYNOMIAL The Hermit polynomial enables us to construct an approximation of the objective function in which its values and derivatives are specified at the given points of the parameters. Thus, we divide whole region of the parameters into several small sub-regions and apply the Hermit polynomial to approximation of the objective function in every sub-region. The objective function and its derivatives at any point inside the region may be calculated by means of calculation of the Hermite polynomial at the point. Therefore, it is key to construct the Hermite polynomial. For a rectangular sub-region with two parameters, i.e., p and q, the Hermite polynomial fh(p,q) can be expressed as follows
74
f h(P, q) -- f ijcrU + f i+,,j(Zi+,,j + f i,j+,(Zi,j+, + f i+,,j+,ai+,,j+, + f i',j(p)fli,j + f i'+,,j(p)fli+,,j "]- f i',j+l(p)~i,j+l "{- Z'+l,j+l(p)~i+l,j+l 47 Z",j(q) Yi,j "~-Z"+l,j(q) Yi+l,j "~-Z " , j + l ( q ) ~ f i , j + l -~ f i'+l,j+l(q) ~fi+l,j+l "~-Z.",j(pq)JTi,j "~-s
(1)
"~-fi"j+l(pq)JTi,j+l q- Z"+l,j+l(pq)~Ti+l,j+l
where all of these interpolation functions are polynomials with six powers and have been given in some textbooks of numerical methods. The procedure of constructing two-dimensional divided-region Hermite polynomial has four steps[2]. We need the finite element meshing and solving only once at each comer point. So, only through a few times of finite element computation, the sub-region Hermit polynomials with six-order can be built in the whole region.
COMPUTATION OF SENSITIVITY It is necessary to calculate the first-order and the second-order cross sensitivities in order to construct the sub-region Hermit polynomials. As an example, we only discuss the electric field problem. In general, the electric field intensity is often selected as an objective fimction to be optimized in design of insulation structure for a high voltage apparatus. We can derive the following finite element equation of electric field without space charge distribution K (,o -
0
(2)
where (p is nodal potential vector, K is stiffness matrix. If three-node triangular element is used, K on each element can be calculated by
K~j -- ~ IJAe V N e
" VN;dxdy
(3)
where e is permittivity of medium, Ne is shape fimction of triangular element. The electric field intensity in the e-th element is expressed by
E e-
~(
e 2 Ex) +(Ey)e
2
(4)
where E~ E~ are x and y components of the electric field intensity vector in the
e-th element respectively.
One Parameter Problem Let p be a geometric parameter, the first-order sensitivity of e ewith respect to p is calculated by x =
x
bE e
Y _. __ E eY
3p
e
A e 3p
3p
OA
~0i
3p
+
2 A e i=i
e
A e 3p
1 ~ ( (~i-~-p 3c, +
b,
',
(5)
3p ci a~o, 3p 1
(6)
2Ae i=l
In (5,6), we need to calculate sensitivity of nodal potential (Pi with respect to p that may be derived through differential of (2), i.e., 3~o aK ~o 3p = _ K _ 1 -~-p
(7)
where the nodal potential vector (p is solution of (2) The matrix ate in (7) can be formed by assemblage 9
of sub-matrix -~p ate,; on the
e-th triangular element that may be calculated by
75
(8) Two Parameter Problem Now suppose that p and q are two geometric parameters to be adjusted in design. Similarly, we can also derive a formula to calculate the first-order sensitivity of g ~ with respect to the parameter q. Moreover, from (1), we can see that it is also necessary to derive a formula of the second-order cross sensitivity with respect to p and q. Based on (5,6), we have
~=~2Ee Op~kq
1 ~E e ~E e E e ~gp Oq
+
1 bEe bEe -I Eex b2Exe F 1 ~ E y E ~ ~9p ~gq E e OpOq E ~ Op
e
~Ey -! Ey e
Oq
e
E e
~2gye
(9)
OpOq
where ~2E~e and ~2Ey in (9) can be calculated from (5),(6) and (7).
~)p~)q
3pi)q
APPLICATION The automatic design of electromagnetic apparatus based on sensitivity analysis and the finite element technique has been widely used [3]. A simplified model of the high voltage winding in a 500kV power transformer is shown (see Figure 1). In Fig. 1, B is distance between the low voltage winding and the high voltage winding and R I is radius of the electrostatic ring. In the design, B may be adjusted from 65mm to 105mm and R1 from lmm to 15mm and Rz=2.0mm, H=450.0mm and S=12.0mm. For having enough insulation level, in general, the design of insulation structure needs to adjust geometric parameters B and R~ in order to assure the maximum value of electric field intensity on outer surface of insulation layer of the electrostatic ring is lower than a specified limit.
I'l
It Ii II
w ! I ! I
!
II II
i
IT,
Figure 1 Insulation structure of a 500kV transformer.
Procedure of automatic design We may set a procedure of automatic design in form of a block diagram(see Figure 2). Deterministic optimization techniques including the direct search and the gradient methods may be used in the procedure shown in Fig. 2. In this paper, the genetic algorithm is used as an optimization tool. Automatic design of electric field intensity In this design, the objective function is defined by
f(B,R,)-(E-Eo)
2
(10)
where E is the maximum of electric field intensity on the outer surface of the insulation layer of the electrostatic ring and Eo is the specified design electric field intensity. Now, we hope to obtain a design so that E0=5.60kV/mm when 500/43 kV is applied between the high-voltage winding and the low-voltage winding. Applying above procedure of automatic design based on the genetic algorithm to the design,
76 Applying above procedure of automatic design based on the genetic algorithm to the design, through computation of 6 generations and 37 seconds CPU time, we can obtain a desired design with E=5.60kV/mm in which B=83.0mm, R~=10.7mm. In order to check verification of the design, we also use the finite element method to calculate the maximum of electric field intensity that is 5.64kV/mm. The relative error is 0.71% between the electric field intensities calculated by the finite element method and by the sub-region Hermite polynomials. Therefore, above procedure of automatic design is very effective.
CONCLUSION
Dividing zagion of paxaztmtezs ixtto several ~lb-regiort~
r
,
,
Based oft finiteelemertt meslaix~
sokatioz4eakaxlatix4gvakms
and ,e~itivities of the objective foxmtio~t at all ixtterpolatedpoixtts
]
............. ~ .........
Co~tzuctiz~ suh-zeNrt gezxrtite polyxaoaxd~ of the objective Fur~tion
Gi~
.
.
.
.
.
.
.
.
.
.
.
.
a ~peeif'md objective valtm
and initial desi~ of the paxametez~ Calculatiz~ the objective fiaxtctiort by r~az~ of sah-regiortHermite pol3rnomiaJs
I opt~tioxt tec~
to obtain a new desigrt
Based on the finite element method and sensitivities No of the nodal potential to geometric parameters, the first-order and the second-order cross sensitivities of the electric field intensity to geometric parameters are derived for triangular element. The sub-region Hermite polynomials with two Figure 2 A block diagram of the automatic design geometric parameters are constructed to approximate the objective function. By means of the sub-region Hermite polynomials and the genetic algorithm, we may set a procedure of automatic design to adjust geometric parameters. Numerical results show that above formulations and procedure are very effective to the automatic design of the insulation structure in a high voltage and big volume power transformer.
ACKNOWLEDGMENT This work was supported in part by the Chinese Special Scientific Research Foundation of Doctor Degree in Colleges and Universities(No.98007901) and Youth Research Fund of North China Electric Power University(No. 09320027).
REFERENCES 1. Coulomb J.L., A methodology for the determination of global electromechanical quantities from a finite element analysis and its application to the evaluation of magnetic force, torque and stiffness, IEEE Trans. Magn (1983), vol. 19, no. 6, 2514-2519 2. Yang Liu, Xiang Cui, Sensitivity analysis of electric field intensity to geometric parameters in shape optimization, Proceedings of the Fourth International Conference on Electromagnetic Field Problems and Applications, Tianjin, China
(2000), 230-233 3. Xiang Cui, Guoqiang Zhang, Sensitivity analysis and automatic design of voltage ratio in an optical instrument voltage transformer, IEEE Trans. Magn.(1999), vol. 5, no. 3, 1769-1772
77 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Influences of Annealing Method on the Space Charge Properties in LDPE Wang Ninghua l, Zhou Yuanxiang I, Liu Hongbin l, Gao Bin 1, Liang Xidong 1, Guan Zhicheng l, Tatsuo Takada 2 ~. State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering, Tsinghua University, Beijing, 100084, China 2. Electronic Measurement Laboratory, Musashi Institute of Technology, Tokyo, Japan, 158-8557
Abstract: In this paper, low-density polyethylene (LDPE) films were prepared by three kinds of annealing methods which were different in cooling velocity. The crystallinity of the LDPE samples were measured and compared. Surfaces of samples were observed. Higher cooling velocity results in lower crystallinity. High DC negative voltage was applied on the samples, and then samples were open-circuit. Space charge formed in samples was measured during above procedure. The space charge properties were discussed based on cystallinity and morphology. Key words: Space charge, annealing, LDPE, morphology
INTRODUCTION When a voltage were applied on insulating materials with enough electrical strength, space charge will appear and accumulate in the material. Space charges in materials is well known to distort the local electrical fields and affect high-field conduction and breakdown phenomena ~' 2j. So a large number of studies have been made on space charge storage properties of insulating materials to explain and improve the electrical properties of materials. Polyethylene (PE) is a kind of semi-crystalline polymers which is widely used in power cables and wires. Space charge can form in calbes during the cable is in services and routine DC high voltage test. Those space charge is very bad for life of cables. With the change of annealing conditions, the morphological microstructure of polyethylene changes t31. Some electrical properties of PE, such as tree phenomena and elctrical conduction, are influenced by morphology of polyethylene t3-sj. In this paper, three kinds of annealing methods were used in the preparation of LDPE samples to make the samples different in their morphology. Cystallinity of samples were measured and discussed. Space charge formed in samples on DC high electrical filed were measued and analysed. EXPERIMENTAL Sample preparation and treatment Morphology of PE samples in experiments can be controlled by annealing condition E~, 4]. In this paper, three kinds of annealing methodswere used. The raw material used in this experiment was pellet LDPE made by some company in China. Pellet samples were laminated between two pieces of cover glasses. They were pressed using a 5 kg steel block, and kept at 180 ~ in a oven for 20 min to make samples melt. Then films with about 100 ~tm thickness and about 40 mm diameter were cooled respectively in low velocity (cooled with hot
78 steel block together), normal velocity (cooled in air) and high velocity (cooled in ice water). The three kinds of cooling velocity were respectively about" 0.03 ~ 10 *12/s and 50 ~ Morphology Olympus microscope CX 40 and Sony digital camera F717 were used to observe samples surfaces and take photos. The crystallinity of all the three kinds of samples was measured and calculated by Fourier Transform Infrared (FTIR) technology. Space charge measurement Pulse Electro-Acoustic method (PEA method) was used in space charge measurement [61. The principle of PEA method is shown in Figure 1. In a PEA system, an externally applied pulsed electrical filed is applied to the sample and induces a perturbation electrical force on sapce charge in sample. This force causes the space charge to move slightly in its position. And this movement lunches an acoustic pressure wave. The wave is collected and analysed to get the space charge profile in the sample.
Fig. 1. The basic theory of PEA method
Experiment procedure Samples were put into PEA system. DC negative high voltage and 1 kV pulse voltage were both applied on samples. Aluminium was used for earthed electrode and semi-conductor was used for high voltage electrode. The DC electrical filed was in a range from 40 kV/mm to 70 kV/mm. The voltage was applied on samples for 1 hour and then the DC voltage was cut off and the two sides of samples were open-circuit for 10 minutes. Space charges formed in samples were measured during the above procedure. Silicon oil was used between electrode and sample to make good contact and to be acoustic couplant. RESULTS Annealing effect on morphology Figure 2 shows the photos of surfaces of three kinds of samples which were cooled in different velocity. It is clear that lower cooling velocity results in bigger spherulites. Crystallinity of samples was measured and calculated by Fourier Transform Infrared (FTIR) technology [7]. Figure 3 shows the difference of crystallinity of three kinds of LDPE samples. Lower cooling velocity results in higher crystallinity.
Fig. 2. Photos of samples which were cooled in: (a) high velocity; (b) normal veiocity; (c) low velocity Space charge properties For one sample cooled in high velocity, 60 kV/mm electrical filed was applied on it for 1 hour and the space charge formed in sample is showed in Figure 4. Then the two sides of sample was opencircuit for 10 min. Space charge profile in the open-circuit procedure is showed in Figure 5. In Figure 4, there are two peaks at the two interfaces of samples respectively. Peak at the interface is composite of interface charge and space charge near surfaces. In Figure 5, homo-charge can be found near surfaces.
79 o
AI+
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o
55%
t~
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.,.q
o. 0002 .=. ~45%
CD laO M
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o |
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~
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~
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0
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,
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|
High
-0. 0002
Normal Low Cooling Velocity
[
Fig. 3. Crystallinity o f three kinds o f L D P E samples
'0
Thickness(~tm)
6 0 mm O i ni n ]
Fig. 4. Space charge profile in a s a m p l e w h e n 60 k V / m m electrical filed w a s a p p l i e d on it.
Figure 5 shows the difference of 1 min and 10 min after sample was open-circuit. In samples cooled in normal velocity or low velocity, this difference was much bigger than the sample cooled in high velocity as shown in Figure 6. The sample in Figure 6 was cooled in low velocity in its preparation. AI+
0.0001 o.oooo8 0.00006 0.00004 0.00002 g o ~ -0.00002 -0.00004 -0.00006 -0.00008 -0.0001
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0 0 0
! I !
0 0
I I I
!
0
}
0.0001 0.00008 0.00006 0.00004 0.00002 g 0 -0.00002 -0.00004 -0.00006 -0.00008 -0.0001
0
:
I
AI+
~m o o
120
~ 1
Thickness0tm)
10
Fig. 5. Space charge profile in a sample 1 hour later than a 60 kV/mm electrical filed was applied on it. (The sample was cold in high velocity in its preparation.)
min
SC-
0
!
0
!
,I
:
!
!
:-._...! o
! !
,
:
:
,
! 0 0 !
! ! 0
120
0 ]
Thickness(pro)
min
Fig. 6. Space charge profile in a sample after 1 hour later than a 60 kV/mm electrical filed was applied on it. (The sample was cooled in high velocity in its preparation.)
In Figure 6, hetero-charge was found near cathode which is very different to Figure 5. And for samples cooled in normal velocity, it's found near cathode, there is maybe homo-charge and maybe hetero-charge also. DISCUSSION Figure 7 shows amplitude of charge density near anode just when the voltage was applied on the sample with different electrical filed. It's found that the amplitude of space charge increases with the increase of strength of filed increase similarly linearly. For all three kinds of samples, most samples had homocharge near anode. So it's more convenient to compare the amplitude of charge density peak near anode than that near cathode. Figure 8 shows this relationship. 0. 0005 O. 00045 o 0. 0004 O. 00035 O. 0003 .,-4 th = O. 00025 O. 0002 9 0.00015 0.0001 0.00005 [ 0
0.00005 A v
a
~[] O
--'4,'-b A c
"-"
=O
0.00004
a
---I1--- b
A
0.00003
c
0.00002 0.00001
i.
0 - -
30
I
40
,
_1___
I
5~kV/mm~0
-0.00001
i
70
80
Fig. 7. Amplitude of charge density near anode just when high voltage was applied on samples. In their preparation, The samples were cooled in: (a) high velocity; (b) normal velocity; (c) low velocity
.
30
40
.
.
.
.
50 60 (kV/mm)
70
80
Fig. 8: Amplitude of charge density in sample near anode after I hour high voltage applying and I 0 rain open-circuit. In preparation, samples were cooled in: (a) high velocity; (b) normal velocity; (c) low velocity
80 It's very interesting to find in Figure 8 that the amplitude of charge density near anode decreases with increase of electrical field. Figure 8 also shows charge density near anode in samples cooled in high velocity was bigger than the other two kinds of samples. It is said that the electrical properties in amorphous region is weaker than in spherulites. So we presume the lower crystallinity results in the higher amplitude of space charge for samples cooled in high velocity in Figure 8. Figure 6 and other experimental data shows space charge of samples cooled in low velocity and normal velocity decays much faster than that of samples cooled in high velocity. It means much shallow trap exit in samples cooled in low velocity and normal velocity. Because of the rejection effects during the process of crystallization, more and more impurities and uncrystallizable polymer molecules will be settled outside the transcrystals, simultaneously ts]. The electrical properties in amorphous region is weaker than in spherulites, and further more, the electrical properties between spherulites in polymer with higher crystallinity is weaker than that with lower crystallinity. But the trap corresponding to that area between spherulites is shallow trap. It's easy to fall into shallow trap, but it's also easy to run out of shallow trap. So in experiments, samples with high crystallinity had faster charge decay rate.
CONCLUSION (1) Annealing method influences morphological microstructure of LDPE samples. Higher cooling velocity results in lower crystallinity. (2) In general, after 1 hour applying high voltage and 10 min open-circuit, more space charge exits in samples cooled in high velocity than the samples cooled in normal and low velocity. (3) Due to the high crystallinity, in samples cooled in low velocity, space charge has faster decay rate.
ACKNOWLEDGEMENT These authors are very grateful to National Natural Science Foundation of China for financial support of the research project NSFC 50277023 and NSFC 50347010. This paper is also supported by the Basic Research Foundation of Tsinghua University coded JC2001020 and "Chunhui" Project of the Ministry of Education. REFERENCES 1 T. Mizutani., "Space charge measurement techniques and space charge in polyethylene," IEEE Tran. On Dielectrics and Electrical Insulation, vol. 1, No. 5, pp. 923-933, 1994 2 T. L. Hanley, R. P. Burford, R. J. Fleming and K. W. Barber, "A general review of polymeric insulation for use in HVDC cables," IEEE Electrical Insulation Magazine, vol. 19, no. 1, pp. 13-24, Jan/Feb. 2003 3 Y. Zhou, X. Wang, P. Yan, X. Liang and Z. Guan et al., "Annealing effect on the morphology of polyethylene materials and the tree initiation voltage," 2001 Annual Reprot Conference on Electrical Insulation and Dielectric Phenomena, CEIDP2001, Kitchener, Canada, pp. 241-244, Oct. 14-17, 2001 4 P. Yan, Y. Zhou, G. Sun and N. Yoshimura, "Influence of morphology and thermal stability on tree initiation in polyethylene films," 2001 Annual Reprot Conference on Electrical Insulation and Dielectric Phenomena, CEIDP2001, Kitchener, Canada, pp. 249-252, Oct. 14-17, 2001 5 Y. X. Zhou, N. H. Wang, P. Yan, X. D. Liang and Z. C. Guan, "Annealing Effect on DC Conduction in Polyethylene Films, " J. of Electrostatics, vol. 57/3-4, pp. 381-388, Mar. 2003 6 Y. Li, M. Yasuda and T. Takada, "Pulsed Electroacoustic Method for Measurement of Charge Accumulation in Solid Dielectrics," IEEE Tran. On Dielectrics and Electrical Insulation, vol. 1, no. 2, pp. 188-195, Apr. 1994 7 K. Teranishi et al., "Studies of the Branching and the Crystallinity in Polyethylene bu Infrared-Method", Kobunshi Kagaku, vol. 23, pp. 512-520, 1966
81 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Magnetic Field of Long Straight Current-Carrying Wires with Discrete Distribution Honglian Li, Lifei Li, Xiaoting Li, Zhonghua Zhang Supervision Institution of Quality and Technology, Hebei University, Baoding 071002, China
This paper built a theoretic model based on the logarithm transform function. The vector magnetic potential A of long straight current-carrying wires with discrete distribution is calculated using the model. Based on this model, the value of A at any dot is further gained by numerical calculations. Thus, the distribution figure can be obtained, demonstrating the relation of the magnetic field of the wires. This also displays the distribution of main magnetic flux and the leakage flux. Furthermore, the equations of magnetic-curve boundary and the position of the boundary on the axis can be calculated theoretically on the model.
INTRODUCTION The applications of Long Straight Current-Carrying Wires with Discrete Distribution (LSCCWDD) are very popular in practice [1, 2]. The analysis and numerical calculation on the magnetic field of LSCCWDD in theory is still not sufficient although many different techniques, such as image method [3], the Biot-Savart law [4], Stokes's theorem [5]and so on, have been used to calculate the magnetic field in the past years. Therefore, we are trying to develop a more accurate and convenient method. In this paper, we report on modeling the magnetic field of LSCCWDD based on the logarithm transform function, which comes from complex function [6, 7].
MODEL The outer magnetic field can be considered as a two-dimensional field since the current density out of LSCCWDD is zero, and its vector magnetic potential A satisfies the Laplace equation. The vector magnetic potential A of any dot has the same direction that points in z-axis, as shown in Figure 1. Thus, a theoretic model is built based on the logarithm transform function. Here, a complex function is defined: z Y
-7
27
Figure 1 LSCCWDD is arrayed in the direction of x-axis, and A points in the z-axis
~(2) =
-ll~ ~Ln(z + nd)+r 2Ic ,=_~
(1)
Where z is a dot in complex plane, n is the total number of wires and d is the distance between the two adjacent wires. The real of ~ is A, i.e. A = Re ~ . In order to simplify (1), we invoke the equation"
82
1
n=l n 2 .--
=
a2
111
2a
-
]
~'cot(,~)
And we have"
llo I ~-,Ln(z+nd)+~o = ltOI Id z ~ ~(z)
- -
2--~-,,=~
-
2---~
,,=_~ z +
1 = - / / ~ Ln sin nd 2,n"
+ 9"o
!
To make it simple, assume go - O. Thus, we have:
~"~
=-
,,i sial7) 2-7
The outer value of the vector magnetic potential:
Ao,,, - R e ~ - -
]lnsin()l
(2)
2----~-
SIMULATION For a random dot z in complex plane, if z = x + iy is inserted to Eq. (2), the following equation can be obtained:
out
--~
2zc
d
d
(
+ cos
d
sh
d
(3)
Figure 2 The magnetic field of long straight current-carrying wires with discrete distribution The locus of A which have the equivalent value is magnetic-curve [8]. If the left part of Eq. (3) is considered as a referential variable, Eq. (3) is the equation of the magnetic flux density B. Thus, the distribution figure as shown in Figure 2, which demonstrates the relationship of magnetic field of LSCCWDD, can be gained.
DISCUSSION The equation of magnetic-curve boundary can be obtained through further analysis on the model, and the position of boundary on the axis can be calculated theoretically. All the results are presented directly in the figure, containing the apparent distribution of main magnetic flux and the leakage one. Assuming Eq. (2) equal 0, the boundary can be derived from it: sin(d)l - 1
(4)
83 From Eq.(4), it is found that the boundary lines are determined by the distribution of the wires, and independent with L If insert z - x + iy into Eq. (4), the equation of magnetic-curve boundary in complex plane is as follows: [sin(d] Ch(d3] 2 + [cos(d ) Sh(dJ]2 - 1
(5)
Then, the equation of the intersections where the magnetic-curve boundaries cross x-axis is: sin(~)-_+l So the intersections are: x - (+ n + l ) d ,
n - O,1, 2, 3A A
(6)
The equation of intersections where the magnetic-curve boundaries cross y-axis is" sh(d~-~) = +1 y - + ln(~f2 + l)d - +O.28d
(7)
CONCLUSION In this paper, a theoretic model is presented for calculating the magnetic field distribution of LSCCWDD, and the simulated results are as expected. Moreover, our calculated results are consistent with those from the simulation. This work is very important to calculate the leakage flux and leakage inductance, and is instructive for the design of circle curls, such as choke, induction regulator.
ACKNOWLEDGMENT This work was a sub-project of <2002DEA20015> carried out under the support national science and technology ministry.
REFERENCES 1. Fawwaz T. Ulaby. Fundamentals of Applied Electromagnitics [M]. Beijing: Science Press and Pearson Education North Asia Limited, (2002), 47-64. 2. Kraus, Fleisch. Electromagnitics with Applications [M]. Beijing: Tsinghua University Press, (2001), 123-130. 3. Nathan Ida, Joao P.A. Bastos. Electromagnetics and Calculation of Fields [M]. Springer-Verlag New York Berlin Heidelberg, (1999), 123-135. 4. Yulan S., Calculation of magnetic field distribution of an infmite current-carrying ribbon. Journal Harbin Univ.Sci.&Teeh.[J], (1998), 3(2): 104-106. 5. Zaijun W., A discussion on curl of the magnetic field on an infinite long straight line with a steady current and the application of the Stokes Formula [J]. College Physics, (1996), 15(2): 24-26. 6. Chufang X., Kejin R., Electromagnetic Field and Electromagnetic Wave [M]. Beijing: People's Education Press, (1979), 179-188. 7. Jiarong Y., Complex function [M]. Beijing: Higher Education Press, (1992), 33-36. 8. GuangzhengN., Principle of Engineering Electromagnetic Fields [M]. Beijing: Higher Education Press, (2002), 128-146.
84 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Research on Back Corona Physical Model on Deposited Dust Layer of collecting Electrode Sun Keping, Li Xuewen Research Section of EMC and Electrostatics (Box l 119), Shanghai Maritime University 1550 Pudong Dadao Road, Shanghai, 200135, China, E-Mail" [email protected]
Abstract: This paper, based on resistance-capacitance model of dust layer, presents a surface instantaneous voltage equation of layer and its influential factors. Keywords: back-corona; dust layer; model; precipitator
INTRODUCTION As is known, back corona, which decreases flash-over voltage, as well as increases working space current, not only makes dust-collecting efficiency reduce obviously, but also influences steady operation of static dust precipitator tremendously. Back corona becomes one of the obstacles baffling dustcollecting stable operation. Moore illustrates the conditions of generating back corona [ 1], but he does not discuss the properties of current and voltage related to back corona in detail; Although Bohm deduce instantaneous expression of the depth of dust layer [2], he doesn't discuss it further. Most scholars lay emphasis on the research for restrained technology of back corona, while they intentionally avoid discussing the physical process of back corona. Starting from resistance-capacitance model, this paper intends to present surface instantaneous voltage equation of dust layer and its influential factors in order to deal with back corona including its generation, development and influence.
MODEL Let us presume t indicates specified moment at random, so an elementary area on the dust-collecting electrode is covered with deposited dust layer whose thickness is 1. Within dt moment, the thickness of deposited dust layer steps up dl. Supposing the elementary area equals ds, the current of the elementary area received will consist of two parts, that is the current density Ji of free ion and the current density J p carried by charged dust. Therefore, the current of elementary area can be indicated as"
dI
= Jids + Jpds
(l)
Assuming for which q express electric quantity transferred by newly deposited ion of dust layer in unit volume, the second current density Jp above can be estimated from
qdsdl dl Jp = ds----~=q-~
(2)
The substitution of (2) into (1) gives
dI = (J~ + q d-~l.)ds at
(3)
85 The electrical property of dust layer can be modeled into a shunt circuit by using a resistance and a capacitor, as is shown in Figure 1. ~_ds ~~, C.
l
t
~~
I
I'
glm
I I I I
Tci I'
1
! ! I !
i-I
Figure 1 the equivalent circuit of dust layer Where p~, er represent resistivity and relative dielectric constant of dust layer respectively. Applying puande r to (3) the following equation can be obtained: dI
(4)
u + C du : uds = e oe r dsdu du R dt p.l l dt
Where u represents surface voltage of dust layer. From equation (3) and (4), it can be easily deduced that du dt
u
§
-
dl l(J, + q -") dt
p~g~g o
(5)
=0
8og r
Suppose the approximate expression of l (the thickness of dust layer) to t (time) obeys the fundamental relationship [2]" l-
U [l_exp(___t)l_k[1
exp(_ t ) ]
(6)
Where U is the power-supply voltage of precipitator; J is the current density of inner dust layer (A/m2), "z',, is time constant during the dust layer deposited. Substituted (6) into (5), the result of integration of t is kq "l',,
u - k exp[-
t
kq Ji
] + kp~ {J~ +
Pveoer
exp(--L) l_PveoSr
r,,
z',
exp(- 2t) }
l_2PvSoS~
g'u
(7)
~,
"fu
Where k is integral constant. From entry condition ( t - 0 and u - 0), the value of k can be estimated, then, using the value of k in equation (7), the above equation is reduced to u _ kp~{J,[l_exp(_t)]+
'~"e
kq-Ji~, '~t't,t -- ~'e
[exp(_t)_exp(_t)] 'Z'u
Te
kq "/'u -- '~'e
[exp(_2t)_exp(_t)] } 'flu
(8)
~'e
is the time constant which features the electrical property of dust layer, that is ~'e -- PvEo~r It is only when internal condition and external condition, make the potential of dust layer increase to the extent that gases contained in dust layer generate ionization and form partial discharge, the so-called back corona occurs. When positive ions emitted by back corona are driven by electric field, these positive ions enter into working space of dust collection, where they will certainly meet negative ions, thus interfere the normal work of precipitator. Where
'~'e
DISCUSSION From equation (8), we can see that there are many factors that affect surface voltage of dust layer. This is the reason that back corona can't be restrained easily and is even more difficult to forecast. What's more,
86 complicatedly back corona is both a physical process and a chemical process, because it not only includes discharge process and recombination process of ions, but also accompanies chemical reaction as well. Back corona, whose generation, development and result (namely its effect) are under the influences of internal factors and external factors, is influenced mainly by two internal factors. 1) As far as back corona is concerned, the resistivity of dust layer plays a decisive role. Besides z'~ is direct proportion to p~, u is also proportion to Pv. That is the reason why the higher special resistivity of dust frequently occurs to back corona. As to resistivity of dust layer, whether it attains critical value of generating back corona or not, some scholars consider it as 108f2, others deem it as 109f~, even much higher. There is no unanimous conclusion. In the author's opinion, a key point lies in the resistivity of dust layer is not a solely decisive factor which makes back corona occurred. 2) r e (Time constant of dust layer) also influences back corona tremendously. During the course of deduction, as is pointed out, the equation ~'e- tOv~oEr is simply the approximate expression. In fact, because it is inevitable that the dust layer contains bubbles or gas layer (that is just one of conditions generating back corona), therefore, ~'e should be related to the thickness of gas layer, gaseous component, shape and structure of the layer. External factors mainly include applied voltage (from the equation k - %
we can see that k is vJ~
direct proportion to U), waveform, current magnitude, current attenuation caused by suspending particle, temperature of gases and deposited dust layer. Synthetic factors involve 7:~(time constant of the process of forming dust layer). It is related not only to property of dust layer (thickness 1, size distribution of dust Pv, J relative ion electric charge), but also to electrode gap, collection area and shape factor.
REFERENCES 1. Moore, A.D., Electrostatics and its applications. New York: Elsevier Scientific Company, 1981 2. Bohn J., Electrostaticsprecipitators. Prague: SNTL Publishers of Technical Literature, 1982
87 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Physical Model of Dielectric Function and Radiofrequency for NaCI Solution and Application of the Seawater Xu yuan l, Tang Shu Pian 2, Yan Chen Guang 2, Tang xun 3 College of Sciences, Hehai University, Nanjing, 210098, China, e-mail" xuyuanl 915@ 163.com 2 College of Sciences, Hebei Science and Technology University, Shijiazhuang 050054, China 3 College of traffic and oceanography, Hehai University, Nanjing, 210098, China
Abstract: In this paper, based upon Debye theory, we establish a physical model of Dielectric Function for NaC1 solution. We suggest that the natural frequency is plasma oscillation frequency for NaC1 solution, and that ionic polarization in solution is considered as average effective polarization. The results application of the Seawater, the physical model provided a better agreement in comparison with the exiting models (experiments). Keyword: Debye theory; NaC1 solution; polarization; dielectric constant; plasma oscillation frequency; conductance; relaxation time.
INTRODUCTION There are ionized material in sea, river and atmosphere. The movement of this material would produce electromagnetic waves. The investigations and experiment show that waves can be measured. We think that electromagnetic waves are related to the quality of liquid. The objective is to establish a physical model through electric character of liquid. We chose the solution of NaC1 for research, so we can apply our results to seawater. Based upon Debye theory, the solution dielectric function is given by as e (v,T,S) - e. +
Es --E.
1+ j 2 ~ r v
+j
~
2xve 0
(1)
there e depends on frequency v, liquid temperature T, and NaC1 density S. v is the radiation frequency, e .(T, S) is the dielectric constant at infinite frequency, e~(T, S) is the dielectric constant for zero frequency (i.e., the static dielectric constant), and z'is the relaxation time. The last term accounts for the conductivity of the solution. In this term, o(T, S) is the ionic conductivity of dissolved NaC1. Our goal is to obtain physical analysis for ~(T, S), &(T, S), o(T, S) and z(T, S) as functions of T and S in the Debye model. With these functions, in theory, one can then calculate e(v, T, S) for any value of v, T and S in the physical significance ranges.
THE ELECTRIC MODEL OF NACL SOLUTION By chemical principle in the solution of NaC1, Na and C1 appear respectively in ionic form. Na + ion does not combine with OH-ionized from water; similar, Cl-ion does not combine with H § ionized from water either. Therefore, ionization equilibrium of water is not affected, the solution present electric neutrality. For that ionic polarization in solution is considered as average effective polarization. On the other hand, so long as an excess of charge appears in small sphere for internal the solution of NaC1, the excess will produce a collective oscillation of electrons. The trend, Na § ion and C1- ion maintain the
88 macroscopic electric neutrality. Therefore we can regard Na § ion and C1- ion in the solution as plasma oscillation.
THE DIELECTRIC CONSTANT OF NACL SOLUTION Through Clausius-Mossotti formula we can obtain with/~-/3/3e 0 ,then: 6Noct - 1
1 = ~ ( N e l O t e , + Ne20te2 + N,a,). eNoct + 2 3e 0
(2)
where ael, ae2 is respectively the electric polarization for Na+and Cl-ion, a~ is ionic polarization N is the number of ion-pair, E mean external electric field.
Static Dielectric of NaC1 In formula (2), by practically measure, the electric polarization of Na+ion is Cte~=0.22x 10"4~ 2, the electric polarization of Clion O~e2=3.83x104~ F'm 2. The two different electron polarization can be established. From Debye sphere model, we know, when a group electron drift relatively a distance x on ions, the electric field E = ~ (nex) can be yielded, n is the number of ion in unit volume. As no external magnet field effect, the equation of motion per electron is d2x ne e2 me~ =--~x, dt2 s there me is electron mass. The oscillating angular frequency I
(nee2) ~ meEo
co-2n~, o is equivalent to ionic polarization, ai. =e2/ke, ke = moo 2, where m is effective mass, natural frequency of plasma oscillation in NaC1 solution:
2nie2) l I
O)pi
(3)
miEo
--
By the sense of physics, N~l = Ne2--Ni =/Ve. Dielectric constant in the solution of NaC1 is ENaCt--1 = Ne (O~'el+/~e2 +~')" e'N~ct + 2 3eo On the other hand, the solution for motion equation of electron is x(t) - a cos(co t + O) x'(t) - v(t) - -acosin(co t + O)
there Vm=aO), a is the amplitude for electric oscillation, we think a=AD, i.e., amplitude of oscillation will be equal Debye length. Thus, on the assumption that electrons move in the characteristic thermal velocity(kT/me) ~, so k is Boltzmann constant. The time taken that electron accomplish the motion of a Debye length is: !
--~
\m e
1
'
,v~D -
Be e2
,
the dielectric constant of NaC1 solution: !
enact - 1 +2
e 2 (kTel-2) Ne + OCe2 + 3e0 --e, mGt, moj
(4)
89 High Frequency Dielectric constant of NaC1 Solution When electromagnetic wave propagate, and co >cop, is the oscillation pulsatance for dielectric plasma. In this case, wave number k-+
1-
N~q_____~ 60mo) 2
is real, and the phase of electric/~ and magnetic/1vector for electromagnetic wave is same. Thus c~ - 1 - NZ2 e 2 = 1 _ a)~ E o m CO2
(.0 2 "
(5)
the solution of NaC1, ion is in quasi-free state, each ion on which energy level is probabilistic, and the transition appear continuously through inter-collision and interaction with electromagnetic radiation. After thermal equilibrium, the number of ions on each level is in accord with Boltzmann canonical distribution u0
N-
NNacte '~.
At high frequencies that are near optical frequencies the ionic polarization is too sluggish to allow effective ionic polarization to contribute to &. Thus, relative dielectric constant & at optical frequencies, is given by coo - 1 = __1 (O~,el+ e~ +2 3e0
6ge2)Njvacte-,~.
(6)
Where v is the jump frequency, Nmct molecule number in unit volume.
CONDUCTIVITY OF NACL SOLUTION In solution NaC1 is dissociated into Na § and C1- ion. Since thermal oscillation of molecule, NaC1 molecule can be dissociated the positive and negative ion, Na § and C1-; on the other hand, the dissociated positive and negative ion, Na+and C1- recombine also into NaC1 molecule. In a liquid, the dissociation and recombination process is dynamical balancing' NaC1 = Na++ C1-. The distances between Na and C1 atomic cluster depend upon total molecular energy, energy of thermal vibration for molecule is satisfied with Boltzmann distribution, the effective vibration number produced the dissociation is v~exp~-"~kr) in unit time. Suppose the density of molecule (NaC1) is NO, the rate of dissociation for molecule, i.e., the molecule number N dissociated in unit time is Ua
N = Novoe 2kr.
(7)
When Na § and C1-ion recompose into NaC1 molecule, the rate of composite z depend on the density nN~ and nct ofNa+and Cl-ion, z=~ nNa nct, ~ is the composition coefficient. In liquid-medium, ~-3.24x10lZm3sl, as monomolecular dissociation, nNa=ncFno, under the dyna- mic equilibrium, the dissociation and recombination rate for molecules is same, N=z, no - i n y~:~ e 2kr. u~
(8)
If ionic density is no, the ion is considered nearly as thermal vibration in six directions of three perpendiculars. Since transition probabilities of ion in each direction are same, it can be considered, as that ionic density of possible transition should equals" n_
no
6
U0
-~.
Voe kr
(9)
90
under the action of external electric field, the ionic over mobility in the direction of electric field is uo
Au
An - n~ Voe-k--i[eTf 6
Au -e-k-Y].
Under the action of weak field, Au<
An= no ~O(2Au~ noq Sv ~ ~o 6 v~ e--fiE,
(10)
where 8 is mean transition distance, q ionic charge, v 0 ionic oscillating natural frequency, no ionic density, u0 the average potential energy surmounted ion transition in liquid. Thus, the ionic macros- copic average drift speed v in the direction of electric field is: An q 6 2Vo -u--z~ v = ..... 6 = e krE. no 6kT
In the solution, impurity ionic electric conductance is principal, the ionic macroscopic average drift speed should have a coefficient depended T. Thus j = n o q v = n~176
cr
6kT
neVo q2~2
,rE _
~
~-~
T
oe
-~-
e
~r
E, cr =
the ionic specific conductance
0.= j_~neVo q282 /T_~ .o -E
~
6k
~To ve
..
*re 2kr
(ll)
THE RELAXATION TIME The relaxation process is the transition of ions from non-equilibrium to equilibrium. The relaxa- tion time indicate the process going on fast or slow. The effect of collisions between Na+and C1- ion the range of the critical radius are Debye length 2D, the can be regarded as upper limit of collision parameter. Here the collision is Coulombian; a kind of them is near impact (back-scattering), the mean value of collision for Maxwell distribution is Z, Z2e 2. _ ZlZ2e 2 (bo) - 4n'eo~2 (v22) - 4~reoKr = 2 t.
(12)
-(t) _ R.~2 The near collision cross-section can be regarded as ff~2,, The other kind is far collision; the collision parameter is in the range of(b0)
o'(t)12,f -- 2]~
~~)bdb
- ~(A 2
- (b0)2).
Comparing two kinds of collisions and taking account of 2o >>(b0), we can have -1--
,zo
=A
91 102
!
,
,
|
,
,
|
"", ~ '~,~
|
102
,
|
|
,
!
|
~',
,
|
|
,
Tang
Tang Klein & Swift Ellison
............. Klein & Swift Ellison
101
I0 t
I
10
I
20
I
30
I
I
I
40 50 60 Frequency (GHz)
I
70
I
80
I
90
100
Figure 1. Real part of the dielectric permittivity (function) of liquid versus frequency at 25~
I
10
I
20
I
:30
I
I
I
40 .50 60 Frequency (GHz)
I
70
I
80
I
90
100
Figure 2. Imaginary part of the dielectric permittivity (function) of liquid versus frequency at 25~
THE CONCLUSION APPLY TO THE SEAWATER Such as above we have an ideal physical theoretical model. In seawater, NaC1 is major ingredient of the seawater, so our conclusion can apply to it. Put formula (3),(4),(5),(11),(13)into formu- la(1), we have curved line presented in Figures by continuous. A comparison of our permittivity functions with KleinSwift [~] and Ellison [2] models is in Figures 1 and 2 by dashed line. The dielectric constant e; as given by our physical model, is actually large than Klein-Swift's prediction by 5% at 10GHz and 25~ 1% at 20GHz up to about 50GHz and 25~ The dielectric loss factor e " estimated by the physical model is consistent with Klein-Swift's estimation up to 100GHz (within 5%) whenever but is substantially large than the Klein and Swift prediction in warm sea condi-tion, from about 17% at l 0GHz, about 5% at large than 30GHz. So the application of plasma model achieved satisfied result. The physical error between the theoretical and practical results is probably differences of chemical compositions in liquid.
ACKNOWLEDGEMENT This work was supported by the fund of scientific and technical creation of Hehai University.
REFERENCES 1. L. A. Klein, and C. T. Swift, IEEE Trans. Antennas Propag., AP25(1),(1977) 104. 2. W. Ellison, A. Balana, G. Delbos, K. Lamkaouchi, L. Eymard, C. Guillou, and C. Prigent, Radio Sci. 33(3), (1998) 639.
92 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Theoretical and experimental study of the electromagnetic field generated by ESD* B i Zengjun, Liu Shanghe ~, Yang Jiangping Air Force Radar Academy, Wuhan, PR. China 1Shi Jiazhuang Mechanical Engineering College, Shi Jiazhuang, PR. China
In the paper, electromagnetic field radiated by a thin wire with ESD current injected is studied theoretically and experimentally. A numerical model of the field distribution is established using FDTD method and characteristics of the radiation field are analyzed after calculating. The results show that the radiation field generated by the thin wire with ESD current injected is a kind of oscillation field and is far stronger than that generated by ESD spark at the same condition and the calculation results obtained by FDTD method are in agreement with the experimental results.
INTRODUCTION With the development of modem electronic technology, electronic systems become more and more integrated, mini-sized and low power waste. While functions of the electronic systems are enhanced, they become more and more sensitive to electromagnetic interference and very low over-voltage and energy can cause them work abnormally and even damaged [1]. Electrostatic discharge (ESD) is a familiar harmful electromagnetic source and the transient radiation field generated by the initial heavy current pulse with fast rise time and short duration time during the discharge process can cause interference and damage to circuits. Thus, to study the characteristics of the electromagnetic field generated by ESD is very significant to further study the relevant electromagnetic protection measures.
THEORETICAL STUDY OF THE PROBLEM When ESD current is injected into a thin wire with small dimension, it can be seen as a dipole model and studied using analytical method for the uniform current distribution in it [2]. But for a thin wire with large dimension, the current distribution is complex z and numerical method can be easily used to E (i a + 1 k a + 1) x 7 'j~' solve this kind of problem. Finite-Difference Thin wire Time-Domain (FDTD), presented by Yee in 1 1966 [3], is one of the numerical method to Ez(i a +l,jJa ,ka + ~) E (ia,Ja,k a +1)=0 | solve electromagnetic problems, especially z H (i + & Ja ka ) y a 2' ' suitable to solve the problem of transient +l /,,y Ex (ia 2' J~ ~ ~ electromagnetic pulse for its direct time (ia , Ja , k a ) ~ -t"domain calculation characteristic. So, the ~z(ia,Ja,k a __1~ _VEsD FDTD method is used to analyze Groundplane wcharacteristics of the electromagnetic field / / generated by a thin wire with ESD current injected in this paper. Figure 1 FDTD model of the thin wire
l
Project supported by the NSFC (No. 50077024, No. 50237040)
93 Establishment of the numerical model For a long perfectly electrical conducting (PEC) thin wire vertical to an infinite ground plane with ESD current injected through a 50 f~ matched resistance from its bottom end (see Figure 1), to simulate the thin wire using the FDTD grids with the dimension as the radial dimension of it will cause the calculation space very large and the computer resources are hard to meet that requirement, then sub-cell technology for thin wire should be used [4]. First, assume that the magnitudes of each radial electric field (E-field) and each looping magnetic field (M-field) nearest to the wire vary with the reciprocal of the radial distance away from the center of" the wire and the E-field and the M-field parallel to the wire don't vary and the E-field within the wire is zero. Then Faraday's Law can be applied to the grid composed of every field component shown in Figure 1 and the looping M-field nearest to the wire can be expressed as follows: H ; +l/2 (i
+• a
2'
j ,k a
+ l ) = H;-1/2 a
(i
2
+• a
j
k
2 ' a'
+ L) + a
2
A____Lt ,L/0Ax
-~ , J a , ka + 1 ) -
'ttoAZ
2
. E n (i
ln(Ax / a)
z
+ l, j a
k a'
-e • a
2
(1)
( i a + -~ , J a , ka )
Other three M-field components nearest to the wire can be gotten using the same method and the Mfield components except ones nearest to the wire and all the E-field components are the same as the ones in free space. At the ESD current feed point of the wire, the electric field can be expressed as" E x (i feed, j , k ) = -Ves D ( n A t ) / A x
(2)
ESD current used in the model is the humanbody-metal model specified in IEC61000-4-2 [5] and a current expression i(t) = I o (1 - e -t/'' )P e -'/'~ + I, (1 - e -'/'~ )q e -t/r4
(3) 30-
based on pulse function [6] is used to represent it to computer conveniently and its current waveform while discharging at +8kV is shown as Figure 2. The Mur absorbing boundary condition [7] is used in the model and the space step is 0.01m in all directions and the time step is 0.017ns, which meets the Courant stable condition. Thus, the model can be used to compute the radiation field of the wire.
20,
.<__
6
2'0
~o
~o
go "1~o
tins
Figure 2 ESD current waveform based on pulse f u n c t i o n
Computation results and analysis When the thin wire is 22cm length and 0.6mm radius, Figure 3 and Figure 4 are the E-field waveform and
50:1
10
-500J
,E .10001
...............
~-~"~"
=.-.
.......
E
-15oo 1 ?u" -2ooo]
-2500] -3000-! -3500
2:
0,
-5
-10
io
"
4'o
fins
6'0
do
16o
Figure 3 Electric field waveform at the distance of 10cm
'
io
'
4'o
'
t/ns
6'o
"
go
' 1~o
Figure 4 Magnetic field waveform at the distance of 10cm
94 the M-field waveform respectively computed using the model at the distance 10cm away from the wire and 4cm above the ground. Seeing from the two figures above, we know that most component of the E-field and all the component of the M-field are decaying oscillation 1500 with high frequency. The cause is that the fast 1000, discharge current pulse (the first peak in Figure 2) of ESD with subnanosecond level reflects back and forth 500, at both ends of the wire and the current change is the E O, greatest at the two ends corresponding to the strongest ~ " -500, radiation field. Besides the decaying oscillation, there is also a slow changing E-field component, shown as -1000, the slow changing red curve in Figure 3, which is the -1500, induction field generated by the slow discharge current b " 2'0 4'0 6'0 a'o ~6o pulse (the second peak in Figure 2). This component t/ns decays rapidly with the distance far away from the Figure 5 Electric field waveform at the wire, Figure 5 shows the E-field at the distance of distance of 40cm 40cm away from the wire, in which there is nearly no induction field component. As far as the amplitude of the transient field component is concerned, the peak value of the electric field generated by ESD spark at the same condition is 170V/m and that of the magnetic field is 0.65A/m [2], which is much lower than that of the thin wire with ESD current injected.
EXPERIMENTAL STUDY OF THE PROBLEM Experiment setup The experiment setup of the electromagnetic field generated by the thin wire with ESD current injected is shown in Figure 6, in which a metallic thin wire is placed on a large metallic ground plane vertically and the discharge electrode of the ESD simulator gun contacts the bottom end of the thin wire. To eliminate the influence of the electromagnetic field generated by the ESD gun, the ESD simulator and the gun are placed in a shielding room. An electrically short monopole antenna with the length 5cm is also placed on the ground plane vertically and the receiving signal is transmitted to an oscilloscope through a 50 f~ matched coaxial cable. To eliminate the influence of the electromagnetic environment around, the oscilloscope is placed in another shielding room. Ground plane
Thin wire
Shielding room
Measurement antenna Shielding room
Discharge gun ~
Coaxial cable Oscilloscope
ESD simulator_]
u
L
Figure 6 Measurement system setup of electromagnetic field generated by thin wire with ESD current injected Experimental results and analysis When the discharge voltage is +0.2kV, the length of the thin wire is 10cm and the receiving antenna is 20cm away from the thin wire, the normalized waveforms of the computed and measured electric fields radiated by the thin wire with ESD current injected are shown in Figure 7, in which the waveform of the computed field is gotten using the forenamed numerical model and the ESD current used to compute is the measured current with the discharge voltage +0.2kV (see Figure 8).
95 1.0
9P
-----Computed
0.8"
......... Measured
0.7 0.6
0.5 t.t.l" 0.0
0.5 0.4 :o,.,
0.3 0.2
-0.5-
0.1
-1.0
0.0
~
; o 1 ' 5 2 ' o tins
Figure 7 The computed and the measured normalized electric field waveforms of the thin wire with 10cm length
-0.1 -50
6
5'olbol~o2bo tins
Figure 8 The measured discharge current waveform of humanbody-metal model
Seen from Figure 7, the computed field waveform is in good agreement with the measured field waveform and the results of other lengths of the thin wire are the same. The amplitudes of the respective field waveforms can further be compared after the measurement system is calibrated.
CONCLUSIONS Radiation field generated by a thin wire with ESD current injected can cause severe electromagnetic interference to electronic equipments. In this paper, a numerical model based on the thin wire sub-cell technology is established using FDTD method and the experimental work is done to validate it. From the computed results and the analysis we know that when ESD current is injected into a thin wire vertical to the ground, there is decaying oscillation radiation field with high frequency and the E-field has induction field component near the wire. The amplitude of the field generated by the thin wire with ESD current injected is far stronger than that generated by ESD spark at the same condition and the computed results obtained by FDTD method are in agreement with the experimental results.
REFERENCES 1 Lai Z. W., Electromagnetic interference protection and electromagnetic compatibility, Atomic energy press, Beijing, P. R. China (1993) 2 Sheng S. L., Tian M. H. and Liu S. H., E-field calculation related to ESD based on an improved dipole model, High voltage technology (2002) 2___888-10 3 Yee K. S., Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media, IEEE Trans. AP (1966) 1__44302-3 07 4 Umashankar K. and Taflove A., Calculation and experimental validation of induced currents on coupled wires in an arbitrary shaped cavity~ IEEE Trans. AP (1987) 3__551248-1250 5 IEC 61000-4-2: Electromagnetic compatibility (EMC)-Part 4-2: Testing and measurement techniques- Electrostatic discharge immunity test, International Electrotechnical Commission, Geneva (2002) 6 Zhang F. Z. and Liu S. H., A new function to represent the lightning return-stroke currents, IEEE transactions on EMC (2002) 44595-596 7 Mur G. Absorbing boundary conditions for the f'mite-difference approximation of the time- domain electromagnetic filed equations, IEEE Electromagn Compat (1981) 2__33377-382
96 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Quadrupole Corona Discharge Ammonia Radical Shower Non-Thernmal Plasma System For Combustion Flue Gas Treatments And Conversion To Useful Products Chang J.S. l, Urashima K. 1, Wang W. 2, Hu H. 2, Tong N.Y. 2, Liu W.P. 2, Itoh M. ~, Obara
S. 3
1McMaster University, Hamilton, Ontario L8S 4M1 2Wuhang TengTscheng Environmental Co., Wuhang, P.R. China 3Doshisha University, Dept. of Chemical Eng. & Materials Science, Kyotanabe, Kyoto, Japan
Large bench scale experiments have been conducted for the removal of SOx and NOx from combustion flue gases by a quadrupole corona discharge ammonia radical shower non-thermal plasma system. The SOx and NOx will be converted to useful ammonium nitrate and ammonium salphate mixture for agriculture applications. Unlike the ordinarily corona radical shower (CRS) - plate electrodes, the CRS-quadrupole electrode system can be enhanced local electric field as well as discharge current flux, hence much higher De-SOx and NOx energy efficiency can be obtained. Here, the CRS electrode is pipe with multi-nozzle electrode where ammonia-air mixture gas was injected to flue gas stream after passing through nozzle discharge zone for activations. Experiments were conducted in two system one for 0 to 600 Nm3/h and the other system for 0 to 20 Nm3/h large bench scale test facilities. The results show that the energy efficiency of SOx or NOx removal decreases with increasing the specific energy density (kWh/m 3) for a various flue gas temperature, ammonia injection rate, flue gas flow rate and electrode gap distance. The ranges of energy efficiency is 1 to 12 kg (SOx)/kWh and 100 to 600 g(NOx)/kWh. By comparisons with CRS-quadrupole and CRSplate electrode system, the quadrupole system shows less then 10 to 20% more efficient compared with plate system. Nevertheless, the CRS system is one or more order of magnitude higher efficiency by compared with dc corona, barrier discharge and pulsed corona methods as well as electron beam methods.
INTRODUCTION Several attempts [1] have been conducted to use pulsed corona, electron beam, and barrier discharge based non-thermal plasma techniques for simultaneous removal of SO2 and NOx from combustion flue gases. However, the direct plasma treatment of flue gases may not be energy-efficient since the majority of energy will be lost to the vibrational and rotational excitations of CO2, H20, N2, etc. Therefore, the non-thermal plasma radical injection techniques were proposed [2-7]. In the corona discharge radical injection technique, corona discharge is generated in front of a hollow electrode where ammonia, hydrocarbon, steam, oxygen, nitrogen, etc., were injected. Therefore, we can select radicals required for pollution gas treatments and minimize activations of unwanted flue gas components. The principle of the ammonia radical shower system is as follows [2-5]: (1) Adiabatic expansion of ammonia contained gas to form core aerosol particles from homogeneous condensation from nozzle exits. Therefore, SO2-aerosol surface reactions can be promoted during discharge zone. Aerosol surface reaction rates are a few orders of magnitude higher than that of the gas phase reaction rates;
97 (2) Formation of N(P), N(D), H, N2*, NH and NH2 radicals at the exit of nozzle electrode where strong electric field and high density plasma exist. All these radicals have higher reduction reaction rates with NOx; (3) Oxidation of NO, NO2, SO2 by O, 03, OH, and H202 generated in wide plasma zone between nozzle to plate. Hence, NOx and SO2 converted to aerosol particles at downstream of reactors react with undissociated slip NH3 and core aerosol particles generated by homogeneous condensation and ion induced aerosol formations. In this work, the non-thermal plasma technology based corona discharge radical shower system was tested in two different types of grounded plate and quadrupole electrodes.
EXPERIMENTAL APPARATUS Schematics of experimental test facility is shown in Figure 1 [6]. The test facility consisted of the air heater, the corona radical shower system, the bag filter for discharge by product collections, the induced fan for flue gas flow control and the secondary stack as shown in Figure 1. Gas temperatures T and gas analyses (sampling ports SP) were measured at four locations as indicated. Corona radical shower system (0.5 x 0.2 x 2 m) consisted of 10 corona radical injection electrodes (CRS) as shown in Figure 2, where the present version of multiple-nozzle electrodes were placed between quadrupole grounded electrodes or plate type grounded electrodes with 5 cm distance. Second bench scale system is similar to the Figure 1 except CRS reactor is single flow channel with four CRS electrodes [7].
Figure 1 Experimentaltest loop
EXPERIMENTAL RESULTS SO2 removal efficiency as a function of input electrical power (or SED) is shown in Figure 3. Figure 3 shows that SO2 removal efficiency increases with increasing applied power or specific energy density (Wh/m 3 = input power/flue gas flow rate-SED). Depending on gas flow rate, 60 to 86% of SO2 can be removed by corona radical shower system without applied voltage due to aerosol formation by the adiabatic expansion homogeneous nucleation of ammonia in air as has been oloserved in bench scale tests [2], where the aerosol surface reaction between NH3 and SO2 for ammonia sulfate is few order of magnitude faster compared with gas phase reactions. Figure 3 shows that the quadrupole grounded electrode always shows significantly higher SO2 removal efficiency by comparison with the plate type grounded electrode due to the electric field enhancement from electrode geometry. Energy efficiency of SO2 removal by CRS-plate and CRS-quadrupole electrodes system is shown in Figure 4 and 5 respectively for various gas flow rate, gas temperature, NH3 to SO2 initial concentrations. In-spite of CRS-quadrupole electrodes system shows more than 10 to 20% higher De-SOx removal efficiency, the energy efficiency in-terms-of kg [SO2] removed by the 1 kWh of electrical energy in-put remaining similar, however, the CRS-plate system have an advantage to operated in smaller specific energy density region. Hence, the CRS-plate is more effective that that of the CRS-quadrupole system.
98 For both systems, the energy efficiency decreases with increasing gas temperature. NH3/SO2 ratio, and gas flow rate while the energy efficiency increases with increasing S02 initial concentration.
Figure 2 Schematics of quadrupole and plate type corona radical shower system and corona injection electrodes
Figure 3 SO 2 removal efficiency as a function of input electrical power or SED for two types of grounded electrodes
Figure 4 Energy efficiency of $02 removal as a function of SED for CRS-plate electrode system
CONCLUDING REMARK An experimental investigation for the quadrupole corona radical shower system SO2 removal from flue gas has been conducted and compared with the conventional plate type corona shower system, and the results show that: (1) Corona discharge current increases with increasing applied voltage and decreases with increasing injection gas flow velocity; (2) Removal efficiency of SO2 increases with increasing applied power and ammonia-to-acid gas molecule ratio and decreases with increasing gas flow rate, SO2 initial concentration, and gas temperature;
99 (3) The conversion of 802 to ammonium sulphate aerosol particles was confirmed and the size of particle observed are for the ranges of 2 to 60 #m with peak bimodal particle sizes for 6 to 10 and 20 to 24 #m; and (4) Quadrupole type corona radical shower systems always show significantly higher SO2 removal efficiency and energy efficiency by comparison with the conventional plate type corona radical shower systems. However, the energy efficiency for the SO2 removal by CRS-plate system is slightly higher compared with CRS-quadrupole system.
Figure 5 Energy efficiency of 802 removal as a function of SED for CRS-quadrupole electrode system
ACKNOWLEDGMENTS The authors thank R. Yamaguchi, M. Nimura, G.P. Xu, Z. Li and P.C. Looy for variable discussion and comments. The authors also wish to thank the State Environment Protection General Agency of P.R. China, and the Natural Sciences and Engineering Research Council of Canada for their financial support. REFERENCES 1. Chang, J.S., Lawless, P. and Yamamoto, T., IEEE Trans. Plasma Sci., (1991) 19 1152-1166. 2. Park, J.Y., Tomicic, I., Round, G.F. and Chang, J.S., J. Phys. D: Appl. Phys. (1999) 32 1006-1011. 3. Chang J.S., Looy P.C., Urashima K., Tong X., Liu W.P., Wei H.Y., Yang F.M. and Liu X.J., Proc. (2000) SPP-17, 579-601. 4. Kanazawa, S., Chang, J.S., Round, G.R., Sheng, G., Ohkubo, T., Nomoto, Y. and Adachi, T., Comb. Sci. and Tech. (1998) 133 93-105. 5. Li, R. and Xin, L., Chem. Eng. Sci. (2000) 55 2481-2489. 6. Tong, X.Y., Wang, W.M., Liu, W.P., Urashima, K., Chang, J.S., Proc. G.D. 2002 (2002) PP. 112-115. 7. URASHIMA, K., TONY, X.Y., LIU, P.W. AND CHANG, J.S., PROC. AOT-5 (1999) PP. 79-80.
100 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Electrohydrodynamic flow patterns in a wide spacing spike-plate electrostatic precipitators under negative coronas 2
1
1
1
2
2
D. Brocilo, J. Podlinski, J. Dekowski, J. Mizeraczyk, K. Urashima, J.S. Chang i
2
Institute for Fluid Flow Machinery, Polish Academy of Sciences, Gdansk, Poland Dept. of Engineering Physics, McMaster University, Hamilton, Ontario, Canada L8S 4L7 In this work, electrohydrodynamic (EHD) flow patterns in a wide-spacing spikeplate ESP under negative corona were categorized based on the 3D particle image velocimetry method. The formation of EHD flow patterns as well as their effect on the transport of submicron and micron dust particles was discussed based on dimensionless analysis of particle transport equation. Based on the experimental results five EHD flow patterns have been characterized and correlated to the ratio between EHD number and Reynolds number squared.
INTRODUCTION In order to prevent the back discharge phenomena and enhance the collection efficiency of electrostatic precipitators (ESPs) for submicron high resistivity ashes, a wide spacing ESP with spike-type corona discharge electrode was used. The spike orientation, parallel with collecting electrode, was used since it reduces the ionic current density near the collecting electrode. However, the studies have showed that the main gas flow may be also influenced by the electrohydrodynamically (EHD) induced secondary flow (or ionic wind generated by the corona discharge), spike orientation, ESP width, and the magnitude of applied voltage. Depending on the electrode arrangement, the presence of EHD induced secondary flow may enhance or degrade precipitator efficiency due to its effect on: (a) the onset of the vortex, (b) EHD induced turbulence, (c) particle transport, (d) particle charging, and (e) re-entraiment of already collected dust particles. The effect of EHD flow on the main gas flow streamlines is studied experimentally and numerically by various authors for various geometries for low Reynolds numbers (laminar flow) [ 1-6]. For wire-plate geometries, experimental studies indicate strong dependence on the polarity of the applied voltage [1], where for positive corona the EHD flow tends to produce a recirculation vortex near the collecting plates, more or less opposite to discharge electrode. Based on experimental and numerical 2D vorticity-stream studies of Yamamoto and Velkoff [3], and Adachi et al. [2], those modifications were first observed when the Ehd number is greater than the Reynolds number squared (Re2). R e - U~ " Eha = Vg
IrL3
(1)
2
A p g V g ,ly i
where U0 [m/s] is the mean gas velocity, L [m] is the characteristic length (plate-to-plate distance), Vg [mZ/s] is the gas kinematic viscosity, Iv [A] is the total discharge current, A [m 2] is the surface area of the collecting electrode, pg [kg/m 3] is the gas density, and gi [m 2/Vs] is the ion mobility. Here the new IEEE standard for Ehd number was used [9] as shown above. For negative corona, irregular locations of discharge tufts on the surface of the wire introduce quasisteady EHD flows that contribute to redistribution of pre-existing turbulence, and oppose to formation of large scale secondary flow. In the case of rods with pins or spikes where the negative tuft location can be controlled, the ion flow patterns may induce transverse recirculation vortices associated with each discharge point. The overall effect on the orientation and intensity of vortices depends on the main gas velocity, current density, and discharge electrode geometries. Numerical studies by Yamamoto et al. [6] for negative tuft corona (rod with needles)showed complex Goertler-vorticity-type structure of the gas flow resembling spiral ring structure.
101 In this work, EHD flow patterns in a wide-spacing spike-plate ESP under negative corona were categorized based on the ratio between EHD number and Reynolds number squared by using the 3D particle image velocimetry (PIV) method. EXPERIMENTAL EQUIPMENT The experimental set-up for the Particle Image Velocimetry (PIV) system shown in Figure 1 was the same as that used by Mizeraczyk et al [7]. The TiO2 powder (particle size diameter dp~0.2gm) was used as seed particles for a flow visualization. The experiment was conducted for flow velocities from 0 to 0.6 m/s at positive and negative applied voltages ranging in magnitude from 0 to 30 kV. The studied ESP discharge electrode has 12 triangular spikes oriented upstream and downstream to the flow channel in a staggered mode (Fig.2a) and placed parallel with 10 cm spaced collecting electrodes (widthxlength = 20x60 cma). The main flow in the ESP was in the transition region from laminar to turbulent based on the Reynolds number (Re=4000). The typical PIV of Plane A (-100
Figure 2. (a) spike-type discharge electrode (top view y-z coordinates) and (b) typical PIV image of laminar flow in the central sections (x-y coordinates) of plane A.
TRANSPORT OF FINE PARTICLES Transport of ultrafine particles (dp<0.1gm) can be evaluated from particle transport equation for diluted particle density model [8] as follows:
~g "VN~a - BodV" (Nod~) - DcdVZNcd - ~ kNiN~d i
(2)
The first, second and third term on the left hand side represent convective, mobility (or electric field), and diffusion transport, respectively. The right hand side is particle charging rate for neutral and charged particles. Here, Ug[m/s] is the gas velocity vector, Ncd[#/m3] is the charged dust density number, E is the electric field vector, Pcd[m2/Vs] is the mobility of charged dust, Dcd[m2/s] is the diffusion coefficient of charged dust, Ni[#/m 3] is the ion density number, and k is the charging rate coefficient. From dimensionless form of Eq.2, the relative importance of transport of particle by convection can be evaluated based on the Diffusion Reynolds number (Rata) versus Electric field number (FF) ratio"
102 ~
Race =Re'Scud = f
qe "f
UOL
v
v
Dne
~
(3)
qe . e V o / k r
Here, Race=UgL/Dce is the dimensionless Diffusion Reynolds number of charged dust, Fe is the dimensionless electric field number, Re is the Reynolds number, Scce is the Schmidt number, qe is the number of elementary charges on the surface of dust particle, Uo [m/s] is the mean gas velocity, L[m] is the characteristic length, Dnd[m2/s] is the diffusion coefficient, Iio[11] is the applied voltage magnitude, r[K] is the gas temperature, k=1.381 x lO-23[j/K] is the Boltzmann constant, and e=l.602x 10 -19 If] is the elementary charge.
RESULTS AND DISCUSSION The experimental results from the PIV image analysis show that the EHD flow patterns can be characterized in four regions based on the dimensionless number ratio (Eha/Re2) as shown in Figures 3a-d. Without an applied voltage (Ehu=O), laminar flow (Fig.2b) has been observed. Time dependant wake, caused by the
Figure 3. PIV images of typical EHD flow patterns in the central section of plane A. electrode structure, was not observed since the Reynolds number based on the hydraulic diameter (ReH=75) of the spike electrode was below the critical value. However, once Ehe number has been increased over Ehd=2.91 x 105, the magnitude and type of the EHD flow were dependant on the upstream (Plane A) or downstream (Plane B) orientation of the spike. Steady wakes behind the electrode were observed in Plane A and C even for Ehd/Re 2<0.01 as shown in Fig.3a (Regime A: EHD induced steady wake). First formation of the unsteady wake has been observed in the plane B at approximately Ehd/Re 2~0.01. Wider and longer wakes were observed in plane C at which the ionic flow and gas flow enhance each other. The on-set of EHD induced Karman Vortex like laminar flow (Regime B) was observed at Ehd/Re2=0.2-0.5 in the plane A as shown in Fig.3b. The EHD induced unsteady forward wake together with the downstream EHD vortex-field that filled in the central section of the channel (Fig.3c) was observed at Ehd/Re2~0.5-1 (Regime C" EHD induced unsteady wake). For the cases when Ehd/Re 2<1, the EHD flow was not significant near the wall of the flow channel. Fully developed EHD vortex flow (Regime D) that occupied the portion of the upstream and the whole central and downstream area of the channel was observed for Ehd/Re 2 > 1(Fig.3d). At the plane of the upstream oriented spike, the pair of upstream vorticies force the flow streamlines to move towards the collecting plate, whereas the pair of downstream vorticies try to pull the flow streamlines towards the discharge electrode (Figure 4a).
103 This could be one of the reasons for contamination of discharge electrode surface by dust particles. In the plane B, the size of vorticies is much smaller as shown in Figure 4b. Based on the dimensionless analysis (3), the particles from 1 to 10 nm are not significantly influenced by the EHD flow since Racd/FF_,<1. For the present ESP geometry and operating conditions, the particles from 10 to 100 nm are influenced by EHD flow since Racd/Fe >1. As the particle size increases over 1 micron, the particles start to be highly charged hence, Ra~a/Fe ratio decreases and the mobility term dominates their transport especially in the area of high electric field. I D I ~ L s ,,,blu,,tr,.vs
C l n i l r , - zsks,-erev,l,-
.
Dlem#,,, ~l.lls/~l.',l, d A
~l'~|lflll A l d f ~ / ' ~ l s
[ I
~0
r
5
I
Plate electrode
z l,m in)
Plate electrode
x t m m/
Figure 4. Flow streamlines for the fully developed EHD flow (Pattern D) at: (a) Plane A, and (b) Plane C.
CONCLUSSIONS The following concluding remarks were obtained based on the experimental and theoretical investigations: a) The Ehd/Re 2 proved to be good indicator that may be used for categorization of EHD flow patterns for negative corona. b) Spike electrode generates complex 3D EHD flow. The magnitude and type of the EHD flow depend on the orientation of the spike tip (upstream or downstream) relative to the main gas flow direction. c) The on-set of EHD forward wake can be observed at Ehd/Re2=0.5.Wheras, the on-set of the fully developed EHD flow that occupied the upstream and downstream area of the discharge electrode was observed at lower value (Ehd/Re2 =1) than for the wire-plate ESPs (Ehd/Re2=4) [7]. d) For the spike-plate geometry, the EHD flow at negative corona onsets at lower electric field numbers than for the positive corona [7]. e) Theoretical analysis shows that the EHD induced vortex mainly influences the transport of submicron particles. f) Modeling of 3D particle transport are required due to the complex 3D structure of ionic density distribution, electric and gas velocity fields. REFERENCES 1. T. Adachi, Ionic Wind in the Electrostatic Precipitator Experimental treatment by Schlieren Method, Elec. Eng. In Japan (1973) 93/4 47-48 2. T. Adachi, T. Ohkubo, T. Murakami and J. S. Chang, Analysis of Flow Field in ESP, IEEE Trans. IAS. (1990) 26, 542-549 3. T. Yamamoto and H. R. Velkoff, Electrohydrodynamics in an Electrostatic Precipitator, J. Fluid Mech. (1981), 108 1-18 4. J.H. Davidson and P.J. McKinney, EHD Flow Visualization in the Wire-Plate and Barbed Plate Electrostatic Precipitator, IEEE Trans. On Industry Applications (1991), 27/1 154-160 5. D. Blanchard, L. M. Dumitran and P. Atten, "Effect of Electro-aero-dynamically Induced Secondary Flow on Transport of Fine Particles in an Electrostatic Precipitator," Journal of Electrostatics (2001), 51 &52 212-217 6. T. Yamamoto, M. Okuda and M. Ohkubo, Three-dimensional Electrohydrodynamics in Electrostatic Precipitators, IEEE Trans. IAS. (2004)40 7. J. Mizeraczyk, M. Kocik, J. Dekowski, M. Dors, J. Podlinski, T. Ohkubo, S. Kanazawa and T. Kawasaki, J. Electrostatics (2001), 51-52 272-278 8. D. Brocilo, J.S. Chang, and R.D. Findlay, Proc. of 8th International Conference on Electrostatic Precipitation (2001) Alabama USA, II/A4-3, 1-18 9. IEEE-DEIS-EHD Technical Committee, Dimensionless parameters for EHD flow, IEEE Trans. DEI, (2003) 10 3-6.
104 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier. ISBN 0-08-044584-5
Synergy of Nonthermal Plasma and Catalysts in the Decomposition of Hydro flu o roc arb o ns Futamura, S. and Annadurai, G.
National Institute of Advanced Industrial Science and Technology AIST Tsukuba West, 16-10nogawa, Tsukuba, Ibarala', 305-8569 Japan
In the decomposition of hydrofluorocarbons such as HFC-32 and HFC-23 with silent discharge plasma or surface discharge plasma, MnO2, TiO2-SiO2, and A1PO4 show catalytic effects. MnO2 and TiO2-SiO2 promote the oxidative decomposition of hydrofluorocarbons in the presence of gaseous oxygen, while A1PO4 in nonthermal plasma promotes the cleavage of C-F bonds in them.
INTRODUCTION Hydrofluorocarbons (HFCs) have been widely used as substitutes of perfluorocarbons and hydrochlorofluorocarbons for refrigerants, foaming agents, etc. Highly efficient technologies for decomposition of these compounds are urgently required due to their large global warming potentials. Nonthermal plasma has been applied to the decomposition of fluorinated hydrocarbons since it can be facilely operated at ambient temperature [1-4]. We have been evaluating the performances of dielectric barrier discharge plasma reactors such as silent discharge, surface discharge, and ferroelectric packed-bed reactors in this class of reaction. This paper focuses on the synergy of nonthermal plasma and different types of catalysts in the decomposition of HFCs such as HFC-23, HFC-32, HFC-134a, HFC-125, etc. The action mechanisms of the catalysts will be discussed, relevant to the synergy of nonthermal plasma and catalysts.
EXPERIMENTAL In this research, two types of dielectric barrier discharge plasma reactors were used: a silent discharge plasma reactor (SDR) and a surface discharge plasma reactor (SFR). Aluminum tape and a punched rod made of stainless steel (punch density: 25 cm -2) [5] were used as the external and internal electrodes of SDR, respectively. The reaction length and the gap distance of SDR were 10 cm and 1 mm, respectively. A stainless steel coil of 18.2 cm with 22 turns, which was housed inside of the quartz tube (o.d 15 mm~), i.d. 13 mm~)), was used as the internal electrode for SFR. Aluminum tape was also used as the external electrode for SFR. Both the reactors were energized with 50 Hz to 10 kHz ac at up to 25 kV (rms) by using a Neon Transformer or a high voltage amplifier (20/20C, Trek Japan, Co., Ltd.) and a function generator (Agilent 33120). All the HFCs were commercially purchased in cylinders balanced with N2 (Takachiho). MnO2 (Wako, special reagent grade), A1PO4 (Nippon Sanso), TiO2-SiO2 (HQA 12) (Shinto V Cerax) were pulverized and dried at 120~ for 18 h before use. A1 the reaction gases were introduced to the reactor through a Teflon tube. Substrate concentration and gas flow rate were adjusted with sets of mass flow controllers and a gas mixer. Reaction gases were directly introduced to the 10 cm gas cell with a BaF2 window in a FTIR spectrophotometer to continuously monitor and quantify the substrates and products. Applied voltage and plug-in power were
105 measured with a digital wavemeter and a digital powermeter, respectively. After the reactions, 02 was passed through the reactor at 8 kV for 5 min to clean the reaction line, and then, it was evacuated.
RESULTS AND DISCUSSION Table 1 shows the effects of power supply, 02, and MnO2 on the HFC-32 conversion in use of SDR as a reactor. HFC-32 conversions are extremely low in N2 with a Neon transformer as a power supply, but it triples by replacing 5 % of N2 by O2. Furthermore, on addition of MnO2, a 15-fold increase was observed in HFC-32 conversion. It is well known that SDR is an ozone (03) generator and that 03 is not an active oxidant in the oxidative decomposition of HFCs. We have already reported that hybridization of SDR and MnO2 is effective in the oxidative decomposition of benzene [6]. Even without MnO2, rateaccelerating effect was observed in the presence of 5 % O2. A part of 03 is decomposed to give oxygen atoms in situ and these species are also generated directly from 02 in SDR. It is considered that oxygen atoms attack the C-H bonds in HFC-32, promoting its oxidative decomposition. In the reactions at higher reactor energy densities [RED - Reactor power consumption (kW) / Gas flow rate (L/s)] with 20/20C, HFC-32 conversion jumped with increases in Oz content and RED. When frequency was increased from 10 to 20 kHz, HFC-32 conversion decreased, which corresponded with the decrease in RED, i.e., reactor power consumption in use of 20/20C as a power supply. Table 1 Effects of power supply, O2, and MnO2 on the HFC-32 conversion 02 (%)
Catalyst
Frequency (kHz)
Applied voltage (kV)
RED (kJ/L)
Conv. (mol%)
0 5 5 5 5 20 20 20 20
None None MnO2 None MnOa MnO2 MnO2 MnO2 MnO2
0.05 a)
11.08 10.92 10.92 8.40 8.40 8.40 8.00 8.00 8.00
0.32 0.33 0.33 0.074 0.074 0.074 1.29 1.50 0.92
0.9 2.8 42 0.7 9.6 15 93 98 77
0.05 ") 0.05 a) 0.05 b) 0.05 b) 0.05 b) 5.0 b) 10.0b)
20.0 b) Reactor: SDR, MnO2 6.60 g, 200 ppm HFC-32 in N2, Q = 0.1 L/min. a) Neon transformer, b) 20/20C.
As Table 2 shows, additive effect of MnO2 in the decomposition of HFC-23 is less remarkable than in the case of HFC-32. These findings are ascribed to the different numbers of hydrogen atoms per molecule for HFC-32 and HFC-23. The mechanism presented above is supported by these corroborations. Table 2 Effects of O2 and MnO2 on HFC-23 conversion O2 (%)
Catalyst Frequency (kHz) Applied voltage (kV)
RED (kJ/L)
Conv. (mol%)
5
None
0.05
8.40
0.073
0.3
5
MnO2
0.05
8.40
0.074
4.5
20
MnO2
0.05
8.40
0.072
7.2
8.00
1.28
47
1.51
50
20 .
20
5.0
MnO2 .
.
.
MnO2
.
.
.
10.0
.
.
.
8.00 .
20
MnO2
20.0
8.00
.
.
.
0.94
38
Power supply: 20/20C, reactor: SDR, MnO2 6.60 g, 200 ppm HFC-23 in N2, Q = 0.1 L/min. A1PO4 is used as a catalyst in the catalytic decomposition of fluorinated hydrocarbons such as CF4 and other HFCs at higher than 450~ Our research interest was activation of this catalyst in nonthermal plasma at ambient temperature. With a Neon transformer, HFC-32 conversion more than triples on addition of A1PO4. In use of 20/20C, HFC-32 conversion increases with RED, but its conversion decreases in the frequency range of 10 to 20 kHz as in the case of MnO2.
106 Table 3 Effects of power supply, frequency, and A1PO4 on HFC-32 conversion Catalyst
Frequency (kHz)
Applied voltage (kV)
RED (kJ/L)
Conv. (mol%)
None
0.05 ")
7.85
0.15
4.2
None
0.05 a)
11.08
0.32
6.8
A1PO4
0.05 ")
11.08
0.32
25
A1PO4
0.05b)
8.40
0.074
6.2
A1PO4
5.0b)
8.00
1.29
80
AIPO4
7.0b)
8.00
1.35
88
A1PO4
9.0b)
8.00
1.74
94
A1PO4
10.0b)
8.00
1.50
91
A1PO4
20.0 b)
8.00
0.92
65
AIPO4 2.43 g, 200 ppm HFC-32 in N2, Q = 0.1 L/min. a) Neon transformer, b) 20/20C. Figure 1 shows the plausible action mechanisms for MnO2 and A1PO4. 03 is decomposed on the surface of MnO2 to give oxygen atoms. These species oxidatively decompose HFCs. On the other hand, the effect of A1PO4 is observed in N2 in the absence of 02 or H20. The reaction mechanism remains to be unraveled, but the major carbon fragment should be the carbon radical CHxFy (x + y = 3) due to the different electron affinities of F and CHxFy. The interaction between HFCs and this catalyst is enhanced in nonthermal plasma to give C-F bond cleavage products. In this reaction, addition of up to 5 % of 02 is also necessary to oxidize the carbon atoms in HFCs to CO2. Further increase of 02 is not desirable because NOx is formed as byproducts.
(
1
D
)
~
Products
HFCs Nonthermal Plasma
F H--~--F .....-..
=-
CH2F 9 + F-
6 Figure 1 Plausible action mechanisms for MnO2 and A1PO4 When SFR was used as a reactor, addition of A1PO4 or HQA 12 gave higher applied voltages at fixed plug-in power consumptions. 30 min after the reaction gas was flown through SFR, no adsorption of HFC-32 was observed and the constant level of the base peak was attained. Figure 2 shows the catalytic effects of the above catalysts in the decomposition of HFC-32. Apparently, higher conversions are obtained with HQA 12 than with A1PO4. However, their catalytic activities cannot be compared at this moment because their loading amounts and surface areas are not controlled. In SFR, intense light emission was observed. It has been reported that HQA 12 hybridized with SDR shows a catalytic effect in benzene decomposition [6]. In this reaction, OH radicals formed on the surface of HQA 12 would promote the oxidative decomposition of the HFCs [7]. It has been confirmed that the TiO2-based photocatalyst is activated in the different types of barrier discharge plasma reactors such as SDR and SFR also in the decomposition of the HFCs.
107 In the decomposition of HFC-134a and HFC-125, the catalytic effect of A1PO4 has been less significant. These findings can be ascribed to the occurrence of the non-catalytic cleavage of C-C for these HFCs since C-C bonds are weaker than C-H and C-F. 100 80
m
Zk
60 40
m
A 20
O m
o
,m
0.0
5.0
,
0
o ,
,
10.0 15.0 20.0 Applied voltage (kV)
,
25.0
Figure 2 Catalytic effects of A1PO4 and HQA 12 in the HFC-32 decomposition Power supply: neon transformer, 200 ppm HFC-32 in N2, Q = 0.1 L/min.
The fluorine atoms in the HFCs were recovered as HF with small amounts of CF4 irrespective of the catalyst present. The fluorine balance was not necessary good due to the adsorption of fluorine species in the reaction line outside of the reactor although its temperature was maintained at 105~ with a heating tape. In the A1POa-catalyzed reactions in N2, the fates of the carbon atoms in HFCs were not fully characterized. In use of MnO2 and HQA 12, the major product was CO2, and much smaller amounts of CO and trace amounts of carbonyl fluoride were detected.
REFERENCES 1. Oda, T., Takahashi, T., Nakano, H., and Masuda, S., Decomposition of Fluorocarbon Gaseous Contaminants by Surface Discharge-induced Plasma Chemical Processing, IEEE Trans. Ind. Appl. (1993) 2___?787-792 2. Yamamoto, T. and Jang, B.-W. L., Aerosol Generation and Decomposition of CFC-113 by the Ferroelectric Plasma Reactor, IEEE Trans. Ind. Appl. (1999) 3___5573 6-742 3. Arkadiy, G., Ogata, A., Futamura, S., and Mizuno, K., Mechanism of the Dissociation of Chlorofluorocarbons during Nonthermal Plasma Processing in Nitrogen at Atmospheric Pressure, J. Phys. Chem. A (2003) 1078859-8866 4. Park, J.-Y., Jung, J.-G., Kim, J.-S., Rim, G.-H., and Kim, K.-S., Effect of Nonthermal Plasma Reactor for CF4 Decomposition, IEEE Trans. Plasma Sci. (2003) 3_1_11349-1354 5. Futamura, S, Einaga, H., and Kabashima, H., Synergistic Effect of Silent Discharge Plasma and Catalysts on Benzene Decomposition, Cat. Today (2004) 8__9989-95 6. Einaga, H., Ibusuki, T., and Futamura, S., Performance Evaluation of a Hybrid System Comprising Silent Discharge Plasma and Manganese Oxide Catalysts for Benzene Decomposition, IEEE Trans. Ind. Appl. (2001) 3__7_71476-1482 7. Einaga, H., Ibusuki, T., and Futamura, S., Photocatalytic Oxidation of Benzene in Air, J, Solar Energy Engin. (2004) 2789793
108 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Modeling of NOx, VOC, S02 removal and ozone synthesis by streamer discharges Amirov R.H., Filimonova E.A. Institute for High Temperatures, Izhorskaya 13/19, Moscow, 127412, Russia
The modeling was performed for ozone synthesis and removal of NO, SO2 VOC from pollutant gases utilizing the streamer type discharges. The influence of hydrocarbon additives on the removal of NOx from a diesel exhaust gas has been studied. The nonuniform distribution of the active species associated with the existence of many streamers or discharge channels in the reactor was taken into account. The modeling was carried out for a pulse series calculating the chemical and diffusion processes inside and outside streamer trace after each pulse.
FUNDAMENTALS OF CHEMICAL MODEL Development of non-thermal plasma sources to produce of highly chemically active components has mainly been associated with facilities for removal of harmful impurities from pollutant gases. Over the last decade detailed experimental studies had been performed on removal of NOx ,SO2 and VOC by barrier and corona discharges. The volume-averaged distribution of the chemically active particles was used for modeling of chemical processes in a pulsed corona or barrier discharge chamber [1]. This approach enables one to obtain qualitatively correct results. The averaged concentration of active components is much lower than the concentration of the same components in the streamer channels where the non-linear interaction of species leads to their mutual annihilation In this paper the modeling was based on the approximate mathematical model for a plasma cleaning of a waste gas and described in the [2]. The influence of non-uniform species distributions arising from a great number of streamer or microdischarge channels in a discharge chamber and sequence of discharge pulses was taken into account It is suggested that concentrations of the chemically active atoms and molecules arising in streamers and microdisharges are known. The following stages of the process including action of sequence of discharge pulses and chemical reactions in expanding streamers are considered. According to these approximations the gas parameters are found as a solution of a problem of diffusion expansion of one streamer trace in reactive gas. The set of equations for the concentrations of components ni with according boundary conditions is written as
dn i (t, r) dt
= ZQij +Qdif j
where function Qij describes the source of the i-th component production in j-th chemical reaction, Qaif gives the change of i-th agent by diffusion. The program calculates the streamer trace composition and changes the concentrations of species of the background gas due to action of electrical pulse series. Concentrations of active components in streamers are calculated in the frame of G-factors approach [1 ] utilising specific energy in streamers Wst. and q value, where q value is a fraction of energy that consumes for production of active components.
109 OZONE SYNTHESIS Ozone synthesis by pulsed corona discharge was carried using cylindrical metal reactor 30 cm of length and 6 cm of diameter [3]. The inner wire electrode had a diameter 1.4 mm. Amplitude of pulse voltage and pulse repetition frequency was 40 kV and 10 Hz. Gas flow rate of air with 60 % humidity at the room temperature was 2 1/min. The growth of input energy per pulse was afforded by changing the rate of voltage rising from 2.5 to 11 kV/ns. Residence time in the discharge chamber did not exceed 0.4 s. The modeling has been carried out on the assumption that overall specific energy W~t was used to produce active particles, i.e. q = 1 and W~t was estimated as 0.002 J/cm 3. The values Wac changed from 1.8x104 to 2.7xl04J/cm 3. The electron concentration in the streamers was equal to 1.3x1014 1/cm 3. The fractional volume and repetition pulse frequency under these parameters was F0=0.009-0.016 andf=10 Hz. Figure 1 shows the comparison of the calculation of 03 concentration with experimental data. Figure 2 illustrates the result of calculation of some species at sufficient put energy. 100
1.6
No3,
ppm
.
1.4
,.., E Q.
10
.2
1
1.2
0.1
#
f
//
~
J
o
1.0
r
!'..
0.01
,
6.0xlO -5
i
8.0xl 0 "5
,
l
l.OxlO 4
i
i
1.2x10 4
,
i
,
HNO 2
1.4x10 "4 -
,
0.000
......... N20
-... i
"-...
0.005
W, J c m -3
Figure 1. Ozone concentration versus input energy in air. Composition of matrix gas: 77.5%N2+20.5%O2 +2%H20
3
-. ".."'%.
0.8
0
.......... NO
I
0.010
Energy
|
- ........... NOo I
i
0.015
(J/cm
~"
0.020
|
0.025
3)
Figure 2. Dependence of concentrations of some species from input energy
MODELLING OF VOC REMOVAL FROM AIR BY PULSE CORONA In ethene removal experiments the reactor consists of two regions" an active zone with repetitively pulsed corona discharge followed by an inactive volume between the discharge chamber and the diagnostics [4]. Two different experiments were made: direct and indirect treatment. In the direct treatment case ethene goes through the discharge, in the indirect case ethene is fed into inactive zone after the discharge zone. Figure 5 shows the results in the direct treatment case, the indirect case is presented in Figure 6 as a function of deposited energy in to the active zone. The calculated results were obtained for the following conditions: specific energy put into the discharge chamber per period was 8.8-10 -5 J/cm 3, gas flow rate was 2 1/min, the frequency was changed from 0.7 Hz to 3 Hz. The gas residence time was 212 sec and 113 sec in the active zone and inactive zone respectively. The initial concentration of ethene was 400 ppm.
SO2 AND NOx REMOVAL FROM AIR Figure 3 shows the removal efficiency of SO2 against the gas flow rate when the initial SO2 concentration is 160 ppm for the adopted composition of air (2% H20). There is a good agreement between the experimental data [2] and calculations. The calculations show that the amount of the removed SO2 depends on the energy transferred to the gas with the pulse corona process. Concentrations of active components in streamers were calculated at the field in "head" of streamer E - 2 0 0 kV/cm [1]. The calculation has been carried out under the assumption that only 0.6 of transferred energy was used to produce active radicals. The value W~t was estimated as 0.0033 J / c m 3 according to [5]. The calculations show that the main processes of SO2 conversion are"
110 802 + 03- ~ 803 "+ 02 SO2 + OH + M ~ HSO3 + M 80
100 .....................................................................
. J
80
i I
o
o~ 60
J
=,60 "1" ro 40
O I
I
/
20
20
0~
'
o, b2
I
I
'
0,04 3 ' Energy, J/cm
0,06
Figure 2. Removal of ethene in the direct treatment
0~
50 40
I
0,02
,
I
I
0,03
I
0,04
0,05
Energy, J/cm 3 Figure 3. Removal of ethene in the indirect treatment
"L.
60
i
0,01
100 I
80~
v
O 30 09
o
-
~",-,.,.,.
.
20 10
A
A I
NOx
9
calculations
-.~
experiment I
I
I
I
,
I
,
I
10 20 30 40 50 ' 6 0 Gas flow rate ( I / m i n )
Figure 4.
00-'260
...... 46o
'
66o
800
NO and NOx, ppm
removal as a function of gas flow rate with the average discharge power P = 8 W Figure 5. NO and NOx (NO+NO2) removal versus initial NO concentration
SO2
An example of experimental [2] and calculated results on NO and NOx removal from air-water vapour mixture is shown in Figure 4. Gas flow rate is 15 1/min and discharge power is 8 W. The removal of NO is determined by the reactions with ozone, OH, HO2, atoms O and N. The main processes of NO removal are NO + 03 => NO2 + 02 NO + N => N2 + O. Produced in the first reaction NO2 forms then HNO3 and HO2NO2 in reactions with OH and HO2. The conversion of NO is limited in first pulses by diffusion of NO coming from the gas outside the streamer trace. In last pulses the conversion is limited mainly by the reaction because a sufficient amount of NO2 was formed due to the reactions with active particles. NO2 + O ::::>NO + 02, The variation of some component concentrations in streamer channel after an electrical pulse was analysed. The species that are produced in streamer channel after discharge as 03 and HO2 on the first stage are increased due to reaction with active components. Then these concentrations decrease in consequence of diffusion expansion of the channel. At first the active radicals delete NO from channel and NO concentration has a minimum. This minimum is filled when the NO molecules coming from the gas outside the streamer trace. It may be concluded that diffusion processes are important in description of the conversion processes of NO and SO2 in streamer discharges.
111 INFLUENCE OF HYDROCARBONS ON REMOVAL OF NOx IN A DIESEL EXHAUST GAS The influence of temperature and hydrocarbon additives on the NOx removal by streamer corona has been studied by numerical modelling for a synthetic gas mixture typical for diesel exhaust. The NO reduction of more then 99% was achieved at the energy cost of 14 eV per NO molecule in the presence of 550 ppm C3H6 additive at T=393 K. The simulated results agree well with the experimental data measured in the NO and NOx removal and C2H4 and C3H6 decomposition [6]. The C3H6 additive does not sufficiently suppress the conversion of SO2 to H2SO4. Figure 6 shows the influence of C2H4 and C3H6 on the NO remediation process at three values of temperature. The variations of C2H4 and C3H6 concentrations are also displayed at T=393 and T=493 K. The results are given in dependence on input energy in the atmospheric condition (T=293 K, p=l atm). There is a good agreement between the experimental and calculation results for NO and HCs variation in the presence of C2H4. Special modeling has been performed to check the influence of C3H6 on the SO2 conversion. The matrix gas included 4.8% H20, 495 ppm NO, 50 ppm SO2 and 545 ppm or 1500 ppm C3H6. The SO2 concentration diminished by 49.3 ppm with C3H6 for both concentrations and by 49.4 ppm without C3H6 at the input energy W=30 J/10.
(a)
600- N [ppm] ,
--... ..... , .... ...... o :~:.-...o.... -t..I"
9,
400
.....
9
500 ~ .....-'.7"'-~.,,
~_"
..... ~, .....
":.'.-.
4
- .......
\
500 ~..
'~.?-..
s
300
~176176" " ~
200
. /2 ~176176176
,
I
10
n
n
20
~'72.....-~4 9".. ~ . . . .
\
'.,
"~
-..~ ....~. /
- 'j,,.v.---< -,v~ 3
100
0
~
'.,X ~,'-.::~:.,... ,.,, o..
9...........................--
200
0
400
...... t~........... "..............
"""~
300
(b)
600 N [ppm]
,
Energy, J/1
i
30
'
" . . . . ~'""
40
/ ""%,.
100
~'' ~ - - ..~....,,.
'
,
0
0
=
10
t...,
,5.
\
..... -............... ~ Z I - -......... . -.-..... 9
1
v ,
20
k.=~..~...=.._
Energy, J/1
,
30
,
I
40
Figure 6. Temperature effect on concentrations of NO and HCs in dependence on input energy in the presence of (a) C2H4 and (b) C3H6.Symbols are experimental data, and the curves are the calculated results. Gas composition is given in Tablel. 1" NO removal, T=293 K; 2: NO removal, T=393 K; 3" NO removal, T=493 K; 4: HCs variation, T=393 K; 5" HCs variation, T=493 K
REFERENCES 1. Penetrante B.M., Plasma chemistry and power consumption in non-thermal DeNOx, In Non-Thermal Plasma Techniques for Pollution Control, NATO ASI Series, 34GA, Springer, Berlin, (1993) 65-89 2. Amirov R.H., Chae J.O., Desiaterik Yu.N., et al. Removal of NOx and SO2 from air excited by streamer corona: experimental results and modeling, Japan Journal of Appl. Phys. (1998) 37 3521-3529 3. Shepelin A.V., Amirov R.H. and Samoilov I.S., Influence of direct current voltage and form of high voltage pulses on ozone synthesis in pulse corona, Preprint IVTAN N 1-372, Moscow, (1994) 4. Filimonova E.A. and Amirov R.H. Simulation of Ethylene Conversion Initiated by a Streamer Corona in an Air Flow, Plasma Physics Reports, (2001) 27 708-714 5. Babaeva N.Yu. and Naidis G.V., Two dimensional modelling of positive streamer dynamics in non-uniform electric fields in air, J. Phys. D: Appl. Phys., (1996) 29 2423-2431 6. Filimonova E.A., Amirov R.H., Hong S.H., Influence of temperature and hydrocarbons on removal of NOx and SO2 in a diesel exhaust gas activated by pulsed corona discharge, Hakone VII, International Symposium on High Pressure, Low Temperature Plasma Chemistry, Estonia, (2002) 337-341
112 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Recent advances of power conditions for streamer corona plasma applications K. Yan, S.A. Nair, G.J.J. Winands, E. J .M. van Heesch, and A.J.M.Pemen, Department of Electrical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven The Netherlands, e-mail" [email protected]
This paper reviews the state of the art of power conditions for streamer corona plasma applications; it also discusses some critical issues when developing industrial systems. Based on streamer generation and interaction between power sources and reactors, the power conditions can be divided into two groups, namely HPPS and DC/AC. Today, single and multiple switch circuit topologies become available to scale the HPPS system up. DC/AC sources are being introduced into the market. The data available would be sufficient enough for commercial-scale design for either odour emission control or exhaust gas cleaning. We foresee that by retrofitting available ESP, a plasma based gas cleaning system to simultaneously remove polluting gases, heavy metals, and particles will be applied in the near future.
INTRODUCTION Over the past 20 years, pulsed corona plasma system was expected to be integrated together with electrostatic precipitator for simultaneous removal of dusts, SO2, NOx and heavy metals from exhaust gases [1]. Unfortunately, lack of cost effective corona plasma generation and processing techniques discouraged industries. Nevertheless, three industrial corona plasma demonstration systems with up to 50100 kW in average power were recently reported in Japan, Korea and China [2]. All of them are based on the magnetic compression technique with pulse duration of 200-500 ns. The main technical difficulty for applying such pulsed corona plasmas arises from simultaneous requirements on power rating, energy conversion efficiency, lifetime and cost. Moreover, industrial systems also bring up the main issue of the matching between the source and the reactor. In the first place, it is worth to note that by applying a positive voltage pulse in non-uniform electrode configurations, such as point-plate, wire-plate, and wirecylinder, streamer corona plasma will absolutely be generated once the applied voltage becomes beyond the inception; generation of streamer corona plasma, however, does not always need a pulsed-power source; DC and DC/AC ones can also be used. Thus, in principle, two kinds of power conditions: namely an ultra-short (20-50 ns) hybrid pulsed-power system (HPPS) [3] and DC/AC modulator [4] can be applied for industrial applications.
SIMULTANEOUS AND RANDOM STREAMER CORONA PLASMAS In a non-uniform electrode arrangement, electron avalanche can lead to streamer formation. Discharge channels in the form of streamers appear in the electrode gap. Generally speaking, there are two types of streamers: positive and negative ones. They are similar to the so-called cathode and anode directed streamers in a uniform electric field. Recent investigations on fundamental features of corona plasmas were mainly carried out by means of advanced electrical, optical and chemical diagnostics, and computer modelling. Based on the state of the art, a positive streamer can be described as: in a non-uniform electric field, highly ionized plasma, called streamer head, propagates from anode to cathode with a velocity of
113 105 - 3x106 m/s. The size of the plasma region is around 100 m during the propagation. Between the plasma and the anode, there is an almost dark streamer channel with a diameter similar to the diameter of the streamer head. After the streamer bridges the electrode gap, a current may keep flow via the formed channel, which is called secondary streamer. During the primary streamer propagation, a single streamer may branch to several. The average electric field in the channel is about 5-7 kV/cm in air and around 8 kV/cm in flue gas, respectively. It approximately equals to the streamer stability field, which is the minimum field for streamer propagation in a uniform electrical field. If the applied voltage is insufficient to supply the field for a streamer channel to bridge the electrode gap, the streamer head stops propagation before reaching the cathode. Thus, in order to generate corona plasma with a maximum streamer length inside the reactor, a minimum voltage for building up the streamer channel is required. The voltage can be a DC bias or a voltage pulse. As a result, a HPPS system has been considered as the most cost effective for pulsed streamer corona plasma applications. Figure 1 shows a mobile HPPS system. Sixteen wirecylinder reactors in-parallel are used to match a 10-30 kW HPPS source. The length and inner and outer diameters of each reactor are 1000, 3, and 160 mm, respectively. Detailed discussions are reported elsewhere [3]. By taking ICCD pictures with high resolution in space and in time, it was observed that inside a wire-cylinder or a wire-plate corona reactor, many parallel streamers propagate almost simultaneously from the corona wire towards the ground electrode. The time delay between individual streamers generated at different locations is close to the time required for voltage pulse to propagate from the one location to the other. As a consequence of many streamers in parallel, a large current pulse is needed for the generation. In this paper, we call this kind of plasma generation technique, which is obviously based on pulsed-power technologies, as simultaneous streamer generation. In contrast to using pulsed-power technologies, it is well lmown that for a point-plate electrode arrangement in air, a positive DC electrical discharge may change from onset streamer to glow, prebreakdown streamer and then to spark breakdown when increasing the applied voltage. The discharge patterns are dependent on electrode geometry, gas flow rate and compositions. The glow and streamer coronas can be distinguished by means of optical and electrical measurements. Unfortunately, generation of a large volume streamer corona with a DC source can face two technical problems. The first one is related to the effects of gaseous composition on the corona discharge pattern. The second is related to the sensitivity to electrode miss-arrangements. Non-uniform gas distribution and miss-arrangements of electrode configurations can cause the transition from streamer corona to glow discharge. As a result, glow and streamer may be generated simultaneously. In order to overcome the above technical problems and generate large volume corona plasma with a simple power source, a DC/AC energization technique was introduced: DC bias with superimposed high-frequency AC (10-60 kHz) [4]. Electrical, optical and chemical characteristics of DC/AC energized corona plasmas have been under investigations. In contrast to a corona discharge with a DC power source, DC/AC (10-60 kHz) energized corona plasmas are less sensitive to gaseous compositions and electrode miss-arrangements provided the AC peak-peak voltage is larger than 1.0 kV. Optical and electrical measurements show that streamers are produced randomly along the high-voltage electrode, and the peak current and the energy transfer differ per streamer. Figure 2 shows an industrial 1-2 kW system for deodorization. The length, height, and plate-plate distance are 1000, 1000 and 150 mm, respectively [2]. With a DC/AC source, streamers are not generated at the same time; thus, it becomes unnecessary to use a pulsed-power source for the plasma generation. In this paper, we call this kind of plasma generation technique as random streamer generation.
Fig. 1. A mobile HPPS system.
Fig.2. A mobile DC/AC system.
114 ENERGIZATION AND MATCHING Matching a high-voltage pulse generator to a corona plasma reactor becomes more important when scaling the system up. Optimizing the energy transfer increases the initial radical production; and improving the energy conversion efficiency reduces both investment and operational costs. Earlier reported technique for improving the matching is to use a DC bias in addition to a voltage pulse. Detailed guideline was just proposed to optimize peak voltage, rise time, output impedance, pulse duration, average power, corona reactor and also processing. Figure 3 shows the related logical steps and issues for optimization of the power source and the reactor. Experiments were carried out with a wire-cylinder reactor in air under a pulse repetition rate of up to 900 pulses per second (pps). The length and inner and outer diameters of the reactor are 800-3000, 3 and 155-160 mm, respectively. By increasing the peak voltage, the equivalent impedance of the reactor approaches to the output impedance of the generator as indicated in the lower sector, which gives a maximum energy transfer. For a corona plasma reactor, a minimum peak voltage is required in order to achieve the maximum energy transfer from the generator to the reactor. The total peak voltage can be obtained by superimposing the voltage pulse to a DC bias. When the applied voltage is below the minimum, there is always oscillation between the power source and the reactor. For almost all available pulsed-power circuit topologies, the oscillation not only leads to reduce the energy efficiency, but also could cause serious damage to their high-voltage switches. On the other hand, if the oscillating energy can be recovered, the energization technique shifts from pulse to DC/AC. Both capacitive and inductive coupling circuit topologies as shown in Fig. 4 can be adopted for design of a DC/AC power source. These two are the most common circuits for generation of DC/AC voltage. All kinds of switch mode techniques may be adopted for both AC and Fig.3. The primary streamer duration and the impedance ratio vs the applied voltage. DC parts. A direct DC/AC generation is also possible with a limited peak-peak AC voltage.
I
I
AC I _1_ ~ m
(a)" Capacitive coupling Fig.4. Typical circuit topologies for DC/AC energization.
115 For improving the chemical efficiency, the duration of pulsed power should be designed in accordance with the primary streamer duration as indicated in the upper cure in Fig. 3. Thus, a minimum peak voltage and a maximum duration as indicated in Fig.3 become important to obtain the maximum energy transfer and at the same time to avoid secondary streamer development. Otherwise, the interaction between the power source and the reactor leads to either high-frequency oscillation or large energy transfer via secondary streamers. Previous publications suggested that the DC bias should be below the onset voltage in order to avoid DC corona. In a HPPS system, however, the DC bias can be much higher than the onset but below the spark breakdown voltage. Our criteria are not to generate DC glow, but to generate DC onset streamer. Further scaling the average power up, multiple switch circuit topologies have to be applied in order to extend the lifetime of the switches [5]. Bridging the electrode gap by a streamer does not necessarily lead to full spark breakdown. However, spark breakdown occurs only after streamer bridging the gap and a streamer channel, or Townsend like glow discharge, is formed. The time delay for the streamer-glow-spark transition ranges from 0.2 to 25 ~ts. In contrast to the above ultra-short pulse, a DC/AC source may keep a long current flow when the streamer channel bridges the gap, and then lead to full spark breakdown. It seems that there is only one way to avoid the transition is that DC/AC plasma is generated below a maximum voltage, which can be approximated by the minimum voltage for streamer to bridge the gap. The plasma is indeed onset streamer discharge. The resulted drawback is limited plasma density per unit volume of the reactor. Fortunately, it is still high enough for air, flue and fuel gas cleaning.
CONCLUSION Two types of corona plasma energization techniques have been developed for simultaneous and random streamer generations. For a HPPS system, a minimum peak voltage and maximum pulse duration should be applied for improving both the matching and the efficiency. For a DC/AC system, the applied voltage must be below a maximum for streamer not to bridge the gap. Either secondary streamer or full spark-breakdown will not occur due to a low applied voltage. The power source and the reactor can be designed as a single oscillator. Today, the data available are sufficient enough to scale both HPPS and DC/AC up for industrial applications, and at the same time, much more R&D activities are called of for industrial applications.
REFERENCES [ 1] Dinelli G, Civitano L., and Rea M., (1990), Industrial experiments on pulse corona simultaneous removal of NOx and S O 2 from flue gas by means of impulse streamer corona, IEEE Trans. IAS, 25, 535-541. [2] Yan K., Winands G.J.J., Nair S.A., Pemen A.J.M., and Van Heesch E.J.M., (2004), From electrostatic precipitation to corona plasma system for exhaust gas cleaning, 9th Int. Conf. on Electrostatic Precipitation, May 17-22, South Africa. [3] Winands G.J.J., Yan K., Nair S.A., Pemen A.J.M., and Van Heesch E.J.M., (2004), A hybrid-pulsed power system for industrial applications of corona plasma techniques, Hakone IX, August 2004, Padova, Italy. [4] Yan K., Yamamoto T., Kanazawa S., Ohkubo T., Nomoto Y., and Chang J.S. (2001), NO removal characteristics of a corona radical shower system under DC and DC/AC superimposed operations, IEEE Trans on IAS, 37, 5, 1499-1504. [5] Yan K., Smulders H.W.M., Wouters P.A.A.F., Kapora S., Nair S.A., Van Heesch E.J.M., Van der Laan P.C.T., and Pemen A.J.M., (2003), A novel circuit topology for pulsed power generation", Journal of Electrostatics, 58, 221-228.
116 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Application of a plasma-catalytic system for removal organic pollutants Chae J.O., Demidiouk V.I. *, Yeulash N.M. Department of Mechanical Engineering, INHA University, Incheon, Korea. [email protected] *Department of Chemistry, Moscow State University, Moscow, Russia. [email protected]
The basic characteristics of the plasma-catalytic decomposition of toluene, butyl acetate, and isopropyl alcohol are investigated. The different kinds of plasmas such as corona, dielectric barrier and surface discharges are investigated in present work. It is found that non-thermal plasma alone cannot solve the problem of VOC removal due to formation of by-product such as CO, ozone, aerosols. Several catalysts for the VOC decomposition are introduced in a combination with plasma treatment. It is found that the plasma treatment significantly increases the catalytic decomposition rate and The Pt-based catalyst completely removed the CO produced by plasma reactor.
INTRODUCTION One of the promising ways of low-temperature VOC decomposition is non-thermal plasma technique. It is suggest that plasma technique has many advantages compared to conventional catalysis. The toxic compounds decompose at room temperature, so there are no needs to heat the toxic before the treatment. Besides, the plasma discharge works like an electrostatic precipitator and can be used for dust and liquid droplet collection. However, it is found that the plasma treatment leads to formation of by-products such as CO, 03 and aerosol particles [ 1,2]. Hence, in order to improve and increase the combustion of VOC's, an innovative technology was proposed where plasma reactor was coupled with a catalytic reactor [2-4]. Such a combination helps to bring down the disadvantages of both catalytic and plasma treatments. In the present paper, plasma-catalytic decomposition of toluene, isopropyl alcohol and butyl acetate is reported. The experimental studies for indoor air control as well as for industrial application are described here.
EXPERIMENTAL DESCRIPTION AND RESULT Catalysts preparation, The catalysts used for VOC decomposition in the present studies were honeycomb platinum catalyst and pellet type metal oxide catalysts. A cordierite honeycomb structure (60 channels/cm 2) was used as the support for Pt-catalyst. The honeycomb was coated with 7-A1203 and then impregnated with Pt(NH3)4(OH)2 aqueous solution. The catalyst was dried and reduced in the nitrogen-hydrogen mixture flow at 400~ The metal oxide catalysts were prepared from nitrate solutions of nickel, copper and manganese. The prepared solution was mixed with alumina pellets (diameter 3-4 mm and total surface 165m2/g). The catalysts were dried at 120~ and calcined at 400~
117 To C h e m i ~ Analysis
Application of pulse corona discharge for VOC decomposition The pulse plasma reactor was constructed using simple wire-cylinder geometry, Fig.1. The wire electrode was shaped in spiral form in order to increase the energy density in the reactor volume. The effective reactor length was 160 mm and the diameter was 22 mm. The reactor was energized using high voltage positive pulses. Experiments were carried out in two steps in the present studies. Firstly, VOC was decomposed using a plasma-catalytic reactor by passing VOC's mixed with air through the Inlet 1 (Inlet 2 was closed) as shown in Fig.1. In the second step, only air is passed though the Inlet 1, that is through plasma reactor to produce ozone. VOC's mixed with air was passed through Inlet 2. This reactor system is referred to as ozone-catalytic reactor.
VOC + Air (or Air only)
Fig. 1. Schematic diagram of the hybrid plasmacatalyst reactor.
VOC decomposition in Plasma-Catalytic system The main disadvantage associated with the plasma treatment of VOC's is the by-product formation. The radicals produced by plasma discharges react incompletely with VOC's leading to the formation of by-products such as CO, 03 and aerosol particles. The formation of CO was minimized when plasma reactor was combined with Pt-catalyst. The metal oxide catalysts did not lower the CO production. In fact, metal oxide catalysts exhibited CO formation even in the absence of plasma reactor. Fig.2 shows variation of CO concentration with plasma energy density for both plasma reactor and plasma-catalytic reactors. As observed in the figure, the plasma reactor combined with Pt-honeycomb Fig.2. Carbon monoxide formation in plasma catalyst was found to be better in terms of less catalytic reactorInitial concentration: butyl acetateformation of CO. 120 ppm, toluene- 280 ppm Fig.3 shows the decomposition of butyl acetate as a function of energy density. The plasmacatalytic performance is compared with plasma alone performance. It should be noted that plasma reactor was always operated at room temperature. In the figure, Line 1 represents the catalytic decomposition alone and Line 2 represents the plasma-catalytic decomposition. It was found that performance of plasma-catalytic reactor is significantly high for all the VOC's under study (butyl acetate, isopropyl alcohol and toluene). The removal efficiency of the plasma reactor determined as (/'plasma only-- [(Cinitial-Cfinal)/Cinitial]
where Cinitial and Cfinal are VOC concentration before and after plasma reactor correspondingly. It is interesting to separate plasma and catalytic stages and to calculate the efficiency of the catalyst activated by the plasma treatment. A parameter (Zcatalyst in plasma/catalyticwas used for this purpose which is defined by (Zcatalyst in plasma/catalytic -- [(Cafter plasma-fafter catalyst)/Cafte r plasma]
118 where, Cafter plasma and Cafter catalyst are VOC concentrations before and after catalyst in plasma-catalytic reactor respectively. The results of the calculation are presented in Fig.3 as Line 4. VOC Decomposition in Ozone-Catalytic system In order to find out the mechanism of plasma enhanced catalytic decomposition, ozone fed catalytic reactor was investigated and compared with plasma-catalytic reactor. For this, the VOC's mixed in 2% of air was passed through catalytic reactor alone (through Inlet 2, as shown in Fig. 1). The plasma reactor was used as ozone generator by passing pure air through it. Such system is referred as "ozone-catalytic". Fig.3. Butyl acetate decomposition in different systems. The performance of ozone-catalytic reactor is Initial concentration was 120 ppm, gas flow rate was presented and compared with the other reactors in Fig.3 through Line 3. The presented data with ozone-catalytic reactor shows that the enhancement of catalytic activity by plasma in the plasma-catalytic reactor includes reaction of ozone with catalyst surface. Ozone, produced by plasma decomposes on the active centers on the catalyst surface and generates surface oxygen radicals. This leads to the increased efficiency of catalytic centers. It is important to note that the improved effect is higher at low catalyst temperature. At high temperature, no significant difference was found between catalytic and ozoneFig.4. Schematic diagram of the hybrid plasmacatalytic decomposition rates because of lesser catalyst reactor for the indoor air control lifetime of ozone molecules at high temperatures.
PLASMA APPLICATION FOR INDOOR AIR CONTROL It has been reported that the plasma treatment could be successfully applied to indoor air cleaning, and it is suggested that plasma treatment lead to decomposition of gaseous pollutants as well as to formation of oxygen ion clusters, which is reported to play a very important role in the indoor environment [5,6]. The ammonia and toluene decomposition was investigated as a model of the deodorizing process here. Fig. 4 shows the scheme of the plasma reactor combined with catalyst. In this investigation a glass tube coated inside with copper film was used as a high-voltage electrode, and a metal net outside the glass tube was utilized as a ground electrode. It is suggested that the combination of silent and surface discharge is formed in such construction. The plasma catalytic reactor was placed in 0.5 m 3 closed acryl chamber. The reactor was fed with the 60 Hz frequency AC power supply. Applying of voltage leads to the rapid decomposition process. It was found that the plasma discharge is quite effective for ammonia and toluene decomposition. But high ozone concentration was formed in this case. We completely disagree with [6] that health concerns with plasma ionization can be solved by ozone concentration control. Our experimental data show that low ozone concentration generated by plasma reactor means extremely low removal efficiency in toluene and ammonia decomposition. It was found that catalyst increases the removal efficiency of decomposition in an initial period. But then it showed the similar removal efficiency in case of plasma discharge without catalyst, as it is shown in Fig.5 in case of toluene decomposition.We suppose that toluene as well as ammonia does not react with
119 the catalyst at room temperature. Therefore, there was no chemical reaction here, and adsorption on the surface of catalyst was happened in the initial time only. Catalyst reduced the ozone concentration dramatically. For example, Mn-Cu oxide catalyst decreased ozone more than 10 times. In addition, the use of catalyst allowed CO to be removed, too. Unfortunately, it is very difficult to find the catalyst which can remove CO up to "zero" at room temperature. But in any case catalyst application is very important. One of the merits of the plasma treatment is the purification effect of" positive and negative ion charges generated by plasma discharge. The presented plasma system generates high amount of negative ions (up to 40000 ions/cm -1) which are important for human health. But catalyst application decreases a little bit the ion concentration. adjusted in accordance with 1) ozone concentration, compounds and 3) ion concentration.
50
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
"~" 4 0 r--
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f /
/ Plasma only
---o--- Plasma+Catalyst(V) Plasma+Catalyst(Ni)
~ 0
20
4'0
Plasma+Catalyst(Mn-Cu) 6'0 8'0 Time(rain)
100
1~0
Fig.5. Removal of toluene by plasma catalytic hybrid system with different type of catalysts. Initial concentration of toluene was 30 ppm, voltage - 9 kV.
Therefore, the plasma catalytic system should be 2) removal efficiency in decomposition of toxic
CONCLUSION The performance of plasma-catalytic reactor for decomposing toluene, isopropyl alcohol and butyl acetate was demonstrated in the present studies. It was found that plasma significantly enhances the catalytic activity. Further, catalyst helps in minimizing the formation of byproducts. The performances of plasmacatalyst and ozone-catalyst reactor systems for VOC decomposition were compared. It was shown that ozone plays an important role in enhancing the catalytic activity. Catalyst application can be promising for the air ionization and deodorization.
REFERENCES 1. Oda, T., Takahashi, T., Yamaji, K., Nonthermal plasma processing for dilute VOCs decomposition, !EEE Trans. Ind. Appl. (2002) 38 873-878. 2. Oda, T., Non-thermal plasma processing for environmental protection: decomposition of dilute VOCs in air, J. Electrostatics (2003) 57 293-311, 3. Futamura, S., Einagaa, H., Kabashima, H., Hwan, L.Y., Synergistic effect of silent discharge plasma and catalysts on benzene decomposition Catal. Today (2004) 89 89-95. 4. Demidiouk, V., Moon, S.I., Chae, J.O., Toluene and butyl acetate removal from air by plasma-catalytic system, Catalysis Communications (2003) 4 51-56,. 5. Kinoshita K., Fujiyama K., Kim H.H., Katsura S., Mizuno A., Control of tobacco smoke and odors using discharge plasma reactor, J. Electrostatics (1997) 42 83-91. 6. Daniels, S.L., On the ionization of air for removal of noxious effluvia_.(Air ionization_Air ionization of indoor environments for control of volatile and particulate contaminants with nonthermal plasmas generated by dielectric-barrier discharge.), IEEE Trans. Plasma Science (2002) 30 1471-1481.
120 Paper Presented at the 5th International ConJerence on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Plasma Assisted Selective Catalytic Reduction of Nitrogen Oxides Chae J. O., Demidiouk V. I.*, Ravi V., Yeulash N. M., Choi I. C. Department of Mechanical Engineering, INHA University, Incheon, Korea, E-mail: [email protected] *Department of Chemistry, Moscow State University, Moscow, Russia
In this study, the effect of plasma pre treatment for NOx control on a SCR catalyst was investigated. A wire-cylinder plasma reactor was energized by short rising high voltage pulses. A SCR catalytic reactor was placed ahead of the plasma reactor. The significance of the plasma reactor was found to be conversion of NO to NO2. Plasma effect resulted in 35% increase in NOx removal efficiency on the catalyst at 180~ for an energy density of 47 J/1. The effect of plasma was found to be decreasing with temperature.
INTRODUCTION Reduction of nitrogen oxides (NOx) is considered as a great challenge in the overall task of keeping the environment clean. Presently, various industries employ selective catalytic reduction process to control NOx emissions. The limitation of SCR process is that it can not efficiently remove NOx from low temperature emissions. Pre-treatment of the exhaust gas by electric discharge plasma has been found to be helpful in enhancing the catalytic activity [1-3]. In the present work, a pulsed corona reactor has been used in combination with industry supplied SCR catalyst to control NOx from a simulated flue gas mixture. The role of plasma in the combined system at different operating temperatures is discussed. The effect of water on the combined system is studied.
EXPERIMENTAL SETUP
Figure 1 Schematic of the experimental setup The schematic of the experimental setup used in the present studies is presented in Figure 1. The treatment was carried out on gas mixture consisting of NO (120 ppm), 02 (15%), CO2 (3%) and N2 (balance). NH3 (120 ppm) was added to facilitate the SCR process. Some experiments were conducted by
121 adding water to the above gas mixture. Addition of water was ensured by passing the above gas mixture through a beaker containing water. The concentration of water was adjusted by varying the vapor pressure by means of heating the water. In such experiments the gas composition maintained was NO (120 ppm), 02 (15%), CO2 (3%), NH3 (120 ppm), water (10%) and N2 (balance). In both cases the flow rate of the gas was constantly maintained at 20 liters/minute. A stainless steel cylinder having a wire passing through in it co-axially was the plasma reactor. The length and diameter of the reactor were 240 mm and 30 mm respectively. The plasma reactor was energized by pulse power having a voltage range of 0-30 kV. The frequency of the pulses was kept constant at 200 Hz. Measurement of voltage and current was carried out using an oscilloscope (Tektronix TDS-754C). Energy per pulse was calculated by integrating the product of voltage and current. The discharge power was obtained by multiplying the energy per pulse with number of pulses per second. The catalytic reactor was placed ahead of the plasma reactor. The catalyst used was a SCR catalyst (supplied by FiberTech, South Korea). The space velocity of the catalyst was calculated to be 28,000 h ~ (volume of the catalyst was 43 cm3). Both plasma and catalytic reactors were placed inside an electric heating system and the experiments were carried out at temperatures from 180~ to 280~
RESULTS AND DISCUSSION Initial experiments were conducted using plasma reactor only. Experiments were carried out at temperatures 180~ 230~ and 280~ Figure 2 shows the ratio of NO2 in the plasma treated gas as a function of energy density. It can be observed that with increase in temperature of the gas mixture the NO2 conversion decreases. For example, at 180~ 44% of NO2 was obtained as against 25% at 280~ for an energy density of 47 J/1. The reason for decrease in NO oxidation at higher temperatures in plasma discharge is provided in [4]. This indicates that plasma reactor can be used effectively at low exhaust temperatures. The significance of plasma reactor in the plasma assisted SCR catalysis is to increase the NO2 concentration in the feed gas to the catalyst. 5 0 ~. .
.
.
.
.
.
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Energy density (J/I) Figure 3 NOx removal efficiencies at different gas temperatures using plasma assisted SCR catalysis as a function of plasma energy density
The gas-phase conversion of NO to NO2 by plasma in excess of oxygen is an essential intermediate step in enhancing the selective catalytic reduction activity. The NOx removal efficiency in catalytic process strongly depends on the plasma energy and consequently NO2 concentration in the gas mixture. Figure 3 shows the NOx removal efficiencies obtained using plasma assisted SCR catalyst at different gas temperatures as a function of plasma energy density. The 'zero' energy density on the X-axis represents the catalytic activity in the absence of plasma power. It is observed that with increase in plasma energy
122 density the catalytic activity increases. It is also observed that the effect of plasma on the catalytic activity decreases with increase in gas temperature. Figure 4 clearly shows this effect at three different temperatures. It was found that effect of plasma resulted in 35% increase in NOx removal at 180~ At 230~ and 280~ the plasma effect resulted in 27% and 13% respectively. The decrease in plasma effect is due to the low conversion of NO to NO2 by plasma reactor at higher temperatures. The plasma reactor can be made efficient even at higher temperatures too. The addition of hydrocarbons to the gas mixtures increases the oxidation rate of NO using plasma reactor at higher temperatures [4].
Figure 5 NOx removal efficiencies in dry and humid gas mixtures using plasma assisted SCR catalysis
Figure 4 Comparison of NOx removal efficiencies on SCR catalyst with and without plasma (plasma energy density: 47 J/l)
Further experiments were carried out by adding water vapor to the gas mixture. Despite the fact that water aids plasma conversion of NO to NO2, it was found that water addition led to decreasing the NOx removal efficiency in the plasma assisted SCR process. Figure 5 compares the NOx removal efficiency in dry and humid conditions. It was found that there is a marked difference between the results of dry and humid gas. In our opinion, water molecules react with active centers of catalyst thereby decreasing the removal efficiency. For example, the catalytic activity for NOx removal in dry gas is more when compared with that in humid air as can be seen in the figure. Table 1 Comparison of present results with those available in the literature
(oc)
Initial NOx (ppm)
HC Injection (ppm)
52
150
1000
1000
43
30
180
200
600
Tonkyn [7]
80
15
170
200
1800
Ravi [8]
78
50
200
300
750
Present work
70
47
230
120
NOx removal (%)
Energy J/1
Temperature
Mizuno [5]
70
Yoon [6]
Research groups
NH3 injection (ppm)
300 120
The results obtained in the present studies were compared with the other few results available in the literature. Table 1 shows such comparison. Parameters such as gas temperature, initial NOx concentration, hydrocarbon and/or ammonia additives are included. The present results are found to be reasonably good compared to other results from additive concentration and energy consumption points of view.
123 SUMMARY
Plasma assisted SCR process for removing NOx from low temperature emissions has been successfully demonstrated. It is possible to make SCR process more efficient in the presence of plasma. The combination is helpful when treating low temperature industrial emissions.
REFERENCES 1. Hoard, J, Plasma-Catalysis for Diesel Exhaust Treatment: Current State of Art, SAE (2001) 01FL-63 2. Kim, H. H, Takashima, K, Katsura, S,. Mizuno, A, Low-Temperature NOx Reduction Processes Using Combined Systems of Pulsed Corona Discharge and Catalysts, Journal of Physics D: Applied Physics, (2001) 34, 604-613 3. Penetrante, B. M, Brusasco, R. M, Merritt, B. T, Vogtlin, G. E, Environmental Applications of Low-Temperature Plasmas, Pure and Applied Chemistry, (1999) 71 1829-1835 4. Ravi, V, Mok, Y S, Rajanikanth, B. S, Kang, H. C, Temperature Effect on Hydrocarbon-Enhanced Nitric Oxide Conversion Using a Dielectric Barrier Discharge Reactor, Fuel Processing Technology, (2003) 81 187-199 5. Mizuno, A, Shimizu, K, Yanagihara, K, Kinoshita, K, Tsunoda, K, Kim, H. H, Katsura, S, Effect of Additives and Catalysts on Removal of Nitrogen Oxides Using Pulsed Discharge, IEEE-IAS Annual Meeting- San Diego, CA (1996) 1806-1812 6. Yoon, S, Panov, A. G, Tonkyn, R. G, Ebeling, A. C, Barlow, S. E, Balmer, M. L, An Examination of the Role of Plasma Treatment for Lean NOx Reduction Over Sodium Zeolite Y and Gamma Alumina: Part 1. Plasma Assisted NOx Reduction Over Na-Y and A1203, Catalysis Today (2002) 72 243 -250 7. Tonkyn, R. G, Barlow, S. E, Hoard, J. W, Reduction of NOx in Synthetic Diesel Exhaust via Two-Step Plasma-Catalytic Treatment, Applied Catalysis- B: Environmental (2002) 1240 1-11 8. Ravi, V, Mok, Y. S, Rajanikanth, B. S, Kang, H. C, Studies on Nitrogen Oxides Removal Using Plasma Assisted Catalytic Reactor, Plasma Science and Technology (2003) 5 2057-2062
124 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Improvement of Energy Efficiency in the Dilute Trichloroethylene removal by Using Nonthermal Plasma Processing combined with Manganese Dioxide Sangbo Han, Tetsuji Oda Department of Electronic Engineering, The University of Tokyo7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
In order to improve energy efficiency in the dilute trichloroethylene removal by the nonthermal plasma process, source types of barrier discharge reactor was experimentally studied. Decomposition efficiency was improved as 99% at the specific energy of about 40J/L with passing through manganese dioxide. This result is ascribed to the application of catalytic surface reaction in the nonthermal plasma process.
INTRODUCTION The nonthermal plasma technologies in the treatment of gaseous pollutants have investigated by many researchers [1]-[7]. Recently, these processes of nonthermal plasma technologies showed a tendency to combine with catalysts for the improvement of the energy efficiency. For the decomposition of gaseous trichloroethylene (TCE; C2HC13), S. Futamura et al. [5] reported the detailed identification of volatile byproducts with ferroelectric pellet filled reactor. Chlorinated compounds should be fixed before releasing to our environment, due to its toxicity on our health and sources of environmental problems. The author group had also reported on the catalytic effects (V205, WO3, TiO2) for the decomposition of dilute TCE by using catalyst's filled barrier discharge reactor [3]. The objective of the present study is to improve the energy efficiency combined with catalysts at the downstream of barrier discharge reactor. Catalyst of manganese dioxide (MnO2) is used for its high ability for the ozone decomposition [8]. Variation of byproducts was investigated in detail related with specific energy density (SED).
EXPERIMENTAL SYSTEMS TCE-contaminated synthesized air was adjusted by injecting liquid TCE with a micro-syringe pump. TCE concentration was constant at 250ppm. In addition, manganese dioxide (MnO2; 25g less than 3mm length) filled in Teflon tube (Inner Diameter: 8mm, filled zone: 250mm) is arranged at the downstream of barrier discharge reactor. Specific surface area of manganese dioxide (Pyrolusite; 13-MnO2) was 12.14 m2/g. GCMS-QP5050A (Shimadzu Co.), FT-IR (Shimadzu Co., Prestige 21), ozone meter (Okitronics, OZM700G), and chemical luminescence NOx gas analyzer (Shimadzu Co., NOA-7000) were used for the analysis of byproducts variat.ion. The barrier discharge reactor is composed of a quartz tube and a stainless steel bolt as shown in Figure 1. The inner diameter of quartz robe is 16.4mm with thickness of 1.6 mm and the diameter of a discharge electrode is 12mm. The discharge region is long about 200mm, and the discharge gap was 2.2mm. The discharge power is measured by Lissajous-figure method.
125
Figure 1 Schematics of experimental setup and barrier discharge reactor
EXPERIMENTAL RESULTS In Figure 2(a), decomposition efficiency of TCE versus SED improved as about 99% at the specific energy of about 40J/L in the case of passing through manganese dioxide. Without passing through manganese dioxide, namely plasma processing only, decomposition efficiency of about 99% is attained at the specific energy of about 240J/L. As a result, barrier discharge plasma processing combined with manganese dioxide is an effective approach for the decrease of energy consumption. However, maximum COx yield does not exceed 50%, and main chlorinated-byproducts in any cases of below 100J/L are DCAC (dichloro- acetylchloride, CHC12-COC1), TCAA (trichloro-acetaldehyde, CC13-CHO), and C12. TCAA is generated from the oxidation of TCE, not from DCAC. It is confirmed from the comparison of Figure 2(a) and Figure 3(a) relevant to the variation of TCAA and decomposition efficiency of TCE. Oxidation byproducts of DCAC and TCAA are generated from barrier discharge plasma processing and catalytic surface chemical reaction, respectively. Therefore, those oxygen radicals cause the different reaction kinetics. From results of COx yield in Figure 3(b), surface chemical reaction by oxygen species at catalysts increases CO and CO2 concentration. This is very important result to improve energy efficiency through catalytic chemical reaction. 100-
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However, complete oxidation of TCE into COx is required to about 400J/L in these experimental conditions at 250ppm. CO2 selectivity is about 60%, and NxOy (NO, NO2, N 2 0 ) is not generated largely. For the complete oxidation of byproducts, the required energy is very high despite of the improvement by the combined process with catalysts. Consequently, it is necessary to improve energy efficiency more than this result. For that, relation between SED and the initial concentration of pollutants as well as byproducts distribution are necessary. In addition, it is required to the consideration of catalytic parameters such as specific surface areas, geometry, gaseous pollutants, and so on.
126
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EXPECTED CHEMICAL REACTIONS Chlorine radical chain reaction is a plausible decomposition mechanism in the barrier discharge. It might be initiated from collisions of electron or excited species. Rectangular marked substances are main byproducts detected in this experiment. This mechanism is only limited on radical reactions, not considered ionic reactions as shown in Figure 4. Subsequent catalytic reactions after barrier discharge plasma processing are inferred from the increase of COx concentration with passing through manganese dioxide. Those reactions are thought as, generation of O radicals from dissociation of the chemisorbed ozone on the surface of manganese dioxide. Then, additional generation of reactive chlorinated intermediates such as 02, C10, and 0 0 2 from chlorinated byproducts. Those reactive species might cause the energetic chemical reactions to increase of COx concentration. From this process, additional chemical methods are required for the fixation or conversion of final byproducts of C12 using solutions of NaOH or Ca(OH)2.
127 t
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CONCLUSIONS Experimental results are summarized as follows; decomposition efficiency was improved as 99% at about 40J/L with passing through manganese dioxide. However, complete oxidation into COx is required to about 400J/L. Chlorine radical chain reaction is a plausible decomposition mechanism in the barrier discharge plasma processing.
ACKNOWLEDGEMENT The authors wish to acknowledge the financial support from Ministry of Education, Science, and Culture in Japan.
REFERENCES 1. Baldur Eliasson, Ulrich Kogelschatz, IEEE Trans. Plasma sci., Vol. 19, No. 6 (1991) 1063-1077 2. Kuniko Urashima and Jen-Shin Chang, IEEE Trans. Dielec. and Electri. Insul., Vol.7, No. 5 (2000) 602-614 3. Tetsuji Oda, Kei Yamaji, and Tadashi Takahashi, IEEE Trans. Indus. App., Vol. 40, No. 2 (2004) 430-436 4. Atsushi Ogata, Daisuke Ito, Koich Mizuno, Appl. Catal. A, General 236 (2002) 9-15B 5. Shigeru Futamura, Toshiaki Yamamoto, IEEE Trans. Indus. App., Vol.33, No. 2 (1997) 447-453 6. THEODORE MILL, MINGGONG SU, others, Radiat. Phys. Chem. Vol. 50, No. 3 (1997) 283-291 7. Teruyuki Hakoda, Shoji Hashimoto, and Takuji Kojima, Bull. Chem. Soc. Jpn., 75 (2002) 2177-2183 8. B. Dhandapani, and S. Ted Oyama, App. Catal. B, environ. 11 (1997) 129-166
128 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Micro-discharge in porous ceramics for exhaust gas cleaning **
*
.
*
Jun Sawada*, Yoshihiko Matsui*, Karol Hensel , Ippei Koyamoto, Kazunori Takashlma, Shinji Katsura* and Akira Mizuno* * Department of Ecological Engineering, Toyohashi University of Technology Tempaku-cho, Toyohashi, Japan 441-8580 Comenius University, Faculty of Mathematic, Physics and Informatics Department of plasma Physics, 842-48 Mlynska dolin~t, Bratislava, Slovakia
In this study, a novel NOx removal method using micro-discharge in porous ceramics for exhaust gas cleaning was examined. Micro-discharge consists of many discharges in narrow channels inside porous ceramics, and transition to flashover can be suppressed due to narrow channel. The micro-discharge was generated by 60Hz ac high voltage using 29 mm diameter ceramics plate with 10 W electrical input, and was applied for the cleaning of exhaust gas from diesel engine. Two kinds of ceramics with different pore size of 15 ~t m and 90 ~t m were used. Simulated gas consisted of NO, 02, N2 (0.01%, 10%, balance), and C2H4 (0%, 0.3% or 0.6%) was supplemented as additive at some conditions. NO oxidation experiments were carried out at 20~ and 150~ As a result, oxidation ability without the C2H4 addition was higher than that with the additive at 20~
INTRODUCTION Nitrogen oxides (NOx) in exhaust gas from internal combustion engines, especially from diesel engines, cause air pollution and health problems. Conventional NOx removal process for automobile engines is a catalytic process. Such a catalytic process, however, requires high temperature and low oxygen concentration. Recently, non-thermal discharge plasma or combination of non-thermal discharge plasma and catalysts has been extensively investigated for NOx removal, because non-thermal discharge plasma can induce chemical reactions under moderate temperatures [ 1]. The packed bed type is a NOx removal reactor that can be used in combination with pellet type catalysts. In this reactor, an intense plasma is generated in limited area around many contact points between the pellets. The packed bed reactors achieved good performance in spite of the small plasma volume [2]. However, most catalysts used in practical processes are honey-comb structure, because it has high conversion efficiency, a large surface area and prominent durability. Therefore, combination of plasma and honey-comb process should be very effective for NOx treatments. If an effective combination of plasma and honey-comb catalyst is developed, the performance will be improved. For this purpose, we examined the NOx removal using the micro-discharge. Porous ceramics were used to generate the micro-discharge due to electrical breakdown in micro channels. This microdischarge can possibly be used to generate discharge plasma in honey-comb catalyst having porous structure with microchannels.
MICRODIScHARGE IN POROUS CERAMIC PLATE When an Electrostatic Precipitator (ESP) is used for dusts with apparent resistivity more than about 5 X 10 ~~0 cm, breakdown takes place in a dust layer. This is called back corona. In this research,we examined
129 a NOx removal process using back corona, or electrical breakdown inside the ceramics. This process can be used for the combination of a catalyst and non-thermal discharge plasma. Fig.1 shows a schematic illustration of the micro-discharge in porous ceramics plate. AC or DC high voltage is applied to a needle (or a mesh electrode placed on the surface of the ceramics instead of the corona electrode), and corona discharge charges up the surface of the ceramics to cause breakdown (1, 2) The breakdown can be confined in narrow channels of the ceramics, and transition to arcing can be avoided.(3), and this microdischarge can be stabilized.
Fig. 1 Schematic illustration of micro-discharge (e-: negative ionic charge)
EXPERIMENTAL SETUP Fig.2 shows a micro-discharge reactor. Experiments were carried out using AC 60 Hz high voltage. Two disk electrodes (18 mm-diameter) made of fine stainless steel mesh were placed on both sides of the ceramics disk. Disk-type porous ceramics plates (3 mm thickness and 29 mm diameter) were used in the experiment. Table.1 shows the properties of the ceramics. Ceramics A and B with different pore size were sintered from alumina powders of different size.
Table.1 Properties of the ceramics A1203 contents Pore size Powder size Porosity [%] [~tm] [~tm] [%] Ceramics A
92
15
40
42
Ceramics B
92
90
180
37
Fig.2 Reactor of micro-discharge Fig.3 shows a layout of the experimental setup. The gas composition of NO, 02, C2H4 and N2 was adjusted using mass flow controllers. The simulated gas contained 100ppm NO, 10% of oxygen and 0 or 300 ppm C2H4 in N2 base gas. Gas flow rate was 0.6 LPM (liter per minutes) and the pressure loss were 1.5 kPa and 140 Pa for ceramics A and B, respectively. The input power was kept constant at 10W in all experiments. The reactor was placed in an oven, and the temperature was set at 20~ or 150~ The NO and NOX (=NO+NO2) concentration were monitored with a NOX meter (HORIBA PG-250). The concentration of C2H4 was measured using GC-FID (Shimazu GC-14B). The voltage waveform was monitored by an oscilloscope (Tektronix TDS 350) with a high voltage probe (Tektronix P6015) during the experiment.
130
Fig.3 Schematic diagram of the experimental setup
RESULTS AND DISCUSSION Fig.4 shows the concentration of NO and NOX with and without C2H4 at 20 ~ Fig.4(a) and (b) correspond to the results with ceramics A and B, respectively. In Fig.4(a), NO concentration rapidly decreased after starting the voltage application with or without the additive. NOX concentration, on the other hand, was not changed by the voltage application. These results indicate that NO was oxidized to NO2 due to the micro-discharge but no further reaction, nor absorption took place to remove NO2. NO oxidation ability without additive was higher than that with the additive. C2H4 was not decreased even when the plasma was generated in this case.
Fig.4 Concentration of NO, NOx and C2H4at 20~ -Condition of Fig.4 a, b; Gas flow rate:0.6LPM, Temperature:20~ Space Velocity, a:38000h-l b:43000h-~ 300ppm of C2H4 was used as additive, AC high voltage(60Hz, a: 16kVp.p,b: 15kVp_p),Input power" 10W In the ceramics B as shown in Fig.4(b), the oxidation ability of NO with or without the additive were higher than that of ceramics A. Concentration of C2H4 decreased by 70ppm. The oxidation ability of NO without the additive was higher than that with the additive in this case, too. Under this condition, the additive (C2H4) did not enhance the oxidation of NO. This NO-oxidation characteristics using the micro-discharge were quite different from those using DBD (Dielectric Barrier Discharge) or pulsed corona, in which NO oxidation can be enhanced using C2H4 [2].
131
Fig.5 Concentration of NO, NOx and C2H4at 150~ using ceramics B -Condition of Fig.5 a,b; Gas flow rate:0.6LPM, AC high voltage (60Hz, 1lkVp_p), Input power:10W The results at 150 ~ is shown in Fig.5. The experiment was carried out using the ceramic B with (a) 300ppm and(b) 600ppm of C2H4 as the additive. In Fig.5(a), the oxidation ability of NO with the additive was slightly higher than that without the additive. The concentration of NOX with and without the additive were increased by about 10-20ppm when the microdischarge was generated. In Fig.5(b) with 600ppm of C2H4, the NO oxidation ability was slightly higher but similar to Fig5(a). CONCLUSIONS We studied the NOx removal using the micro-discharge. Microdischarge can be generated with ac 60 Hz energization of 10 W input power, using two kinds of ceramics plate of 29 mm diameter of average pore size of 90 la m and 15 ~ m. The oxidation of NO using ceramics with average pore size of 90 ~ m at 20~ without C2H4additive showed the highest performance among the conditions tested in this study.
REFERENCE [1] Naoki Takahashi et al., Catalysis Today, Vol.27, (1996), 63-69 [2] Yoshihiko Matsui et al., SAE Technical paper, No.2001-01-3511
132 Paper Presented at the 5th International ConJerence on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Decoloration of azo dye using active species formed by bipolar pulsed discharge in a three phase discharge reactor Zhang Ruobing, Li Guofeng, Wu Yan, Wang Ninghui Institution of Electrostatic and Special Power, Dalian University of Technology, Dalianl 16024, China
Removal of Amaranth, a commercial synthetic azo dye widely used in the dye and food industry, was examined as a possible remediation technology for treating dye-contaminated water. Effects of various parameters such as gas flow rate, solution conductivity, pulse repetitive rate and ect., on decolorization kinetics were investigated. Experimental results show that packed bed reactor exhibits a good performance in treating the azo dye wastewater. Decolorization reaction of the amaranth in water is a pseudo first-order reaction. Rate constant of the reaction is dependent on the experimental conditions. TOC of the solution decreases after non-thermal plasma treatment.
INTRODUCTION Non-thermal plasma has been an established method for cleaning of gases from ecologically harmful impurities such as VOCs abatement, flue gas desulphurization [ 1] and ect.. However, discharge in water has only recently received attention. Pulse electrical discharges in water have been studied to removal several organics from wastewater streams [2]. Water treatment by pulsed discharge plasma seems to be a promising and alternative technology for the removal of the non-biodegradable pollutants. In our previous study, electrical discharges in a water-air mixture have been used to remove several dyes in water[3][4]. In order to perfect the reactor and strengthen the mass transfer process, we packed dielectric fillings into the reactor, and a packed-bed reactor was constructed. Electrical discharge characteristics of this reactor have been studied, with indigo carmine worked as the probe organics [5]. Azo dyes, the largest class of synthetic dyes used in the food industries, are characterized by the presence of one or more azo bonds (-N=N -) in association with one or more aromatic systems. Many studies indicate that these dyes are toxic or carcinogenic. However, these dyes are not normally removed by conventional wastewater treatment systems. Therefore, the employment of these dyes must be controlled and the effluents must be treated before being released into the aquatic and terrestrial environment. In the present investigation, bipolar pulsed barrier discharge in the packed-bed reactor has been used to remove one azo dye(amaranth) in the polluted water. Effects of the several parameters on decolorization kinetics of the solution have been studied to find an optimized operating condition of the system.
EXPERIMENTAL SYSTEM Analytical grade Amaranth and potassium chloride were used in all the investigations and the dye solution was prepared in batch to avoid possible error. The plasma chemical reactor is a glass tube( ~ in • L=60 mm • 500 mm),with grounded reticulate stainless steel electrode tightly attached to its inner side. A stainless steel high voltage electrode, having dimensions of 2 mm outside diameter and 350 mm in length, is concentrically placed in the glass reactor. A quartz glass insulator fully covers the whole surface of the stainless steel electrode to protect it from
133 erosion, and to enhance the inner electric field between the two electrodes. Air aerator which can give bubbles of micron size is fixed at the bottom of the reactor and the distance between the aerator and the
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bottom end of the high voltage electrode is 10 ram. Glass beads were used as the fillings and packed into the volume between the two electrodes. Height of the packing layer is 180 mm and effective electric height was 220 mm. Fix the height of the fillings, and regulate the flow meter to a target value. Add water to reactor and switch on the power of the bipolar pulsed power supply. Electrical discharges occur when the applied voltage is above the breakdown voltage of the system. All the experiments were conducted in a batch mode. Typically, 5ml samples were taken from the reactor vessel at lmin intervals during each run. Dynamic UV-Vis spectrum of the solution was scanned using a Jasco V-550 UV-Vis spectrometer. Absorbance of the solution was also measured at 522 nm with the deionized water as blank. Three trials were made for each experimental condition and resulted in errors of less than 5%. All the experiments gave a high reproducibility during the experimental process.
RESULTS AND DISSCUSSION 0.55
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Effect of initial solution conductivity Initial solution conductivity is another important factor Table 4 depen_dentof_k0nsolution pH....... that affects the reaction kinetics of the plasma pH k (min -I) Ra reactor(table 3). As the initial conductivity of water 3.07 0.02105 0.99969 increases, the number of the ions increases. The direct 4.95 0.01603 0.9996 result is that the establishment of the high partial electric field much more difficult and the number of 7.78 0.02315 0.99983 breakdown micro-channels decrease and influence of 8.2 0.0238 0.99986 space charge on the electric field distribution is lowered. 10.25 0.0269 0.99963 In addition, the quantities of ions present in the solution can strongly alter the propagation of the streamer by quickly compensating the space charge electric field on the streamer head of the plasma channel and that lead to the decrease in the generation of chemically active species. ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: : : : : : : : : : : : : : : : : : : : : : : : : : : :
.......
::
::
:: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :
Effect of effect of solution pH PH of the solution has much effect on the rate constant for that pH of the solution not only affects the characteristics of the dye molecules, but affects the generation and reaction of some active species contained in the plasma. Generally speaking, alkaline solution is favorable for the decoloriaztion process of amaranth in the plasma reactor (table 4). Effect of pulse repetitive rate Rate constant increases with the increase of pulse repetitive rate, as is shown in table5.At higher pulse repetitive rate, much more energy is injected into water per unit time and a higher energy density per unit volume of water-air mixture obtained. Under the same experimental conditions (Vpp, initial solution characteristics and gas flow rate), the number of micro-discharges during every unit of time increases, broken down bubbles and the quantities of chemically active species would greatly increase, which finally leads to the increase in the collision and even reacting probabilities of the generated species with the pollutants. The absolute quantities of reacting active species increase and higher color removal efficiency is obtained.
135 Variation of TOC It is evident that the plasma chemistry process is not involved only the decolorization of the dyes, i.e. the cleavage of azo groups. The aromatic fragments are also degraded, but at a slower rate than that of decolorization. Consequently, the non-thermal plasma treatments of dyeing wastewater not only provide decolorization, but also an appreciable degree of aromatic ring destruction in the dye molecules. Figure 4 shows the degradation of the TOC of the solution during the treatment process.
Table 5 dependent of k on pulse repetitive rate .
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25 50 75 100
CONCLUSION Based on the experimental investigations presented in this paper, the following conclusion may be made: 1. Decolorization reaction of the azo dye amaranth is a first ordered reaction. 2. Experimental conditions such as power supply (Vpp, pulse repetitive rate), physical characteristics of the solution (conductivity, pH), air flow rate (Q air), have significant influence on the reaction constant rate k. 3. TOC of the solution decreases during the treatment process.
.
235 230 22s ~ 220
9
k~...,
i
,
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k (min-1) .
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0.02333
0.99978
0.03381
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0.99899
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i
--=--Vpp=6OkVVgas=O.75m3/h f=50Hz 9
i
!
9
.
E 215
O
~- 2~o. 205200~950 ' 2'0 ' 4'0 ' do ' 8'0
'
i
100
9
i
12o
t(min)
Fig. 4 Variation of the TOC
REFERENCE [1] Wu Yan, Li Jie, Wang Ninghui, Li Guofeng, Industrial experiments on desulfurization of flue gases by pulsed corona induced plasma chemical process. Journal of Electrostat, (2003) 57233-241 [2] Grymonpre D. R., Sharma A.K., Finney W.C.et al.The role of Fenton's reaction in aqueous phase pulsed streamer corona reactors, Chemical Engineering Journal, (2001) 8_22189-20 [3] Zhang, R. B., WU, Y., Jin, C. Y., Li, J. Research on bipolar narrow pulsed dielectric barrier discharge(DBD) reactor for water treatment and its performance. J. DUT (2003) 4__33719-722. [4] Zhang Ruo-Bing. Water treatment by pololar pulsed barrier discharge. MS dissertation of DUT. DUT, Dalian, 2002 [5] Zhang Ruo-bing, Wu Yan, Li Guo-feng, Wang Ning-hui, LI Jie. Plasma Induced Degradation of Indigo Carmine by Bipolar Pulsed Dielectric Barrier Discharge (DBD) in the Water-air Mixture. J. Environ. Sci. (2004) 16 (in press) [6] Zhang Ruo-Bing, Wu Yan, Li Jie, Li Guo-Feng, Li Teng-Fei, and Zhou Zhi-Gang. Water Treatment by the Bipolar Pulsed Dielectric Barrier Discharge (DBD) in Water-Air Mixture. J. Adv. Oxid. Technol. (2004) _7 (in press)
136 Paper Presented at the 5th International ConJkrence on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Theoretical Study on Electrode Configuration of Wire-plate Reactor with Pulse Streamer Discharge Dong Bingyan 1'2, Wu Yan 1, Li Guofeng ~, Li Jie I Institute of Electrostatics and Special Power, Dalian University of Technology, Dalianl 16024, China 21 Department of Environment and Architecture Engineering, Jiangxi University of Technology, Ganzhou 341000,China
The electrode configuration of wire-plate pulse corona reactor is a critical factor that influences characteristic and DeSO2 efficiency. In this paper the electric field distributions in the reactor under different electrode configuration have been calculated by numerical modeling. And we combine the modeling results with the conditions of electric field required for streamer corona inception, development and propagation to optimize electrode configuration. The simulation results show that the optimization wire-to-wire spacing is 0.6-1 times the size of the wire-to-plate spacing. The comparison with experimental results shows a good qualitative agreement.
INTRODUCTION Pulsed streamer corona discharge can be produced by the application of fast rising narrow high voltage pulses to non-uniform electrode geometry. The pulsed corona discharge produces streamers with a diameter of the order of 100 ~t m, in which many kinds of radicals, excited particles, and ions are produced by electron impact processes. Those chemical species produced in the streamers decompose the pollutant molecules via chemical reactions [1-3]. At present, the reactor design is a main factor for affects the energy cost, the pulsed generator matching and the industrial application of pulsed streamer corona discharge. Therefore, studies have been focused on determining the optimization of the reactor design for improving streamer corona energy injecting and reducing power cost [4-5]. Therefore, from theoretic to optimize electrode configuration will provide valuable instruction for the reactor design, manufacture and industrial application. The paper presents a numerical simulation of electric field distribution of reactor in air at atmospheric pressure. THE CONDITION FOR THEORETICAL MODELING Pulsed streamer corona discharge is a transient process according to pulsed voltage. Therefore, some conditions required for the inception, development and propagation of streamer corona in the pulsed duration [6-9]" (1) exist free electron, (2) applied field on the discharge wires above the corona onset field, the corona onset field as given by Peek's formula [10], (3) external field near grounded plate ought not to less than stability field. Though streamer created by the high field but it also can propagation until the grounded plate in low applied field regions. The lowest external applied field that makes the propagation of streamer energetically stable is called the stability field. Its value in ambient are is roughly 5 kV/cm. If the external field in low field region is up to 5 kV/cm, the streamer can stable propagate and bridge the electrode gap with the maximum electric field keep constant in the streamer head [8-9]. In wire-plate reactor for DeSO2, (1) to insure the inception and development of streamer corona, the peak value of applied pulsed field on the discharge wires must above the corona onset field; (2) to insure the stable propagation of streamer corona, the external applied field (quasi-uniform electric field) in wire-plate spacing must reach 5 kV/cm. So, from the point of view of engineering application, it is a simple method
137 using external applied field distribution to judge the inception, development and propagation of streamer corona take no account of the complex physics kinetics of electrons and ions in the streamer channel.
THE NUMERICAL MODELING OF APPLIED ELECTRIC FIELD The applied voltage ( V t ) is equal to superimpose vt 1 tJi .~C the peak pulsed voltage on a DC-bias voltage 9 i (Vd). Fig.1 shows the i ideal voltage waveform. The streamer corona X wire inception, development vd g,.~-l:r4 and propagation mainly plate time(ns) occurs under the peak Fig.2. The geometry of reactor pulsed voltage duration ig. 1. Applied voltage waveform because the front rise time is very short. Therefore, the peak value of applied voltage determines the inception, development and propagation of streamer corona. So, the numerical analysis is performed in a peak pulsed voltage duration by solving the Laplacian equation. 9
General assumptions The following general assumptions are made for the numerical modeling: (1) pulsed voltage is applied to the wire, (2) there is atmosphere in the inter-electrode region, (3) discharge electrode is a round and smooth wire, (4) reactor works under NTP, (5) variation of voltage in the direction of the discharge wire is negligible, reducing the model to two-dimension. Boundary_ conditions The solution domain in the wire-plate reactor geometry is shown in Fig.2 Due to the double spatial symmetry of the reactor, the domain consists solely of the rectangle ABCD, AB equal s is one-half wireto-wire spacing, AD (equal to h) is wire-to-plate spacing, respectively. It is assumed that the solution will hold for all similar rectangles within the reactor. The following boundary conditions are applied to the specified domain [11]" ( i ) E x - 0 and E y - 0 at points A and B (electric field in x and y coordinates), (ii)Ey - - ~ V / O y - O
along line AB, (iii) E x - - ~ V / ~ x - O
along lines BC, CD and AD, (iv) At point A
(wire), V-Vt (applied voltage), ( v ) V-0 along line CD. Method of solution The electrical conditions inside the reactor have been analyzed that there is no space charge distortion the external electric field because ions leave in streamer channel not to diffuse in such shorter pulsed duration. So, the governing electrostatic equations are VZv - 0
(1)
E - -VV
(2)
The governing equation (1) and equation (2) with boundary conditions are numerically solved in two dimensions using finite-element method.
RESULTS AND DISCUSSION In this modeling, the radius of the discharge wire is 0.2 cm, the corona onset field given by Peek's formula is 39 kV/cm.
138 At fist, we choose the wire-to-plate spacing is 10 cm, the applied voltage is 80 kV (DC-bias voltage is 20 kV, the pulsed voltage is 60 kV), so at these conditions, Fig.3 (a) (b) (c) (d) shows the equipotential lines distribution of different wire-to-wire spacing. Fig.4 shows the electric field distribution along AD of different wire-to-wire spacing.
Fig.3. Potential distribution of different wire-to-wire-spacing, with 4kV equipotential lines wire-to-wire spacing: (a) 4cm (b) 6cm (c) 8cm (d) 10cm
Distance from wire to plate(cm) Fig.4. Electric field distributions along AD of different wire-to-wire spacing
From Fig.3 and Fig.4 we can see high external electrics field is concentrated near the discharge wire and its region is very small. Potential and electric field of the region reduce very quickly. In the gap between wire and plate low electric field region is very large, the equipotential lines and electric field tend to uniformity. These distributions accord with the law of the pulsed streamer corona discharge that streamer was generated in high field strength and developing along the electric field line, then enter into the quasi-uniform electric field and stable propagation. The change of wire-to-wire spacing has great influence on the electric field distribution. When the wire-to-wire spacing decreases, the high field region shrinks and the field strength decreases. On the contrary, the low field region augments and the equipotential lines become denser, which corresponds to an increase of the electric field near the grounded plate. Besides, the electric field distribution of low field region tends to quasi-uniform distribution. Fig.3 and Fig.4 show when wire-to-wire spacing is 4 cm, the electric field on the wire surface is 36kV/cm for the strong interference of wire-to-wire. But the average electric field of low field region is up to 7 kV/cm. Therefore, the pulsed streamer corona can't initiate under this electrode configuration because the maximum surface field of wire is less than the corona onset field. When wire-to-wire spacing is 10 cm, the electric field on the wire surface is 62 kV/cm, the average electric field of low field region is 4.8 kV/cm. Although the pulsed streamer corona can incepts, propagates and bridges the electrode gap but the maximum electric field of streamer head will decrease, the propagation velocity reduces because the electric field of low field region is less than 5 kV/cm. The electric field of streamer head decreases, which corresponds to a decrease of the energy inject into reactor. So, this leads to the DeSO2 efficiency decreases. Therefore, when the wire-to-wire spacing is in the range of 6-10 cm with the wire-to-plate spacing is 10 cm, the pulsed streamer corona can incepts, develops and stably propagates because the electric field of high or low field region meet to the conditions which requires for streamer corona inception, development and propagation. Fig.5 shows the electric field distribution along AD of different wire-to-wire spacing under the wireto-plate spacing is 7.5 cm, the applied voltage is 60 kV. Fig.6 shows the electric field distribution along AD of different wire-to-wire spacing under the wire-to-plate spacing is 12.5 cm, the applied voltage is 100 kV. Similarly, the optimal wire-to-wire spacing is in the range of 5-7 cm, 7-11 cm under the wire-to-plate spacing is 7.5 cm, 12.5cm, respectively. The numerical modeling results show that the optimization wirewire spacing is 0.6-1 times the size of the wire-plate spacing.
139
50000
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Distance from wire to plate(cm) Fig.5. Electric field distributions along AD of different wire-to-wire spacing
Fig.6. Electric field distributions along AD of different wire-to-wire spacing
THE EXPERIMENTAL VALIDATION The experimental setup was depicted in [12]. Fig.7 shows the influence of wire-to-wire spacing on per pulse effective energy under difference wire-to-plate spacing. We can see that per pulse effective energy 2.0-
1.8~
.-j
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9
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,
i
,
i
9
i
,
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9
i
12
9
i
13
0.0
1'0
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Wire-to-wire spacing(cm)
1'4 " i'8
Fig.7. Variation of per pulse effective energy with the wire-to-wire spacing
was up to maximal when the wire-to-wire spacing was in the range of 4.5-7.5cm with the wire-to-plate spacing was 7.5cm. Similarly, as the wire-to-plate spacing was 10cm, 12.5cm, the optimal wire-to-wire spacing was in the range of 6-10cm, 7.5-1 l cm, respectively. The experimental results show when wirewire spacing is 0.6-1 times the size of the wire-plate spacing, the pulsed energy can be injected into reactor effectively, the effective energy utilization of reactor is maximal. The comparison with the modeling results shows a good qualitative agreement.
CONCLUSIONS From the point of view of engineering application and on the basis of analyzing the mechanism of pulsed streamer corona discharge, the electrostatic field distribution of the reactor under different electrode configuration have been calculated by using numerical modeling. The results of numerical modeling show the optimization wire-to-wire spacing is 0.6-1 times the size of the wire-to-plate spacing. And the comparison with experimental results shows a good qualitative agreement.
140
REFERENCES 1. G.Dinelli, L.Civitano, and M.Rea, Industrial experiments on pulse corona simultaneous removal of NO2 and SO2 from flue gas, IEEE Trans.Ind.Appl. (1990), 26 535-541 2. A.Mizuno, J.S.Clements, and R.H.Davis, A method for the removal of sulphur dioxide from exhaust gas utilizing pulsed streamer corona for electron energization, IEEE Trans.Ind.Appl. (1986), IA22 516-521 3. Yan Wu, Jie Li, and Ninghui Wang, Industrial experiments on desulfurization of flue gases by pulsed corona induced plasma chemical process, Journal of Electrostics (2003),5_7_7233-241 4. Zhang Yanbin, Wang Ninghui, and WU Yan, Design and operation of system of SO2 removal from flue gas by pulse corona discharge, Journal of Dalian University QfT.echnology (1997), 37 (5) 551-554 5. Li Guofeng, WU Yan, and Wang Ninghui, Research on Line-plate Model Pulse Corona Discharge System, High Voltage Engineering (1999), 25 (1) 4-6 6. I.Gallimberti, G.Bacchiega, Anne Bondiou-Clergerie, and Philippe Lalande, Fundamental pocesses in long air gap discharges, C. R. Physique (2002),31335-1359 7. E.M.van.Veldhuizen, W.R.Rutgers, Pulsed positive corona streamer propagation and branching, J.Phys.D:Appl.Phys. (2002), 352169-2179 8. Yu V S erdyuk, A Larsson, S M Gubanski, and M Akyuz.The propagation of positive streamers in a weak and uniform background electric field, J.Phys.D:Appl.Phys. (2001) 3__4_4614-623 9. Allen.N.L, Ghaffar.A, Conditions required for the propagation of a cathode-directed positive streamer in air, J.Phys.D:Appl.Phys. (1995), 2__88331-337 10. F.W.Peek, Dielectric Phenomena in High-Voltage Engineering, McGraw-Hill, 1929. 11. J.R.McDonald, W.B.Smith, A mathematical model for calculating electrical conditions in wire-duct electrostatic precipitator devices, J.Appl.Phys. (1977), 2___882231-2243 12. Wu Yan, Dong Bingyan, Li Jie, Li Guofeng. Influence of electrode configuration on energy utilization of DeSO2 reactor by pulsed corona plasma, Journal of Engineering For Thermal Energy and Power. (2004), 5 Accepted
141 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Removal of SO2 from Flue Gas by Water Vapor and NH3 Activated in Positive DC Corona Discharge Sun Ming, Wu Yan, Li Jie, Li Guofeng, Wang Ninghui, Shang Kefeng Institute of Electrostatics and Specific Power, Dalian University of Technology, Dalian 116024, China
Investigation on removing SO2 by activating water vapor or NH3 in positive DC corona discharge has been conducted at the flow of flue gas being 65Nm3/h. Results demonstrate that when water vapor or NH3 is activated, SO2 removal efficiency is obviously higher than that when they are not activated. The SO2 removal efficiency increases with input power, and to some extent, with the flow of water vapor or humidity of the flue gas. In addition, the total SO2 removal efficiency in pulsed corona discharge process was increased by water vapor or NH3 activated.
INTRODUCTION Increasing NOx removal efficiency by radical shower system in non-thermal plasma process has been put forward in1980's. In 1986, Chang pointed out that, NH, NH2, OH and H etc. exist in the electric field with NH3 and H20, and they are helpful for removing NOx [1]. After this, adding the shower apparatus of radical, such as NH3, CH4, CO2, H20 etc. in removing NOx or SO2 in discharge plasma process have been researched [2-7]. The results of these investigations demonstrate that it is very useful for increasing the SO2 and NOx removal efficiency, but further studied and bigger scale experiments are needed for its industrial application earlier. In this paper, the experiments of SO2 removal from simulated flue gas by water vapor and NH3 activated respectively have been conducted. The conditions of the experiments were: the flow of flue gas being about 65Nm3/h, the temperature of the simulated flue gas being kept between 65~85~ and NH3 being added as the stoichoimetric ratio of NH3"SO2 1"1. In all experiments, the concentration of water vapor in the flue gas is unsaturated.
EXPERIMENTAL APPARATUS There are two sets of discharge electrodes in the reactor for DC corona discharge and pulsed corona discharge, respectively (see Figure 1). Simulated flue gas consists of air, SO2 and water vapor. Nozzleelectrodes are placed in the midst of two-grounded plate electrodes and parallel to them (see Figure 2). Spacing of nozzle-to-plate (S) and nozzle-to-nozzle (Sn) are 50mm and 30mm. Pairs of nozzles (n) are 25, and outer- diameter and inner-diameter of nozzle (d) are 2mm and l mm respectively. Water vapor and NH3 are injected into the reactor by the nozzle-electrodes.
142
Discharge-electrode for activating
I'--E
-S-~
lh~lse d Power
D C Pow~
L L d(o)
Insulator
E
NH~ Absorbed
Area for pulsed dischameelectrode Precipitator
Air Heater
so~ .""3 Vapor
F
Induced Fan
Discharge-electrode
so2 Analyzer
Reactor
Figure 1 Sketch of removing SO2 system from flue gas
Figure 2 Schematics of discharge-activated-electrode
EXPERIMENTAL RESULTS SO2 removal efficiency by water vapor or NH3 activated Experiments of SOz removal efficiency by activating water vapor and NH3 in positive DC corona discharge have been conducted (see Figure 3 and Figure 4). When water vapor and NH3 are not activated, they are added into the reactor by the flue gas import. The results show when water vapor or NH3 are activated, SO2 removal efficiency is higher than that not be activated, obviously. The humidity of the flue gas (H) in the experiments of NH3 activated is 1.3%(w%). 80
76 72
CO: ~ Ow :4.5m3/h
68
~ectrc~lE 14 QF: 67r"~n3/h-'~ NH3~ d i ~ C0:1~,-NH3~ g a s inlet 12 H :1.3% 10
- n - water from gas in3:xxt - o - - water activation
o,-..--"
___m__----nu ._.._.m----
m-.-----r-
8
,IF
~6
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22
'
l
23
,
i
24
,
i
25
,
i
26
,
i
27
i
i
28
I
i
29
22
V/kV
Figure 3 S O 2 removal efficiency as a function of applied voltage for water vapor activated
,
I
23
,
I
24
,
I
25
,
I
26
,
I
27
,
I
28
,
I
29
,
30
V/kV
Figure 4
S O 2 removal
increased efficiency as a function
of applied voltage for NH3 activated
The influence of water vapor flow or humidity of flue gas on $02 removal efficiency Firstly, the SO2 removal efficiency increases with the flow of water vapor and the humidity of flue gas when water vapor activated or NH3 activated, after some extent, the increasing trend is not obvious (see Figure 5 and Figure 6).
143
80
QF:65Nm3/h
76
25
--o--no applied voltage ---,---water activation
~0:2000ppm
QF: 65Nm3/h CO: 2000ppm
20
72 68
15
{64
ml0
60
o~"
5652 48
,
2
t
,
3
I
4
,
I
5 ew/m3/h
~
I
,
6
I
7
0
8
Figure 5.802 removal efficiency as a function of water-vapor-flow in activating water vapor process
,
l
,
1
l
,
2
l
3
9
l
4
,
I
5
H%
I
I
6
n
I
7
a
I
,
8
I
,
9
10
Figure 6. S02 removal efficiency as a function of humidity of flue gas in NH3 activating process
Influence of input power on SO2 removal efficiency The results of the experiments show that the 802 removal efficiency increases with the input power when water vapor or NH3 is activated, respectively (see Figure 7 and Figure 8). 72 - QF" 65Nm3/h 70 C0:1968ppm
70
--,,--no applied voltage
--=-- water vapor activation
Qw:4"5m3/h
68
QF:65Nm3/h
68
C0"2000ppm
--m--without activation - - e - - activation
66 -H '1.7%
66
64
64 62
~" 62
60
60
58
m-----"
56
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--
4
,
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,
i
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58
a
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,
i
14
,
l
16
,
l
18
,
20
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Figure 7 SO2removal efficiency as a function of input power in water vapor activated process
56
4
,
I
6
,
l
8
,
I
10 PIW
,
I
12
,
I
14
,
16
Figure 8 802 removal efficiency as a function of input power in NH3 activated process
SO2 removal efficiency by pulsed corona discharge process with water vapor or NH3 activated in positive DC corona discharge The experiments demonstrate that SO2 removal efficiency is increased by water vapor or NH3 activated in pulsed corona discharge process, obviously (see Figure 9 and Figure 10) CONCLUSIONS The results of the investigation of $02 removal from flue gas by activating water vapor or NH3 in positive DC corona discharge demonstrate that when water vapor or NH3 is activated, SO2 removal efficiency is obviously higher than that water vapor or NH3 is not activated The SO2 removal efficiency increases with input activated power. To some extent, the SO2 removal efficiency increases with the density of water vapor molecules or the humidity of the flue gas. In addition, when water vapor or NH3 is activated, SO2 removal efficiency increases obviously in pulsed corona discharge process.
144 95
100 QF: 95
70Nm3/h
90 ~.QF:70Nm3/h - - e - - n o DC discharge
_ A , _ with DC m 9--without DC
Qw: 3.5m3/h
85 -H "1.3% 80
CO: 2000ppm
90
75
85
65 60
80
55 50
75 70
- - A m applied DC discharge
2
,
,
3
., Qw(m3/h)
,.. 4
,
5
Figure 9 Effect of water vapor activated 802 removal efficiency in pulsed corona discharge process
45 800
'
12'0'0
'
16'00 C0/ppm
'
20'00
Figure 10 Effect of NH3 activated on SO2 removal efficiency in pulsed corona discharge process
ACKNOWLEDGMENT The authors thank the National Natural Science Foundation of China for its funding support.
REFERENCES 1. J. S. Chang. Chemical reactions leading to an aerosol particle formation and growth by an irradiation of high energy electron beam, in Aerosol formation and reactivity. G. Israel et al., Eds., Pergamon Press, Oxford, 1986 867-870. 2. J. S. Chang, K. Urashima, Y. X. Tong, W. P. Liu, H. Y. Wei, F. M. Yang and X. J. Liu. Simultaneous removal of NOx and SO2 from coal boiler flue gases by DC corona discharge ammonia radical shower systems: pilot plant tests. Journal of Electrostatics. 2003, 5___7__7313-323. 3. J. S Chang, P. C. Looy, J. Pevler, T. Yoshioka, K. Nagai. Reduction NOx from a combustion flue gas by a corona radical injection method. Proc. IEEE/IAS. Annual Meeting, 1993 1969-1975 4. J. S. Chang, K. Urashima, M. Arwuilla, and T. Ito. Reduction of NOx from combustion flue gases by corona discharge activated methane radical injections. Combust. Sci. and Tech. 1998, 1..3.331-47 5. J. Y. Park, R. Li, G. F. Round and J. S. Chang. Removal of SO2 from combustion flue gases by corona radical shower systems. J. Adv. Oxid. Technol., 1999, 4(3) 1-7 6. K. Yan, T. Yamamoto, S. Kanazawa, T. Ohkubo, Y. Nomoto and J. S. Chang. Control of flow stabilized positive corona discharge modes and NO removal characteristics in dry air by CO2 injections. Journal of Electrostatics. 1999, 46 207-219 7. Y. Wu, J. Li, N. Wang, G. Li, and D. Xu. Study on Increasing the SO2 Removal Efficiency with the Radicals Produced by H20 in Pulse Discharge Plasma Process. Jpn. J. Appl. Phys. Part2, 2001,4__0_0(8A)L838-L840.
145 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Theory and application of cyclone impulse electrostatic precipitation Li Jiwu, Cai Weijian Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
Abstract: In this paper, the structure characteristics and operating principle of cyclone impulse electrostatic precipitation (CIESP) were introduced, the solid-gas separation mechanism of CIESP was presented. The paper set up hydromechanics equation of particle in solid-gas separation. The application experiment of CIESP on cleaning molecular gas in catalyst factory was explained emphatically. It concluded that CIESP was very suitable to clean viscous molecular gas in catalyst factory, had high overall collection efficiency, the migration velocity was approximately 2 times more than the electrostatic precipitation, up to 0.15-0.18m/s. Key words: cyclone impulse electrostatic precipitation (CIESP), molecular gas, electrostatic precipitation, collection efficiency
Cyclone impulse electrostatic precipitation (CIESP) combines merits of cyclone precipitation and electrostatic precipitation, which is widely applied in environmental protection. Cyclone has simple structure and low cost, but has poor collection efficiency, especially for fine particles. Electrostatic precipitation has good collection efficiency, but consumes much steel and cost. When airflow with particles passes CIESP with high voltage impulse electrostatic field, the particles is separated from gas for composite effects making by centrifugal force and impulse electrostatic force. Some researches have been done mainly aimed at cyclone with electrostatic (CESP) enhanced [1-7], which use direct current. Our researches have done mainly aimed at CIESP, which use impulse power supply [8, 9]. Some tested results reported that CIESP has good collection efficiency, but which not verified by application. This paper introduced hydromechanics equation of particle in solid-gas separation. The application experiment of CIESP on cleaning molecular gas in catalyst factory was explained emphatically. The theoretical formula of particles migration velocity were concluded and verified with application experiments.
THE STRUCTURE AND WORK PRINCIPLE OF CIESP The structure trait In Figure 2, a CIESP consists of particle collecting hoppers, collector wall, discharge electrode system, dirty gas inlet, clean gas outlet and rapper system. Its traits are as follow: (1) It is vertical straight-tube type, tangentially inlet. (2) The discharge electrode is prickle which good mechanical strengthen and high discharge intensity. (3) It has better collection efficiency and higher flow rate of treated gas than that of same diameter conventional cyclone. (4) It has operation reliability, maintain simplify, and low cost. Work principle of CIESP As Figure 1 and Figure 2 show, the gas enters through a rectangular inlet, normally arranged tangentially to the circular body of the CIESP, so that the entering gas flows around the circumference of the cylindrical body, not radial inward. The gas spirals around the outer part of the cylindrical body with a downward component, then turns and spirals upward, leaving through the outlet at the top of the device. During the spiral of the gas, the particles are driven to the wall by centrifugal force and impulse electrostatic force, where they collect, attach to each other, and form larger agglomerates that slide down
146 the wall by gravity and rapper and collect in the dust hopper in the bottom.
EQUIVALENT MIGRATION VELOCITY AND OVERALL COLLECTION EFFICIENCY Particle.movement differential equation As shown figure 1, when particles revolve with airflow in CIESP, particles are affected by centrifugal force F~ and electrostatic force Fe, and move to collecting wall. According to Newton's second law, we can get that particle differential equation in solid-gas separation in CIESP [12]" Nomenclature
F~ centrifugal force, N Fe electrostatic force, N F drag force, N E electric field strength, v/m Ep pulse electric field strength, v/m Er base direct current electric field strength, v/m vt tangential gas velocity, m/s M particle mass,~rdp3p/6, kg p particle density, kg/m 3 r radius of particle in a circular gas flow, m dp particle diameter, m e~ dielectric constant of the particle, 4.2 for catalyst particles eo electric constant of vacuum, 8.854x 10~2 Nm2/c 2 q~s charge on the particle, electrons O)p, (D r radial or migration velocity of particle of pulse and dc respectively, m/s dynamic viscosity of gas, 1.82x 10-5kg/m s at 20~ C Constant Vo inlet tangential gas velocity, m/s Ro electrocyclone separator cylinder radius, m ro radius of balance cylinder, m. n experimentation coefficient Q gas volume, m3/s H electrocyclone separator height, m Xp pulse width, 1-30 ~ts T pulse periods, 0.02s
V0
Particle V . /- ................ 4.,.
!/" \,..
vt
F
Inlet
""\
wall
/
~
Discharge electrode
Figure 1 The forces acting on a particle in CIESP
147
v2t qes E + M
dco
(1)
3~pdpro = M dt
r
dr
9
oo=~=r
dm ~ -
d 2r
"" -
From the definition of radial velocity: dt , also dt - ~ t 2 - r . Inside electrocyclone separator, the tangential gas velocity distribution equation vt r~=voRon=C(constant)[12], so vt=C/r ~, we can obtain 9.
Eqes
r= M
c2 +
~
r 2"+1
3~rludp . ~ ( r
M
co r )
(2)
we applied chaos theory to solve the problem, and gained formula of cut diameter for CIESP [ 10] and CESP [ 12] respectively. Equivalent migration velocity The particle radial velocity co (migration velocity) can be given by formula (1). Because impulse energization is applied in experiment, migration velocity a b in peak voltage and ~ in base voltage must be calculated relevantly in itself period. We definite equivalent migration velocity in CIESP as follow formula (3) [ 11 ]: rpgOp + ( T -
"t'p )gOr
(Jo-
(3)
T
we can get equivalent migration velocity formula (4)" dpgrgoEp[rpEp (0
+(T-Z'p)Er]
-
ppdp2vt +
(e r + 2)ltT
181cltr
2
(4)
~, e~,/t, dp, pp are all constants, fp, T, Ep, Er, can be gotten from impulse waveshape, so the co can be calculated in a certain condition. The overall collection efficiency Substituting formula (4) into the well-known Deutsch equation, we can get overall collection efficiency in CIESP as follow: r/- 1-exp
l
~ cQ o
1
(5)
Formula (4) and (5) show that overall efficiency of CIESP is determined by some factors such as pulse electrical field strength Ep, tube height H, grain size dp and gas volume Q, etc'
APPLICATION EXPERIMENT Tested condition The molecular gas in catalyst factory, which has high temperature, humidity, corrosiveness and dust concentration, is difficult to be treated. Properties of the molecular gas changes greatly with raw materials of catalyst, technology and spray vapor, etc. In normal operation, flow rate of the molecular gas is 4 0 0 0 ~ 8000m3/h (test flow rate about 1500 m3/h), temperature of gas is less than 260~ dust concentration in gas is 1~50 g / m 3, it consists of H20(>30%), NH4C1, NH3 and molecular dust. Particles median diameter is 3.1 gm, and diameter less than 51am particles is over 90 percent. Flow diagram for removal dust from molecular gas using CIESP is shown as Figure 2. The molecular gas from catalyst was cleaned by CIESP, then, cleaned gas to stack was emitted. Flow rate of the fanner is 500-1600 m3/h, the pressure of fanner is from 2100 to 2500 Pa, power of fanner is 1.1 kw. Pulse energization used is composed of base voltage adjusting circuit, pulse generator, and protective circuit, etc. Pulse amplitude is from 1.1 to 3 times of the base d.c. voltage, pulse repetition rate is in the range 50-100 pps, Pulse width in the range 30 gs, output current in the range 30 mA, output base voltage
148 in the range 0-120 kv. The diameter of cylindrical body of CIESP is 430 mm, total effective high of field is 3.5 m. The wire electrode is made of diameter 10mm stainless steel pipe with length 10mm prickle. Electromagnetic rappers are used to clean collecting and discharge electrode.
Figure 2 Flow diagram for removal dust from molecular gas using CIESP
Methods The isokinetic sampling and filter paper weighing is used. After dust concentration is deterimined, collection efficiency can be calculated with the equation (6): r/=
QiCi -QoCo • 100% QiCi
(6)
where Qi and Qo are inlet and outlet gas volume respectively, m3/h. While air leak percent is ignored, Qi =Qo. ci and Co are inlet and outlet average particle concentration respectively, g/m3. rl is collection efficiency, %. To contrast collection efficiency of CIESP, the collection efficiency of cyclone with electrostatic (CESP) and cylone were measured respectively. Results and discussion The inlet and outlet dust concentration were measured respectively, shown as Table 1. Collection efficiency can be calculated in formula (6). From collection efficiency experiment and formula (5), we can get tested migration velocity co. The theoretical migration velocity COTcan be calculated after every known parameter is substituted in formula (4), here impulse voltage Ep= 1.5Er, dp=3.1 lxrn. Theoretical and tested migration velocity is shown in Table 1. Form Table 1, we know that all test migration velocity of CIESP are higher than that of CESP at same gas velocity and voltage. All theoretical migration velocity are nearly equal to tested migration velocity at same condition, it indicates that formula (4) is correct. Table 1 Theoretical and tested migration velocity of molecular gas Precipitator cyclone CESP CIESP
Ur kv 0 62 70 62 70
Q m7/h 1110 1108 1150 1120 1150
vi m/s 7.7 7.7 8.0 7.8 8.0
Ci mg/m3 1076.2 1079.3 1341.1 1078.3 1346.1
Co mg/m3 425.1 264.4 265.6 105.7 99.6
~ % 60.5 75.5 80.2 90.2 92.6
co m/s 0.092 0.110 0.153 0.176
COT
m/s 0.104 0.124 0.148 0.193
149
CONCLUSION Cyclone impulse electrostatic precipitation (CIESP) combines merits of cyclone and electrostatic precipitation, has many advantage. The application experiment shows that CIESP was very suitable to clean viscous molecular gas in catalyst factory, had high overall collection efficiency, the migration velocity was approximately 2 times more than the electrostatic precipitation, up to 0.15-0.18 m/s. All test migration velocity of CIESP was higher than that of CESP at same gas velocity and voltage. All theoretical migration velocity was nearly equal to tested migration velocity at same condition.
ACKNOWLEDGEMENTS The authors wish to acknowledge National Science Foundation of China for its financial support (approval number: 50064002)
REFERENCES 1. Huang zhen, Wang wenliang. Research on the models of straight-through flow electrocyclone precipitation. Journal of Southeast University, 1996, 26(5): 119~123. 2. Guo jinji, Zhang kangzhi. Theoretical computation of driving velocity of the air dust concerning spreading cyclone separators with electrostatic Precipitation. Journal of Zhong Shan University, 1996, 35(5): 20-24. 3. Sun yijian, He quan. Study on electrostatic cyclone model ZDS. Journal of Hygiene Research, 1995, 24 (2) :125-128. 4. Dietz P W. Electrostatically enhanced cyclone separators. Power Technology, 1982,31 (2): 221-226. 5. Plucinski J, Gradon L, Nowicki J. Collection of aerosol particles in a cyclone with an external electric. Journal of Aerosol Science, 1989,20(6): 695-700. 6. Xie Guangrun, Chen Cixuan. High-voltage electrostatic for dust collect. Beijing: Press of Hydraulic and Electric,1993. 7. Li Jiwu, etl. Experiment Study of the Performance of Cyclone Impulse Electrostatic Precipitation. A CTA SCIENTIAE CIR CUMSTANTIAE, 2002,(2),39 8.Li Jiwu, etl. Theory and application of a pulse source for electrostatic precipitations. The 4th int. Conf. Appl. ELECTROSTATICS, 2001,DALIAN 9. Senichi. Masude, Shunsuke. Hosokawa. Pulse energization system of electrostatic precipitation for retrofitting application. IEEE Trans. Industry Appl., 1988, 24(4):708-710. 10. Li Jiwu, Cai Weijian. Study of nonlinear problem of cyclone with impulse electrostatic. Progress of natural science, 2002,(10),1101-1104 11. Jiwu Li, etl. Study of Solid-gas Separation Mechanism of Cyclone with Impulse excitation. Journal of Electrostatics, 2003, 57(3), 225-233 12. Jiwu Li, Weijian Cai. Study of the cut diameter of solid-gas separation in cyclone with elelctrostatic excitation. Journal of Electrostatics, 2004, 60, 15-23
150 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Development and application of high voltage pulse energization system in electrostatic precipitations Cai Weijian, Li Jiwu Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, China
Abstract: In this paper, history of pulse engergization for electrostatic precipitations was introduced simply, principle of pulse engergization was studied, a new pulse engergization for ESP was developed and tested on electrical and dust performance in ESP. etc.. This pulse engergization is difference from formerly pulse engergization which pulse is yielded in highvoltage of transformer, its pulse is yielded in low-voltage of transformer, and then is boosted and rectified by vertoro. Pulse width is in the range 0.1-10 ~ts, pulse amplitude is from 1.1 to 2 times of the base DC voltage, pulse repetition rate is in the range 50-100 pps. Output base voltage is in the range 50-120 kv, and is continuous and adjustable. It is concluded from experiments and applications that distribution of collecting plate current density on ESP is more uniform, derating of dust concentration at exit with pulsing are in the range 50.4---79.6% in contrast to DC power supplies, under identical gas factors. Keywords: electrostatic precipitations (ESP), pulse engergization, current density, collection efficiency, DC power supply
THE OVERVIEW OF PULSE ENERGIZATION Electrostatic precipitation (ESP) emerged from nearly a century of being a laboratory curiosity to a successful method for removing fine articles form industrial gases in the early 1900's [ 1]. ESP has been applied widely in environmental protection. Successful ESP depends critically upon the method, quality and control of electrical energization properly applied. The alternating current transformer and the synchronous mechanical rectifier were applied to an adequate high voltage power supply for ESP in early. The conventional direct current power supply is applied broadly in ESP, but there is some problems such as back corona, which decreases collection efficiency and effects operation, especially for high resistivity ash. Some researches have shown the pulse energization system has many advantage and is very suitable to be applied to ESP [2] - [7]. It is necessary to define pulsing terminology in the context of ESP. Pulse energization for ESP refers to high frequency pulsing at nominal pulse width < 1 to about 300+ps, pulse repetition rate typically 3 0 ~ 300+ per second. Pulse energization is the only really new basic method of electrical energization introduced since the days of Cottrell. Modem ESP pulse energization began with the pioneer research and development work of H.J. White and H.J. Hall during the period 1947-1952. Both men were involved in microsecond, high voltage, high power pulse development for radar systems beginning early 1941 at Massachusetts Institute of Technology [1]. The pioneer work of White and Hall demonstrated major advantages of pulse energization and brought pulse development to a commercial prototype stage. Up to now, there are two ways to achieve pulse energization. Firstly, high base DC voltage and pulse are yielded by themselves a set of device, then high voltage pulse is formed through superposition. In this way, hard tubes, hydrogen thyratrons, triggered spark gaps and rotary spark gaps are used for pulse switching. There are at least four in existence as commercial pulsers [1][6], which pulse switching in high-voltage of transformer and some serious component reliability problems. Secondly, high voltage
151 pulse is formed by only a source. We designed pulse engergization [4] [5] as shown in Figure 1. In this way, SCR are used to pulse switch in low-voltage of transformer. Nanosecond pulse is yielded by oscillating circuit that is composed of natural capacitance, inductance, and resistance of ESP system circuit, then is boosted and rectified by vertoro. It is good compatibility for new or old device, low cost.
IPpsl
~
ESP
,,1[
V
....
Transformer rectifier
Pulse generator
Figure 1 Our pulse engergization system schematic diagram
+
K C
L
=liR
~.Vc-
Figure 2 Equivalent circuit of ESP system
DEVELOPMENT OF PULSE ENGERGIZATION Equivalent circuit of pulse engergization and analysis Pulse engergization system circuit is shown in Figure 1. SCR are used to voltage regulator and pulse switching. Nanosecond pulse is yielded by LRC oscillating circuit. According to law of impedance transformation, capacitance and inductance of high voltage rectifier, load impedance and capacitance of ESP are transformed equivalent circuit as shown in Figure 2. Where C is equivalent capacitance, R is equivalent impedance, L is equivalent inductance, K stands for reverse blocking tetrode thyristor shown in Figure 1. Capacitor C is charged before SCR do not breakover, and discharge to load circuit of ESP while SCR breakover. Under right condition, load circuit yielded oscillation impulse. According to Kirchhoff's current law, we obtain di 1 L--~ + Ri +--~ J[dt =0
(1) l ' ' " " -
where, i is circuit current. While R < 2~ L , L R C circuit yielded oscillation. From initial condition: while t=0+, i=0; t=-0+, Vc=V. We can get solution of formula (1) [5]" i - - ~ V e _~ sin ca coL _
V
V c - ~ e
-6~
(2)
sin(aX+ ~a)
where, (o = arctg--z,
(3)
8 = 2L '
co =
- (--~)
While circuit impedance R is enough small, 3= R / 2 L --~ O, from formula (2) and (3), we can get approximately i =-V1] C sin cot= 1 m sin cot
(4)
IlL,
Vc - V sin(cot + f
p
)
(
5
)
From above, we know that circuit current i and voltage Vc make sinusoidal resonance that amplitude are Ipm .and V relatively, both angular frequency are co. parameters of pulse engergization To satisfy resonance condition, we must select reasonable component parameter to make circuit quality factor O_~_l~ to reach definite value. It is necessary that external capacitance Ce is selected reasonably to obtain good pulse waveform.
152 Overcurrent and overvoltage are yielded by variation of power network and load of ESP, and current commutation, are harmful to SCR component and vertoro. It is necessary to take effective protective device. We developed a pulse engergization that is composed of base voltage adjusting circuit, pulse generator, and protective circuit, etc.. Pulse engergization technical parameters are followed: (a) pulse amplitude is from 1.1 to 2 times of the base DC voltage. (b) pulse repetition rate is in the range 50-100 pps. (c) Pulse width is in the range 0.1-10 ~ts. (d) Output base voltage in the range 50-120 kv.
EXPERIMENTS AND APPLICATIONS Distribution of collecting plate current density on ESP Distribution of collecting plate current density is one of important factor to effect collection efficiency of ESP. the more uniform distribution of collecting plate current density is, the higher collection efficiency is. In pulse engergization and DC power supplies, distribution of collecting plate current density on ESP are contrastively measured. The measured collecting plate area is 15• is scribed 36 small cell area 2.5x2.5cm2, which each other are isolated. The current in small cell are measured. Current density is calculated by follow formula (6).
(6)
Ji.--[i/Am
where, Ji-----current density on number i small cell, Aom-2. Ii---current on number i small cell, Aom2. i=1, 2...36. Am---area of cell, m2. Distribution uniformity of collecting plate current density are assessed by distribution standard deviation of current density, its calculation formula follows as (7).
I i~=l(j n i _ j p )2 luJ =
i
n
(7)
Jp is average collecting plate current density, pj is distribution standard deviation of current density. The smaller pj is, the better distribution uniformity of collecting plate is. The results are shown Table 1. Table 1 Result of distribution of collecting plate current density at base voltage 55kv Distance of homoelectrode, mm 300 300 400 400
Supply mode DC PPS DC PPS
Jp/10-4A-m 2
/q/104Aom -2
52.7 29.3 28.8 19.6
20.1 14.4 14.0 9.61
The collection efficiency We set up experimental ESP device to measure collection efficiency in pulse engergization and direct current supply. The cross section area of ESP experiment model is 2.4 m2, length of ESP is 4m. Experiment dust is talcum powder, its real density is 2500 kg/m3, its resistance is 8.06x 108f~-cm. Direct current supply type is CK10 mA/100kv. Flow rate of gas 10320 m3/h. During pilot tests, the isokinetic sampling for particulates is applied to measure dust concentration. The results of test are shown Table 2. Table 2 The results of test collection efficiency of ESP model Order 1 1 2 2
Supply mode DC PPS DC PPS
Voltage, kv 56 56 50 50
Concentration at inlet, mg/m 3 4520 4862 3925 2784
Concentration at exit, mg/m 3 390 166 420 206
Efficiency % 91.3 96.6 89.3 92.6
Derating of concentration at exit,% 57.7 51
153 Applications There are six pulsers were installed on ESP on treating gases from zinc melting fin'nace, at Zhuzhou Smelter, in 1998. Pulsers have operated continuously without difficulty. ESP's effective sectional area is 35 ma, gas temperature is 320 ~ ash resistivity >1012 ohm cm. Under identical gas factors, collection efficiency of pulser and DC power supply were measured relatively. Results of collection efficiency are shown in Table 3. We can obtain that derating of dust concentration at exit with pulsing are in the range 50.4---79.6% in contrast to DC power supplies, under identical gas factors. Table 3 Both collection efficiency of pulser and DC supply
Order Supply Gas flow Dust concentration Efficiency Derating of concentration ...........................mode .. ..........rate,m3~, . ...............atex!t, . mg/m!: ...........................0_/0 . .......................................atexit,% .. ........................ 1 DC 94936 54 99.1 1 PPS 95324 11 99.8 79.6 2 DC 95164 115.8 99.3 2 PPS 95519 57.7 99.6 50.4 3 DC 96114 110.4 98.8 3 PPS 96421 52.6 99.3 52.3
CONCLUSION The pulse energization has been accepted as a viable, reliable, and effective method for improving the performance of existing ESP. The pulse engergization introduced is difference from formerly pulse engergization which pulse is yielded in high-voltage of transformer, its pulse is yielded in low-voltage of transformer, and then is boosted and rectified by vertoro. Pulse width is in the range 0.1-10 lxs, pulse amplitude is from 1.1 to 2 times of the base DC voltage, pulse repetition rate is in the range 50-100 pps. Output base voltage is in the range 50-120 kv. The results show that distribution of collecting plate current density on ESP is more uniform, derating of dust concentration at exit with pulsing are in the range 50.4---79.6% in contrast to DC power supplies, under identical gas factors.
REFERENCES 1. Herbert J. Hall. History of pulse energization in electrostatic precipitation. UJoumal of ElectrostaticsU, 1990, 25: 1-22. 2. P. Lausen et al.. Energy conserving pulse energization in electrostatic precipitation. UIEEE/IASU, 1979, 26 : 163-171. 3. Naoji Tachibana. Intermittent energization on electrostatic. UJoumal of ElectrostaticsU, 1990, 25: 55-74. 4. Li jiwu. A pulse source for electrostatic precipitation. China youth scholar discuss environment. Beijing: China environment science press, 1997:397-399. 5. Li Jiwu, Cai Weijian. Theory and application of a pulse source for electrostatic precipitations. UThe 4UPU ~tJPu int. Conf. Appl. ELECTROSTATICSU, DALIAN. 2001.10:589-593 6. Senichi. Masude, Shunsuke. Hosokawa. Pulse energization system of electrostatic precipitation for retrofitting application. UIEEE Trans. Industry Appl.U, 1988, 24(4):708-709. 7. S. Masuda, S. Obata and J. Hirai. A pulse voltage source for Electrostatic precipitators. UIEEE/IASU, 1978, 78:1C.
154 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on Trapping Inhalable Particles by Non-Thermal Plasma Zhu, Y, Zhang, M, Su, P, Chen, H, Huang, L NTP Appl. Technol. Lab, Dalian Maritime University, 116026 P. R. China Abstract: The experiments study the dust collection of a novel non-thermal plasma (NTP) mode on inhalable particulates (IPs), and compare the collection results with other commercial air cleaners. The results reveal that DC streamer discharge has the same discharge energy with pulsed corona discharge, and thus make particulates overload charging; applied DC HV produces even and stable electric field, and increases the collection rate of charged particulates. In fact, the collection rate of IPs from 0.3~tm to 101xm has reached above 80% within 20min, and the CADR is up to the magnitude of 102m3/h. Keywords: non-thermal plasma, inhalable particulates, CARD
INTRODUCTION 7 cities in China are ranked as top 10 worst polluted cities of the world. Less than 1% of over 500 Chinese cities can meet with the air quality standards of World Health Organization (WHO), and among which 68% have the problem of IP pollution. IP is one of the major causes of death rate rising, and can result in or emphasize the respiratory diseases; it is responsible to global climate change, smog phenomenon, ozone layer destruction and other serious environmental problems. Currently, main IP collection technologies on indoor air mainly focus on filtration, electrostatic removal and anion adsorption. However, the application on product air cleans may encounter the following problems. To filtration cleaners, they have relatively large wind resistance that will influence on flow rate, and they also need to change filter elements regularly for chemical reactions or sediment of solid/liquid particulates. In fact, the collection efficiency of electrostatic cleaners is not satisfying. Also, the adsorption of anion to suspending particulates in air can produce a serious pollutant, heavy ions. On the other hand, some NTP air cleaner have been observed relatively good results as blow. A DC corona discharge mode with needle to net electrodes is able to remove particulates in the air [1]. Particulates are charged by exposing in corona discharge and trapped by bubbling under water in a tube closet [2]. Using needle to tube electrodes can reduce wind resistance [3]. It is believed that the combination of electrostatic and NTP technologies overweighs any of the traditional technologies [4]. In terms of dust collection method of Panasonic, with the effects of plasma, HEPA filter can amplify its collection efficiency to 10 times. A survey report has studied on collection efficiency and ozone releasing of 27 types of air cleaners in Hong Kong. The results have shown wire to plate air cleaner can release ozone, and the releasing rate has no relation with particulate removal ability according to CADR (Clean Air Delivery Rate) calculation [5]. Purification efficiency of 0.3-2.5~tm (diameter) particulates has been tested in a 50m 3 closed lab room. After 2h corona discharge, ozone smell can be detected [6]. The authors have prompted a novel NTP mode in the previous work, i.e. needle matrix to plate discharge electrode structure [7]. The air cleaner adopting this technology has been proved to reduce suspending particulates concentration to below 0.15 mg/L in 30min running in an artificial smoking room; under light particulate pollution, the particulates concentration can be reduced into the magnitude of 10-2mg/m3. Based on it, the paper will verify that the NTP air cleaner performs a high efficiency on IPs collection, and will explain the theoretical reasons of the high collection rate on IPs.
155 EXPERIMENTAL SETUP AND RESULTS Figure 1 (a) is the outer appearance of the non-thermal discharge air cleaner with the length of 500mm, the width of 290mm, and the height of 1753mm. Two round air inlets are set at the lower part of each side panel. The front panel can be divided into two parts: the upper one and the lower one. Two other stripe inlets are placed on the edges of the lower part, while two outlets are placed on the upper corresponding edges. Additionally, a square auto-shuttering outlet is put on the upper of the front panel, and the control board and display screen are set below. The inner structure of the air cleaner is displayed in Figure l(b) including blower fan, non-thermal discharge generator, DC high-voltage source, electrical control system, etc. Taking advantage of the electrode structure in our previous patent, i.e. the structure of needle matrix to plate, a discharge reactor is made up. The reactor has the size of 450mm long, 200mm wide, and 300mm high, and totally has 9 channels. The separation between needle point and plate is 18mm, and the separation between two needle points is 15mm. The maximum output power of the highvoltage source is 100W, output voltage is graded into 8, 9 and 10KV, and maximum current is 10mA. In a closed room of 5 • 6 • 3m 3, at normal temperature, with relative humidity about 45-55%, indoor air is cycled and purified in the following way by the air cleaner. First, air is intaken into the air cleaner by blower fan, and then it is processed in the discharge area, finally it returns to the room. The cycling flow rate is marked as high, medium and low levels at about 1100m3/h, 900m3/h and 700m3/h each. HV electric parameters are measured and recorded by a high-voltage divider (Tek P6015A), a current probe (Tek A6303 Am503S) and a digital oscilloscope (Tek Figure 1 Outer appearance(a)and inner structure(b)of TDS3032B). A sampling point is set on the bracket in the NTP air cleaner: 1. Components of front panel 2. Air center of the closed room, at the height of 1.5m above intaking components 3. Side panel 4. Air inlet 5. Blower fan 6,7. NTP reactor 8. Power supply and ground. The sampling air enters a particulate counter (Suxin electric control system 9. Outlet. Notes: The arrows LZJ-01D), and the amounts of IPs are counted. direct the way of airflow. The natural decay amounts of IPs in different size were recorded as blank tests respectively. And air samples of 2.83 liter each were taken every 5min during the discharge treatment. The IP amounts at different time and different particulate diameter were observed and drawn into Figure 2. Thus several principles were concluded on studying the amount changing tendency as following" the high collection rates of NTP air cleaner have all been observed on the particulates of indoor air, ranging from 0.3-10~tm, within 30min. The greater particulate diameters are, and the higher collection rates are. And high flow rate and high discharge strength have both shown positive effects on collection rate.
DISCUSSION As Niu et al. shown in their paper [5], CADR is expressed as CADR=V(Ka-Ka,n), where V is the volume of the test chamber, Ka is cleaner removal performance decay constant (hl), Ka,, is natural decay (when no cleaners are running) constant that is approximately 0.03h l. In addition, Ka value can be calculated as the function of pollutant concentration in terms of the first-order decay model Ct=Ciekt, where Ct is the concentration at time t (mg/m3); Ci is the initial concentration (mg/m3); k is the decay rate (hl), t is time(h). As Table 1 shown, the CADR and Ka,, values were calculated according to the above optimized experimental results. Considering ___20% repeatability error of the particulate counter and natural fluctuation effects of particulate concentration, the accuracy of particulate amounts counted in the test may be affected. However, the general increasing tendency can still be detected along with the growth of particulate size. Comparing with the data provided in the research of Niu et al. [5], the Ka,,,values of the NTP air cleaner are at the same magnitude with theirs, however, the CADR values increase one magnitude in ours. The following discussion will further explain the mechanism of the considerable performance of the NTP air cleaner.
156
According to the theory study and experimental research of particulate charging [8-10], pulsed corona discharge could make particulates oversaturated charging, i.e. the electric quantity carried by particulates is greater than the quantity carried in DC electrostatic effects. Also, according to the calculation and experiment results in our previous work [ 11 ], needle matrix to plate electrode structure 120
100
,.-1
100 ~ •
80
~
60
~" 90
O. 3 ltm P a r t i c u l a t e s
~. r
~ 60 • ,~ 50
O
~
20
~O
~
80
} 7o
0 0
5
10
15
20
25
g O
4O
<~
3O
~
20
~
10
~
o
180
160
140 N 120
,~
120
100
•
100
x 8o
~
80
~
O
~ 6o o
20
25
30
6O
~
20
.,..~
0
0
5
i0
15
20
25
~
0_
~
0
5
I0
Time (rain)
15 Time (rain)
500
180
450
ee~ OO
400
160 140
~ 350
120
300 ~250 200
O
~ 150 100
~ ao ~ o a,
30
~ 4o
40
,-..,
~
25
160
N 140 O
20
Time (rain)
Time (rain)
~
15
10
30
100
<
80
t~
60
.~
40
t~
20 0
0
5
10 Time
15
20
5
10 Time
(min)
15
20
25
(rain)
Figure 2 The amount changes of IPs in different particulate diameters as a function of discharge time: blank test (0), flow rate of 1100m3/h, voltage of 8kv (A); flow rate of 900m3/h, voltage of 8kv (m); flow rate of 700m3/h, voltage of 8kv (o); flow rate of 1100m3/h, voltage of 10kv (A); flow rate of 900m3/h, voltage of 10kv (n); flow rate of 700m3/h, voltage of 10kv (o). Table 1 CADR and Kd, n values after 20min running of the air cleaner. IP Diameter(gm)
0.3
0.5
1.0
3.0
5.0
3.61 322
3.07 273
4.85 434
5.70 510
10.16 912
10.0" ii
Kd,n(h-1) CADR(m3/h)
9.80 879
can generate electric field strength of above 10kV/cm within 3mm radius around needle point, and the field strength is equal to the one produced by pulsed corona discharge. On the other hand, the injecting energy intensity is even higher than that of pulsed corona discharge in wire to plate type reactor; therefore, this mode has both higher discharge field strength and energy intensity.So it is certainty that the discharge
157 mode, like pulsed corona discharge, is able to make fine particulates oversaturated charging. It was detected that the collection rate of pulsed corona discharge has not direct relation with the charge quantity [8]. The electric wind generated in the pulsed corona field has the speed of above 30m/s [12], which enhances the air turbulence. Leonard et al. pointed out the effects of turbulent diffusion on electrostatic collection of charged particulates [13]. So, the enhancement of turbulence in pulsed corona discharge is tmfavorable of the collection of charged particulates. Meanwhile, the average electric filed strength of unit space in pulsed corona discharge is less than the strength in DC corona discharge, which slows down the particulate driving speed to the collection plate. To increase dust collection rate, some researchers prompted that pulsed corona discharge is used in charged particulate while DC electrostatic field for dust collection. In fact, since DC HV power supply is utilized for producing the discharge in this work, the electric field generated in the discharge area between needles and plates are stable enough for the high collection rate. Consequently, the special discharge mode combines the virtues of both pulsed corona discharge and stable electrostatic field, that is, oversaturated charging of particulates, and effective collection of charged particulates. It results in the high collection rate of IPs. At the same time, the special design of discharge channels reduces the wind resistance, and thus the flow rate of our cleaner can be greatly larger than that of other air cleaners. So the NTP air cleaner increases the times of cycle treatment as well as saves the energy consumption. It is the reason why the NTP air cleaner has a much better CADR value but has the similar Kd, n value with other commercial air cleaners. Furthermore, the ozone releasing in the NTP processing is controlled under the safety limitations since ozone generation requires electron effects at certain energy and enough residence time in discharge area. For this air cleaner, the residence time can be counted on the magnitude of 10ms, and the discharge strength and energy can be modulated with room space. Additionally, during the NTP discharge, the needle points have smallest area and highest temperature, so IPs mainly are trapped in the plated electrodes and the plates laying the needles, and the dust can hardly stack on the needles. So the NTP discharge can be continuously carried out and it is unnecessary for frequently cleaning of the dust collection plate. CONCLUSIONS The experimental research and discussion conclude that DC streamer discharge mode of needle matrix to plate reactor has stable electric field with high strength and injected energy; the NTP air cleaner developed from the discharge mode has high collection rate and CADR on IPs; also, the air cleaner features low ozone releasing, low wind resistance and long continuous operation period. ACKNOWLEDGEMENT Deeply appreciate the financial supporting Of 50276006 and 50208005 from the National Natural Science Foundation of China. REFERENCES 1. Stanley, W., Corona discharge device for destruction of airbome microbe and chemical toxins, (2000) Patent Number US 6042637 2. Oono, Takashi, Apparatus for indoor air purification, Jpn. Kokai Tokkyo Koho (1993) JP 05285419 A2. (Japanese) 3. Miyamoto, M. et al. Corona-discharge air purification apparatus. Jpn.Kokai Tokkyo Koho (1999) JP 11342350 A2 (Japan) 4. Kuroki, T. et al., Development of new electric air cleaner for controlling particulates and odors, Earozoru Kenkyu 2000 15(2) 116-123 (Japan) 5 Niu, J. L. et al. Quantification of dust removal and ozone emission of ionizer air-cleaners by chamber testing, J. of Electrostatics (2001) 51-52 20-24 6. Zygmunt Grabarczyk, Effectiveness of indoor air cleaning with corona ionizers, J. of Electrostatics (2001) 51-52 278-283 7. Zhu, Y., Plasma source equipment of DC streamer discharge, China National Patent (2000) 00201301.0. (Chinese) 8. Masuda, S. et al., Fundamental behavior of directcoupled submicrosecond pulse energization in electrostatic precipitators, IEEE Ind. Appl. (1987) 23(1) 120-126 9. Fitch, R. A. et al., Enhanced charging of fine particle by electrons in pulse energized electrical precipitators, IEE Proc. Pt. A (1987) 134(1) 37-44 10. David, B. et al., Aerosol particle charging by free electrons, J. Aerosol Science (1989) 20(3) 313-330 11. Wang, X. and Zhu, Y., Determination of clearance between electrodes of multi-needle to plate for negative corona discharge, High Voltage Engineering (2003) 29(7) 40-42 12. Spyrou, N. et al., Gas temperature in a secondary streamer discharge: an approach to the electric wind, J. Phys. D: Appl. Phys. (1992) 25 211-216 13. Leonard, G. L. et al. Experimental study of the effect of turbulent diffusion on precipitator efficiency, J. Aerosol Science (1982) 13 271-284
158 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Comparison of I-V Characteristics in Two Types of Wire-Plate Electrostatic Precipitators Kang Yan-ming *, Chi Jin-hua *, Dang Xiao-qing*, Zeng Han-hou* * School of Environmental Science and Engineering, Donghua University, Shanghai, 200051, China * School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China Abstract: The performance of electrostatic precipitators (ESPs) was usually obtained under different geometric parameter values and operation conditions. In the present paper, the effects of some geometric parameters on the I-V characteristics of two different types of ESPs, one is a conventional wire-plate ESP, the other is a tri-electrode ESP, are explored experimentally. The results show that in a tri-electrode system, the corona current will be limited in the zone between two additional electrodes, the width of the cross channel should take the same magnitude as in wire-duct ESPs with the comparison of the two types of ESPs. Keywords: tri-electrode electrostatic precipitation, width of cross channel, wireto-wire spacing, corona current density, wire-duct electrostatic precipitator
INTRODUCTION The electrostatic precipitator (ESP) is one of the most commonly applied particulate control devices to reduce fly-ash emission from coal-fired power stations, cement industries and many other industrial processes. The collection efficiency of an ESP is increased as corona power increases. However, when high resistivity dust particles deposit on the surface of collecting plates, the ideal design of an ESP is changed [1,2]. One of the major problems for a wire discharge system is back corona. A back corona reduces the spark-over voltage, and thereby narrows the voltage interval within which the unit can be operated. Under back corona conditions the particle path changes substantially, they are apt to move reversely and often oscillate back and forth in an irregular fashion [ 1]. Wide spacing technology is a new approach for the development of ESPs with high efficiency. The conventional plate spacing of an ESP is usually around 200 to 300 mm [3]. But for the plate spacing in the range of 250 to 500 mm, Darby [4] indicated that the wide spacing ESP would lead to high power consumption. Navarrete et al. [5] showed that a wide plate spacing of 400 mm is a convenient device for the collection of high resistivity fly ash particles. An ESP with a plate spacing of 300 mm showed a better performance for the collection of low resistivity fly ash particles. The tri-electrode ESPs are used for improving the collection efficiency of high resistivity dust particles in current days in China. In the present paper, current characteristics are tested for indicating the differences between tri-electrode and wire-plate ESPs.
EXPERIMENTAL APPARATUS AND EVALUATION INDEXES Two types of test models are used in the present study. One is a conventional wire-plate ESP, the zigzag collecting plate is used, and spike discharge wires are used see Fig. 1a. The other is a tri-electrode system, as shown in Fig 2b, rod-curtains are used as collecting electrodes, thus the ESP can be divided into the charging and collecting sections, and the three electrodes are made of steel tube with same radius, so the discharge electrodes are barbed pipes.
159 .~.collecting electrodes
,! (a) wire-plate system
(b) tri-electrode system
Fig. 1 Schematic diagram of experimental models used for I - V study of the two types of ESPs
Tassicker's boundary biased-probe (BBP) method is used to determine the corona current distribution at the surface of collecting electrodes in the presence of space charge [6,7,8]. The probe is connected in series with a current measuring device and a variable-dc voltage bias source, the current is measured by biased-probe. In the present paper, two index are employed to predict the characteristics of the two ESPs with different geometrical configurations, these are (1) Average current density on the collecting plates, J, which is defined as y=l~
nS
JiSi
(1)
1=1
where n and S are the total number of measuring points and total area of collecting surface, respectively, J/is tested current density at ith point, and Si is the corresponding area of the ith zone. For the tri-electrodes system, it can be simplified as --
1 n
J :n~Ji
(2)
(2) Maximum to average ratio of corona current density
Jmax/J. Where
Jmax is the max value of tested
Jmax/J indicates the fluctuation feature of current density in the charging region. dimensionless distance, .F = 2x/B, is introduced for convenience of discussion, with the definition,
current density, and
(3) An see in Fig 1, dimensionless distance at the point which a corona electrode normal to the collecting plate, is .F = o, and the point at the middle of two adjacent corona electrodes, is .F - 1.
EXPERIMENTAL RESULTS AND DISCUSSION Current density in a tri-electrode ESP with the change of A and C(or B) 3.0
3.0 2.5
~ E
+ - El-
A=300mm A=350mm
--A--'V-"
A=400mm A=450mm
_ E =3kV/cm
2.5
2.0
2.0
!.5
1.5
~.."--.-- ..... v . . . . . . ~.-._.-.~:-:.~.--.-.
"4
1.0
1.0
0.5
0.5 "
0"000
2
1 0
'
t
140
,
i . . . .
160
~
180
,
.
0.0
200
C (mm)
(a) Current density affected by the variation of C with different A
A-'-300mm A=350mm
- "~7-"
A=450mm
E=3kVlcm
A=409mm
~. ~-A--:
~ ~ - ~ - " - ~ ~ ~ ' ~-~ .
100
---O~ - El-- A - -
,
.
120 I
I~o ' ,60 .....,~0
./200
C (mm)
(b) The fluctuation of current density affected by the variation of C with different A
Fig.2. Current density distribution on the surfaces of collecting electrodes affected by the variation of A and C(or B) in a tri-electrode ESPs When the additional electrodes are introduced in a wire-rod-curtain system, the ionization zone are mainly restricted in the region between two adjacent additional electrodes, and the current density distribution on the surfaces of collecting electrodes will be affected by the variation of A and C(or B), see Fig. 2, where E is the average field strength. Fig.2(a) indicates that, when A__ 3 50mm, Y increased with the increasing of C first, the maximum of 7 (--2.30mA/m2)can be get at C =160mm, and then Y becomes to decrease, when A>350mm,the result is
160 exactly the reverse compared to that of A _<350mm, Y reduced to its minimum magnitude ( Y 1.48mA/m 2) when C=160mm. The relationships between Jmax/J and C under different values of A is shown in Fig.2(b). It can be seen that for A>350mm, the peak of Jmax/J can be obtain when C=165mm, but for A_<350mm, Jm~/Yhas no maximum value, and the change of C has no effect on the variation of Jmax/J. AS in a conventional ESP, weak fluctuation and relatively high level of Y in charging zone has more benefit for aerosol collecting, this means that in a tri-electrode ESP, large values of the width of crossing channel is not necessary. Current distribution on the collectin~ plate in a tri-electrode ESP According to the analysis in the previous passage, distribution of Y along the collecting plate in a trielectrode ESP are measured for C =105mm, 135mm, 165mm and 195mm when A - 3 0 0 m m and 350mm, respectively, the result are shown in Fig.3. 2.5
E =3kV/r '"I I'"~"*.~ .
q,
E
- "~,-" C=195
.I;/ /I~~....- 0
2.0
fill/
1.5
-II-
~
,/'7
i 1.0 t,..~
0.0
0.2
0.4
0.6
0.8
N
:;/I
0.0
0.0
--0-" C==135m. ._Q__C=105mm
", ~.~
.'..'i
0.5
0.5
-'Z~'C:195 mm -- II-- C= 165 m m
f:i 11/~,,, '* *':~ if, t/ ~
•I•1.5
- - Q - - C"105 mm
i"
,~ 1.0
]/
mm
C-165mm
E =3kV/em
.t/•/I•_~.'~"1,"
2.0
0.0
~,',.N
0::2
'
0:4
0.6
0.'
X
X
(b) A =350mm
(a) A =300mm Fig.3 Variation of J vs. X
It is readily be found from Fig.4 that ff is relatively high when 0< X < 0.6, and the particle will acquiring charges in the zone. In fact, when X >0.6, the charged particles are in the "collecting zone", thus the particles are charged and collected in two different zones and, and "back corona" effect can be reduced. Fig.3 also shows that for A=300mm and 350mm, the increases of C can enhance the discharge intensity in the same range of X , but the homogeneity of Y will be reduced when C > 165mm. Comparing Current distribution with the wire-plate syste.m Fig.4 shows the differences of current distribution on the plates 2 5[ ~'-'.~kWcm between wire-plate and tri-electrode systems. In the test wire-plate 9 / ~.. - E l - - A=350mm. C=135mm [ I~ % - - I - - No tri-clcetrt'xle. A=350mm system, the effective width of plate-to-plate is A=300mm, 350mm, [ i ~ l lg_ and the wire-to-wire spacing are B =240mm, 270mm, respectively. ,5~ ,7 ~, ~_. l ..a--~>,.o ,,~-.,T\ The result also indicates that the corona current distributions 1.0 ~ . . II.r~.. -" x "" 0 on the zigzag collecting plate are different from that of on rod" [~Ii~" O~ '~, Zigzag plate, E =5kV/em curtains in a tri-electrode system, but to some extent, the "" !"f ,~ - s - ^=.O.,..C--;20n~ t/ ,, homogeneity of ff has the similar characteristics as the latter. In 0.0 ~ I 0.0 0.2 0.4 0.6 0.8 1.0 1.2 the conventional ESPs, no obvious "charging zone" and X "collecting zone" exist for there is no additional electrode arranged Fig.4 Current distribution comparison of in such a system, when the additional electrodes are removed, the the two types of ESPs current distribution is somewhat like in a conventional ESP. There is another characteristic in the tri-electrode system, the values of J are almost twice compared with the wire-plate system under each X although the average electric strength is lower than the latter. i/
m
- o-
^=.,OOmm.,.:=,,mm
SUMMARY The performances of two types of ESPs are compared with the experimental data, the effects of some geometric parameters on the I-V characteristics of two different types of ESPs, are tested and discussed. The results show that in a tri-electrode system, the corona current will be restricted in the zone between
161
two additional electrodes. The width of the cross channel should take the same magnitude as in wire-duct ESPs with the comparison of the two types of electrostatic precipitators, and too large wire-to-wire spacing is not necessary in application.
REFERENCE 1. Bohm, J. Electrostatic Precipitators. Elsevier Scientific Publishing Company, New York, 1982 2. McLean, K. J. Electrostatic Precipitators, IEE Proc., 1988, 135A(6): 347-362 3. Meyer-Schwinning, G. The increased passage width-development steps and results achieved with industrial installations, Proc. 2nd Inter. Conf. on Electrostatic Precipitation, Kyoto, Japan, Air Pollution Control Assoc. 1984,, 929-936 4. Darby, K. Plate spacing effect on precipitator performance, Proc. 2nd Inter. Conf. on Electrostatic Precipitation, Kyoto, Japan, Air Pollution Control Assoc., 1984, 376-383. 5. Navarrete, B., Canadas, L., Cortes, V., Salvador, L., and Galindo, J. (1997). Influence of plate spacing and ash resistivity on the efficiency of electrostatic precipitators, J. of Electrostatics. 39:65-81 6. Tassicker, O. J. Measurement of corona current density at an electrode boundary, Electronics Letters, 1969, 5(13): 285--286 7. Jones, J. E., Stark, W. B.Assessment and improvement of electric-field measurements using a bias probe with particular reference to twin-point-plane geometry, IEE Proc., 1987, 134A(4):317-327 8. Shi, X. M., Yumoto, M., Sakai, T. On Tassicker's measurement formula in the boundary biased-probe method, IEEE Trans., 1999, 35A(3):549-553
162 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Analysis of the reason about the distribution of dust density and size in vertical electrostatic precipitator Qing Li, Fengming Wang ,Zhiqiang Liu Electrostatic Research Institute of Hebei University, 071002
This paper introduces the distribution of the density gradient and particles in different gradient of dust in vertical electrostatic precipitator under the different voltages, analyses the reason for this kind of situation mainly from corona discharge and electrification, and shows the optimum working voltage of different situation.
PREFACE The working efficiency of the electrostatic precipitator is a question that involves wider and important subjects, and there are a lot of factors influencing it like collecting electrode interval, polar plate area, discharge-electrode interval, particle size, working voltage and working environment, etc. In this paper, the key research is the impact on dust-collection efficiency of particle-size. The article regards coal dust as the research object, calculates through a series of theories that study with the experiment and carries on detailed analysis to dust-collection efficiency in the situation of different voltage and particle-size[1 ].
THE OPERATION PRINCIPLE OF THE ELECTROSTATIC PRECIPITATOR The operation principle of the electrostatic precipitator is to make the electriferous dust pass the highvoltage electrical field, utilize the principle of electrostatic adherence to caught and collect dusts. The dust-collection course is entirely divided into two stages" One stage for charged stage which makes neutral dust take the negative electricity among the electrical field; The second stage is to make these electriferous dust move to the polar plate under the force of electrical field and achieve the goal of accepting dust[.
ELECTRIFEROUS DUST'S STRESS AND MOVEMENT IN ELECTRICAL FIELD Now we analyze the electriferous dust's movement rule by the stress situation of electriferous dust. Having unity for simplified calculation and test, here we make an assumption as follows" suppose the dust enter the electrical field from top to bottom in the form of free falling body. At this moment, electriferous dust's stress situation is shown as Pie. 1. First, gravitation Fg; second, electrical field force Fd; third, dielectric resisting force Fz. The assumption can make the analysis of stress in the twodimensional space comparatively simpler. Fg--mg (1) Fo--EcQp~ (2) Fz-- 6 ~dr/ro (3) thereinto: d particle's diameter q ----dielectric viscosity co ----particle's driving velocity
163 Q p s - - p a r t i c l e ' s saturation quantity of electric charge We know from the function direction of stress" The particle's geometric locus is the parabola form in the picture 1. The concrete distance b of sport relates to the composite force of Fg and Fz. In a situation that the electrical field is certain, Fd should be involved in Qps, and the saturation quantity of electric charge is Qps thereinto:
Fd
12eeom/2E
-
FZ
(4)
~+2 e o - - - - v a c u u m dielectric constant
b
----particle's relative dielectric constant -- --particle's size
g
therefore: Fd= QpsE--
12eeo nd 2 E 2 e+2
(5)
Pic. 1
Based on past experience, the process that dust enter electrical field and carry on electricity and reach saturation, we may conclusion that is finished instantaneously. Suppose saturation electric dust is at the edge of corona outside the district, so such movement distance of dust will be the biggest at this moment. In normal occasions, the time that dust reaches final velocity necessary is shorter than the time that the dust stays in electrical field. This mean when dust under electric field stress function to move to the collecting electrode, electric field stress and dielectric resisting force reach the balance quickly. At this moment, the velocity of deflection of the particle is:
QmE
co - ~ 6m/r/
(6)
from formula (4): (o--
2e0PdE 2
(7)
3r/
thereinto : p - -
3E
e+2 From the above formula, the charged particle's driving velocity is in direct proportion to the particlesize. The larger particles are, the heavier saturation quantity of electric charge is, and the more electric field stress is, the larger the driving velocity is. According to the formula of Duestch, we can know the efficiency is even better. EXPERIMENTAL FINDINGS AND ANALYSIS Table 1" the date form about dust's mass which correspond adsorption length ~ p u A waiting" easurement Dust mass which correspond adsorption length hysical Voltage No-lood Current The max antity output current output Current 0--10 10--20 20--30 30--40 40--50 50--60 output scope ~ (KV) (mA) (mA) (mA) cm cm cm cm cm cm particle-size 32.86 50 ! 60 32.86 60 Ii 32.86 ~.50 60 32.86 50 60 !
76-- 109urn ~A--'7~,,m
38-- 54um
38um
0.175 0.65 1.1 0.18
0.185 0.66 1.11 0.185
0.195 0.68 1.12 0.2 1.18 0.185 0.71 1.16 0.18 0.69 1.16
1.3985 2.0725 1.6074 1.3634 1.526 0.9919 1.209 1.7845 1.0143 1.2214 1.4853
2.2940 1.1726 1.5589 0.9633 1.133 0.9683 1.9062 1.2188 1.5117 1.0363 1.5886 1.5173 1.69117 1.3009 1.7133 1.3369 1.4471 1.3508 1.5235 1.1405 1.1463 0.9868
1.0197 0.8171 0.9177 1.099 1.05 1.3404 0.9240 1.0759 1.132 1.0322
0.8482
0.9125
1 1678 09182 0 9473 1 0451
1.0179
0.8295
164 The experiment facility adopted a line --barrel type, the barrel diameter is 300mm. Through the repeated test, the data is shown in table 1:[2][3] From data and chart we can find particle-size influences dust-collection efficiency. We can summarize the relationship between coal dust particle-size and dust-collection efficiency as follow: In case of outputting the voltage certainly, with the increase of the particle-size, it is shorter to accept the length of absorbing corresponded on the polar plate of dust, which proves that the dust is absorbed on the polar plate within short time, it is relatively high to dust-collection efficiency. Particle-size will certainly output voltage under the different situation, dust-collection efficiency of electrostatic precipitator increase as output the increase of the voltage. As voltage being 32.86kv relatively at the low-voltage, relatively long to absorb length, prove dust-collection efficiency not very kind; When the voltage is the high pressure of 50kv or 60kv, the absorb length is relatively short. When the coal particle-size within the range of particle-size that the experiment is used, adopting the voltage of higher output ( greater than about 60 kv), the effectiveness of dust's charge will be better, namely, the dust-collection efficiency is higher.
CONCLUSION From the data result from the experiment we know: particle-size heavy dust relatively short to absorb length, and particle-size little dust relatively heavy to absorb length. The shorter length the dust is absorbed, the heavier the thickness is. It is good that the ones that explain dust are absorbed, the higher dust-collection efficiency is; On the contrary, the longer length the dust is absorbed, it is the smaller to pile up the thickness, the lower dust-collection efficiency is. That is to say, the experimental result is in accordance with the analysis result of theory: particle-size influences dust-collection efficiency of the electrostatic precipitator. But there is a point must for attention: with the increase of external voltage, the demand of insulating part will increase. So in the actual design of precipitator ,the request from every part must be considered synthetically in order to extract rational service voltage.
REFERENCES 1 LiyanD, Discussionof the distribution of particles size, (2004) 2 Zhengyu T, Haixiang G, Measurement method of powder concentration and development of the instrument, Journal of Sichuan University,(2000),32(4) 3 Modica A, StepakoffG, Rosenbaum H .A shock tube study of plasma alleviation by Oxide dust[ M].NASA SP -- 232, (1970):531.
165 Paper Presented at the 5th International ConJerence on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The statistic method and result of mobility of charged dust in electric field Zhiqiang Liu, Qing Li, Wenjie Zhou ,Qing'an Zhang Electrostatic Research Institute of Hebei University 071002
One of the important parameters which determines the efficiency of electrostatic precipitator is the mobility of static charged dusts. In this paper the mobility of dust under the condition of different electric field and different density of dust is presented through statistic methods for experiments and the result or experiments is analysed. The computing method of this kind of statistic is given, and the relation between the mobility of dust and the electricity is gained.
The principle of electrostatic precipitation is that the smog particles as dust are charged suspending in air, then these charged particles are got rid of through oriented movement produced by the electric field force. Corona discharge is generally adopted to make the dust particles charged. In the electric field, the space ions produced through corona discharge is probably 107-108 / cm 3. Improving the number of space ions and helps the dust particles to charge, helps to improve the moving-rate of charged dust and removal efficiency. And these situations depend on the electric field energy and electric distribution of electric field. Any observable macroscopic quantity of material is behavior of collective characteristic of a large number of microscopic quantities. As to the research on the moving-rate of charged dust in the electric field, it is a very complicated computational process that macroscopic behaviors are achieved with microscopic quantity and with the method of statistics. Let's come to the microscopic whole behaviors with macroscopic test, and it will be simple[1 ][2]. The velocity distribution of gas molecules, namely Maxwell's velocity distribution function, is got when analysing the average kinetic energy of the perfect gas. f(v)-
lim A N = l d N Au-~o N A v
N dv
It can be seen from the formula above, the number of molecules in corresponding velocity unit is much if f ( v ) is larger. So the velocity distribution curve of Maxwell drawing is as Fig. 1. According to the Fig. 1, most probable velocity increases and the distribution width of velocity reduces when the whole area is constant under curve, can several speed most, speed, that is to say, the average velocity of gas molecule is improved to some extent. And this is exactly the result that we want in the dust removal system. According to the regularities of Boltzmann distribution: An - n o
e
xr
AVxAVyAVzA)cAyAz
where E k is the kinetic energy of molecule and Ep is the energy of molecule in force field and An is the numbers of molecule under constant velocity and space. From the above formula and figure, the particle always has priority to occupy the low-energy state. That is to say, for particles there is a trend of moving to collection electrode and uniform distribution. In the electrostatic precipitator, it is very difficult to measure the moving velocity of individual charged particle. The designing for the electrostatic precipitator is not very significant even the measurement has been carried on. The drive velocity of particles in the electrostatic precipitator is a collective reflection of effect of enormous quantity of particles, so it is possible to analyse through the measurement of macroscopic quantity. The design of experiment is as Fig. 2 shows.
166 f(v) 1
_..&
FF
/ v
Fig. 1" the velocity distribution curve of Maxwell drawing
Figure 2
In the structure above, dust particles are sent to the electric field with certain wind-force FF. Distance that the particles deposited in collection electrode will be different with different electric field voltage and particle diameter and wind velocity. Regard welding powder as the subject for investigation in this experiment, the following experimental result is achieved: (neglect of gravity) Adsorptive length under different voltage and particle diameter unmeasured output ",,~rameter voltage particle (KV) diameter 32.86 50 76-- 109um 60 32.86 50 54--76um 60 32.86 50 38--54um 60
no-load current
output current
(mA)
(mA)
0.175 0.65 1.1 0.18 0.62 1.1 0.17 0.66 1.1
0.185 0.66 1.11 0.185 0.63 1.14 0.18 0.68 1.12
maximum Corresponding output adsorptive current(mA) length(cm) 0.195 0.68 1.12 0.2 0.64 1.18 0.185 0.71 1.16
,
50 40 30 60 44 40 90 50 50
According to the above data, the dust-removal distance is reduced with the improvement of the voltage and particle diameter. So it can be thought that under the certain voltage the moving-rate of particles increase with increase of particle diameter. The distribution of dust diameter is very wide in the actual application, and it is possible to analyse the proportions of particles with different diameter to the total dust (under TSP situation). So the driver velocity of the minimum diameter of utility is confirmed through the above experimental method, then the dust-removal efficiency under that density is individually calculated according to Dutsch equation, thus the optimum design of electrostatic precipitator is achieved.
REFERENCES 1 Leonord G L, et al. Partic transport in electrostatic precipitators. A tm os Enriron, (1980), 14:1289 2 Yam am oto T, et al. Electrohydrodynam ics in an electrostatic precipitator. J Fluid Mech, (1981), 108" 10-18
167 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Effects of charged dust on dust-collecting electric field Zhiqiang Liu, Zengwei Peng, Qing Li, Dongxu Pang2 Electrostatic Research Institute of Hebei University 071002 The 2nd company of QinHuangDao port 066003 In this paper, the electrical state of dust particles in different radius is analysed through the method of mathematical analysis, and the effect on corona electric field from statistic charged dust is explained in theory and experiment. The variation of dust's moving static in the electric field is presented under this condition.
THEORETICAL ANALYSIS In electrostatic precipitator(ESP), carrying capacity of particles is relevant to diameter of particles and electric field intensity and staying time. In the electric field of dust removal, there are two ways of the charging of particles" one is electric charge; the other is diffused charge. The specific form of charge is in accordance with the particle size. Generally speaking, particles that are smaller than 0.2um rely mainly on diffused charged; particles that are greater than 0.5um rely mainly on electric charge. As regards to the real work of ESP, most rely on electric charge basically.[ 1] For ESP of tube-type, the intensity of electric field between discharged electrode and collection electrode has something to do with corona intensity of discharged electrode, namely distribution of space charges. When no corona discharge, electric field can be regarded as the static field. So the distribution of electric field between the two electrodes is like Fig. 1 shows" E
E-electric field r: interval of discharged electrode
"-
r
Figure 1
When there is corona discharge on discharged electrode, corona current is formed. When space charged particles exist, individual electric field of charged particles will influence greatly the electric field between discharged electrode and collection electrode (main electric field) because the moving-rate of charged particles is far smaller than the one of particle. Namely strong effect of space charges. Charged particles disperse in the whole electric field. Electric field that charges of particles produced make whole main electric field uniform, which makes electric field near collection electrode rise. There is influence of two sides on ESP under this kind of situation. First, it easily causes the spark to discharge; second, it helps the movement of charged particles. It is possible to restrict effectively spark discharge through controlling density of dust. The second factor is favorable to the improvement of dust removal efficiency.[2][3] In order to analyse the effect of charged particle on space electric field under electric charge, some supposition are made as follows" 1 uniform distribution of dust in discharging area 2 no disturbance between electric field of charged particles each other 3 The size and property of dust particle are homogeneous and spherical shape According to the Possion equation: divE- 41CPv
168 namely" V2U - - 4 n p ~ where: U~potential of known spot, Pv-- density of space charges In the system of coordinates of column, the above-mentioned equations are solved, get: E o~ Ap~r 3-k-Br
E=
When no corona discharge, the distribution equation of static electric field is as following: U rln(rb/q)
(1)
(2)
where" U-- potential difference between charged electrode and collection electrode ra~radius of corona wire, rb--radius of collection electrode, r ~ i n t e r v a l of discharged electrode. The intensity of electric field apart from discharged electrode is improved because of the existence of charged particles through comparing equation (1) and (2). This kind of effect is more and more remarkable with the increase of the carrying capacity of dust[4]. EXPERIMENT In order to verify this relation, a series of experiments are made and the following data table 1 and 2 is achieved (X is the vertical distance to collection electrode in dust-collecting electric field): temperature: 26~ humidity: 68%RH Table 1 X Input voltage No dust condition Dust condition Cm Kv voltage: Kv Current: uA 12.5 60 36 1700 10 60 25 1700 Spark discharge 7.5 60 21 1700 12 1700 60 X Cm 12.5 10 7.5 5
Input voltage Kv 55 55 55 55
Table 2 No dust condition Current: uA Voltage: Kv 32 1400 24.5 1400 18 1420 17.5 1420
Dust condition Voltage" Kv Current: uA 33 1440 27 1480-- 1520 18 1440--1520 18 1440-- 1500
CONCLUSION Range of action of electric potential gradient is enlarged when corona voltage increases. During experiments, electric field only in the area of obvious electric potential gradient is influenced when density of dust in electric filed is changed, and the effect will change with the variation of density of dust. But generally amplitude of effect is not large, and corona current is influenced remarkably by the variation of density of dust. From the result of experiment, we know that under corona discharge, it is impossible to get the satisfactory result if electric field is analysed simply according to the formula above. The main reason is that the action of illegal motion of space charged particles on electric field is unnegligible. REFERENCE: 1 ZhengchunX, ZhenghuF, The influenceof dust to the distributionof electric fieldin a wire-plateESP, Joumal of ZhejiangUniv. (1994),3 2 John P G, Norman L F. A Theoretically Based Mathematical Method for Calculation of Electrostatic Precipitator Performance, Journal of APCA, Feb., (1975), 25"108~113 3 T. Yamamoto, S. Nakamura, H.R. Velkoff. Numerical Study of Secondary Flow Interaction in an ESP, Univ. Press of Virginia, (1980), 3-12 4 Saverio C, GiorgioD and Mauro F, Numerical Computation of Corona Space Charge and V -~ I Characteristic in do Electrostatic Precipitator, IEEE Tran. on I. A., (1991), 27(1)"147"-154
169 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The effect of discharge-electrode interval on corona current Qing Li, Zengwei Peng, Zhiqiang Liu, Zisheng Zhang Electrostatic Research Institute of Hebei University 071002
According to the researches on characteristic of the distribution of electric field between wire-plate electrode. It shows that different discharging interval will affect greatly the homogeneous degreases of electric field. Thus it produces the remarkable change to the unit corona current and the total current. Depending on a series of experiments and formulae analysis, this paper defines the optimum value of corona current achieved through different interval of wire-plate electrode under natural conditions and offers certain theoretical direction for optimum design of electrostatic precipitator of wire-plate electrode.
THE THEORETICAL ANALYSIS OF ELECTRIC FIELD AND CORONA CURRENT Electrostatic precipitator is made up of two large divisions: one is the electric source which creates high voltage and direct current, and the other is the main body of precipitator. The main body is chiefly made up of dust collection plate and discharge electrodes. The area of collection plate determines the gas volume that it will treat. Dust collection plates and discharge electrodes composite the discharge electric field and the dust collection electric field together. The primary function of discharge electrodes is to create corona and large quantity of free ions. The strength of discharge is determined by the shape and interval of discharge electrodes, the interval between collection plates etc. And then the charges of dusts in the gas can affect the driving velocity of dusts and the efficiency of electrostatic precipitator greatly. Generally, electrostatic precipitator can be divided into two models: tubular type (or vertical type) and horizontal type. Discharge electrode in tubular type precipitator is independent relatively in each dust control unit, so there isn't interrelationship between the discharge electrodes. Now consider the horizontal precipitator and the structure of its elementary dust control unit is shown in figure 1. As is shown in figure 1, that the discharged electrodes are equal-intervaly arranged in dust collection channel and every corona electrode creates electric fields without interaction. Once a corona discharge is created, the discharged ability of the discharge electrodes and the bound of the corona zone must occur great variation accompanied with the redistribution of space charge and the variation of discharge voltage. Then the distribution of the electric field which leads to stress on the charged dust between the discharged electrodes and the collection plates must be influenced by the variation. Since the dust collection efficiency will be influenced eventually. Nowadays vertical type is generally adopted for large-scale precipitators, so it is necessary to research the influence on the electric field from the homopolar separation. 0
0
0
Discharge electrode
0
Collection electrode Fig. 1 A
--f.O
From the Deutsch equation r / - 1 - e Q ,if the volume(Q) of the fume which is treated and the dust collection efficiency( rl ) is constant, the area of the collection plates will be obviously reduced under the condition that the driving velocity of the charged dust is increased, so the factory cost of the precipitator will be reduced greatly.
170 In theory, the space charge density increases with the increase of the corona current. Then it will lead to the increase of the effect charging the dust. And the driving velocity of the charged dust increases with the increase of the strength of the electric field. So in order to improve the dust collection efficiency or in order to induce the area of the collection plates, it is necessary to increase the corona current and the strength of electric field. There are two parameters used to measure the corona current: One is the current density of the discharge electrodes (A/m), the other one is the current density of the collection plates (A/m3). If the area of the collection plates is constant, the dust collection efficiency improves with the increase of corona current. In this paper the current density under the condition of different space between electrodes is got through series of experiment [1][2][3].
EXPERIMENTAL FACILITY In this experiment, the wire-plate device is adopted. The heavy bob round line electrodes are all hung vertically along the collection plates (figure2). The corona electrodes (round line) which are fixed position by stabilizing shell are hung up on the shell and they are strained by the heavy bob at the lower end. When negative high voltage is add to the corona electrodes and the voltage of the collection plates is kept zero, high voltage electrical field which lead to gas ionization and large quantity of positive-negative ions will occur between the wires and the plates. Then the direction finding removing forms the corona current. And the corona current varies with the variety of the space between the corona electrodes or the collection plates.
~
"
1
2
Figure 2, corona electrode (1.discharge electrode; 2 collecting electrode)
EXPERIMENTAL DATA AND THE FIGURES The experimental results below are all got without any edge effect. (1) Now keep the effective area of the collection plates constant. Then be sure that the space length (D) of the homopolar plates is 250mm, and the corona electrodes at the edge are fixed and the place between them is 900mm. While corona electrodes are added to the inter-space between them one by one, the changing curve in total current by the number of the corona electrodes is got (figure 3). As is shown in figure 3, the total current increases gradually with the increase of the number of corona. But the rising amplitude is reduced. When n is 7, the current is almost invariant and the place between the corona electrodes is 150mm here. According to the theory, the best space length between the discharge electrodes is d=0.31D+75mm. And under this condition D is 250mm. So d=152.5mm and the experimential result keeps accordance with theoretical value on the whole.
171
Fig. 3 (2)Be sure that the homopolar space length is 200mm, and only two pieces of corona electrodes are used. Then the space length is alternated gradually and the changing curve in meter-current by time is got (figure 4).
Figure 4 As is shown in figure 4, meter-current increases with the increase of the space length between the corona electrodes. But when the space length is bigger than a value, the meter-current is almost a stable value. It shows that when the space is small, there will be interaction between the corona electrodes and this will lead to the decrease of meter-current. But when the space is bigger, there will not exit interaction. Then the meter-current will increase and tend to be a stable value. CONCLUSION The surface current and the line current are discussed though two groups of data above. The dust collection efficiency of a precipitator is mainly determined by surface current and the effective total energy of a precipitator is mainly determined by line current. As is shown by the analysis of these data, the best dust collection efficiency and the best energy supply have different expects to meter-current. In order to get a result of optimization, there must be general considerations when the precipitator is designed. REFERENCE 1. Junjie G, Jinxiang L. Theoretical calculation of current in electric field in ESP, Journal of nanjing Architectural and Civil Engineering institute, (1996),4 2. Shuangzhong Z, etc. The research on the electric field theory of wide-space ESP, Journal of Shenyang Institute of Aeronautical Engineering, (2000-9),3 3. Zhibin Z, Guoqua Z, Nex model of electrostatic precipitation efficiency accounting for turbulent mixing, J Aerosol Sci. (1992_23) 21:115--- 1 21
172 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISB,V 0-08-044584-5
The analysis for even wind method of the vertical electric precipitator Qing'an Zhang ,Qing Li, Zhiqiang Liu Electrostatic Research Institute of Hebei University 071002
The more even the wind speed is on the section theoretically, the more favorable to improve dust removal efficiency. The entering wind of the vertical electric precipitator is vertical to the wind in the electric field. Because of its structure characteristic, it is comparatively complicated to realize the even wind. Based on the structural characteristic of the vertical electric precipitator, the article states an evenwind structural, providing vertical electric dust remover a better scheme of achieving even wind with hydro-mechanical computational analysis and method that test.
PREFACE: Entrance of vertical electrostatic precipitator, where uniform-wind device is installed, located between ashhopper and electric field. Even wind is that speed of air flow from even wind cylinder is basically along the length orientation of even wind cylinder, thus, it is basically even wind speed of a section when multi-even wind cylinder are used side by side. Commonly, the shape of air flow exit of even wind cylinder is strip-gap, which is installed in midpoint of uniform cylinder bottom along the length orientation of even wind cylinder. Below the even wind effect of equity-section even wind cylinder is analysed.
THEORETICAL ANALYSIS In order to analyse easily, sketch map of even wind cylinder is follow as Fig. 1"
A !
!
v1 Fig. 1
Where" V0---wind speed in the entrance of even wind cylinder, m/s P0---static pressure in the entrance of even wind cylinder, Kg/m 2 A .... section area of even wind cylinder, m 2 Vi---the average wind speed in section 1-1, m/s Vi+dVi---the average wind speed in section 2-2, m/s Pi---static pressure in section 1-1, Kg/m 2 Pi+dPi---static pressure in section 2-2, Kg/m 2 L---length of even wind cylinder (length of strip-gap), m a---width of even wind cylinder, m b---height of even wind cylinder, m
173 h---the least section-width of air flow from strip-gap, m H---width of strip-gap (exit), m According to Beruonlli equation (from section 1-1 to section 2-2)[3]: pVi 2 p(Vi + dVi) 2 2pVi 2dl pV~ 2 + + +~-'h Pi + ~ = Pi + dPi + 2 2 2D 2 where: D---equivalent diameter of even wind cylinder D = 2ab/(a + b) Z h---local resistance of strip-gap (exit)
(1)
~ h - (pVt2 . 2
---coefficient of local resistance V l---velocity of flow in the least section of strip-gap (exit)
m/s
While the wind speed the exit of strip-gap is uniform, the relation of wind speed in the entrance of even wind cylinder and average wind speed of section in even wind cylinder is: Vi=V0(1 - - l / L ) Clean (1) up and get: dPi pVi2 2pVidVi
(2)
pdVi 2 2pVi2dl pV~ 2 pVi 2 ~ + + I +~h-~ 2 2 2 2D 2 2 Where the most of hypoitem of differential coefficient is leaved out:[ 1] P Vo2 2pL Vo2 [ p V2 (1 l 2pL V~ ( I _ I 3] P V~2 P i - P0 -t ~ ~?~h 2 3"2D 2 L) 3"2D L) 2 --
--
~
_
While 1 is zero:
(3)
+
Pi - Po
pVI2 2
While 1 is equal to L: Pi = Po ~
2
_
(4)
~
(5)
~h
p V2
2pL V~
p V~2
2
3"2D
2
~--]h
(6)
According to the formula above, Pi decrease with the increase of the length of even wind cylinder. 3D While L - ~ static pressure in the entrance of even wind cylinder is equal to that in the exit. 2'
Pi- Po-I pV2 (12
1
- ---2--p V~ (1-137 )
7)
1
p V~
~ h
(7)
3D While L = ~ , equation (7) is average static pressure on any section in even wind cylinder. 2 While 1 is equal L, Pi is the biggest, and While l _ -3'L Pi is the smallest, and
Pi max - P0 - pV'2 _ ~ h 2 4 PVoz pV~2 Pi m i n - P0 - 27 2 2
For design of project, the alteration of Pi to P0 is less than 15%,
~-]h
Pi m a x - Pi m i n
P0 4 pVo2 1 P0>27 2 0
.
1
5
(
S
<15%
)
While the condition of equation (8) is meet, the equality-ratio about the quantity of wind from the stripgap exit along the orientation of length in even wind cylinder is more than 85%.
174 STRUCTURE PARAMETER OF EVEN WIND CYLINDER 2ab . where D - ~ 2, a+b The relation of wind speed of air flow in the least section in exit of strip-gap in even wind cylinder and wind speed in the entrance is:
Length of uniform cylinder: L =
Vo A - L h V,
h -
3D
AVo
where 9h---width of the least section in air flow exit of strip-gap Vi---wind speed of the least section in air flow exit of strip-gap According to the property of thin-walled seam flux in hydromechanics, the relation of width H of strip-gap in the bottom of even wind cylinder and width h of the least section in air flow exit of strip-gap is:[3] H 1 h
Cc
where' C,.---contraction coefficient of section.
TEST AND MEASURE Fig. 2 is the simulate device of even wind cylinder, A.B.C.D.E.F. is measured holes. Measured apparatus used is thermoglobe anemomter which is QDF-3 type. Measurement: stick gage anemometer is inserted in measured holes. When the wind speed in the entrance of even wind cylinder is stable. Thermoglobe is dead against the below strip-gap of even wind cylinder and keep a certain distance from strip-gap. Measured conditions: size of even wind cylinder: 2ab a=0.05m b=0.13m D -0.072 a+b 3D -- 1.66m where 2, = 0.13 . H=0.0 l m L=0.97m L < ~ 2 Wind speed in the entrance of even wind cylinder: V0 - 15m/s Measured result" wind speed of A.B.C.D.E.F. points" A=12 ~ 13m/s. B=I 1 ~ 13m/s. C = l l ~ 1 2 m / s . D=I 1 ~ 12m/s. E=10-~ 1 lm/s. F=I 1 ~ 12m/s. 3D , wind of B. C. D. E. F. is less than wind speed of A. This is equal to (4). Because of L is less than 2 e x i t of? ~tir flow
t r u a k ot? ~t~ti,_-
Figure. 2
175 CONCLUSION For the even wind cylinder with constant section, it is impossible to get complete even wind in theory. 3D While L is less than and the static pressure P0 in the entrance meets equation (8), the wind speed in 2 the exit of strip-gap of even wind cylinder is basically uniform. The fabrication of the even wind cylinder with constant section is simple. It is easy to meet the design requirement. In general, structure the even wind cylinder is cylinder. Even wind cylinder is uniformly installed in the same section between ash-hopper and electric field and don't affect ash dropped. It requires that the distance from top of even wind cylinder to bottom of corona wire should be larger than the heterpolar distance. The factor of affecting electric field even wind also include electric field wind, uniformity between corona and collecting polar, top suction etc. This paper only analyses low even wind in the electric field of vertical electrostatic precipitator.
REFERENCES: 1 Juyun R, Shu J, Universal procedure of design of suction pipeline, Textile transaction (1996).6 2 Yaoqing L, Design handbook of heating and ventilation publishing company of building industry of China (1987) 3 Jingchao S, Hydromechanics of hydraulic pressure Zhengjiang unicersity
176 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The high voltage electrostatic precipitator system based on fieldbus for the workshop of unloading coal Zisheng Zhang, Hongshui Li*, Xiuming Zhao** Electrostatic Research Institute of Hebei University 071002 *Baoding Banknote Paper Mill 071000 **Baoding College of Finance 071000
Fieldbus is a rising new science, by which a new revolution is made in automation. In this paper, fieldbus is applied to the auto-control system of the coal unload workshop. It introduces the process of fieldbus standardization. This paper explains the theory of electrostatic precipitator and fieldbus technology. It discusses the setting-up of the model, and discusses the design and the realization of the fieldbus control system.
INTRODUCE With the developing of controlling, computer, communication and network technology, control system of the industrial production process is developing to intelligence, digitization and network. Information exchange and communication are rapidly covering to each level from equipment on-the-spot of the factory to controlling and management. In order to realize the informationization and digitization of control in production process, the field of automatic industry has put forward the concept of fieldbus. The fieldbus control system is not only an open communication network but also a kind of whole distribution control system. As the connection link of intelligent equipment, it connect the intelligent equipment which hang on the bus line as network node into network system and form further automation system, and realize comprehensive automation function such as basic control, compensational calculation, parameter modification, alarm, display, monitoring, optimization and the unification of control and management[ 1][2].
CHARACTERISTICS OF THE FIELDBUS Comparatively, DCS is a kind of half digital, half scattered and half open control system; FCS( the fieldbus control system) is the continuous development on DCS foundation, they are same in many ways such as the relation between man-machine interface operating station and advanced control. Three main characteristics of the fieldbus technology is shown in the blow: (1) Digitization of Signal Transmission The essential advantage that it brings to the system is" systematic precision rises; information of onthe-spot equipment increases tens of times, it may be used in self-diagnosis, systematic debug and management and enhance systematic validity have raised; one cable can link several many equipments which save cable 70~90% and work quantity. For example, the systematic operating station can read the equipment on each bus line easily. Staffs need not to check everyone like 4~-20 mA appearances between scene and control room. Besides value of itself, the process variable of each fieldbus still possesses it's condition, such as good, bad, uncertainty etc. This content may give operaor reference through display, convenient system under operation condition diagnose and maintain on-the-spot equipment.
177 (2) Open System DCS only makes the part above the operating station open and can not make control layer open. But FCS is completely open. There are some difference in different open degree and difficulty of bus line, for example, opening difficulty of simple bus line of I/O is lower but open mutual operation of systematic bus line is harder. (3) Control Scattered Completely The advantage that fieldbus brings to user is: the equipment on-the-spot of high intelligence completes dispersedly the function of DCS controllor and weakens or even canceled the level of concentration controllor, and reducs the cost of facility, make the control risk scattered, rise reliability and the autonomy of systematic control. Simple bus like I/O does not possesses this characteristic and advantage. But this is related to the occasion of use, for example, logic control algorithm is simple but speed is rapid, so PLC usually do not require to control thorough dispersion[3].
THE HIGH VOLTAGE ELECTROSTATIC PRECIPITATOR SYSTEM BASED ON FIELDBUS FOR THE WORKSHOP OF UNLOADING COAL System Structure High-voltage electrostatic precipitator in HD coal overturn workshop of the second load and unload company of Qinhuangdao load and unload is used as the replacement of former bag-type electrostatic precipitator introduced from Japan. This system is made up of low-voltage circuit, high-voltage circuit, main body of dust collector, FF control system and accessory system. Controlling part of the system include two low-voltage controlling cabinets, six high-voltage controlling cabinets, start-up cabinet of wind-machine with one-section and a controlling platform. Each dust collector need to measure the temperature of main body of dust collector, the pressure of coal powder weight. Dust exit and entrance density sensor are set up at the corresponding position of the main body of dust collector respectively. Electric current, voltage, starting and stopping of wind-machine, starting and stopping of stiring, electrical machinery controlling of shaking of each dust remover are fieldbus centralized controlled. The necessary collecting signal of FF network is as table 1 below: Table 1. Collected signal for fieldbus network Serial number Name Type Serial number Quantity 1 Temperature measurement FTI (Temperature) DT01-10 6 2 Pressure measurement FPI(Pressure) DP01-10 8 3 Entrance d e n s i t y FID(Dense) ID01-10 2 4 Exit density FOD OD01-10 2 5 Primary current FIC EEC01-10 6 6 Secondary current FEC EC01-10 6 7 Primary voltage FEEV EEV01-10 6 8 Secondary voltage FEV EV01-10 6 9 Current of system FSEC SEC01 1 10 Operator AD 16 11 Logical input DI 60 12 Controlled output CO 60 Realization of the system Characteristic of FF monitored control system of computer network in this paper: (~Original manual operating system is compatible and it is convenient to switch over; (~It is centralized to manage and dispersing to control; (~Multi-strategy control is realized and dependability of the system is improved. @ The routine control is coexisting with the network control.
178 Collection and function of the main computer system: The central control computer uses a ordinary multimedia PC (dominant frequency 2.4GHz, hard disk 80G, 3.5" floppy drive, DVD speed optical drive, 256M memory, 21" ultra fiat colored CRT), and a PSON1600KIII printer is used to be a FD of whole system. It is used to interact in man-machine information. It mainly has the following functions: (~)It realizes advanced control strategy of fieldbus system, including optimal energy control to fire, self-feedback closed control of dust-collection efficiency etc. (~It gathers the data signal of every FD and outputs the control signal to the carrying out device; (~) There is a good man-machine interface, including beautiful practical operation emulation show picture of every precipitator, system wiring diagram, flow process chart, warning picture, real-time and historical trend picture, report form, etc. (~It can autotype in real time and accept the order of operator. O I t can carry on the communication with the previous networks through Modem[4]. Other control equipments. It mainly includes 50 FF instrument which is 302 series of instruments of SMR company tentatively, ten temperature transducers FF302, ten pressure transducers LD302, eight three-channel fieldbus to current converters FI302-8, eight three-channel current to fieldbus converter IF302 and six self-made total control boards on each of which there are 10 signals and amount to 60. Other functions of the system. Including: Typing, saving data, consulting history etc. Typing includes: real-time controlling picture type, all teams and groups craft parameter autotype, real-time warning record type, noting record type, write down curve or data type. Data save includes systematic parameter save automatically, real-time warning record save automatically, curve and datum save automatically and field craft parameter saves in real time. CONCLUSION Characteristics of the high voltage electrostatic precipitator system based on fieldbus for the workshop of unloading coal includes: digitized signal transmission, thoroughly open system and completely scattered control. The realized scheme of the system in this paper is very valuable in practice.
REFERENCES 1. Kesi Si, Present Status and Development of Fieldbus, Automation Read Extensively (2000),4 114-115 2 XianhuiYang, Fieldbus Technology and Its Application, Tsinghua university publishing company(1999) 23-25 3. Peng Li, Jingsu Wen, Fieldbus and Inteligentmeters, Electrical Measurement Instrumentation(2003) 12 55-56 4. Zisheng Zhang, Control System of High Voltage Electrostatic Precipitator Coal Ash Based on Fieldbus Technology, The 4th Int.Conf Appl.ELECTROSTATICS 2001 DALIAN600-602
179 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Control system model of high voltage electrostatic precipitator based on foundation fieldbus Zisheng Zhang, Xiuming Zhao*, Hongshui Li* Electrostatic Research Institute of Hebei University 071002 *Baoding College of Finance **Baoding Banknote Paper Mill 071000
Foundation fieldbus (FF) was applied to the control system of high voltage electrostatic precipitator coal ash in this paper. This paper explains the theory of electrostatic precipitator and FF. It compares FF with distributed control system(DCS).It probes into the whole model of the control system. It mainly discusses the design and the realization of the model.
INTRODUCTION At present, with the rapid development of industrialization and modernization of countries all over the world, the environmental pollution become serious gradually, the attention to environmental protection all over the world grows with each passing day. The high-voltage electrostatic polluted air treatment technology of Hi-Tech gets constant development and extensive application. It is a new developing discipline which incorporates technology in many aspects, such as environmental protection, machinery, electricity, electron, computer etc. It is extensively applied to many trades, such as electricity, metallurgy, building materials, coal, chemical industry, pharmacy etc [2]. At present, control system of high voltage electrostatic precipitator operated extensively on the spot is control system of integrated circuit which is isolate and scattered control system. Its defects are that" employee is many, the work environment is formidable, occupational disease appears often, artificial record is convoluted, automatic degree is low, it is very difficult to find and deal with various kinds of trouble in time, it is apt to cause equipment loss and a large amount of waste of manpower and fund. With the development of the technology of the computer especially expansion of the range of application in the field of industrial control of network technology and promotion of the standardized process of the products of DCS (distributing control system) gradually, the technology of FF develops rapidly. It has completely realized the integration of control technology, computer technology and communication technology more. Its characteristic is that: dependability is high, performance is stable, anti-interference ability is strong, costs of maintenance and system expansion is low, cost of performance of the system is high, and it has already been extensive applied in countries of American-European. At present, applications of fieldbus technology at home are basically digestion, absorption and popularization of foreign corresponding technology[ 1].
TECHNOLOGY OF FOUNDATION FIELDBUS FCS system based on FF can be regarded as a DCS system made up of digital communication equipment and monitor equipment. Its main function is to accomplish measurement of various kinds of parameter during the process of industrial production, signal conversion, control display, and calculation etc. Automatic measurement, monitoring, adjusting, controlling and automatic protection of the production process are realized. It guarantees that industrial production is safe, steady and economic.
180 FF is made up of low-speed (FF-H1) and high-speed (FF-HSE). The network of FF-H1 bases on model of ISO/OSI whose physical layer (PL), data link layer (DLL), and application layer(fieldbus message specification FMS and FAS included) are used. A user layer is added upon application layer. All formed the communication models of four layers. FF-H1 is mainly used in the automation in production process(continuously control). Its transfer velocity is 31.25Kbps, the distance of communication can reach 1900m (It is related to the transmission medium and it can be prolonged by adding repeaters. Then the total length can reach 9500m). The system involved in this paper is only used to network of FF-H1. The characteristics of FF-H1 which is suitable for the course automation is that" @It supports buses current supply. @It supports security. @It supports the visiting mechanism of token bus.
THE REALIZATION OF CONTROL SYSTEM MODEL OF FF Foundation of network model Ten unit of HD type high voltage electrostatic precipitators of Qinhuangdao load and unload second company is used to substituted the bag type electrostatic precipitators introduced from Japan. Ten series of high voltage control cabinets and the inlet wire of total power are all installed in a large-scale control room in the middle part of 10 precipitators. The network of FF is shown as figure l in the following pictures. Master PC
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Figure 1" Control System Model of High Voltage Electrostatic Precipitator Based on Foundation Fieldbus
Each precipitator consists of 6 sensors: temperaturesensor, pressure sensor, density sensor, current sensor, voltage sensor and controller. 60 sensors are required in the 10 precipitators altogether. Each precipitator is a Field Device (FD). The following points must be paid attention to when the model is realized: 1. Laying of the terminal device: The terminal device, an impedance match device, should be placed on the ends of the main line in order to prevent the reflection of the signal. When the frequency varieties from 7.8kHz to 39kHz, the resistance of the terminal device should be kept 100~. In the course of the construction of this system, all of the field device increased lie on an extended cable which is shorter than 100m. Then the terminal device was kept on the original position of the first device. 2. Branch line. The shorter the better! The length of branch line in this paper is all from 0 to30 meters in the 61 sets of field devices of this system, and the longest one is the density sensor whose branch line is 20m. Length of the total branch lines is limited by two aspects: the branch line counts and quantity of the devices on each branch line. 3. Repeater. If the cable is longer than 1900 meters, the repeater is necessary. The repeater serves as a field device. Using it means new beginning, another cable of 1900m can be added. Three repeaters are installed in the system in this paper. There are individual 16 devices on the first and fourth branch line,
181 one of the devices is repeater. The second line connects with 18 sets of devices (one of them is host computer PC, two are repeaters). And the third one connects with 17 sets of field devices, and among them two are repeaters. The quantity of devices can also be increased besides length of network. The number of device can be increased to 240 in one network and the length of the network can be increased to 9500m by using repeaters. 4. Shield. Typical method of shield of FF cable is that only one point on shield line is ground at whole cable. The shielding line mustn't be used as lead of electric source. If more points are grounded there will be interference, and the network will unable to work naturally. One point grounded in collecting and controlling room is adopted in the system in this paper. 5. Polarity. Manchester signal used to FF is altemate voltage and the polarity changes once or twice per bit. When the network of system in this paper is linked, all the (+) ends are linked together, so do the (-) ends. Then the linking can be made easier by using the colored mark line. There are non-polar devices certainly, it can make automatic polarity measurement and adjusting, so the polarity of the devices can be let alone[3]. Topological structure of FF There are four type of topological structure of FF practically. 1) Bus-type topological structure with branch line 2) Daisy chain-type topological structure 3) Tree-type topological structure 4) Mix-type topological structure Tree-type topological structure is adopted in this subject. It can meet the field request and is very convenient to install, maintain and measure.
CONCLUSION The control system model of high voltage electrostatic precipitator based on FF is made up of four parts: host computer, interface card, fieldbus and field device. It gathers control technology, computer technology and communication technology in itself, its characteristic is that the dependability is high, the performance is stable, the ability of anti-interference is strong, and the data transmission is timely. When the network is realized, several keys such as polarity, branch line, repeater, terminal device, shield, topological structure, etc should be paid attention to.
REFERENCES 1. http://www. Fieldbus.Org/news/IEC 61158. 2. Zisheng Zhang, Application of high voltage electrostatic precipitator in coal transportation line, The 3rd Intemational Conference on Applied Electrostatics, 97Shanghai. 3. Technical Overview Wiring and Installation Intrinsically Safe Systems, 1--26.
182 Paper Presented at the 5th International ConJerence on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The supervisory system of precipitator based on CAN bus Wenjie Zhou, Zisheng Zhang, Qing Li Electrostatic Research Institute of Hebei University, 071002, China.
For CAN bus is more reliable, real-time and flexible than CAN bus is introduced into the supervisory system of improve its performance. This paper introduces the design project of the data acquisition module based on CAN bus supervisory system of precipitator.
traditional bus, precipitator to and implement in detail in the
INTRODUCTION With the serious increasing of the air pollution and the reinforce of the pollution control of air, the electrostatic precipitator is got wide application, because it has high efficiency in dust removal and low cost in operation and maintenance. Because there are more and more equipments and the attendant's workloads, it is necessary to monitor the precipitator in order to grasp the systematic operation conditions, deal with systematic malfunction and defect in time, provide users with the flexible and superior performance service, improve the dust removal efficiency and at the same time raise the automatic degree of the dust removal system. CAN bus is a kind of serial data communication protocol, which is designed by the BOSCH Company in German at first in order to solve a large number of data interchange between control test instrument, sensor and execution agency inside the modem motor. In view of the special working environment in the automobile, CAN bus has the following characteristics" the dependability of data communication is guaranteed by adopting CRC checkout, unique way of showing data signal, the function of discerning mistake and sending again automatically; the real-time of data communication is guaranteed by high data transmission rate (1Mbps) and the priority which high PRI data can occupy the bus; the bus structure of many main station and bus node can communicate directly, which guarameed the flexibility of data communication. This paper puts forward the dust removal monitoring system based on CAN bus.[ 1]
TOTAL BLOCK DIAGRAM This system is made up of several pieces of modules: various sensors, photoelectric isolators , data acquisition module, CAN bus controller, transition card from CAN bus to 232 interface and background computer. The working course is as follows" the voltage signal offered by each sensor, was transformed the different measure parameters by A/D of the data acquisition module; through can bus, can bus transfer to 232 interface card send background computer, computer places the corresponding data into the data base; if the measure parameters go beyond certain range, audible alarm should be activated and remind operator of attention; other computers among the LANs can visit the data base by landing in account. As Fig.1 ACQUISITION MODULE DESIGN Hardware design CAN bus controller is adopted SJA1000 and 82C250 interface driver of Philips Company. In order to _
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increase systematic anti-interference ability, realize the isolation between the bus and the controller and improve the operational reliability, two high- speed photoelectric isolators 6N137 are used between SJA1000 and CAN bus transceiver 82C250. CAN controller can be chosen to accept the send data from RXO TXO or RXI, TX.I.When using RXO TXO work, a steady level is had to need to receive RXI. Each 82c250 can join 110 contacts, generally speaking, which can be so abundant as to satisfy the demand. As Fig.2. vcc
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Software design System initializes SJA1000 and carry on resource allocation at first. Judge whether there are data accepted and sent at the same time. If there are, transfer the corresponding module to deal with. Entering mode before CAN bus is initialized, and only being the reposition mode, the systematic control register can be set up like command register, interrupt register, state register, receive register, receive mask register, and so on. Finally entering the work module of SJA1000 to receive and dispatch the data[2]. As Fig 3 and 4. Background monitoring program design Background monitoring program is programmed mainly based on windows database. It can realize the functions as follows: 1. Sending the inquire frame to all. 2. Showing the receiving data in real time, and at the same time storing the data at certain time interval. 3. Receiving the alarm message of data acquisition contacts, storing it and giving audible alarm in real time. 4. Real-time querying and typing of the data. 5. Allowing the computer in the LAN to inquire about the relevant data through the account.
184
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CONCLUSIONS By monitoring the precipitator and grasping the systematic operation conditions, in favor of the abatement of nuisance, ensuring the security and normal running of the system, the convenient systemic maintenance. It has made better result in practical application.
REFERENCES 1 Yueming Z, Chuang L. A kind of popular field bus CAN bus. Modem Electronic Technique. (2003). 24:61-63 2 Hong-liang D. The high--speed data dollection dystem based on VxD. Journal of Changchtm University of Technology. ~2003).24(4) -53-55
185 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The research of high temperature and high voltage electrostatic dust-collection technology Zisheng Zhang, Qing'an Zhang,Wenjie Zhou Electrostatic Research Institute of Hebei University 071002
High temperature is a problem to high voltage electrostatic dust-collection technology. This paper probes into high temperature and high voltage electrostatic dust-collection technology based on its theories. It discusses the effect that high temperature brings to the electrostatic dust-collection system. It analyzes the method which can eliminate influence of high dust-collection temperature, and also analyzes the method which make use of high temperature to improve efficiency of dust-collection.
PREFACE In industrial production, such as chemical industry, petroleum industry, metallurgical industry, electric power industry etc., high temperature dusty gas that is produced including chemosynthetic raw materials gas, furnace gas, high-temperature exhaust gas that coal's or reactor's burning produce must be collected. That is to say under high-temperature condition separation of gas and solid is carried on. In development and research of high temperature dust-collection technology, it should base on the high starting point, which make the high benefit of the industrial development, low energy consumption and reducing discharge, energy-conservation, environmental protection and reduce the equipment's wear from dust, lengthen the purpose of service life of the equipment. High temperature and high-efficient dust-collection technology has the following characteristics: high temperature of wanted purify dusty gas from -1400 to 600~ Particles is small diameter of smoke and dust particle is smaller than 5gm-10pm even in the sub-micron grade; High purifying standard demands concentration of exporting is 10mg/Nm3-50mg/Nm3. High temperature and high-efficient dustcollection technology expect much, and it is impossible to adopt simple device to separate gas and solid.
PRESENT SITUATION OF HIGH TEMPERATURE ELECTROSTATIC DUST-COLLECTION AT HOME AND ABROAD High-temperature electrostatic dust-collection technology is a new cross-centennial technology both at home and abroad, since the seventies of the 20th centuries, research of high-temperature electrostatic dust-collection technology have been carried on. About 1975, U.S.A. adopted firstly high temperature electric dust collection to prevent electrostatic precipitator from the anti-corona. Afterwards, Japan began to use high-voltage and high temperature electrostatic dust-collection technology for thermal power generation too. At present, Germany, U.S.A., Japan has already begun the research of corona type hightemperature electrostatic dust-collection. Up until now high-temperature dust-collection technology includes mainly: two poles or three series cyclone separator, surface filter and particle layers of filter relying mainly on ceramic material, electric dust-collection and acoustic conglobation cyclone separator etc. According to technological economic analysis of U.S.A. Gilbert/common wealth.inc on 10 commercial high-temperature dust-collection system of scale, considering from total fabrication cost and dependability, electrostatic precipitator is the most rising.
186 High-temperature electrostatic precipitator is corona type generally, and one without corona in electrostatic precipitator has appeared in recent years. In no corona electrostatic dust-collection technology precipitator's flat launch negative pole is made of some materials with low surface overflow work, the positive collection pole of dust-collection is essentially identical with routine corona type electrostatic precipitator. In development of such novel dust-collection technology, research of negative material is a key[ 1].
EFFECT OF HIGH-TEMPERATURE ON ELECTROSTATIC DUST-COLLECTION Electrostatic dust-collection face a lot of difficult problems at the technology under high-temperature terms for example, it is difficult to keep phenomenon of corona under high-temperature and high voltage, life of electrode is short, dust-collection efficiency is low, electrical insulation is difficult to realize and it is sensitive to exhaust gas composition etc, those prevent static dust-collection from further popularize under high-temperature terms. Only overcoming these difficult problems high-temperature electrostatic precipitator could be popularized extensively. Our country in this respect made already heavy progress at present[2]. Effect of high-temperature on character of electric field of electrostatic dust-collection Lower limit of working voltage of electrostatic precipitator is discharge inception voltage, upper limit is break-over voltage if difference of the two voltage is much, it benefit to the work of electrostatic precipitator, and it is easy to control their operation voltage but temperature's rise can influence discharge inception and break-over voltage. In order to produce corona there must be original electronic source and enough quantity of electrons to maintain electronic avalanche, it is necessary that there are enough time between two collisions, and electrons are accelerated to reach the degree of ionization. Discharge inception voltage is related to density of the gas. When temperature rise, gas density reduce (when pressure is constant), increase of distance between molecule will make mean free path to increase, average free sport time of electron increase too, so the time between two collision is longer when electric field is lower, electrons can be accelerated to reach the velocity which can make gas ionize, namely, discharge inception voltage will reduce with the rising of temperature. Equally, when temperature of exhaust gas rise, motion of gas molecular will aggravate, inner energy of gas molecule increase, and it is easy to ionize, so insulativity of gas decline, break-over voltage decline too, which make the difference of discharge inception voltage and break-over voltage become very small and cause working range of electric field of high-voltage electrostatic precipitator become narrow, it further cause that phenomenon of corona is difficult to maintain under high temperature. In addition because of the decline of break-over voltage, electric field intensity decline corresponding, which cause effective driving velocity of dust reduce and the time which smoke and dust reaching collect pole increase, thus dust-collection efficiency drops; In addition, if temperature rises, the gas coefficient of viscosity increases and resistance that charged particles that move to collection pole received increase, which make driving velocity decrease, and dust-collection efficiency drop too. Effect of high-temperature on entity Effect of high-temperature on entity is mainly two respects: one is on corona wire, the other is on collecting electrode. First, for corona wire, under long high-temperature environment, corona wire will be distortion because of lots of heat, at the same time under the high- temperature, it is easy for corona wire to be corroded by the high-temperature gas and to rupture because the content of corrosive gas is generally high. So for corona line there are not only good performance of discharge such as low inception voltage and high corona current but also higher mechanical robustness and corrosivity, which can keep distance between two poles to be regulate. Second, for collecting electrode, under high-temperature condition, heat stress, heat fatigue and heat impact erosion and oxidizing and so on should be considered. When temperature is higher, steel will occur creep deformation and creep rupture because of heat stress. Metal component and machine components exist heat fatigue and destroy in the high temperature. For high temperature and high-voltage electrostatic precipitator, because the fluctuation of temperature of exhaust gas is relatively heavy, heat fatigue should be paid enough attention to.
187 Effect on electrostatic dust-collection solid insulating material of High-temperature The insulating material of the high-temperature electrostatic precipitator is different from insulating material of general electrical engineering. Not only it adapt to the polluting the environment of the hightemperature electrostatic precipitator, namely appearance with long electric creep distance and without accumulating of dust, but good machine, electricity, heat performance are required in order to ensure normal reliable work under high-temperature exhaust gas environment. Insulating materials of electrostatic precipitator are not too many, most of which are ceramic materials. Other high molecular materials such as resin, glassfibre, are used little because they are not able to bear the high temperature. Once creeping draw occurs, they are easy to charry. It is proved through production practices that high aluminium (corundum) porcelain 85 or 95 has long performance life, insulating effectual, and it is able to bear the high temperature Its cost performance is obviously superior to the quartz glass and organic material[3].
CONCLUSION (1) Specific resistance of smoke dust appears to be a nonlinear variation with temperature. (2) The high temperature will make the efficiency of the electrostatic precipitator drop. (3) Special corona electrodes, collecting electrodes and insulating material should be adopted in high temperature and high- voltage electrostatic precipitator.
REFERENCES" 1. Yaping Yang, Huifen Huang, Qidong Wei, The newest progress of high-temperature static dust-collection technology of no corona, Motiveforce project of heat energy(2003),18 116-118. 2. Jingjiao Song, High-temperature dust-collection technical development and able to bear the market prospects of straining the material of high temperature, Chemical industry accoutrementtechnical(2002)5 19-20. 3. Xianglin Gao, Zhiguang Hu, Dust-collection mechanism and equipment, Northchina electric power university(1987)
188 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Analysis on the characteristic of high voltage electric Field of different dust-collection electrode Zisheng Zhang, Wenjie Zhou, Qing'an Zhang Electrostatic Research Institute of Hebei University 071002
Starting from the principle of gas discharging, this paper analyses the physical process of the current halo of high voltage electric field, brush-shape discharging and the discharging of electric act. It carries out an experimental analysis on the characteristics of electric field of plat-board, round, square and honeycomb dustcollection electrode. It also probes into the reason of the changes and the influences on the dust-collection efficiency.
PREFACE Electrostatic precipitator(ESP) utilizes mainly electric field force to separate the dust and particle from dusty gas and achieves the goal of purifying air finally. During the procedure, for different dust-collection electrode, the distribution of electric-field intensity influences the movement and carrying capacity and deposition of dust. The characteristic of electric field plays a important role on dust-collection efficiency, as to this research, it can offer theoretical foundation to the mechanics of the electric dust-collection, the design and technological transformation of the electrostatic precipitator, and improve dust-collection efficiency, etc.
THE EFFICIENCY OF ELECTROSTATIC PRECIPITATOR The dust-collection procedure in ESP can be divided into dust charged and dust deposition and dust removal. For guaranteeing electrostatic precipitator works at high efficiency, it is necessary that the three phase mentioned before are effective very much. The classical equation of ESP is Deutsch equation, the equation is 1 / 1- rl =exp[ 60(A / Q)]
(1)
where: ~ is the moving-velocity of particle (m/s) A is the total area of dust-collection electrode (m 2) Q is gas feed rate (m3/s) A/Q is the ratio of area and gas feed rate It can be prove that the carrying capacity(Q) of particle in the electric field is in the direct ratio relation with the peak value Ep of intensity of discharging and power two times to the diameter of particle ; Q=k-Ep-D E
(2)
Force acted on charged particle is in the direct ratio relation with the carrying capacity and the average Ea of electric field intensity of dust collection: F=K -Q -Ea
(3)
189 Plugging (2) and (3) in the Stoke law of frictional resistance of stable gas motion, then the moving rate ~o is: co=K-Ep-Ea-D
(4)
Where K is constant. According to the equation (4), for moving rate, the voltage applied on ESP play a capstan role. So the moving rate increase through increasing the average Ea of electric field intensity of dust collection[ 1].
OF ELECTRIC
ANALYSIS ON THE CHARACTERISTIC COLLECTION ELECTRODE
FIELD OF DIFFERENT DUST-
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According to the figure before, the density of ling current reduces with increase of the numbers of corona wire. When the numbers of corona wire is certain, the density of line current tends to stability. This is mainly because when there is a corona wire only, electric field was not interfered and discharge is thorough, so the density of line current is relatively big. But when the number of corona wire is increased, it is interfered each other among corona wires. So the whole electric field become uniform and corona discharge become difficult, current reduces too. The density of line current tends to stability when the numbers of corona wire is certain. Analysis on the characteristic curve of V-I of several different type of collection electrode In order to get the characteristic curve of V-I of other type of collection electrode, the followed experiments as table2 are carried on: Table2 Experiment condition Type of collection electrode cylinder square
Experiment condition Length of corona wire(mm) 1000 1000
Type of discharged electrode Copper wire Copper wire
Number of corona wire 1 1
Interval of collection electrode(mm) 300 200
Depends on the above-mentioned experiments condition, the followed curves figure 3 and 4 are gotten" I,-- 91
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191 According to the figure, for ESP of cylinder type and square type, the density of line current increases too with the increase of voltage exerted, and within the range of voltage exerted (3.5-42.5 Vs), it increases promptly.
CONCLUSION (1) For ESP of wire-plate, the density of line current increases with the increase of the voltage exerted, and reduces with increase of the numbers of corona wire and the interval of collection electrode. (2) For ESP of square type and cylinder type, the density of line current increase with increase of the voltage exerted.
REFERENCE: 1. Manyin Hu, Xianglin Gao etc. Research on the characteristic of corona electric field and optimizing of ESP 2. Hongdi Zhang, Research on the intensity of two-dimensional space and the density of current of ESP 3. Xianglin Gao, Manyin hu etc. Experimental research on electric parameters with countless dust on collection electrode
192 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Fieldbus control system and electrostatic precipitator Zhiqiang Liu, Qing Li, Zisheng Zhang Electrostatic Research Institute of Hebei University 071002
Fieldbus technology is a new rising subject which is developed with intelligence sensor, computer, network technology, especially the development of the technology of the large-scale integrated circuit in recent years. This paper analyzes the structure of fieldbus control system(FCS) and electrostatic precipitator. This subject explains the development of FCS auto-control system. It discusses the design and realization of the FCS electrostatic dust-collection system.
INTRODUCTION Our country is a developing country and the environment is a big problem which is influencing and restricting sustainable development of our country all the time. Electrostatic precipitator is widely applied because of character of high-efficient to purification and energy-conservation, it is easy to operate, especially in the trades, such as electric power industry, metallurgy, steel, chemical industry, building materials, etc. With the development of technology of the microcomputer, its application in industry's control system is extensive gradually. High voltage static dust-collection system isn't a exception whose complicated logic control relation rely on hardware circuit no longer, but it is realized through the computer software. In this way, the realization of control function is much more complicated than that of past (adopt originally semiconductor discrete component, small scale integrated circuit, etc.), but control wiring is much simpler, and microcomputer especially chip microcomputer is cheap, integrated level is high, operation speed is high, capacity is small, dependability is high at present. In recent years, with the rapid development of the network technology, utilization of network technology to execute industrial control is becoming riper, especially the technology of fieldbus in the field of industrial control is developing quickly and it offers a new development space for the industrial control.
MECHANICS OF HIGH-VOLTAGE ELECTROSTATIC DUST-COLLECTION AND FF The principle of high-voltage electrostatic dust-collection High-voltage electrostatic dust-collection is realized through high-voltage electrostatic precipitator, it is a kind of dust removal device which utilize electrostatic force (Coulomb(C)s of strength) to realize the particle (solid or liquid particle) separation from air flow. High-voltage electrostatic precipitator is constituted of collecting electrode which is made up of metal sheet and discharge electrode (corona electrode) which is connect to high voltage electrostatic source. Collecting electrode requires reliable earthing and as the positive pole, and corona electrode is extremely the negative pole, linking with output of the high-voltage transformer. The negative and positive poles are isolated by high-voltage porcelain insulator or tailor-built high-voltage insulating post. Corona electrode is put in the center position between positive plates generally. Upper and lower ends of Corona line are both linked with corona shelf by the spring and both are tighted.The purpose is that it is favorable to shake and deashing and remove the negative pole dust(namely overcome the loose
193 phenomenon of negative pole). The dusty gas flow enter the entity of the precipitator from bottom, and move upwards in the electrical field (moves forward to the horizontal precipitator) under the function of the wind power of the draught fan, finally, the cleaned air outflows from the top. Dust-collection course of high-voltage electrostatic precipitator includes three stages: dust charging, dust removal, shake and deashing. The technology of FF FF is organized and developed by Field bus Foundation. The predecessor of foundation is leaded by U.S.A. Rosemount Company, combining with 80 companies' s ISP (Interoperable System Protocol) such as ABB, Foxboro, Siemens, Yok -ogawa, etc and is headed by Honeywell Company, uniting World FIP (Factory Instrumentation Protocol) of more than 150 companies. The field bus Foundation was established in 1994. It is devoted to develop the field bus agreement which is unitive standard in the world. It has got extensive support from the main automatic control equipment supplier in the world and has strong influence in many areas such as North America, the Asia-Pacific area, Europe, etc. FF bus bases on ISO/OSI open system interconnection level model. It adopts its physics layer, data link layer, application layer as the corresponding level of the communication model for FF and adds user layer on application layer. The main function of user layer is to arm at the need of automatic measurement and control, define the unified rule that information access and adopt the device descriptor speech to stipulates the universal functional module set. The above-mentioned company that make up Field bus Foundation is main supplier of automatic control equipment in automatic field, and understand thorough the functional need of automatic system low-layer network, possess enough ability to predominate the developing direction of field apparatus about this field. Thus therefore the field bus norm issued by them has certain authority. Contrast and analyse to FCS and DCS Remarkable difference of traditional DCS and FCS is that DCS turns the analog signal transmission of 4---20 mA in field into digital communication with the character of all-digital, two-way, multidrop, and so it has a series of advantages such as 80% of the cables are saved, 60% of connecting terminal are save, 50% of the anti-explosion bars are saved, and 50% of the I/O cards are saved etc. Meanwhile, maintainability, and openness of system are improved further. Traditional DCS is composed of three layers of structure (operate station, control station, field instrument), but FCS is composed of two layers of structure (operate station, field intelligence instrument). These can rise the whole systematic function especially the maintainability of the field device through various software and relevant message from field apparatus which are provided by FCS system. In control room, user's vision of facility management can be expended from I/O card of traditional DCS to the field apparatus in FCS. These can obviously improve the maintenance level and availability of system and reduce the manpower, material resources, time which are used for system maintenance. FCS AND ELECTROSTATIC PRECIPITATOR The general model of system which use FF technology to realized coal powder high-voltage static dustcollection is shown by picture 1 as follow. FCS
input ~fpower primar) source ~"1
i
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Low tensionloop
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i
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194 1. FF control system is made up of host computer, PC interface card, field apparayus, and accomplishs the acquisition and disposal to the signals which include all the primary and secondary current, primary and secondary voltage of the overall dust-collection system, temperature and pressure of the precipitator entity, the enablement and stop of fan in accessory system, the enablement and stop of shaker. And calculation of information, the monitoring of operation, trend analysis, disposal to the alarm etc[1]. 2. Main function of the low tension loop is to realize the supply of low tension to every precipitator and regulate main transformer's primary input voltage through silicon control. Each precipitator is provided one low tension control cabinet generally. 3. Main function of the high tension loop is to produce high-voltage static about 100kV and produce the high-voltage power, amplitude and wave mode that the system needs through high-voltage rectification circuit and high-voltage antihunt circuit or high-voltage impulse circuit, and supply the charging of precipitator[2]. 4. The main function of the precipitator entity is: particle's charging, collecting and deashing. It was made by the steel construction mainly. 5. Main function of Accessory system is induced air, shaking and deashing. Induced air send the flying coal dust to precipitator entity, shaking system finish the shake to the positive pole and the negative pole. Ash handling equipment will send the dust collected from the house and centralized processing or recycle, such as make into water coal slurry replace diesel oil for heating, make coal briquette use for industrial and agricultural production or people's lives[3].
CONCLUSION FCS signal transmission is digital communication with the character of all-digital, two-way and multidrop Application to high-volage static dust-collection system can simplify the structure of system, increase the transmittability of tense signal, realize dust-collection system's network management, centralized management, far-end and allopatric management, improve the automatic level of the system, and make good social benefits and economic benefits.
REFERCENCES 1.Zisheng Zhang, The control system of coal powder high-voltage static dust-collection which is based on the fieldbus technology, MasterThesis of Engineering(2002)6-7 2.Xilin Zuan ,Thesis about the technology of fieldbus, LittleComputerInformation(1998),54--80 3.Field bus Foundation,The total looks of the information integration openness structure system, Fieldbus Technology ( 2001), 5 29-31 m
195 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Electrical Sterilization of Yakju By Discharged Oscillatory Decay Waveform Circuit Hee Kyu Lee*, Myung Hwan So** Department of Digital&Industrial Electronic Engineering*, Department of Food Science Engineering** Bucheon College,424 Simgok-dong, Wonmi-ku, Bucheon 421-735,. South Korea
Abstract: In the sterilization system by using HV impulse waveform, Yakju was sterilized with HV discharged oscillatory decay waveform. The critical condition of impulse waveform for electrical sterilization has presented the smallest survivability at 20kV,4mH and it's over. The characteristics of this waveform shows oscillatory decay waveform with multiple pulses. And this impulse waveform was more effective to kill total aerobes, lactic acid bacteria and yeast cell than exponential decay waveform. Total aerobes lactic acid bacteria and yeast cell to become musty and sour for Yakju was used as the sample. Yakju is not proper to be thermally sterilized because of specific spicery property and the fact is that the stored property make improve with an artificial preservative. But this Yakju has good effect of electrical sterilization because of higher conductivity than water. Therefore this experiment can be treated sterilization without loss of original taste and perfimae to Yakju. As a result, it is found that Yakju can be sterilized on 20kV, 4mH and it's over by using our designed HV impulse sterilizer. Key wards: sterilization, impulse, survivability, oscillatory decay, exponential decay
INTRODUCTION Electrical sterilization of biological cells has the advantage of conventional, chemical or thermal sterilization and have been studied by many researchers. According to Sale and Hamilton, the condition of sterilization is determined by the product of the pulse length and number of pulses and by the field strength in the suspension[l]. Before we have evaluated the survival ratio of E.coli depend on the characteristics of RC and RLC circuit[2]. The result of that experiment is appeared RLC circuit better than RC circuit in E.coli sterilization[3]. RLC circuit with oscillating parameters, which consists of a capacitive energy storage source and a inductive pulse duration and a resistive cell suspension chamber has been widely used for a discharging network. RLC circuit shows multiple pulses(although oscillatory decaying) are available during the charging and discharging between capacitor and inductance with chamber containing cell suspension. Especially, this multiple pulse has the high efficiency for the same stored energy in capacitor whereas, conventional RC circuit has only single pulse is available by discharging energy stored in capacitor to treatment chamber containing cell suspension[4 ]. Therefore the RLC condition is considered one of the most important point to be investigated for electrical sterilization by HV impulse. The authors carried out an experiment to sterilize Yakju using our sterilizer consists of RLC network. Yakju which is one of major traditional wine in our country. That wine is made from grain and leaven and is used parallel double fermentation method in order to make progress simultaneously saccharification of starch and alcoholic fermentation. But Yakju is limited storage life which resulted from the store because of manufacturing without fired store process and low percentage of alcohol, or because of being microorganism to take part in fermentation and being microorganism contaminated by manufacturing process. And especially, what we call the Lactic acid bacteria well known to the general public as to acidify Yakju possessed the characteristics of only well living in Yakju to contain 10% of alcohol. So it is very important to sterilize the Lactic acid bacteria for the good quality of Yakju. Recently, in the manufacturing company, there make an attempt at improvement in the preservation of Yakju by means of heat treat. But sterilization by heating has the point at issue to be deteriorate the
196 quality of Yakju because of oxidizing or resolving the ingredients of Yakju by heating and because of a product of cloudiness due to the protein degeneration, a product of offensive, loss of original taste and perfume. Therefore this experiment can be treated sterilization without such a point at issue. EXPERIMENTAL APPARATUS AND PROCEDURE Fig.1 shows schematic diagram of experimental apparatus. In pulse generator, C(=0.1uF) of condenser was charged from dc high voltage source and discharge into the electrode(=Tank) by controller. In this case, the pulsed voltage was decayed by time constant(=CR). R and C are fixed, while only L value is changeable for good condition of oscillation decay. The diameter of treatment tank is 40cm and hight is 60cm. and the electrode's diameter is 20cm, and Gap distance of electrode in treatment tank is adjusted to 10cm. The pulse of applied electric field is 2kV/cm and The repetition rate of controller is operated as follows; T = nt;(T; treatment time, n; number of pulse, t: pulse width), n = (f.V)/m(n; number of pulse, f; number of frequency, V; volume(mL) of container, m; flux(mL/s)) and pulse was 10us.
Fig. 1. Schematic diagram of HV Impulse Sterilizer Fig.2 and fig.3 are showed that the sample in the shocked rice wine is diluted to 10-6 range. The 0.1ml of sample are transfered to the surfaces of Rogosa SL agar plates and spread over the surface of agar with a sterile glass rod. Then the plates are incubated at a temperature of 30~ for 5 days and the numbers of colonies are counted.
Fig. 2. Dilution procedure : Dilutions are achieved by adding on aliquot of the specimen to a 0.9% NaC1 solution.
197
Fig. 3. Procedure of sample treatment Therefore the influence of HV impulse on the Lactic acid bacteria has been measured as a survival ratio ( S=N/No, where N and No are a number of active microbes per unit volume after and before the voltage treatment, respectively)
RESULTS AND DISCUSSION In this experiments the energy stored in the capacitor (1/2 CVo2) is used as the energy input to the suspension by one pulse. The energy input was 20J at Vo = 20kV and 45J at Vo = 30kV. In the same condition fig.4 illustrates that the survivability decrease with the change in the treatment time. For example in case of 15kV the survivability decrease by 0.7 orders of magnitude within the range of treatment time 1000 to 4000uS. And in case of the same condition on 2000uS, the survivability decrease by 4 orders of magnitude within the range of voltage 5 to 30kV.
Fig. 4. Survivability on electric field strength against treatment time In fig.5 the survival ratio of Lactic acid bacteria is shown as function of the inductance value against electric field strength. The number of applied pulses was n = 20, for each value the survivability depends insignificantly on the number of pulses. In case of 14mH, the survivability decreases by 3 orders of magnitude even for 30kV. For 0mH a decrease of 0.7 order takes place for 5kV to 30kV. It is evident that the survivability decreases by 3 orders of magnitude within the range of inductance 0 to 14mH. But in case of 4mH and over, the survivability is shown to decrease of 2 orders than that of 0mH. As shown in figure 5 and 6, electric field strength with high L value has sterilized more Lactic acid bacteria cell than treatment time. And in fig.6 there can obtain the effect of sterilization even then lower energy of 100J/ml on the applied liquid temperature of 50 ~ and over. And even if the case of 40 ~ there was happened sterilization of Lactic acid bacteria on the applied energy.
198
Fig. 5. Survivability on inductance value against electric field strength
Fig. 6. Survivability on liquid temperature against applied energy.
CONCLUSION In this experiment, it is appeared that the survivability increases as growth of treatment time with drawing of a slow curve similar to straight line. it means that the sterilization does not happen to the long treatment time and it shows that the factor of electric field strength has a great influence more than the treatment time. And finally, it is found that the survivability of lactic acid bacteria being tested decreases with an increase in L value of 4mH and over.
REFERENCE [1] U.Zimmermann, "Electrical Breakdown, Electropermealization and Electrofusion", Rev. Physiol. Biochem. Pharmacol., Springer Verlag, vol. 105,pp 175-265,1986. [2] U.R.Pothakamury, A.Monsalve-gonzalez,G.V.Barbosa-Ca'novas,and B.G. Swanson, "Inactivation of Escherichia coli and Staphylococcus aureus in Model Foods by Pulsed Electric Field Technology",Food Preservation Proceedings, Natick, MA,1994. [3] Boleslow Mazurek, Piotr Lubicki "Effect of Short HV Pulses on Bacteria and Fungi", Acryl IEEE Trans. on Dielectrics and Electrical Insulation vol.2, NO.3, June, 1995. [4] H.K.Lee, J.Suehiro, M.H.So, M.Hara, D.C.Lee "Energy Efficiency Improvement of Electrical Sterilization Using Oscillatory Waveforms from a RLC Discharging Circuit", IEEE Trans. Dielectrics, El, vol.7, pp.872-874, 2000.
199 Paper Presented at the 5th htternational Co~![erence on Applied Electrostatics (ICAFS'2(~04), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Efficiency-Loss-Relations of Unipolar Nanoaerosol Chargers Marquard A., Bredin A., Meyer J., Kasper G. Institut ftir Mechanische Verfahrenstechnik und Mechanik, Universit~it Karlsruhe (TH) D-76128 Karlsruhe, Germany
A method for the comparison of aerosol charging devices of variable design is applied to a group of unipolar corona chargers for nanoparticles. A variety of charger models, as well as data from literature and own experiments are discussed here. Investigated chargers include geometric and electrostatic principles of varying complexity. We conclude that characterization of chargers according to three measured quantities - average particle charge q, charging efficiency a and electrostatic losses - obtained from experiments with a fixed particle system allows for an objective comparison between systems with different flow profiles and electric modes.
INTRODUCTION The charging of aerosol particles plays a central role in the field of aerosol measurements. For integrated nanoaerosol processes, a charging step promises to become an essential part of the total process chain as a preconditioning step in order to manipulate particle structure and thereby the final product properties. Despite the existence of a variety of aerosol charging concepts, there is no adequate basis for comparison. Published data is often not sufficient for a generalized assessment of these chargers, and most notably, electrostatic particle losses - a very important economic factor- have so far been largely ignored. A comprehensive and general approach to comparisons of aerosol charging devices was recently reported (Marquard et al., [1 ]). Here this concept is applied to a group of unipolar corona chargers for nanoparticles. Experiments were performed with a twin corona charger and a commercially available neutralizer in order to collect a comprehensive data set describing the given charger operation. Based on these data the charging and loss behavior of different particle systems at different electric and hydrodynamic modes is studied. Finally, data from literature are reanalyzed and used to compare the performances of other charger designs according to the charging and loss of 10 nm sodium chloride particles.
CHARACTERIZATION OF CHARGING SYSTEMS In the case of nanoparticle charging by diffusion of ions, the Fuchs model describes the charging process very well (Pui et al. [2]). It gives a theoretical relation between average particle charge q and charging efficiency ~ for a given product of ion concentration and time. But in practical cases this so called N.t product is often unknown. Also, for a more comprehensive description of the real charging performance of any aerosol charger the two charging properties q and ~ have to be supplemented by the electrostatic loss of particles. Hence, an improved description of charger operation has been proposed (Marquard et al. [1]). Whereas the definition of the average particle charge q is simply the current transported by the particles divided by their count rate, two definitions of charging efficiencies are in common use (e.g. Biischer et al. [3], Kruis et al. [4]). The intrinsic charging efficiency Eint (Eq. 1) is the number concentration ratio of charged particles to particles entering the charger, independent of whether or not
200 charged particles are lost in the charger. This loss is treated implicitly by the extrinsic charging efficiency eCxt~, which is defined as the ratio of charged particles leaving the charger to the particles entering the system (Eq. 2). C totai,ch arged
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C out.ch arged
, e ,r = Cin
(1), (2) Cin
In order to avoid inherent ambiguities of these definitions and to overcome definition difficulties related to chargers with additional gas flows (for flow field optimizing purposes, e. g. Biischer et al. [3], Pui et al. [5]) a more transparent description is achieved by considering the fraction of charged particles at the charger exit (Eexit, Eq. 3), the electrostatic loss (lossr Eq. 4) and the dilution factor f (Eq. 5) with flow rates Qin and Qout at inlet and outlet of the charger. C out,ch arged aout
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din
, f =~
(3), (4), (5)
The efficiency F-.exitis a kind of a net efficiency of the charging system, which incorporates the economic point of view, that only particles exiting the charger are available for further processing. Determining the dilution ratio f in accordance with Eq. 5 (defined in the common way, Baron et. al. [6]) when charging is off, ensures that f also includes diffusive losses. By measuring and making plots of the three properties q, F--exit and lossr one can observe charger characteristics that provide direct comparability of totally different charging systems. Note that in the general case of bipolar charging, the quantities q and l~exit have to be considered for both polarities.
EXPERIMENTS WITH TWIN CORONA CHARGER The experimental set-up consists of aerosol generators, a charger and aerosol measurement equipment. The first set of experiments was carried out with a polydisperse (Xg=65nm, Cyg--1.45, c = 105 #/cm 3) DEHS-aerosol. In this case the aerosol was generated by dispersing DEHS in an atomizer (ATM 220, Topas GmbH) and successively evaporating and recondensating the oil droplets (for details see Marquard et al. [7]). In the second set of experiments monodisperse stearic acid particles (Xg =60 nm, Og = 1.1, c = 103 #/cm 3) were generated in an evaporation/condensation process (Sinclair LaMer principle), classified and then neutralized (for details see Marquard et al. [1 ]). The charger consists of a cubic chamber with two charging modules placed opposite each other at two side walls perpendicular to the main flow (11 or 20 slm, resp.). Within these modules ions are generated in a point-ring corona configuration based on the ion gun concept of Whitby [8] and transported by an air flow support (1 or 10 slm, resp.) through the ring into the particle charging chamber. With this charger design it is possible to establish different electrical fields within the charging zone, independent of the ion production process. Aerosol analysis includes measurement of particle concentration (CPC3022,TSI Inc.), particle size distribution (SMPS3934,TSI Inc.) and mean particle charge (CPC & faraday cup electrometer FCE, our design) at the outlet of the charger.
Figure 1a) Charge-loss relation of DEHS aerosol for 3 different flow rate combinations at DC operation, lb) Charge-loss relation of stearic acid aerosol for three cases: no E-field in particle zone (spheres), DC-field (squares) and AC-field (triangles). Both diagrams: increasing loss corresponds to increasing corona voltage (no field) and increasing E-field (DC, AC).
201 In Fig. l a the dependence of the charge-loss relation obtained with the DEHS aerosol on the flow parameters is shown as plots of lossr vs. q curves. The corona voltage was fixed (-7.7 kV), and the DCfield within the particle zone was varied (0-1 kV/cm). The adjustment of the flows is indicated as 'aerosol flow/total electrode flow' in units of slm. As expected, lower residence times (20/10, triangles) correspond to lower charging. Increased turbulence by the electrode module flow (20/10, 11/10, squares) leads to lower losses compared to the 11/1 curve (spheres) (charger residence times correspond to approx. 3 s < t < 10 s, dilution ratios to 1.1 < f < 1.9). In Fig. lb measurements obtained with the stearic acid aerosol are shown for three different kinds of E-fields in the charging zone (fixed flow: 11/10). Either no E-field (spheres), a DC-field (squares) or an AC-field (triangles) was applied. In the first case the ratio of loss to q is worst. With an external electric field in both cases the loss-q ratio improves up to a certain field strength. Above this value a further increase of the field strength leads to a decrease of the efficiency at constantly high levels of loss. This can be explained by the increased deposition forces due to the higher electric fields. The AC-field gives no significantly better loss-q ratio than the DC-field.
EXPERIMENTS WITH TOPAS CHARGER EAN 581 With another set of experiments the applicability of a commercial neutralizer (EAN 581, Topas GmbH) for unipolar charging of nanoparticles is discussed. Whereas the original purpose of this device is to neutralize more or less highly charged gasbome particles (> 100 nm) in a bipolar ion atmosphere, it can also be used as a unipolar charger. The EAN 581 is essentially a corona charger consisting of two corona modules that are mounted on a stainless steel tube, where the aerosol is passed through. They are arranged perpendicular to the main flow direction, one downstream from the other. Each module comprises of a needle-ring configuration with supporting air flow to draw ions out. The modules are similar to those in the previously used charger, but the tings are operated as critical orifices. By increasing the module flow rates the loss of ions on the way to the particle zone can be reduced. Here, the DEHS aerosol was applied to the EAN 581. Aerosol and electrode flow were 11 slm and 50 slm (1 bar operating pressure), resp., yielding a dilution ratio of f = 6 and charger residence times of less than 0.1 s. Again, q, Eexit and 1OSSel w e r e measured. However, within the resolution of the measuring technique, particle losses could not be detected. Therefore, the results are shown by a plot of measured relations of Eexitvs. q in Fig. 2a. The curves correspond to one and two modules active, respectively. 80
0 2 module~
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o
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2b)
Figure 2a) Measured charging efficiency ?exit vs. average charge q of polydisperse 65 nm DEHS aerosol chaged in the EAN 581. Spheres: 2 corona modules active, triangles: 1 module active. 2b) Recalculated data based on HemandezSierra et al. [9](8.5 & 9.5 rim, spheres) and Bfischer et al. [3](8 rim, squares; 10 nm triangles). Arrow: increasing voltages. The efficiencies achieved show the same dependency on the average charge for both cases. The only difference is a higher total charge level in the case of both modules active. Although, optimization of both investigated chargers is not a goal of this study, it is noteworthy, that despite the much shorter residence time in the charging zone, the particles are charged higher in the EAN 581 than the first charger.
202 EVALUATION OF LITERATURE DATA From a large number of available publications dealing with unipolar charging of nanoaerosols, two papers could be selected which provide enough information for the discussed comparison method. In both publications electrostatic effects were measured separately from diffusive effects. Biischer et al. [3] developed a charger for the charging of aerosols at laminar flow conditions in an AC-field, where the ion production zone and the charging zone are separated by a screen electrode. For particle loss minimization the charger incorporates an arrangement where sheath air can be supplied. The dilution ratio of the presented experiments is f = 1.25, and extrinsic and intrinsic charging efficiencies of sodium chloride particles between 5 and 35 nm are provided. The second paper by Hernandez-Sierra et al. [9] deals with a much simpler corona charger, where particles are passed through a DC corona zone. The charger consists of a tube with a conically diminishing exit. A corona needle is mounted in the center facing the exit. The authors present efficiency (eextr) and loss data of the charging of sodium chloride aerosols below 10 nm, from which Eexit can be calculated. Because of equal particle materials and comparable sizes, the reanalyzed data of both papers can be compared directly, even though totally different hydrodynamic and electric conditions are given. The reanalyzed data sets are shown in Fig. 2b as plots of loSSel vs. Eexit. The data for 8 nm and 10 nm particles [3] and for 8.5 and 9.5 nm particles [9] follow closely the same straight line (arrow indicates increasing voltages). Obviously, the charge loss relation is rather independent of charger design and operation. CONCLUSIONS Different charging systems have been characterized by a set of common (average charge q) and uncommon (electrostatic lossel and charging efficiency Eexit) measurement properties. From this, a direct intercomparison of the systems with different designs and operation modes can be achieved. From experiments with a twin corona charger, insight to the relevance of electric and hydrodynamic situation in the charging zone for the particle charge-loss relation was gained. In combination with the analysis of literature data it can be concluded that the best compromise between charging and loss is not neccessarily achieved with more complex charger designs with (additional) AC-Fields. Also laminar flow conditions are not better in all cases. Experiments with the commercial charger employing highly turbulent ion input gave highest charging at negligible loss, presumably because of residence times that were up to 2 orders of magnitude shorter than those of the twin corona charger. REFERENCES 1. Marquard, A., Meyer, J., Ehouarn, P., Kasper, G., Efficiency vs. Loss Characteristics of Aerosol Chargers - General, Concept, PARTEC 2004 Nuremberg, CD-ROM article No.P 116. 2. Pui, D. Y. H., Fruin, S., McMurry, P. H., Unipolar Charging of Ultrafine Aerosols, Aerosol Science and Technology, (1988), Vol. 8, ,pp. 173-187. 3. Biischer, P., Schmidt-Ott, A., Wiedensohler, A.: Performance of a Unipolar "Square Wave" Diffusion Charger with Variable nt-Product, Journal of Aerosol Science, (1994), Vol. 25, No. 4, pp. 651-663. 4. Kruis, F. E., Fissan, H.: Nanoparticle Charging in a Twin Hewitt Charger, Journal of Nanoparticle Research, (2001), Vol. 3, S. 39-50. 5. Pui, D. Y. H., Chen, D.-R.: A High Efficiency, High Throughput Unipolar Aerosol Charger for Nanoparticles, Journal of Nanoparticle Research, (1999), Vol. 1, pp. 115-126. 6. Baron P. A., Willeke, K.: Aerosol Measurement, Van Nostrand Reinhold, New York, 1993. 7. Marquard, A., Meyer, J., Kasper, G., Charging Efficienciy of Nanoparticles in a Tube-type ESP; PARTEC 2004 Nuremberg, CD-ROM article No. 15-3. 8. Whitby, K. T." Generator for Producing High Concentrations of Small Ions, The Review of Scientific Instruments, (1963), Vol. 32, No. 12, S. 1353-1355. 9. Hernandez-Sierra, A., Alguacil F. J., Alonso, M.: Unipolar charging of Nanometer Aerosol Particles in a Corona Ionizer, Journal of Aerosol Science, (2003), Vol. 34, No. 6, pp. 733-746.
203 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Experimental
Study
On Optimum
Of Low-Ozone
Negative
Ion Generator
Liang Ping, Li Jie, Wu Yan, Lv Bin, Xu Minghua* Institute of Electrostatics & Special Power, Dalian University of Technology, Dalian 116023, P.R.China *Changchun Flight Academy of Air Force, Changchun 130022, P.R.China
This paper studies optimum of a negative ion generator with low-ozone emission using corona wire heating technique, and analyzes the effect of the electrode configuration parameter and the electric parameter of negative ion generator on it's performance, such as the negative ion concentration, and the ozone concentration. According to the experimental results, a low-ozone negative ion generator has been designed, and its performance index measures up to the national standard of environment protection.
INTRODUCTION The content of negative ions is a key factor to evaluate the air quality. Negative ions can effectively remove fog, dust and bacilli in door air, which resulting from longtime obturation. Furthermore, it can neutralize positive ion and active the air. So the negative ions are indispensable to family life. It can improve function of the lung and the cardiac muscle as well as sleeping so as to accelerate metabolism and enhance immunity. Negative ion generator with negative corona discharge is a kind of comparatively ideal facility to improve quality of indoor air. But ozone will be generated with negative ions in the process of negative corona discharge, which is not expected for a negative ion generator. The way of corona wire heating can restrain ozone being created [1]. This paper studies optimum of the electrode configuration parameter and the electric parameter of negative ion generator, and designed a negative ion generator using corona wire heating technique. The conclusion will provide practical base for designing similar negative ion generator.
EXPERIMENTAL SET UP grounded ~,,wirecorona . wire -
Figure 1 shows the section view of the experimental set up and the structure of the discharge electrodes. The enclosure of the experimental instrument is polymethyl methacrylate plastics. The top of it is opening. There are four fans under the corona wire and there power supply are some small holes around the instrument. The fans blow the air from the holes to the top of the Figurei The sectionview of the experimentalset up instrument. The electrode configuration is wirewire. The picture shows the layout of two raw of electrodes. The thick line denotes grounded wire (copper, 1.2mm diameter), the thin line denotes corona wire (iron-chromium, 0.3mm diameter), the corona wire is located the grounded wire, and they are alternately arranged with each other. The gap between the two raw of electrodes is adjustable, the length of the wire-wire discharge plate (grounded wire band and corona wire band) is 40cm, the width of it is 30cm. i
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204 This experiment adopts three kinds of discharge electrode gap (1.1 cm, 1.5cm, 1.8cm). The number of the corona wires and the grounded wires are adjustable. Measuring instruments are as follows: DC highvoltage divider (1000:1); AIC1000 positive-negative ion concentration analyzer (made in USA) for measuring negative ion concentration; Z-1200 ozone gas analyzer (made in USA) for measuring ozone concentration. The concentration of the negative ion and ozone were measured at the position one meter from the outlet of the generator. The input of DC high-voltage power-supply is 220V(AC/50Hz). After rectifier, filter, highfrequency inversion, high-frequency step-up transformer and multiple voltage rectifier, the max output DC high-voltage is 50 kV. The heating voltage is also got from the high-frequency step-up transformer. The DC high-voltage and the heating voltage are adjustable.
EXPERIMENTAL RESULT AND DISCUSSION The effect of the electric parameter on negative ion concentration and ozone concentration Experimental conditions: the discharge electrode gap is 1.5cm; the heating voltage is 70V(AC); the corona wire spacing is 2cm; the grounded wire spacing is 2cm.
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Figure 2 shows the curve of the negative ion concentration with the change of corona wire heating voltage. The negative ion concentration of the corona wire heating system is higher than it of non-heating system on the same discharge voltage. The corona wire emitting electrons, negative DC high-voltage provides the escaped power of electrons. With corona wire heating, electrons need less escaped power. Furthermore, corona discharge needs lower applied voltage. Figure 3 shows the curve of the ozone concentration with the change of corona wire heating voltage. The ozone concentration is decrease with increasing heating voltage. The change tendency is opposite to the negative ion concentration. The ozone concentration is mostly related to the discharge voltage, and increases with the rise of the discharge voltage. Under the condition of the same corona current, increasing the heating voltage can result in corona wire temperature elevation, then the discharge voltage and the discharge intensity reduce, so the ozone concentration drops. At the same time, the drop of ozone concentration also results from the ozone dissociation in high temperature. The effect of the electrode configuration parameter on the negative ionconcentration and the ozone concentration The discharge electrode gap Experimental conditions: the discharge electrode gap is 1.1 cm, 1.5cm and 1.8cm, respectively; the corona wire spacing is 2cm; the grounded wire spacing is 2cm; the heating voltage of the corona wire is 70V(AC). The experiments are under the condition of corona wire heating.
205
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Of ~
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On h ~ r
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Figure 5 the effect o f electrode gap on ~
ozone concentration
Figure 4 shows the effect of electrode gap on the negative ion concentration. The negative ion concentration increase with increasing discharge voltage while the electrode gap is same; negative ion concentration increase with the electrode gap diminishing on the same corona voltage. The reasons are as follows" the corona discharge characteristic of the negative ion generator is related to the electrode gap. The corona current and the energy consumption increase with the electrode gap diminishing. The energy of the negative ion getting from electrical field is higher when electrical field energy increases, and the motion speed of the negative ions becomes faster. The probability of negative ions captured by the earth electrode is reciprocal proportion with the motion speed. So the negative ion concentration becomes higher [2]. Figure 5 shows the effect of electrode gap on the ozone concentration. The ozone concentration increases with corona voltage. And it decreases with the electrode gap increasing while the corona voltage is same. The intensity of electric field decreases with the electrode gap increasing at a fixed voltage. So the ozone concentration is reduced. Grounded wire-corona wire array Experimental conditions: the grounded wire spacing is 2cm and 4cm,respectively; the corona wire spacing is 2cm; the electrode spacing is 1.5cm; the heating voltage of the corona wire is 70V(AC). Figure 6 shows the effect of the grounded wire-corona wire array on the negative ion concentration. The negative ion concentration always increases with corona voltage no matter what kind of electrode configuration used. The negative ion concentration in the condition of 2cm grounded wire spacing is higher than 4cm grounded wire spacing under the same voltage. Using dense ....... grounded wire, two grounded wires ~ag~-,6 ,~ ,rr.~t~ orth~~n,~-~-~o,~~ ~-~yo~~ ~ i ~ i~ ~o.~.~t~o, discharge by a corona wire (using thin grounded wire, a grounded wire discharges by two corona wires), so the negative ion concentration increases obviously. Although grounded wires holding up the negative ions increase, the negative ion concentration elevates finally. Figure 7 shows the effect of the grounded wire-corona wire array on the ozone concentration. The ozone concentration in the condition of 4cm grounded wire spacing is lower than 2cm grounded wire spacing under the same voltage. Using thin grounded wire, a grounded wire discharges by two corona wires (using dense grounded wire, two grounded wires discharge by a corona wire), so discharge is less acute, negative ions creating by this kind of configuration is less, reactions with oxygen reduce. As a result, the ozone concentration reduces.
206
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17isure 7 the effect curve of'the earth wiro-cm-~ma wire an'a3, on the ozone c o n c ~ J ) n
CONCLUSION Through this experiment we can conclude that: (1) The negative ion concentration and the ozone concentration increases with discharge voltage. (2) Heating the corona wire can increase the negative ion concentration and reduce the ozone concentration. (3) Diminishing the electrode gap (ensuring corona voltage and spark discharge voltage having enough change scope) can increase the negative ion concentration and the ozone concentration. (4) Increasing the grounded wire spacing can reduce the negative ion concentration and the ozone concentration. In the condition of the corona wire spacing and the grounded wire spacing 2cm respectively, the electrode gap 1.1 cm, the discharge voltage 11 kV, the heating voltage 70v (AC), the negative ion concentration can surpass 1000000 unit / cm3, and the peak value of the ozone concentration is 30ppb. The results measure up to national indoor air quality standard (74ppb)[3].
REFERENCES 1. T.Ohkubo., The Effect of Corona Wire Heating on the Ozone Generation in an Air Cleaning Electrostatic Precipitator, Conference Record of IEEE IAS(1988) 1647m1651 2. Li Jie, Optimum Design of the Ozone Free Negative Ion Air Cleaner, Journal of Northeast Normal University(1996) 4 43-46 3. The national Indoor air quality standard of P.R.China (2003) GB/T 18883-2002 2-6
207 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghag 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Realization of the lower blade inclined spraying in electrostatic oiler Gao Quanjie, Wang Jiaqing School of Mechanical Automatization, Wuhan University of Science & Technology, Wuhan, 430081
Abstract: A project was put forward to solve the problems brought by the lower blade spraying of the electrostatic oiler. This project turned vertical spraying of the lower blade to inclined spraying so that the lower blade could hide under the conductiveboard. The author used ANSYS to simulate the electric field of the lower blade. The results of simulation have proved that the project is feasible. The key factors of influencing the inclined spraying of lower blade realized whether or not were found through the analysis. The author compared the inclined spraying results of different parameter combinations by compiling program and obtained the best parameter combinations. What's more, the author applied the analytical result of the finite element into practice; the lower blade inclined spraying was manufactured. The new inclined blade, which was already used in the new oiler, overcame two problems existing in the vertical lower blade and gained good effect in application. Keywords: electrostatic oiler; atomization; ANSYS; lower blade; spraying
Metal slat electrostatic oiler, which makes use of electrostatic atomization technique, is a high scientific and technical production based on mechanic, hydraulic, high-voltage electrostatic and computer control. Compared with roller oiler and injecting nozzle oiler, the electrostatic oiler has obvious advantages as follows: (1) Better spraying quality and working reliability. (2) It can save the quantity of oil extremely. (3) The high equipment capacity factor and the low maintenance expense. (4) Little pollution. (5) Better economic returns. With the competition of slat material market becoming more and more drastic, because of these advantages, it is an inevitable trend to apply the electrostatic oiler in slat material antirust to develop the appearance of product and improve the market share.
INTRODUCTION OF ATOMIZATION MECHANISM OF THE ELECTROSTATIC OILER Electrostatic oiler is a device that is based on the application of electrostatic atomization technique. Its atomization theory is" after oil blade (see Fig.l.4 and 1.7) switches on the negative electrode of direct current source, it will build a high-pressure electrostatic field between girder and steel plate (see Fig. 1.5). Because the cutting edge of oil blade is very sharp and the radius of curvature is very small, it causes corona discharge at the edge of blade. In such situation, air molecule are ionized and turned into kations and anions. These kations and anions move quickly along the electric-power line. The kations flying to oil blade are neutralized while the anions accelerated by electronic field fly to the steel plate (with kations). On the middle way, the anions will impact oil drops and make the oil drops charged. With the increment of negative charges on oil drops surface, the electrostatic repulsive force in charges will be enlarged. When the electrostatic repulsive forces among charges exceed the tensile force on drops surface, the drops will be broken. This is atomization phenomenon in macroscopy.
208 THE INSTALLING MODE AND USING OF OIL BLADE IN OILER.
Fig. 1 oil room section drawing of rolling conductive-board electrostatic oiler 1- outputstrap 2-oil room shell 3-rolling conductive-board 4- upper blade 5-steel plate 6-input strap 7-lower blade Oil blade is the kernel parts of electrostatic oiler, it relates to the quality of oiler spraying. According to the difference of installation site, oil blade can be divided into two parts: the upper blade and the lower blade. The installation sites of upper and lower blades are shown in Fig.l.The upper blade(See Fig. 1.4)and the lower blade(See Fig. 1.7) are both installed in vertical direction, and their centers are in the same line. The upper blade is down vertical, while the lower blade is up vertical. According to locale trace investigation and users' feedback information these years. We find that the spraying effect of the up blade is better and service life is longer than another one. There are two defects existing in the lower blade: (1) the slot on the cutting edge of the lower blade is only 0.1 ~ 0 . 2 ram. When steel plate is moving to the top of the lower blade, the dirty material on the steel plate (such as dust, metal dust and fibre and so on) will have the chance to get to the cutting edge or cutting edge side, which will destroy the uniformity of electrostatic field of the lower blade and cause oil fog on that part split, therefore causes to leak spraying of steel plate. (2) Because the lower blade is upward, things (such as slitter edge, tool, part and so on) maybe get to the cutting edge of lower blade, which will destroy the cutting edge and cause the blade malfunction.
BRING FORWARD OF THE AMEND PROJECT ON LOWER BLADE Aim at the defects of lower blade, the assignment group put forward an amend project (See Fig.2): tum the vertical lower blade spraying to inclined one that hiding under the conductive-board. Thus it can overcome the two defects existing in lower blade, but the feasibility of the project need to be proved.
ThE FINITE ELEMENT MODEL OF THE AMEND PROJECT ON LOWER BLADE In order to verify the feasibility of the project, the author used ANSYS (the f'mite element software) to simulate the electric field of the lower blade. For the length of the article, the article only offers the detailed analysis of the result.
209
Fig.2 two kinds of spraying mode of lower blade 1---the vertical lower blade, 2~leaning placement lower blade, 3~the left lower conductive-board,
4~steel band, 5 ~ the right lower conductive-board Building the finite element model of lower blade Because the ANSYS restricts the model node number and the field strength of the lower blade electrostatic field distributes evenly, we intercepted fracture plane along the direction that is vertical to blade and abstracted the lower blade electric field to the two-dimension finite element model when building model. During the course of building model, we adopted APDL offered by ANSYS software to compile the program, and then got the finite element model which was easy to be reduplicated and modified. It has brought convenience to the following result analysis.
Fig.3 lower blade electric-power line distributing figure(without secondary atomization device)
210
Fig.4 lower blade electric-power line distributing figure (with secondary atomization device) Analysis of lower blade electrostatic model solution When there is no secondary atomization device in the model, the result of the distribution of lower blade electric-power line is the same to its shown in Fig.3. From Fig.3, we can know that most of oil fog will be sprayed to the left conductive-board. It can't obtain spraying effect. When putting secondary atomization device in it, the result of distribution of electric-power line is the same to its shown in Fig.4. From the distribution tendency of electric-power line, we know that induction voltage on the left conductive-board increases. Then lower blade inclined spraying technology is realized. It is obvious that whether the secondary atomization device is in it or not is the key point to realize inclined spraying technology of lower blade Supposing secondary atomization device already existing, atomization effectiveness is relate to the position of secondary atomization device, the blade, the rake angle and so on. The author simulated the distribution of electric field on different situation by changing the homologous parameters in APDL program (See Fig.4), and got the following conclusions" When the inclined angle of the blade is between 43 degree and 55 degree, model gets the good atomization effectiveness. When blade point is 100mm to 300mm far away from the secondary atomization device, model gets the good effectiveness. The author compared and analyzed the different results and found: when blade point is 115mm far away from secondary atomization device and the incline angle of blade is 50 degree, the atomization effectiveness of lower blade is best (See Fig.4). At that time, most of electric-power lines which are bigger than others in model ran across the gap between left conductive-board and right conductive-board get to steel plate, which means that inclined spraying technology is realized in fact. The author found that inclined spraying of lower blade is feasible through finite element simulation analysis and obtained the best parameter combinations of realizing inclined spraying.
211
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.....
.....
~:
Steel products advance direction
I'
6 ~
,
7
1
2
Fig.5 lower blade inclined spraying sketch map 1 -- lower blade, 2, 3-- atomization iron wire, 4-- ground resistance, 5--1eft lower conductive-board, 6--steel band, 7--right lower conductive-board
IMPLEMENTATION OF LOWER BLADE INCLINED SPRAYING Under the direction of the result of finite element analysis, the assigmaaent group succeeded in developing inclined spraying technology along pitch arc (See Fig.5.1). We put the parameters resulting from finite element analysis into practice and gained good effect. Now, the new lower blade, which has already been used in the new oiler, has overcome the problems existing in the vertical lower blade and gained good effect in application.
CONCLUSION A project was put forward to solve the problems brought by the lower blade spraying of the electrostatic oiler. The author used ANSYS (the finite element software) to analyze the electric field of the lower blade and found the key factors realizing the inclined spraying and obtained the best parameter combinations. The results of analysis have proved that the project is feasible. The article applied the result of finite element analysis to practice, realizing the new inclined spraying technology of blade, and gained good effect in application.
REFERENCES: 1. Bao Chongguang. Electrostatic Skill Principle. Beijing: Beijing College of Science and TechnologyPublication, 1993:24~38 2. Gao Quanjie. Research on Charged Atomization in Electrostatic Oiler. Chinese Mechanical Engineering,2002,13(7):552~554 3. OuyangKecheng. Research on Electrostatic Oil Skill. MetallurgicalEquipment, 1999,(4):13~--16
212 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Biochemistry Effects Of Hydroxyl Radicals to Invasive Marine Species* Xiyao Bai, Xiaohong Xue, Mindi Bai, Bo Yang, Zhitao Zhang Key laboratory of strong electric-field ionization discharge of Liaoning Province; Environmental Engineering Research Institute, Dalian Maritime University, Dalian 116026, Liaoning, P.R.China Abstract: Until now, no any effective method is used in the treatment of ship's ballast water on board. With the method of strong ionization discharge, dissolved hydroxyl radical of 23.4mg/L is produced in 20t~ pilot-scale system and injected into the main pipeline, and the effect of hydroxyl radicals on biochemistry was studied. The results indicate that the main reasons of cell death are the lipid peroxide degree is increased three times. The basic life substances, monose, amylose, protein, DNA and RNA of cell, are greatly destroyed. Also CAT, POD and SOD of antioxidant enzyme system are obviously destroyed. Key Words: Biochemistry processes; Hydroxyl radical; Destruction; Cell death INTRODUCTION Vessels of the world are transferring 10 billion tons of ballast water per year. About 110 million plankton specimens are carried in lm 3 of ballast water. It is estimated that at least 7,000 different species per year are being carried in ship's ballast tanks around the world. Until today about 500 different species are known to have been transported with ballast water. As a result, whole ecosystems are being changed. In the USA, the European Zebra Mussel Dreissena polymorph have infested over 40% of internal waterways and have required between US$750 million and US$1 billion in expenditure on control measures between 1989 and 2000. In southern Australia, the Asian kelp Undaria pinnatifida is invading new areas rapidly, displacing the native seabed communities [111. In the Black Sea, the filter-feeding North American jellyfish Mnemiopsis leidyi has on occasion reached densities of l kg of biomass per m 2. It has depleted native plankton stocks to such an extent that has contributed to the collapse of entire Black Sea commercial fisheries. With the method of strong ionization discharge, the kill of organisms of ship's ballast water was done in laboratory using hydroxyl radicals in 2002. As a result, the mono-algae, protozoan, spore, bacteria were killed 100% with OH" concentration of 0.6mg/L and the quality of ship's ballast water was improved greatly. In this paper, the studies of hydroxyl radicals on biochemistry effects of marine species in ship's ballast water were done.
BIOCHEMISTRY PROCESSES Lipid Peroxidati0n A cell is the basic structural and functional unit of organisms in ballast water. The cell membrane or biomembrane with the thickness of 4-7nm, is mainly composed of protein including enzyme, lipid (primarily phosphatide and amylose), water, metal ions and so on, in which Phosphatide is key structural unit and mainly consist of phosphoglyceride. The phosphoglyceride has a saturated fatty acid molecule and an unsaturated one. The unsaturated fatty acid molecule commonly links with the second carbon atom of glycerin, which is easy to carry on a series of reactions with hydroxyl radicals such as the lipid-bond break, carbon chain break and hydrolyze of unsaturated fatty acid as following (1). Hydroxyl radicals oxidize the unsaturated bond in-R2 chain. In the reaction (2), the carboxylic acid Key Project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900) Key and General Projects of National Natural Science Foundation of China (NSFC: 60031001; 60371035)
213 decomposed from phosphoglycerides is finally decarboxylated to CO2 and H20 because of the strong oxidation of OH'. Cell membrane separates the inside and outside environment of cell, and its permeation and selectivity is the life base. Lipid peroxidation causes the cell membrane destruction and the content overflowing finally the cell death. O II ,C112-O-C- R1
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Oxidation and Decomposition of Amino Acid Protein, a most important substance to keep the life function, is composed of the amino acid linked with the peptide bonds. The amino acid is oxidized and decomposed by hydroxyl radicals shown in reaction (3): Owing to different R radicals, R-CH2-NH2 is continually oxidized. Protein Structure Change Hydroxyl radicals cause the peptide bonds to break and protein to denaturalize. Some amino acids have the activated radical of sulfhydryl -SH to form the disulfide bonds, which is an important chemical bond to keep the space structure of protein. Hydroxyl radical makes the disulfide bond be oxidized and broken to change the space structure of protein, resulting in the proteins to be denaturalized or the enzymes to lose the activity finally the cell death. The reaction of disulfide bond break is as follow (4). DNA Chain Break DNA is an important inheritance molecule in the body of invasive marine specie. Hydroxyl radicals combine with DNA to form DNA Addcuts, which is a forepart damage of DNA, resulting in some changes in DNA structure such as the alkaline radicle replacement and loss, the chain break and so on. The alkaline radical or the glucide and the phosphoric acid in DNA are attacked with hydroxyl radicals to form the chemical damages. Hydroxyl radicals mainly act on the C8 of adenine (A) and guanine (G) as well as the 5th and 6th double bond of pyridine alkaline radical. Also DNA is directly damaged to destroy the its structure leading to the cell death.
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t
EXPERIMENT METHOD Experimental materials The tested seawater was taken from Dalian port and stored in BC type polyethylene container, from which a part of seawater was taken and put into the glass trough of 1.5m3. A little of liquid culture medium of 2216E were put into the trough to do the enrichment of algae and bacteria. The enrichment conditions are as follows" the temperature, 23+1~ pH, 7.2; illumination intensity, 2600Lux. The enriched seawater was poured into the container, in which the contents of algae, protozoan and bacteria are above 104/mL. The phytoplanktons are Chloreua Pyrenoidesa, Chaetocers, and Peridinium; the zoop-
214 -lanktons are Euplotes; the germs are Pseudomonas, Flarobacterus, Vibrio, Acinetobacter, Escherichia, Alcaligenes, and Staphyloccus. Test Methods Bacteria test: The samples of 10mL, 100mL and 150mL were respectively taken from the sampling points, and then were diluted to 104 times in the asepsis condition. Three samples are taken in every point for the test. The 0.1mL diluent from the diluted solution is daubed on the ocean 2216E culture plate to do the count of colonies with the error of 5%. According to the different bacteria colonies, the single colony is chosen to do the purified separation. The bacterium genera are identified according to its character, cell configuration and physiological tests. The bacteria numbers in the sample is difficult to be accurately counted using conventional test method after killed because of the great decrease of bacterium numbers. With the filtration membrane method, the water sample of 150mL after filtered is used to inoculate and then is daubed on the ocean 2216E plate to do the counts of colony with the error of 5%. Algae Test: The samples were taken using 2500mL asepsis glass before and after injecting OH radicals respectively, and then were identified and counted to their living bodies which were done with haemacytometer under microscope. Glucose test: UNICO7200 type spectrophotometer at the wavelengh of 630nm with otoluamide coloration. Total protein: Biuret method. Nucleic acid: UV spectrophotometric method. Catalase (CAT): Ammonium molybdate colorimetry. Superoxide dismutases (SOD) activity: Pyrogallol self-oxidation method. Peroxidase (POD) activity: Aminoantipyrine method. OH" concentration: The ratio concentration of OH" is tested using Fluorescence method of benzoic acid and revised by electrochemistry method. The concentration of other activated particles is converted into the OH" concentration according to their oxidation potential. 20t/h system for the treatment of ship's ballast water is shown in another paper, the title "Treatment of 20t~ Ship's Ballast Water Using Strong Ionization Discharge". EXPERIMENTAL RESULTS AND DISCUSSIONS Lipid Peroxidation From table 1, the cell amount of organism decreases from 6.0• 1010/m3 to no living cells tested and the content of MDA increases about twice to 294.2% when OH" ratio concentration is 0.63mg/L. The results show that hydroxyl radicals have an obvious action on the lipid peroxidation of organisms. MDA is produced by the lipid peroxidation and its content indicates the extent of peroxidation. In this experiment, the content of MDA increases to about 300% after the injection of hydroxyl radical, exhibiting a serious lipid peroxidation to be occurred in cell membrane. The increase of lipid peroxidation extend causes the cell protoplasm leak and the cell death, also the cell loses its activity. Table. 1. Effect of hydroxyl radical on lipid peroxidation J~J..J~_JJ.__::::.:~::::
::: .........
_~_
_::::::_:::
:::::::::::::
..: ....
: ...........
:
:
......
:
.: ........
.::::::..:
Item Cell amount of organism MDA 532nm Absorbance
:::
::
::::::
.
.
.
.
.
.
.
:
:
--::
:
0 6.0x 101~ 0.052
-
~
::
. . . .
: :-
~ .::
-:::::::
:::::
........
::::::::::
...............................
: .....................
:::::::::::::---:
..................
:_:__::
............
:__._.::__
OH" Ratio Concentration (mg/L) 0.63 3
No algae tested 0.153
Saccharide, Protein and Nucleic Acid As shown in table 2, the total protein content is decreased about 33.4%, when the hydroxyl concentration is 0.63 mg/L. RNA, mainly in the cytoplasm and a small amount in nucleolus, is reduced 46.9%. DNA, mainly in the chromosome of karyon, the rest in chondriosome and few dissociated in the cytoplasm, is decreased 80.2%. The above experimental data prove that the hydroxyl radicals cause the destruction of karyotheca and chondriosome resulting in the damage of RNA and DNA in them. Hydroxyl radical degrades the big molecules amylose in organism body to the monose resulting in the increase of content of glucose. Therefore the big molecule is easier to be destroyed than the small molecule. The effect of hydroxyl radical on the three basic life substances is less than that of kill efficiency of organism. Some protoplasm in the cell doesn't completely loss the activity temporarily when hydroxyl
215 radicals kill the algae cells. However the life substances will quickly loss the activity with the cells death. As a result, the contents of saccharide, protein and nucleic acid sequentially decrease with the time.
Table 2. Effect of hydroxyl radical on the saccharide, protein and nucleic acid ~,,,,,;,
.
.
.
.
.
.
,
~
.......
~,~ .
.
.
.
.
.
.
.
Sample
.
.
.
.
.
.
.
.
.
.
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.
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.
.
OH" concentration (mg/L)
Glucose (mg/100mL)
Total protein (mg/100mL)
0
0.246
1.490
0.63
0.492
Organism
.
Filtrate
0.63
.
Nucleic acid (~tg/mg) RNA DNA 2.43
0.993 .
.
.
.
.
.
0.96
1.29 .
.
.
.
.
0.19 .
.
.
. . . . . . . . . . . . . . . .
Note: .... not to be tested Antioxidant Enzyme From the table 3. Peroxidase (POD), Catalase (CAT) and Superoxide dismutase (SOD) mainly consist of the antioxidant enzyme system of organism. When the OH" ratio concentration is 0.63 mg/L, decrease efficiency of POD and SOD are 21.9% and 54.2% respectively. CAT is not to be tested before and after the reaction. In the seawater of organism cell filtered out, the activities of the three enzymes are tested but POD not to be tested. The enzyme activities of CAT and SOD are decreased in some extents because of the strong oxidation of hydroxyl radical. The decrease efficiency of CAT and SOD are 83.1% and 33.2%. The enzyme activities of CAT and SOD are in low level at the normal cell's state. However, the cell can secrete large numbers of activated enzymes when the cells are attacked. The content of CAT and SOD will increase and their activities will enhance if hydroxyl radicals act on the cells. From experimental data, the enzymes, as a kind of protein, decrease with the decrease of the total protein due to the reaction of hydroxyl radicals. The decrease of enzyme activities in some extents indicates that hydroxyl radicals not only inhibit and decompose the enzymes at normal cell state but also do the increased enzymes due to its action. Therefore, the amounts of decreased enzymes are actually much more than that of above experimental data. The three kinds of enzymes are the important function enzymes in the cell's anti-oxidant enzyme system. The experimental results prove that the anti-oxidant enzyme system is almost destroyed using hydroxyl radicals. Table. 3. Effect of hydroxyl radical on the antioxidant enzyme Samples Organism Filtrate Note: .... not to be tested
OH" Ratio concentration (m~/L.) 0 0.63 0 0.63
POD CAT ....................... __(U_~m__g)___.................................. (U/mL_)____. . . . 3.2• -5 .... 2.5• 10-5 .... .... ....
3.770 0.637
SOP ..(U/~) ........ 6.350 2.910 1.230 0.822
216 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Killing of Red Tide Organisms in Ocean Using Hydroxyl Radicals* Mindong Bai, Bo Yang, Xiyao Bai, Zhitao Zhang, Mindi Bai Key laboratory of strong electric-field ionization discharge in Liaoning Province; Environmental Engineering Research Institute, Dalian Maritime University, Dalian 116026, Liaoning, P.R.China, E-mail: [email protected] Abstract: A pilot-scale experiment for the treatment of red tide in the enclosure was done in sea area of Shandong Province, P. R. China on Aug. 25, 2002. With OH" concentration of 0.68mg/L, the kill efficiencies of 29 kinds of red tide organisms such as Chaetoceros lorenzianus and so on reached 99.89%, in which the kill efficiencies of bacterium and vibrio were 100%, and that of Gonyaulax cysts and Prei. Cysts were up to 100%. At the same time, the content of chlorophyll-a was decreased into the lowest limit of test. DO saturation of seawater was greatly increased to 100% because the residual OH" radical was decomposed into H20 and 02 after 20 minutes Therefore the treatment of red tide using OH" radicals is a kind of advanced oxidation technology, which realizes zero pollution, zero emission and zero residual in the process of the production of OH" radicals and the treatment of red tide. Key Words: Strong ionization discharge; OH" radicals, Red tide organisms; AOT INTRODUCTION In 2001, the red tide occurred 77 times in China's ocean and the pollution areas reached 15,000km 2, which increases 49 times and 5,000km 2 areas than that in 2000. In 2002, red tide occurred 79 times in China's ocean and the pollution areas were 10,000km 2. The Red tides occurs mostly in offing of East Sea, Bohai Sea and Yellow Sea of China. The main organism species, the total times and accumulative areas to form red tide are increased greatly year by year [~], which have seriously threatened the ocean environment in china. At present, many methods for the treatment of red tide are studied in the world [2-81. However only killing the red tide organisms by CuSO4 medicament and the clay flocculation methods were done in sea areas t23]. Some problems are as follows. (1) The superfluous toxicity coagulant or CuSO4 medicament makes the ocean ecosystem to be destroyed, and the coagulant sediments have seriously effect on the benthic of seabed. (2) Large numbers of residual coagulants and medicament are impossible to be decomposed and disappeared in ocean resulting in the destruction to other organisms for a long time. (3) Killing and coagulation need a long time about 20min~24hours. The concentrations of coagulant and medicament are greatly decreased to the lowest limit to kill the red tide organisms because of diluting and diffusing of sea wave, so that it is impossible to treat a large-scale red tide in ocean. Until now a few tens of methods and thousands of medicaments for the treatment of red tide are still in the stage of laboratory. Only few methods are possible to be used in natural sea [41. Therefore, A kind of new method for the treatment of red tide is urgently found. The high dissolved concentration OH" radical of 4.2mg/L was produced using the ionization of 02 in air and H20 in seawater, and then was sprayed in the enclosure on ocean. Red tide organisms are killed by hydroxyl radicals belonging to a dissociative radical reaction with a fast reaction rate, which is effective to solve the diluting and diffusing problem of sea wave(Ocean Dynamics). Also there is a broad-spectrum deadly characteristic that is possible to kill organisms meanwhile to bleach and deodorize to seawater.
Key Project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900) Key project of National Natural Science Foundation of China (NSFC; 60031001)
217 Therefore the method for the treatment of red tide using hydroxyl radicals is a kind of AOT, which realizes Zero Emission and Zero Pollution. EXPERIMENT METHOD Experimental Materials On Aug. 25, 2002, a pilot-scale experiment for the treatment of red tide was done in the enclosure in sea area of Shandong Province, P. R. China. In this sea area, the ambient temperature was 32~ seawater temperature was 24 ~ and pH was 7.13. The red tide organisms were cultivated in the enclosure by The First Institute of National Ocean Bureau in Qing Dao. The red tide organisms cultured are as follows:
Chaetoceros lorenzianus, Ch. curvisetus, Ch. decipien, Ch. terres, Ch. didymus, Ch. compressus, Ch. sp., Ch. affinis, Nitzschia sp, Nitzschia closterium, Asterionella japonica, Amphiprora sp, Thalassiosira sp., Skeletonema costatum, Streptotheca thamesis, Eucampia zoodianus, Biddulphia sinensis, Rhiz. stolterfothii, Hemiaulus sinensis, Thalassionema nitzschioides, Licmophora sp., Scrippsiella trochiodea, Peridinium pellucidum, peri. Pallidum, Peri. Bipes, Peri. Steinii, Peri. spp., Peri. Quiquecorne, Gonyaulax polygramme, Prorocentrum tristinum, Gymmnodinium sp., Gyrodinium sp., Dinoflagellates, Gonyaulax cysts, Prei. Cysts, Alexandrium sp, bacterium and vibrio. Experimental System The experimental system for killing the red tide organisms in sea enclosure is shown in Fig. 1. A part of seawater is pumped into the pipe passing the filter 1, which the flow velocity is 1.5m/s. High concentration OH" radicals are injected into the dissolver 5 with a part of seawater to produce the dissolved hydroxyl radicals with the mass transfer efficiency of 98.8%. Hydroxyl is dissolved further through the gas/liquid separator 6 and the residual OH" is removed by eliminator 7. The dissolved OH" concentration reaches 4.2mg/L in pipe and is sprayed in the sea enclosed 10 through the shower nozzle 9. The coniform enclosure was made of polyethylene film with the dimensions of 1.1m diameter and 2.3m depths. Three samples in three sections, the surface, 1.0m and 2.0m depth of enclosure are taken respectively. The average values of three samples in same section are the experimental results. The setup of dissolved hydroxyl radical has the dimension of 0.6m (long) • (wide) • (high). OH" plasma reactor is fiat rectangle with the dimension of 0.24m (long) • (wide) • (high). The discharge gap is 0.47mm, in which the insulation material is placed as the septum. The aA1203 powder is sprayed on the discharges surface by plasma spraying technology to form dielectric layers, which the thickness is 0.2mm, dielectric constant is 10, and insulation intensity is 350 kV/cm. The power supply was applied to the electrodes to produce a continuous strong ionization discharge. The energy cost for the treatment of seawater with red tide organisms is 0.32 kWh/m 3, not considering the energy cost of pump. Before applying the strong ionization discharge, Fig. 1. System for Killing Red Tide Organisms O2 with the purity of 98.5 % enrich by air and H20 at in Sea Enclosure gas state were introduced into the plasma reactor 14. 1. Filter; 2. Electric valve; 3. Liquid flowmeter; 4. Pump; 5. The concentration of HaO in the mixed gases is 3.5% Gas/liquid dissolver; 6. Gas/liquid separator; 7. Eliminator of residual OH'; 8. Monitor of electrochemistry; 9. Shower nozzle; (v/v). The hydroxyl radicals and other activated 10. Sea enclosure; 11. Controller; 12. Transformer; 13. Gas particles such as HO2, HO3", O3", 03, H202 and so on flowmeter; 14. OH" plasma reactor; 15. Valve; 16. Check valve. are produced by a series of plasma reactions.
Test Methods The total numbers of bacterium are counted with the ocean 2216E culture medium plate. The numbers of vibrio are counted on the spreading plate of TCBS culture medium. The numbers of ocean microalgae are
218 c o u n t e d d i r e c t l y w i t h h a e m a c y t o m e t e r u n d e r m i c r o s c o p e after f i x e d b y i o d i n e s o l u t i o n . T h r e e s a m p l e s are d o n e in e v e r y test. T h e e x p e r i m e n t a l e r r o r in m e a s u r e m e n t s o f cell c o u n t i n g is less t h a n 5 % . T h e c h l o r o p h y l l - a o f r e d tide o r g a n i s m a n d D O o f s e a w a t e r are m o n i t o r e d in line w i t h Y S I - 6 6 0 0 - M E n v i r o n m e n t a l M o n i t o r i n g S y s t e m . T h e gas f l o w rate is m e a s u r e d u s i n g a T y p e - L Z J 1 0 F l o w Meter. T h e f l o w rate o f s e a w a t e r is m o n i t o r e d w i t h M o d e l 8035 B u r k e r t F l o w m e t e r 7 ( B u r k e r t Co. in F r a n c e ) . T h e ratio c o n c e n t r a t i o n o f OH" is t e s t e d u s i n g e l e c t r o c h e m i s t r y m e t h o d a n d r e v i s e d b y F l u o r e s c e n c e m e t h o d o f b e n z o i c acid. T h e c o n c e n t r a t i o n o f o t h e r a c t i v a t e d p a r t i c l e s is c o n v e r t e d into the OH" c o n c e n t r a t i o n a c c o r d i n g to t h e i r o x i d a t i o n p o t e n t i a l .
Table 1. Data for Killing the Red Tide Organisms in Sea Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Kill Efficiency Content after Kill efficiency (%) 48h (cell/mL) (%)
Numbers
Species of Organism
Original Content (cell/mL)
Content after 24h (cell/mL)
1
Chaetoceros lorenzianus
2835000
14000
99.5
2
Ch.curvisetus
2646000
.....
100
3
Ch.decipiens
223000
.....
100
4
Ch. terres
63300
.....
1O0
5
Ch.didymus
22000
.....
100
.....
100.0
6
Ch. sp.
14000
100
.....
100.0
7
Ch.affinis
314600
.....
100
.....
100.0
8
Nitzschia sp.
5786000
.....
100
.....
99.9
9
Nitzschia closterium
60600
2000
96.7
.....
100.0
10
Asterionella japonica
601300
4000
99.3
.....
100.0
11
Amphiprora sp.
262000
8000
96.9
2000
99.2
12
Thalassiosira sp.
1533 O0
.....
1O0
.....
100.0
13
Skeletonema costatum
680000
.....
100
.....
100.0
14
Streptotheca thamesis
8000
.....
100
.....
100.0
15
Eucampia zoodianus
4000
.....
100
.....
100.0
16
Biddulphia sinensis
4000
.....
100
17
Rhiz.stolterfothii
2000
.....
100
.....
100.0
18
Hemiaulus sinensis
4000
.....
100
.....
100.0
19
Scrippsiella trochiodea
2000
.....
100
.....
100.0
20
Peridinium pellucidum
3000
.....
100
.....
100.0
21
Peri. pallidum
2000
.....
100
.....
100.0
22
Peri. Bipes
4000
100
.....
100.0
23
Peri. spp.
3000
100
.....
100.0
24
Peri. quiquecorne
9300
.....
100
4000
57.0
25
Gonyaulax polygramme
11300
.....
100
.....
100.0
26
Prorocentrum tristinum
2000
.....
100
.....
100.0
27
Gyrodinium sp.
9300
.....
100
.....
100.0
28
dinoflagellates
11300
.....
100
.....
100.0
29
Gonyaulax cysts
2000
.....
100
.....
100.0
30
2000
.....
100
.....
100.0
31
Prei. cysts Alexandrium sp.
100 100 100
.....
Bacterium Vibrio
2000 46000 31000
.....
32 33
.....
100.0 100.0 100.0
Total
11740000
28000
99.89
14000
99.9
~i%tei''OH'ratio concentration was 0.68mg/L . . . . .
not to be tested.
4000
99.9 100.0
.....
100.0
100.0
100.0
219 EXPERIMENTAL RESULTS AND DISCUSSION Killing the Red Tide Organisms The nutrition salt was put in the enclosure to culture the red tide organisms with the content of 1.74x106/mL. The hydroxyl solution of 4.2 mg/L was sprayed into the enclosure in which the ratio concentration of OH" was 0.68 mg/L. The experimental results of OH" killing organisms such as Chaetoceros lorenzianus etc is shown in table 1, which the tests were done after 24h. The total numbers of red tide organism were decreased from l l.74x106/mL to 0.028xl06/mL. The kill efficiency was 99.89%, in which 27 kinds of organism weren't tested with the kill efficiency of 100%, only Nitzschia closterium and Amphiprora sp were about 96.7%. Having been monitored 48h even if 64h, the organism contents were basically same as that after 24h, no organism regeneration or new propagation. The experimental results of killing bacterium and vibrio in the enclosure are shown in table 1. The contents of bacterium and vibrio are 4.6x 104/mL and 3.1x 104/mL respectively. After 24h of OH" solution injected, the bacterium and vibrio weren't tested with the kill efficiency of 100%. Same results were taken after 64h to be monitored. The salinity, pH and conductivity are basic constant after the injection of hydroxyl radicals. The salinity changes from 31.351 to 31.349, pH from 7.13 to 7.12, and the conductivity from 47.3 to 47.58. Effect of OH" on Chlorophyll-a With the strong oxidation and dissociation effects, the hydroxyl radical can make the ocean microalga be oxidized and decolored to fail to the photosynthesis resulting in the death of red tide organisms. The effect of OH" on the content of chlorophyll-a is shown in Fig. 2. When the ratio concentration of OH" was 0.68mg/L, about 90% chlorophyll-a was decomposed after 10 minutes. The content of chlorophyll-a was not to be tested after 20 minutes, which had the same experimental result after 64h.
Fig.2. Effect of OH" on Chlorophyll-a
Fig. 3. Effect of OH" on DO of Seawater
Effect of OH" on Dissolved Oxygen (DO) of Seawater The effect of OH" on DO of seawater is shown in Fig. 3. When the ratio concentration of OH" was 0.68mg/L, the saturation of DO was increased to 75% after 5 minutes, to 85% after 10 minutes, and to 100% after 20 minutes. The reasons of DO increase are that the residual OH" and the organism bodies were dissociated into 02 and dissolved into seawater. After l h, 1d, 2d, 64h, DO saturation is different in different deep, high in the surface and low in the deep. Therefore the hydroxyl radical is possible to renovate the polluted seawater as same as killing the red tide organisms.
220 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Treatment of 20t/h Ship's Ballast Water Using Strong Ionization Discharge* Mindong Bai, Zhitao Zhang, Xiaohong Xue, Xingwang Liu, Xiyao Bai Key laboratory of strong electric-field ionization discharge of Liaoning Province; Environmental Engineering Institute, Dalian Maritime University, Dalian 116026, Liaoning, P.R.China
Abstract: A pilot-scale experiment of 20t/h for the treatment of ship's ballast water was done in this paper. When the dissolved OH' concentration is 0.63mg/L, the kill efficiencies of bacteria, mono-algae, protozoan reached 100% within 2.67s. At the same time, the ballast water quality was greatly improved. The decrease rates of COD, nitrite and ammonium salt are 100%, 98.3% and 99.5% respectively, and the turbidity is decreased to 50%. DO is increased 77% due to the decomposition of residual OH'. With this method, invasive marine species can be killed in ship in the process of the discharge of ballast water. Key Words" Invasive marine species; Ship's ballast water; Strong ionization discharge; Hydroxyl radical;
INTRODUCTION The introduction and spread of non-native species in freshwater and marine environments is a worldwide problem that is increasing in frequency. There are numerous alien invertebrate, fish, and plant species that are being introduced through various pathways, and are causing significant damage to coastal and freshwater ecosystems, and to the economies that depend upon them. Shipping is still considered the primary vector for new species introductions of aquatic invasive species, due to ballast water discharge, which has been identified as one of the four greatest threats to the world's oceans by Global Environment Facility (GEF)[~-4]. Near 20 years, main methods for the treatment of ship's ballast water are the mechanical, physical and chemical removal of species. With the open-ocean-exchange in mechanical removal, only 95 % of ballast water was discharged at open-ocean when injecting 3 times seawater to Vessels, existing the problems of safety and high-energy consumption [5]. By the heat treatment in physical removal, higher temperatures would be required to deal with thermophilic (heat loving) organisms or more resistant forms such as bacterial spores. The temperature between 30 and 40 would support the growth of bacteria as e.g. Vibrio cholerae [6, 7]. Although a lot of research work was done in the world, Marine Environment Protection Committee (MEPC) and GloBallast think that no high efficient, low cost, non-residual method could be used in the treatment of ship's ballast water [~]. A physics method is studied that the electrons are accelerated and then the gas molecules are aroused using a strong ionization discharge [8-9]. The strong electric field (E~>400Td, 1Td-----10lVVcm2) is formed with the thinner 0t-Al203 dielectric layer in the microgap at a high pressure (P>0.1MPa or n=2.6• 19/cm3). The electrons achieve the average energy of above 12eV. According to the maxwell distribution law, a lot of electrons have the energy of >12.6eV for the mean electric energy of 12 eV because the ionization potential of 02 is 12.5eV and H20 is 12.6eV. With this method, the treatment of ship's ballast water for 20t/h was done for practical application on board in this paper. The method for the treatment of red tide using hydroxyl radicals is a kind of AOT, which is considered as Atom Economy, Zero Emission and Zero Pollution. Key Project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900) Key and General Projects of National Natural Science Foundation of China (NSFC: 60031001; 60371035)
221 PLASMA PROCESSES OF OH" FORMATION The low energy electrons (2~8eV) collide with the molecules of 02 and H20 to produce a few numbers of OH " , not to be the main plasma reactions. The plasma processes of dissociation and dissociative adhesion are as follows. (1) H20 + e ~ H + OH" (2) H20 + e ~ H'+ OH'+ e (3) 02 + e ~ O(ID) + O(3p)
(4) O(lD) + H20 ~ 2 OH" With the strong ionization discharge in microgap, H20 molecules are ionized and excited into OH" radicals as follows. (5) 2 H 2 0 + e ~ H 2 0 + + H20* + 2e The dissociation of H20* molecules at excited state" (6) H20* --+ H" + OH" The dissociative ionization of H20 +" (7) H 2 0 + + H20 --+ H3 O + + OH" (8) H 2 0 + --o H + + OH" With the strong electric field, the reaction of H20 adhesion is as follow. (9) e + H 2 0 ~ e aq e'aq is a kind of special radical, more stable than dissociative electron, which arouses a lot chemical reactions. The plasma reaction processes of 02 ionization with H20 into OH" are as follows. Electron-impact ionization: 0 2 + e ~ 0 2 + + 2e (10) Electron-impact dissociative ionization: 02 + e ~ O + + O" + 2e (11) Similar dissociative ionization processes to produce the molecular ions of N2+, N +, H20 +. Charge transfer reactions to form additional 02 + ions. (12) N2 + + 0 2 ~ N 2 + 0 2 + Formation of water cluster ions" 02 + + H 2 0 + M ~ O2+(H20) + M (13) Dissociative reactions of water cluster ions to form OH"O2+(H20) + H20 ~ H30 + + O2 + OH" ) ( 1 4 O2+(H20) + H 2 0 ~ H 3 0 + ( O H ) + 02 (15) H 3 0 + ( O H ) + H20 ~ H 3 0 + + H 2 0 + OH" (16) The plasma reaction processes for 02 molecule to produce OH" radicals are as follows: 02 -k- O" --+ 0 3 (17) 03 + e --+ 03" (18) 03 ~ 0" + 02 (19) O" + H 2 0 ~ 2OH" (20) 03 + H20 ~ 02 + H202" (21) H202 --~ 2 O H " (22) H 2 0 2 * ~ H + + HO2" (23) H202 + H 2 0 ~ H O 2 " + H 3 0 + (24) HO2" radical can excite a series of plasma reactions to produce OH" 03 + HO2 ~ HO2" + O3" (25) HO2" ,, H + + O 2 " (26) H O 2 - ~ 0 3 ~ 0 2 + 02" " + OH" (27) 02" " + 0 3 ~ 0 2 + 03" " H 2 0 2 + O2" ---+ 0 2 + O H ' + 0 3 + e ~ 03" "
'
03 " + H + ---+ HO3 HO3" ---~ 02 + OH" 02" " + HO3" --~ 2 0 2 + O H " 9
(28) OH"
(29)
(30) (31) (32) (33)
222 e-aq 4 - 0 2 ~ 0 2 " - + H20 (34) H" + 02 ~ HO2" (35) With the plasma reactions (1)~(9), per 100eV energy injected into the discharge electric field is possible to produce 2.80 OH" and 2.75 e aq t1119With the plasma reactions (10)~(16), per 100eV energy injected is possible to make 2.70 water cluster ions to form OH" tz~j. With the plasma reactions (17)~(35), per 100eV energy injected is possible to obtain about 2.46 OH" till. Therefore the Strong ionization discharge is more effective in producing larger numbers of OH" radicals. The plasma processes of OH" dissolving into water are very complicated chain reactions. OH" is the main product in the system, also having other activated particles such as HO2, H02", HO3", OH-, O3OH+, O2-', O3", 03, H202 and so on. -
EXPERIMENT METHOD 20t/h system for the treatment of ship's ballast water 20t/h pilot-scale system for the treatment of ship's ballast water using hydroxyl radicals is shown in Fig. 1. The tested seawater was taken from Dalian port and stored in BC type polyethylene container 1. The dissolved hydroxyl radical is injected into liquid/liquid unit 6 for the adequate mixture, which the ratio concentration is 0.68mg/L in main pipeline. The sample points are in three points of A, B, C, D and E respectively, having the duration of 0.0s, 1.33s, l~ o~ 2.67s, 5.33s, 8.00s. The flow velocity of ship's ~380v ~ ballast water is 1 5m/s, and the flow rate is 20t&. O2,H20 11 12 13~1,~ .o The treated ballast water flows into the gas/liquid 18 ~ separator 7, and then is discharged. The residual ~. hydroxyl gas is decomposed into the molecules of .............. 15 L ~ H20, 02 in the eliminator 8. 3 4 5 ?P 6i~tt The setup o f dissolved hydroxyl radical has ~ (~ the dimension of 0.6m (long) x0.8m (wide) x 1.5m 2 Mainpipe (high). The plasma reactor 12 with the crust of Discha'rge stainless steel is rectangular, which the dimension A BCDE is 260mm (long) x l30mm (wide) x35mm (thick). Fig. 1.20t/h system for the treatment of ship's ballast water Before applying the strong ionization discharge, O2 with 98.5 % enriched by air and H20 at gas state Note: 1. Container of ballast water; 2. Valve; 3. Mechanical were introduced into the plasma reactor 12. The filter; 4. Liquid flow-meter; 5. Pump; 6. Liquid/Liquid concentration of H20 in the mixed gases is 3 5%
~
dissolver; 7. and 16. Gas / liquid separator 8. and 17. Eliminator of residual OH'; 9.Controller; 10. Transformer; 11. Flowmeter; 12. OH" plasma reactor; 13. Electric valve; 14. Check valve; 15. Gas/liquid dissolver; 18. Dissolved
(v/v). The high-concentration hydroxyl radicals are
injected into the gas/liquid dissolver 15 further dissolved in gas/liquid separator 16. With the mass OH'monitor transfer efficiency of 99.8%, the dissolved OH" ratio concentration reaches 23.4mg/L. The residual hydroxyl gas is decomposed into the molecules of H20, 02 in the eliminator 17. This pilot scale experiment for 20t/h was done on December, 2002, the temperature of seawater in container 1 is 8.5~
Elcctric Parameters of Gas Discharge The self-made high-frequency and high-voltage power supply was applied to the discharge electrodes with parameters as follows: peak voltage, 7 kV; frequency, 10.4kHz; the current pulse width, 5~10ns. The electric parameters were measured using HV-60 High Voltage Probe, SS-240 Pulse Current Probe, DS8608A Oscilloscope (Iwatsu, Japan) and Model HC-F1000L Frequency Meter (Hong Chong Electronic Co. Ltd). ASTM D3382-95 National standard in USA is used to test the power and voltage of discharge [12]. The waveforms of current and voltage are shown in Fig. 2. A number of current pulses of microdischarge are superimposed on the positive and negative half-periods of current waveform. The reduced field in micro-gap is measured and calculated using the method of charge-voltage figure [13]. The energy cost for the treatment of ship's ballast water is 50Wh/m3, not considering the energy cost of pump.
223 Test Methods Experimental materials and test methods for Bacteria, Algae, Photosynthetic pigments, and OH" concentration are shown in another paper, the title "Biochemistry Effects Of Hydroxyl Radicals to Invasive Marine Species". Test Method of Water Quality: Nitrate was deoxidized into nitrite by cadmium column. Ammonium salt was oxidized into nitrite by hypobromite. And then Nitrate was tested using N-1-Naphthylenedia- minedihydrochloride spectrophotometric method in UNICO7200 type spectrophotometer. Phosphate was monitored Phosphorous molybdenum blue spectrophotometric method in UNICO7200 type spectrophotometer. As: New silver salt spectrophotometric method in 59WC type spectrophotometer. Pb, Cd and Cu: Non-Flame Atom Absorption method with PE-4110 type Atom Spectrograph with the background calibrate device; HGA-600 type Graphite Atomic Pile; Hollow Cathode Lamp (PE Co. in USA). Zn: Atom Flame Absorption method using VarianAA-857 type Atom Absorption spectrophotometer. Fe: 1.10-Phenanthroljue spectrophotometric method in HWC-2-3 type spectrophotometer. Hg: Aurum Capture Cold Atom Absorption method with CG-1 type Mercury Vapormeter. COD: Potassium permanganate method. DO: Iodimetry. PH: 25 type pH monitor. TOC: TOC-5000 type Total Organic Carbon Meter. Turbidity: GDS-1 type Nephelometer. Salinity: HD-1A type Salinity Meter. Conductivity: 2602 type Conductometer.
Fig. 2. Waveforms of Voltage and Current (t =20~ts/div; V=5kV/div;I = 0.4A/div)
Fig. 3. Hydroxyl duration vs. organism content
EXPERIMENTAL RESULTS AND DISCUSSION Experiment for the kill of invasive specie The bacteria concentration is 2.6• the mono-cell algae concentration is 2.0• the protozoan concentration is 1.5x 104/mL. After the injection of hydroxyl solution, the samples are taken in point B and C. The effect of hydroxyl duration on the organism concentration is shown in Fig. 3. When The ratio concentration is 0.6mg/L, the duration that the hydroxyl radicals kill all of bacteria and protozoan is only 1.33s, the kill efficiencies reach 100%. When the duration is in the range of 1.33~2.67s, the concentration of algae is decreased into 1.1 • 103/mL and no-test respectively. When the duration is above 2.67s, the kill efficiencies of bacteria, mono-cell algae and protozoan are 100%. The experimental results indicate that all organisms in ballast water could be killed in ship in line. Effect of Hydroxyl Radical on the Quality of Ballast Water The samples were taken at C point with the duration of 2.67s. Nitrite and ammonium salt are oxidized and decomposed because of the strong oxidation action of hydroxyl radical, the decrease rates are 98.4% and 99.5% respectively. After the reaction, the nitrate has a little raise. Nitrite and ammonium salt are poisonous to aquatic species, especially nitrite can oxidize low-iron hemoglobin into high-iron one resulting in the losing of transporting oxygen function. Therefore the water quality of ballast water is obviously improved by the treatment of hydroxyl radicals.
224 Hg and As have a little decrease before and after the treatment, the decrease rates are 6.1% and 2.3% respectively. Cu, Fe and Pb are greatly decreased, the decrease rates are 38.1%, 40.3% and 75.4% respectively. The reasons of element decrease are possible to be the intermediate formed in the process of reaction with hydroxyl radicals. Therefore the decreases of poisonous heavy metals and nonmetal elements Table. 1. Effect of hydroxyl radical on the water quality of ballast water .
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Ratio concentration of OH (mg/L) Test item
Chang rate (%) 0 156.8gg/L 66.6g.g/L . . . . 79.8~tg/L 25.9~tg/L . 0.44~tg/L 4.2gg/L
Nitrate Nitrite Ammonium salt Phosphate As Cu Zn Cd Pb Fe Hg TOC COD DO Salinity PH Turbidity
17.2btg/L 0.8~tg/L 6.5gg/L 14.4gg/L 0.033p,g/L 1.68mg/L 0.54mg/L 7.47mg/L 31.351 8.13 0.4
Conductance 9, _ - _ , , , , , _ m ; m , _ , , _ ~
. . . .
::::
:
-:::::::::
0.63 184. lgg/L 1.1~t.g/L 0.4gg/L 32.9gg/L 0.43gg/L 2.6gg/L 68.6~tg/L 0.7~tg/L 1.61xg/L 8.6gg/L 0.031~tg/L 1.70mg/L Untested 13.24mg/L 31.349 8.12 0.2
47.3 ......
:::
:-----:-:
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17.4 -98.4 -99.5 27.0 -2.3 -38.1 298.8 -12.5 -75.4 -40.3 -6.1 1.19 -100.0 77.2 0 -0.1 -50.0
, ,
,
47.58 .
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-:
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~::: ..............
are advantage to improve the water quality in some extent. Zn, which is an un-harmful element to organism and an activated central atom of many enzyme and protein molecules, is increased to 298.8%. The reason is that Zn element dissolved into the ballast water because of the spillage of cell substances after the reaction with hydroxyl radicals. The salinity, pH and conductance, which are three important parameters of water environment especially to have a great effect on aquatic species, are basic constant with the injection of hydroxyl radical. The turbidity decreases 50%, indicating that hydroxyl radicals obviously improve the transparency of water. TOC is a little change. COD is no test after the treatment. DO has a great increase from 7.47mg/L to 13.24mg/L because the residual OH" is decomposed into 02 and H20 and dissolved into ballast water. Therefore the hydroxyl radicals not only kill all invasive species but also improve the quality of ballast water in a great extent. CONCLUSIONS (1) The concentration of killing organisms in ship's ballast water is only 0.63m/L. (2) The duration to kill mono-cell algae, bacteria and protozoan are very fast only 2,67s. (3) The quality of ballast water is greatly improved. With the duration of 2.67s, the decrease rates of COD, nitrite and ammonium salt are 100%, 98.3% and 99.5% respectively, and the turbidity is decreased to 50%. DO is increased 77% due to the decomposition of residual OH'. (4) The equipment of hydroxyl solution has some advantages such as small volume, simple operation and low running cost that is only 1/30 in comparison with the open-ocean- exchange of ship's ballast water.
225 Therefore the treatment of ship's ballast water using OH" radicals is a kind of advanced oxidation technology, which is considered as Atom Economy, Zero Emission and Zero Pollution in the process of the production of OH" radicals and the killing of organisms of ship's ballast water. Invasive marine species can be killed in ship in the process of the discharge of ballast water.
REFERENCES 1. Gregory M Ruiz et al., Nature, (2000) 408, 49 2. Mackenzie et al., New Scientist. (1999), 162,18~19 3. Geoff Rigby, Science, (2000) 289 241 4. Donald M Anderson, Nature, (1997) 388 513. 5. Rigby, G. and Hallegraeff, G. M., Australian Government Publishing Service, (1993) Vol. 2 p.123. 6. Yount, J. D., EPA Workshop on Zebra Mussels and other Introduced Aquatic Nuisance Species, (1990) pp. 1-45, 7. Armstrong G., Prepared for a technical meeting at the Institute of Marine Engineers, (1997) p. 11, 8. M. D. Bai, Z. T. Zhang, X. Y. Bai et al., IEEE Trans. Plasma Sci., 31 (6), (2003). 9. M. D. Bai, Z. T. Zhang, X. Y. Bai et al., Oceanologia et Limnologia Sinica (china), (2003) 34 (5) 484 10. Bernie M Penetrante, J Norman Bardsley, Mark C Hsiao, Jap. J. Appl. Phys, (1997) 36 (7B) 5007. 11. Sun Chunpu, Zhang Jianzhong, Duan Shaojin, "Free Radical Biology Introduction," China Science and Technology University Publication, (1999). 12. "D3382-95 Standard Test Method for Measurement of Energy and Integrated charge Transfer Due to partial Discharge (Corona) Using Bridge Techniques", in 1995 Book of Standards, (1995) Vol. 10.02 Section 10 13. Z. T. Zhang, Y. Z. Xian, M. D. Bai, J. Physics (China), (2003) 32 (7) 458
226 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Effect of Hydroxyl Radicals on Photosynthesis Pigments of Phytoplankton of Ship's Ballast Water* Mindi Bai, Xiyao Bai, Dongmei Zhang, Bo Yang, Keping Zhan Key laboratory of strong electric-field ionization discharge of Liaoning; Environmental Engineering Institute, Dalian Maritime University, Dalian, 116026, Liaoning, P.R.China, E-mail: [email protected]
Abstract: With the dissolved OH" concentration of 0.68mg/L, the kill efficiencies of bacteria, mono-algae, protozoan reach 100% within 2.67s in main pipe of 20t/h ship's ballast water. At the same time, the effect of hydroxyl radicals on the photosynthesis pigments of phytoplankton was studied. The results indicate that the contents of chlorophyl-a, chlorophyl-b, chlorophyl-c and carotenoid are decreased to 35~64% within 8.0s further to the lowest limit of test after 5 minutes. The attenuation efficiencies of photosynthesis pigment are 100%. Therefore the invasive marine species can be killed in the process of the inputting and discharge ship's ballast water. Key Words" Ship's ballast water; Hydroxyl radical; Photosynthesis pigment; Attenuation efficiencies
INTRODUCTION The introduction of invasive marine species into new environments by ship's ballast water, attached to ships' hulls and via other vectors has been identified as one of the four greatest threats to the world's oceans by Global Environment Facility (GEF). Vessels of the world are transferring 10 billion tons of ballast water per year. It is estimated that at least 7,000 different species are being carried in ship's ballast tanks around the world. About 110 million plankton specimens are carried in lm 3 of ballast water. Until today about 500 different species are known to have been transported with ballast water [~5]. Near 20 years, main methods for the treatment of ship's ballast water are the mechanical, physical and chemical removal of species [6]. With the open-ocean-exchange in mechanical removal, only 95 % of ballast water was discharged at open ocean injecting 3 times seawater, existing the problems of safety and energy consumption (7]. By the heat treatment in physical removal, higher temperatures would be required to deal with thermophilic (heat living) organisms or more resistant forms such as bacterial spores. The temperature between 30 and 40 would support the growth of bacteria as e.g. Vibrio cholerae [8,9]. It has to be considered that chemical removal is promising method. In 1997, Donald M. Anderson pointed that more than 4,700 effective chemical biocides could be used to kill organisms in oceans and lakes [5]. However Several tonnes were needed to treat the large amounts of ballast water on a bulk carrier calling for a port area without any cargo. In addition, both inorganic and organic biocides would present a range of health and safety problems related to the storage and handling of chemicals, their compatibility with cargoes carried on board ships, as well as those related to the direct and indirect handling of chemicals by crew members [10]. Also the killing duration ofbiocides needs above 20 minutes, that is impossible to treat over a few ten thousands ballast water on board. Although a lot of research work was done in the world, Marine Environment Protection Committee (MEPC) and GloBallast think that no high efficient, low costing, non-residual method could be used in the treatment of ship's ballast water [~].
Key Project of National Foundation Research from Science and Technology Ministry of China, (2002CCC00900) Key and General Projects of National Natural Science Foundation of China (NSFC: 60031001; 60371035)
227 A physics method is studied that the electrons are accelerated resulting in the excitation, dissociation or ionization of gas molecules by strong ionization discharge [11-121. The strong electric field (E~400Td, 1Td=10~7Vcm2) is formed with the thinner a-A1203 dielectric layer in the microgap at a high pressure (P>0.1MPa or n=2.6xl0"19/cm3). The electrons achieve the average energy of above 12eV. With this method, the kill of organisms of ship's ballast water was done in laboratory using hydroxyl radicals in 2002 [131. As a result, the mono-algae, protozoan, spore, bacteria were killed 100% with OH" concentration of 0.6mg/L. In this paper, the effect of hydroxyl radicals on the photosynthesis pigments of phytoplankton was studied in the experimental system of 20t~ for the treatment of ship's ballast water. EXPERIMENT METHOD AND 20t/h SYSTEM Experimental materials and test methods for Bacteria, Algae, Photosynthetic pigments, and OH" concentration are shown in the paper, title "Biochemistry Effects Of Hydroxyl Radicals to Invasive Marine Species". 20t~ system for the treatment of ship's ballast water is shown in the paper, title "Treatment of 20t/h Ship's Ballast Water Using Strong Ionization Discharge".
EXPERIMENTAL RESULTS AND DISCUSSIONS Experiment for the killing of invasive species The bacteria concentration is 2.6x104/mL; the mono-cell algae concentration is 2.0xl04/mL; the protozoan concentration is 1.5x 104/mL. After the injection of hydroxyl solution, the duration of OH" on bacteria, micro algae are 2.67s in sample point C. As shown in Fig.l, when the hydroxyl ratio concentration is 0.68mg/L, the micro algae are killed 100%. When the ratio concentration reaches 0.45mg/L, the kill efficiency of micro algae is 96.4%, as an inflexion of concentration. When the ratio concentration is 0.55mg/L, the kill efficiency is 98.3%, which is enough to kill the organisms in ballast water. However the bacteria and protozoan are killed above 98% when the ratio concentration is 0.15mg/L, much lower than the concentration of killing Micro algae. When the ratio concentration is 0.25mg/L, the bacteria and protozoan are killed 100% respectively. The experimental results indicate that all organisms in ballast water could be killed in ship in line.
Fig. 1. Hydroxyl Concentration vs. Kill Efficiency of Micro Algae and Bacteria
Fig. 2. Hydroxyl concentration vs. attenuation Efficiency of photosynthesis pigment
228 Effect of hydroxyl radicals on the attenuation efficiency of photosynthesis pigments Hydroxyl radical has strong oxidized and decolored effects on phytoplankton (mono-cell algae). The samples were taken at the point C and tested after 5 minters. The effect of OH" ratio concentration on the attenuation efficiencies of photosynthesis pigment is shown in Fig. 2. When OH" ratio concentration is in the range of 0. l~0.5mg/L, the hydroxyl radicals greatly restrain the increases of chlorophyl-a, chlorophylb and carotenoid, having a sharp attenuation efficiency which increases with the increase of hydroxyl ratio concentration and their curve inflexions are 0.55mg/L. Chl-b, Chl-a and carotenoid have the similar curves. When OH" ratio concentration is 0.55mg/L, Chl-a concentration decreases from 15.39~tg/L to the lowest limit of test with the attenuation efficiency of 100%, considering chl-a to be ~tecomposed complelely. The chl-b concentration decreases from 17.5~tg/L to the lowest limit of test with the attenuation efficiency of 100%, also considering chl-b to be decomposed completely. The concentration of carotenoid decreases from l/3.70~tg/L to 1.06~tg/L, the attenuation efficiency is 92.3%. When OH" ratio concentration is 0.68mg/L, ttte attenuation efficiency of carotenoid is 100%. Therefore, the hydroxyl radicals have much stronger effects on chl-a, chl-b and carotenoid. Effect of hydroxyl radicals on the photosynthesis pigments The effect of hydroxyl duration on the photosynthesis pigments is shown in Fig. 3. The original contents of chl-a, chl-b, chl-c and carotenoid are 21.69~tg/L, 5.62~tg/L, 10.32~tg/L and 13.74~tg/L respectively. When the dissolved OH" ratio concentration was 0.6mg/L in the main pipe of ballast water, the samples were taken at the five point of A, B, C, D and E respectively and the experiments of photosynthesis pigment were done. The curves of chl-a, chl-b, chl-c andcarotenoid are very similar, and the pigment contents decrease to l l.81~tg/L, 2.16~tg/L, 6.71~tg/L and 4.89~tg/L respectively after 8 seconds. The all pigment contents were to the lowest limit of test after 24 hours. Effect of hydroxyl radicals on the phaeophytin The phaeophytin means the chlorophyl to lose the magnesium element, which is impossible to carry on the photosynthesis of phytoplankton. The effect of hydroxyl radical on the phaeophytin of phytoplankton is shown in Fig. 4. The original content of mono-cell phaeophytin in the ballast water is 4.78gg/L. With the hydroxyl concentration of 0.6mg/L after 8 seconds, the content of phaeophytin is increased to 47.21gg/L about 10 times. Therefore, hydroxyl radicals have very strong effect on the photosynthesis pigment of phytoplankton.
Fig. 3. Hydroxyl duration vs. content of photosynthesis pigments
Fig. 4. Hydroxyl duration vs. content of phaeophytin
229 Chal-a, which is the most important photosynthesis pigment of micro algae, consists of the altemate unsaturated structures of single and double bonds. Therefore Chal-a is easy to be attacked by hydroxyl radicals to occur the biochemical reactions of oxidization, bond break, structure damage and decomposition. Chl-b, which is an apparent and main assistant pigment of micro algae, consists of the alternate unsaturated structures of single bond and multi-bonds. Chl-b is very easy to be oxidized and decomposed by hydroxyl radicals. Carotenoid, which is an important assistant pigment of micro algae, is an unsaturated substance including eleven double bonds. Also it is easy to be oxidized and decomposed by hydroxyl radicals. All of the experimental data indicate that the hydroxyl radicals make phytoplankton lose its activity finally resulting in all mono-cell algae to be killed. CONCLUSIONS (5) The attenuation efficiencies of Chl-a and Chl-b are 100% with OH" concentration of 0.55mg/L; that of carotenoid is 100% with OH" concentration of 0.68mg/L. (6) The contents of chl-a, chl-b, chl-c and carotenoid are decreased to 35%-64% within 8.0s further to the lowest limit of test after 5 minutes. (7) The content of phaeophytin is increased to ten times. Hydroxyl radical has strong oxidized and decolored effects on phytoplankton (mono-cell algae), which makes the phytoplankton lose its activity finally resulting in all mono-cell algae to be killed. REFERENCES 1. Global Ballast Water Management Program - The problem, htm, http://globallast.imo.org 2. Gregory M Ruiz etc, "Global spread of microorganisms by ships", Nature (2000), 408 49-50 3. Mackenzie etc, "Alien invaders", New Scientist (1999), 16218-19 4. Geoff Rigby, "From ballast to bouillabaisse", Science(2000), 289 241 5. Donald M Anderson, "Turning back the harmful red tide", Nature (1997), 388 513-514 6. Bai Xiyao, Bai Minong, Yang Bo, "Studies on the Disaster and Treatment of Alien Invaders", J. Nature (China) (2002), 24(4) 223-226 7. Rigby, G. and Hallegraeff, G. M., "Ballast Water Exchange Trials and Marine Plankton Distribution on the MV "Iron Whyalla"", Australian Government Publishing Service, Canberra (1993), Vol. 2 p. 123 8. Yount, J. D., "Ecology and Management of the Zebra Mussel and other Introduced Aquatic Nuisance Species", EPA Workshop Qn Zebra Mussels and other Introduced Aquatic Nuisance Species, Saginaw Valley State University, USA, (1990), 1-45 9. Armstrong, G., "Ballast System Design for a Flow-through Exchange of Ballast Water", Prepared for a technical meeting at the Institute of Marine Engineers (1997), London, 25 March 11 10. Miiller, K.:, "Disinfection of Ballast Water. A Review of Potential Options", Lloyd's Register (1995), 29+ appendix 11. Bai Mindong, Zhang Zhitao, Bai Xiyao et al, "Plasma Synthesis of Ammonia with a Microgap Dielectric Barrier Discharge at Ambient Pressure," IEEE Trans. Plasma Sci (2003), 31 (6) 12. Bai Xiyao, Zhang Zhitao, Han Hui et al, "Research Situation and Progress of Non-equilibrium Plasma Chemistry," Chinese Science Bulletin (China) (2002), 47(7) 529-530 13. Bai Mindong, zhang Zhitao, Bai Xiyao et al, "The killing of organisms in ship's ballast water using hydroxyl radicals", Oceanologia et Limnologia Sinica (china) (2003), 34(5) 484-489
230 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on Radiation of Microgap DBD Plasma at Atmospheric Pressure Zhitao Zhang, Xiaodong Wu, Jianlong Gu, Yang Xu, Xiyao Bai Environmental Engineering Research Institute, Dalian Maritime University, Dalian P. R. China 116026, e-mail: [email protected] ABSTRACT" DBD radiation is used to describe the ionization state of medium gases. In this paper, the radiation of microgap DBD plasma is studied at atmospheric pressure in its device with a transparent electrode and an observed from side view. As a result, the applied voltage, applied frequency and the configuration of DBD can affect on its radiation. Some methods, including the narrow discharge gap and thinner dielectric layer, high-frequency high-voltage power supply, were used in the microgap DBD at atmospheric pressure. These improvements are very helpful in increasing the electrical filed strength and power density in discharge gap of DBD. Therefore, the strong ionization discharge is realized at atmosphere pressure. Index Terms-- dielectric barrier discharge, nonthermal plasma, plasma radiation
INTRODUCTION Dielectric barrier discharges (DBD) can establish nonthermal equilibrium plasma at near or over atmospheric pressure range. The main advantage of this type of electrical discharge is that active species for chemic reaction can be produce at low temperature though the vacuum set-up is taken off. This has led to a number of important application including ozone synthesize, UV lamp-house, CO2 lasers, et al [ 1-3]. In recent years, research on DBD has received significant attention due to new applications in plasma chemical, semiconductor etching, pollution control and large area flat plasma display panels were developed [4-5], and it is becoming a main aspect in nonthermal plasma subject. However, in a number of applications, there are some difficulties in the means for gases ionisation using conventional DBD at atmospheric pressure, as a result of gases ionisation rate is very low. It doesn't obtain satisfying results in some nonthermal equilibrium plasma chemistry process. Recently, many investigations showed that gases ionisation rate can be enhanced by reducing the width of the discharges gap, using o;-A1203 materials for thin dielectric barrier layer, and adopting high applied frequency. Due to DBD radiation can describe effectively the ionization state of medium gases [6], the paper is intended to describe ionisation state of microgap DBD at atmospheric pressure using this means, and primary reveal its collective motion and evolutive principle.
EXPERIMENTAL SETUP Fig. 1 shows the schematics of the experimental setup used to observe radiation of microgap DBD at atmospheric pressure. It consisted mainly of DBD device, power supply, and CCD system. The DBD device includes two different components in this setup. One is T ~ D B D with a transparent electrode used to observe radiation of microdischarges from the upside; and the other is L ~ D B D with a lamellar electrode used to observe evolvement of single microdischarge from side view. All are same in two components besides the figure of electrode, and their run state is same too. In this way, the radiation course of microdischarges may be found out fully. The sheet metal used for blocking off ray and averaging gases current is set in the middle of two components. The DBD device is enclosed a box with
231 the parts for purge exhaust gas so that avoid surroundings is polluted by plasma chemistry resultant. Applied frequency of the power supply is 1~20kHz range, applied voltage range is 1~20kV. Two CCD cameras are used to collect images of DBD radiation. Their results are transmitted to computer for analysis.
Fig. 1 Schematics of the experimental setup 1 power supply; 2 resistance; 3 cover board; 4 box (grounded electrode); 5 transparent electrode; 6 lamellar electrode; 7 dielectric barrier layer; 8 microgap; 9 sheet metal; 10 gases entrance; 11 cooling water entrance; 12, 13 CCD system
Fig.2 Photographs of DBD observed from upside of the transparent electrode
RESULTS AND DISCUSSION Fig.2 shows a few typical photographs of DBD observed from upside of the transparent electrode when the N2 gases flux is 0.21/min, the pressure is 0.1Mpa, and applied frequency is 10kHz. It is obvious that the radiation of DBD depend upon applied voltage. Microdischarge only appear in the part of discharges chamber when applied voltage is less than 2.4kV, and many circular bright dots are individual each other. The distance from a bright dot to adjacent one is approximately lmm (fig. 2a). Microdischarge appear in the whole of discharge chamber in the range of 2.4~--2.6kV, and many bright dots is individual each other yet (fig.2b). In the voltage range between 2.8"~ 3.2kV, though individual microdischarges can are observed yet, but it aren't clear comparing bright dots with its around area (fig.2c). When the applied voltage exceeds 3.4kV, the radiation of DBD is uniform on any position of the transparent electrode surfaces so that individual bright dots disappear on there if we observed from upside (fig. 2d). Those DBD devices using the single dielectric layer and the double dielectric layers yielded similar results observed from upside of the transparent electrode, but applied voltage differed for the same radiation state. However, the patterns formed by filaments are distinct observed from side view. Fig.3 shows 2D patterns of the single dielectric layer from side view. These filaments are individual each other when the voltage less than 2.0kV. Follow about applied voltage enhance, the new filament is brought between two adjacent individual filaments each other. These discharges deposits charges on dielectric surfaces, and formed a circular charges layer encircling its filament by electric field droved, an amplificatory microdischarge radiation pattern is showed in fig.3. The applied voltage is higher, the radius of deposits charges layer is bigger, and it affects other one. Finally, the uniform deposits charges layer is formed on dielectric surfaces by its self organize action, and its radiation is brighter than those formed by lower voltage. Fig.4 shows 2D patterns of the double dielectric layer DBD from side view. In comparison to fig.3, this one is different in two aspects. On the one hand, the deposits charges formed by the discharge filaments are on two dielectric layer surfaces for the double dielectric layer DBD, but they only are on one surface for the single dielectric layer DBD, and the radius of deposit layer is approximately a half than the double dielectric layer DBD, relative intensity of its radiation is less than the double one; on the other hand, when the applied voltage exceed 3.6kV, its radiation is very uniform than the single dielectric
232 layer DBD . Individual filaments can't be distinguished clear in there; the deposit charges distribute greatly uniformity, forming the quasi-glow discharges.
Fig.3 2D patterns of the sin~e dielectric laver from side ~iew Fi~_a 2D patterns of the double dielectric laverfrom side xie~
The causes to bring difference of radiation intensity are mostly in two aspects. First, there is only a dielectric layer in the single layer DBD, but there are two in the double dielectric layer DBD. Due to the material and size of every dielectric layer are same, thereby the amount of charges formed by a discharge filament is more in the single dielectric layer DBD than the double dielectric one, the result is that the radiation is stronger in the single dielectric layer DBD than other one. Secondly, there is the secondary electrons emission on surface of the metal electrode that isn't covered dielectric layer. When the ion impacts the metal electrode, some electrons are off metal into the gases and increase amount of charges, therefore discharges are enhanced in the single dielectric layer DBD. The key causes to bring difference in radiation effect between the single dielectric layer DBD and the double dielectric one are interaction between deposit charges group formed by the filaments. The electric field in every place of the discharges chamber is homogeneity for the double dielectric layer DBD when the applied voltage less than the break down voltage. Along with the applied voltage is increased, the electric field intensity in local region of the discharges chamber exceed the break down value, thus the discharges occur in there. Usually, while the applied voltage is close to break down value, it is stochastic in where does a discharge filament occur due to the electric field distributing is inhomogeneity. However, the results of observation for the experiment show that a lot of discharges filaments break down in the same place. The phenomenon is related to self-induction electric field formed by deposit charges. When a discharge filament occurs, the charges are drove towards electrode by electric field force in the discharges place. Due to mass of an electron is very less than other heavy particle mass, large numbers of electrons deposit on dielectric layer surfaces, these charges set up an electric field that opposes the applied electric field, namely self-induction electric field. The field acts on applied electric field, the result is that synthetical field is abruptly lowered in the localized region. The discharge is discontinuity when the synthetical field is less than the value that maintains discharge, but self-induction electric field exists in there yet. At the half-cycle of applied voltage, the probability that occurs discharge in the same place is very less because of the synthetical field lower than other place all around. However, when voltage is reversed, the self-induction field formed during the preceding half-cycle of the applied voltage reinforces the synthetical field. Therefore, a discharge is most likely to occur in the position of a previous filament due to the field higher than other place all around in there. The course is repeated to occur continuously, it is observed that a numbers of individual filament stand still when applied voltage is very lower. If applied voltage is enhanced, some filaments are likely to occur in those positions of previous non-discharges. The applied voltage is higher, the filaments is more. Many deposit charges occur self-organization phenomenon by charges diffused action, and displaying a bright motion track. If the applied voltage is high enough, it causes discharges in all the spaces, so that the discharges chamber of DBD is filled from one end to another end by filaments. Adjacent filaments are close enough together that no additional filament can occur between them. In this state, a very uniform charges layer is formed by deposit charges, it can adjust self-induction electric field to get uniform distributing in every position. As a result, filaments occur random in whole discharges place but it doesn't repeat to take place in the same position, thus a uniform radiation state is formed. In comparison with the double dielectric layer DBD, there is only an electrode that is covered with dielectric layer in the single dielectric layer DBD, the self-induction electric field can't be form on the surface of the metallic electrode, therefore their radiation is different.
233 Although the patterns formed by radiation are different between the single dielectric layer DBD and the double dielectric layer one, their hypostasis is same, this is collectivity effect formed by filaments. In the experiments, the discharge to form uniform radiation isn't atmospheric pressure glow discharge; it merely is a collective motion result of large numbers of filaments. Besides the applied voltage, other factor also can affect the radiation of DBD, for example applied frequency, discharge gap, et al.
CONCLUSIONS Preliminary results obtained in the course of this investigation indicate that deposit charges affect evidently the course of dielectric barrier discharges. For the single dielectric layer DBD, the radiation formed by the DBD shows clear the micro-discharges character. For the double dielectric layer DBD, the radiation formed by the DBD shows the uniform discharges character due to these deposit charges can uniformly distribute on two dielectric layer surface by self organize motion so that self-induction electric field is very uniform. The atmospheric pressure glow discharge doesn't occur using medium gases N2, 02, H2, H20. The uniform radiation only is a quasi-glow discharges phenomenon for the double dielectric layer DBD, its hypostasis is the result that great numbers of deposit charges occur collective motion effect.
ACKNOWLEDGMENTS The authors wish to thank NSFC (No. 60371035) for their financial support of the research described in this paper.
REFERENCE 1. X.Y. Bai, Z.T. Zhang, M.D. Bai, "Research situation and progress of non-equilibrium plasma chemistry", Chinese Science Bulletin, (2002) 47(7), pp. 529-530 2. K. C. Choi, B.J. Rhee, H.N. Lee, "Characteristics of charged and metastable species in micro-discharges of AC-plasma display panel", IEEE Transactions on Plasma Science, (2003) 31(3), pp. 329-332 3. B Eliasson, U Kogelschatz, "Non-equilibrium volume plasma chemical procession", IEEE Transactions on Plasma Science, (1991) 19(6), pp. 1063-1077 4. N K Bibinov, A A Fateev, "On the influence of metastable reactions on rotational temperatures in dielectric barrier discharges in He-N2 mixtures", Journal of Physics D: Applied Physics, (2001) 34, pp. 1819-1826 5. L Stacy, Daniels, "On the ionization of air for removal of noxious effluvia (Air ionization of indoor environments for control of volatile and particularte contaminants with nonthermal plasmas generated by dielectric-barrier discharge)", IEEE Transactions on Plasma Science, (2002) 30(4), pp. 1471-1480 6. J Martyn, Shenton, C Gary, Stevens, "Optical Emission from atmospheric pressure non-equilibrium plasma", IEEE Transactions on Plasma Science, (2002) 30(1), pp, 184 - 185
234 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Influence of Grain Size on Electronic Properties of Pure Cubic AgCI Emulsion Xiuhong Dai, Rongjuan Liu, Li Han, Guoyi Dong, Xiaoli Jiang, Shao-peng Yang, Xiaowei Li College of Physics Science and Technology, Hebei University, Baoding, Hebei,China 071002
High ionic photoconductivity is an important property as mentioned for AgX photographic theories. It is reported that after exposure the lifetime of photoelectrons is determined by the reaction of trapped electrons with interstial silver ions and it increases with decreasing ionic conductivity. Varied grain sizes of pure cubic AgC1 emulsion grown by double-jet precipitation of AgNO3 and NaC1 exposed to a YAG super short pulse laser (355nm, 35ps) were measured by microwave absorption dielectric-spectrum technique at RT. With the increasing of grain edge length, the photoelectron lifetime becomes longer from tens to hundreds nanoseconds up to a certain grain size.
INTRODUCTION Dielectric constants of AgX materials are larger compared with many other ionic crystals, such as alkhali halides. The high values for the dielectric constants provide for relatively strong shielding of electrostatic forces. In microfield, high ionic photoconductivity is an important property as mentioned for photographic theories. After exposure, ionic conductivity of AgC1 grain increases. Mobile interstitial silver ions and free electrons are current carriers. Taking into account the fact that both the number of interstitial ions and that of electron traps on the surface in a grain are proportional to its surface/volume ratio, Kaneda [ 1] conclude that the reaction of trapped electrons with interstitial silver ions determines the lifetime of photoelectrons. This process corresponds to the first stage of latent image formation. It is well known that the electron lifetime increases with decreasing ionic conductivity. In general, for intrinsic or unsensitized grains, high photoelectron lifetime leads to high photographic efficiency and for sensitized emulsion crystals, low photographic efficiency [2]. Photoelectron decay characteristics in latent image formation process directly reflect photographic efficiency of silver halide crystals. A series of photochemistry and physics reaction in silver halide emulsion occurs after exposure. The reaction process include the light absorption process, trap capture process, recombination process and latent image formation process inscribed by Gumey and Mott model [3]. Because these processes are concern with photoelectron, there is competition in these reaction processes. Competition result decides the decay characteristic of free electron.. From the above analysis, we can see that photoelectron is the foundation of latent image formation, so photoelectron action play an important role to photographic efficiency improvement of silver halide emulsion and attracts much attention of many researchers [ 1-2,3,4-9]. However, limited by experiment instruments, those researchers only studied the photoelectron transportation in the process of the latent image formation, but the kinetic mechanism of the photoelectron decay properties has never been discussed. Photoelectrons produced in the interior of AgC1 emulsion were immediately captured by electron traps on their arrival at surface and not released during the measurement according diffusion-limited kinetics. In this paper, electronic properties of cubic AgC1 emulsion grains were studied by microwave absorption dielectric-spectrum equipment with a high time resolution of less than lns at RT. A YAG laser system with pulse width of 35ps is used as an exposure light [10]. The decay curves of the free photoelectron and the shallow-trapped electron are obtained accurately, and the influence of grain size on the photoelectron action of cubic AgC1 grain is analyzed.
235 EXPERIMENTAL THEORIES AND EQUIPMENT Varied grain sizes of pure cubic AgC1 emulsion (edge length, 239.7-778.2nm) were grown by double-jet preparation of AgNO3 and NaC1. The specimens used in this study were emulsion layers that were composed of gelatin and cubic AgC1 grains. Microwave absorption dielectric-spectrum measuring technique were used in this study. The principle of microwave absorption dielectric spectrum measure equipment has been shown in References [ 10]. A film sample is inserted into a microwave cavity at the position where the electric field is a maximum and is exposed by a 35ps YAG pulse laser, which produces a monochromatic pulse at 355nm with an exposure duration, tp, of 35ps. The laser energy used is 1.5-3mJ. The light absorption process and the photoelectron decay process of some AgX crystals are about several ns, the 35ps YAG pulsed laser is applicable. The time resolution of phase-sensitive detection system of our equipment is less than lns. To examine the influence of free electrons and shallow-trapped electrons on the recombination processes of the photoelectrons due to sensitization specks on the crystal surface, an extremely high time resolution about l ns is necessary. By analyzing the free electron signal and the shallow-trapped electron signal, we obtain the photoelectron action and its influence on the latent image formation. The signals are amplified by an SR440 amplifier (SRS.) and displayed by a TDS3052 digital storage oscilloscope (Tek.). EXPERIMENTAL RESULTS In this work, we measure the photoelectron behavior of pure cubic AgC1 grains. Through calculation we got the free photoelectron decay time (FDT) and the shallow-trapped electron decay time (SDT). Photoelectron lifetime ~" is estimated from semilogarithmic plots of the photoelectron decay curves corresponding to "c--dt/d{ln(V/Vo)} where V is the photoelectron signal intensity, and V0 is the maximum of the photoelectron signal intensity[5].
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time/ns Figure 1 Photoelectron decay curves of cubic AgC1 with edge length 569.2nm at RT: (a) decay curve of free photoelectrons; (b) decay curve of shallow-trapped photoelectrons
0
100
230
300
400
time/ns
Figure 2 Comparison of the free photoelectron decay curve of varied AgX grain edge length from 239.7 to 778.2nm
Figure 1 shows a typical result of measurement of the decay of free and shallow-trapped photoelectrons of cubic AgC1 microcrystals with edge length 569.2nm at room temperature. The free photoelectron decay curve is given in Fig.1 (a). A maximum of the free photoelectron density appears at 6ns after the exposure, and followed by an exponential decay. The shallow-trapped electron decay curve is given in Fig.1 (b). The decay time of the free and shallow-trapped photoelectrons are 245 ns and 247 ns
236 respectively. From the analysis of the decay curve, we can know that SDT is 2ns longer than SDT. The generation and decay of the shallow-trapped photoelectrons are later than that of the free photoelectrons and the decay process is also slower. From the semilogarithmic plot, shown in Fig.1 (c) for free photoelectron, FLT have two parts: the slower one 154ns and the faster one 76ns. The temporal behavior of the photoelectron includes the photoelectrons traped by electron trap, recombination with holes, and the electron capture involved in the silver clusters formation, so the free photoelectron lifetime reflects the information of the latent image formation process. Figures 2 show the comparison of the free photoelectrons decay curve in cubic AgC1 microcrystals with different edge length. It can be seen that the photoelectron decay process becomes longer with edge length of AgC1 crystals increasing. When the edge length increases from 239.7nm to 778.2nm, the photoelectron lifetime increases from 30ns to 413ns linely until up to a certain grain size, which is shown in table 1. Table 1 Photoelectron decay time varies with edge length of cubic AgC1 emulsion Size(nm) FDT(ns)
239.7 30
264.7 64 .
.
.
.
421.9 141
569.2 245
601.3 280
764.5 390
778.2 413
.
CONCLUSION AND DISCUSSION Grain surface is an important factor determining ionic photoconductivity. Mobile interstitial silver ions and free electrons are current carriers. Both the number of interstitial ions and that of electron traps on the surface in a grain are proportional to its surface/volume ratio according to Kaneda [ 1]. After exposure, the lifetime of photoelectrons are determined by the reaction of trapped electrons with interstial silver ions. As we all know, the lifetime of the photoelectron decreases with grain ionic photoconductivity incereasing. With the increasing of grain edge length, the photoelectron lifetime becomes longer from tens to hundreds nanoseconds up to a certain grain size. So we can conclude while grain size increasing, the distance that the photoelectrons move to the surface is becoming longer, more photoelectrons may be captured by more silver ions and thaps on their arrival to the grain surface. So the grain ionic photoconductivity decreases, the photoelectron decay process related with grain ionic conductivity becomes long, that is, the photoelectron lifetime increases. When the distance is two long for the photoelectron moving to the grain surface, they may be trapped at some deep traps or interstitial silver ions to form latent image in the inner of the grain. So if the edge length of the AgC1 cryatal is too larger, the photoelectron lifetime may not increase linealy, so as the photographic sensitivity according to T.Tani[11 ]. ACKNOWLEDGEMENTS This work has been supported by National Nature Science Foundation (Grant No.10354001) and the Natural Science Foundation of Hebei Province,China (Grant No.603138). REFERENCES 1. Kaneda. A New Approach to Estimation of Depth of Electron Trap in AgBr Emulsion Grains on the Basis of the GumeyMott Model, J Imaging. Sci. (1989), 3__33115-120 2. Miissig T. Principles of Microwave Absorption Technique Applied to AgX Microcrystals, J. Imag. Sci. Tech. (1997), 41118-127 3. Hamilton J. F. A Modified Proposal for the Mechanism of Sulfur Sensitization in Terms of Capture Cross Section, J_ Photogr. Sci. Eng. (1983), 2__7_7225-230 4. Kellogg L M. Measurements of Photoelectron Lifetimes in Silver Halide Microcrystals Using Microwave Techniques, J_ Photogr. Sci. Eng. (1974), 1__88378-382 5. M/issig T and Hegenbart G, Microwave Absorption Investigations of AgBrl_xlxCrystals, J. Imag. Sci. Tech. (1994), 38526-532 6. Harada T, Lijima T and Koitabashi T, Photoconductivity Decay Kinetics of Silver Halide Emulsions at Low Temperature, J_ Photogr. Sci. Eng. (1982), 2___fi6137-141 7. Hasegawa A and Sakaguchi T. Detection of Latent Image by Microwave Photoconductivity, J. Imaging. Sci. (1986), 3013-15 8. Ehrllch S H., the Kinetic Process of Formation and Electron-Trapping Efficiencies of Quantum-Sized Silver Bromide Clusters, J. Imag. Sci. Tech. (1994), 3__88201-216 9. Beutel J. Photoconductivity of microcrystalline cubic silver bromide emulsion, Photogr. Sci. Eng. (1975), 1995-99 10. Shaopeng Yang, Xiaowei Li, Li Han,et al. Characteristic of photoelectron decay of silver halide microcrystal illuminated by a short pulse laser[J]. Chin phys lett. (2002), 19(3) 429-432 11. T Tani, et al. Electronic Properties and Photographic Behavior of AgC1 Emulsion Grains. J. Imag. Sci. Tech. (1995), 39233-238
237 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Influence of Electron Trap Capture Cross section on Carriers in Semiconductor Rongjuan Liu,Xiuhong Dai, Guangsheng Fu, Xiaowei Li, Shaopeng Yang, Rongxiang Zhang College of Physics Science and Technology, Hebei University, Baoding, China, 071002
The influence of electron trap capture cross section on the decay of carriers is studied in this paper, after a transient illumination acts on the silver halide material and breaks the electrostatic equilibrium inside it. It is found that when the capture cross section is very large, the carrier amount variation will occur mainly in exposure process; while when smaller, occur after exposure. Moreover, the decay velocity becomes higher with enlarging capture cross section. Simultaneously, the corresponding variations of some physical properties with the decay of carriers, such as electrostatic equilibrium and photoconductivity, are analyzed.
INTRODUCTION Semiconductor material is very sensitive to additional condition such as temperature, illumination, pressure and electromagnetic field etc. when these conditions act on semiconductor material, there will be a great number of imbalance carriers produced in it. The produce of carriers will break the previous electrostatic equilibrium, and result in the changes of dielectric character and other physical characters. Besides, the amount variation and redistribution of carriers will induce electric field energy and distribution to vary. The amount and distribution of carriers interact with the energy and distribution of electric field. Under an unchanged condition the electric field will tend toward a new equilibrium state. Known how carriers to move and distribute, the situation of electric field will be clear. It is well known that there exist a great deal of electron traps in semiconductor material due to impurities and defects. Because of the capturing function of electron traps, it influences the carrier amount and distribution to a great extent. In this paper, the influence of capture cross sections of electron traps on the cartier amount variety is studied. We choose silver halide material as the object to study, which is exposed to an intense light transiently. During the exposure process and after exposure process, carriers are captured by traps all along. It is found that the capture cross section has different effects on the decay of carriers before exposure and after exposure with different sizes of capture cross section. Here, the effect is analyzed in detail.
MODEL AND EQUATIONS It is hardly possible to obtain the precise information of the capture cross section of electron trap from experiment. Therefore, we capitalize on computer simulation to study, which is based on the numerical solution of the differential equations describing the kinetics of the photoelectron and photohole decay, solved through 5th order Runge-Kutta formulas. This way has been used by Callens F. etc.[I-5] and by Aicong G. etc.[6] to study the effect of a combination of electron traps, recombination centers, and hole traps on the photoelectron decay at low temperature and room temperature. They proposed a similar model [5,6] for computer simulation of the photoelectron decay process, in which including two intrinsic electron traps (one is deeper and the other is shallower), a recombination center, and a electron trap introduced by dopants. In the same way, we build a simple model including only one electron trap to study the effect of the capture cross section of this electron trap.
238 Model (in figure 1)' CB
Ne VB Figure 1 the model of silve halide for simulation The kinetics equations" dn = G dn e dt dt
(1)
n e
dt = fle (Ne - rte )rl - ~eNc ne e x p ( - ~ e KT ) (2) Where G is the formation rate of free electron-hole pairs by i l l u m i n a t i o n (cm-3s-1). After exposure, this term will become zero; tp is the exposure time, tp=35ps( because our simulation is based on the microwave absorption technique whose light source is a 35ps pulse laser[7]), I is the excitation intensity, G=I/tp; Ne is the concentration of electron traps; A E e is the electron trap depth; fie is the trapping rate constant, Se is the capture cross section, v e is the thermal movement velocity, fie --Se X Ve; n and ne are the numbers of free photoelectrons and photoelectrons in electron traps, respectively; Nc is the effective state density of conduction band; K, T are the Boltamann's constant and experimental temperature (T = 300K). The term containing exp(-AE e /KT) describes the thermal detrapping.
RESULT AND DISCUSSION Because, after exposure, a great number of photoelectrons and photoholes will be produced in semiconductor, which results in a direct phenomenon that the electrostatic equilibrium is broken and the photoconductivity increases abruptly. The speed for carriers tending toward equilibrium determines the response speed of the photoconductivity. While, the size of the capture cross section of an electron trap is a determinant of the speed for carriers reaching equilibrium. The influence of the capture cross section on the photoelectron decay is shown in figure 2. Figure 2 includes a series of figures of the photoelectron decay curve after exposure with the capture cross section decreasing from 1 x 10 -1 to 1 x 10 -19 c m 2. In the former seven figures, there are two cures in each figure. The dot curve in each figure actually is the line curve in its former figure. Thus the curves are compared in turn with reducing the capture cross section. Although it is impossible for the capture cross section size of one electron trap ranging from 1x 10-I to 1x 10-l~ cm 2. Here, our aim is to show the tendency clearly when the capture cross section changes toward the direction of enlarging. Se=l x 10 -1 to 1x l0 ~~ c m 2 is the extreme situation. It is can be seen that the curves in the figure 1-1 are horizontal lines, which means that photoelectrons do not decay after exposure. The reason for it is that since the capture cross section is too large, the trapped probability and the detrapping probability of photoelectrons are almost equal. The time for being trapped and detrapping of photoelectrons to reach equilibrium is so short that it is no more than the exposure time. Therefore, photoelectrons' redistribution has reached equilibrium before the end of exposure, and the electrostatic equilibrium has been reached too. In general, what we are interested in is the photoconductivity in semiconductor after exposure. In this case, there is not any conductivity existing after exposure. From the figure 1-2 to 1-7, it is can be seen that the initial value of the photoelectron decay curve become larger after exposure with reducing the capture cross section, which leads to a higher initial photoconductivity, and also seen that the value of the photoelectron number in equilibrium is a constant. These indicate that the capturing ability is weakened, the decay of photoelectrons becomes more and more tardily, and the number of photoelectrons decaying during exposure process becomes less with reducing the capture cross section. While the value of the photoelectron number in equilibrium does not change at different capture cross sections. Then, it can be believed that the electrostatic equilibrium is
239
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reached at a certain time after exposure when the capture cross section is smaller than 1 x 10l~ 2, and that the electrostatic equilibrium state is the same for different capture cross sections. The figure 1-8 shows that the decay velocity of photoelectrons has an obvious change with reducing the capture cross section when the capture cross section is smaller than 1 x 1 0 -15 c m 2. The smaller the capture cross section is, the more tardily photoelectrons decay, the longer for conductivity existing, and the longer time the decay needs to reach equilibrium state. And the electrostatic equilibrium state still remains constant. As a whole, when the capture cross section is smaller than 1 x l 0 "15 cm 2, the initial value of the photoelectron number does not change with reducing capture cross section and is not influenced by the prophase exposure process any more; while when it is smaller than 1 x 10-~9cm2, it will be too small to capture photoelectrons, and the photoelectrons do not decay any more. Therefore, when the concentration and trap depth of electron traps are fixed, there exist a range of capture cross section in which the changing of the capture cross section can cause the changing of the photoelectron decay velocity.
240 CONCLUSION The influence of electron trap capture cross section on the decay of carriers and the change of photoconductivity is studied after a transient intense light breaks the electrostatic equilibrium inside the silver halide material. During the exposure process and after exposure process, carriers are captured by traps all along, but whether the variety of carrier is greater during exposure or after exposure depends on the size of trap capture cross section. When the capture cross section is very large, the carrier amount variety and redistribution will occur mainly in the exposure process, photoconductivity are hardly produced; when smaller, mainly after exposure, there will be obvious photoconductivity produced. Whatever the size of the capture cross section, the final equilibrium state will be the same for electron traps when other parameters are not changed. Additionally, the decay velocity will became higher with enlarging capture cross section, and there exist a range for the capture cross section in which the photoelectron decay velocity is influenced by its changing.
ACKNOWLEGEMENT This Project has been supported by National Nature Science Foundation (Grant No.10274017, 10354001), and the Natural Science Foundation of Hebei Province, China (Grant No.103097, 603138).
REFERENCES 1. Van den Eeden, M., Callens, F. et al., Computer Simulation of Transient Microwave Photoconductivity in Silver Halide Microcrystals, J.lmaging.Sci.Tech (1994), 38:475-483 2. Van den Eeden, M., Callens, F., et al., Transient Microwave Photoconductivity and Computer Simulation Study of Ir3§ and Rh3§ Doped AgC1 Microcrystals, J.Imaging.Sci.Tech (1995),3__99:393-402 3. Hua, J. P., Callens, F., et al. Transient Photoconductivity Study of Shallow Electron Traps in [Ru(CN)6]4" Doped AgC1 Microcrystals: Effects of Doping Concentration and Position, J.Imaging.Sci (1999),4__7_7:71-79 4. Hua, J. P., Callens, F., et al. Determination of Capture Cross Sections and Trap Depth Depths of Dominant Centers in AgCI Microcrystals Doped With [Ru(CN)6]4 Complexes, J.Phys.D:Appl.Phys.(2000),33:574-583 5. Hua, J. P., Callens, F., et al., Shallow Electron Traps Induced by [Ru(CN)6]a-,j.Phys.D:Appl.Phys (2000),33 "564-573 6. Aicong G., Xiaowei L., Guangsheng F. et al., Computer Simulation of Photoelectron Decay process of Silver Halide Microcrystals, SPIE-Color Science and Imaging Technologies. (2002),4922:107-111 7. Shaopeng Y., et al., Characteristics of Photoelectron Decay of Silver Halide Microcrystal Illuminated by a Short Pulse Laser, Chinese Physics Letters (2002),1___?:429-431
241 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Surface modification of metal material by N2-DBD Youping Hu*, Yinduo Yang*, Li Yan**, Xinhe Zhu**, Xiyao Bai**, Shidong Fan* * Wuhan University of Technology, 430070, China ** Dalian Maritime University, 116026, China Abstract: The experiment study on surface modification of metal material by nonthermal plasma producing by dielectric barrier discharge (DBD) with N2 is reported, and the relationships between hardness and thickness of nitrided layer with discharge parameters, processing temperature, processing time are discussed. Optimizing parameters is obtained about dealing with 38CrMoA1 Steel by N2-DBD. A novel method of surface modification of metal material by the micro-discharge of dielectric barrier with atmospheric is presented.
INTRODUCTION With the development of industrial technologies, materials required by the manufacture of industrial products have been increasingly various. In order to satisfy special requirements such as high intensity, high hardness, wearability, high refractory, acid-resistance, varieties of alloy materials need to be developed ceaselessly. However, these alloy materials may be usually expensive. People have tried to process the surface of ordinary materials by various surface technologies, changing their surface characteristics and thus making them adapt sophisticated environments. In addition, such invalidation as abrasion and eroding all occurs on the surface of materials. And then the material life can be increased greatly by means of effective surface modification of materials. In recent ten years the method processing the surface of metal materials by plasma is a new surface technology [1,2,]. Due to its remarkable virtues such a s the good quality of the nitrided layer, little metamorphosis of workpieces and no pollution, the method has become very attractive inland and oversea. But the present processing technologies with plasma are all realized in the vacuum systems, in which equipments are of high cost and the techniques process is considerably complex. In addition, the efficiency of energy usage in the vacuum systems is low and it is difficult to handle large-scale workpieces. Although people have made improve on the processing technologies, these technologies cannot break away from the vacuum systems yet. Therefore, how to realize the surface modification under atmospheric pressure with plasma is a most attractive problem [4]. In this paper material surface modification with the new technology of dielectric barrier discharge is presented. Dielectric barrier discharge is known as a kind of gas discharge with some dielectric inserted into discharge space[3,5]. It is an effective way of acquiring nonequilibrium plasma, which is broadly applied m various fields such as generating ozone, gas desulfuring, and surface modification of organic materials. In this paper nitriding experiments on the surface of metal materials are carried out, using DBD electrodes that are made with special techniques. EXPER/MENTAL SYSTEM The experimental system for surface modification of metal materials with DBD is shown in Fig. 1. It consists of four parts: a stove with DBD electrodes, a high-voltage power supply, a temperature control system, a regulation system of gas. The reactor stove with DBD electrodes is the core of the system as shown in Fig.2. As shown in Fig.2 the bottom parallel electrode is a steel board and an AlaO3 layer of 0.64mm thinness is attached to the top electrode. And the specimen is placed on the bottom electrode and it becomes a discharge electrode. Under the DBD electrode is the temperature control system which includes a sensor and ceramic resistance. The gas regulation system has a vacuum pump with which the gas N2 can be fed into the stove. Special designs are made in the whole reactor stove for the sake of highvoltage insulation, gas sealing, heat preservation and heatproofing etc. Thus the system can remain stable under the experimental conditions.
242 The experimental flow is: At first the specimen 38CrMoA1 Steel (10*10*5mm) is quenched at 940~ and tempered at 630 ~ And then the specimen is burnished with sand papers of 800 types and placed into the stove after cleaned. With the gas N2 added, the specimen is heated up to a proper temperature and high voltage is applied to the specimen in order to make the specimen discharge[6]. H.V.supply
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.
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Fig 1. Schematic diagrams of the experiment
The following instruments are used to analyze the characteristics of the nitriding layer" MH6Evorone Hardness Meter measures the hardness, EDX-HS is used to analyze the chemic components and the MM6 optical microscope watch the microstructure. EXPERIMANETAL RESULT AND ANALYSIS Effect of temperature on the nitrided layer On the surface modification of metal materials, the temperature not only influence to the hardness, depth of the layer, but also to the state structure of the component, the shape of the workpieces, thus the suitable temperature is selected with 400~600~ in this experiment study by the related reference. As shown in Fig.3 is the hardness curves when 6.25KV discharge voltage is applied and the discharge interval is d = 1. Omm
1000
1000
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450"C
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800
d=l. 5mm
800
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600
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0
50
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150
to the
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250
300
surface(~m)
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1.5mm and the nitriding time lasts 4 hours with the different temperature 400 ~ and 450~ respectively. When the temperature is 400~ the total depth of the nitrided layer is 150~1601am. When the temperature is 450 ~ the total depth is 200~210gm. The result shows that temperature has remarkable effect on the forming of compound and the depth of nitrided layer. The higher the temperature is, the faster the nitriding speed of nitrogen and the thicker the nitrided layer is. The spectrum analysis also proves that with the temperature rising the penetration amount of nitrogen is increased. Effect of discharge interval on the nitrided layer In this case the temperature is set at 450~ the voltage is 8.75kV with the frequency f=7 kHz and the dielectric is an A1203 layer of 0.64mm thinness. Select three different intervals equal to 1.0mm, 1.5mm, and 2.0mm respectively and then process the specimen. The curve of results is shown in Fig. 4.In the figure it shows that when the interval is equal to lmm the depth of the nitrided layer is the maximum, that is, 200gm. When the interval is 1.5mm the depth is 85gm and reduced by one more times compared with the depth as the interval is lmm. When the discharge interval is changed to 2mm, the depth is 70gm. Thus it can be seen that if the discharge interval decreases the depth of the nitrided layer will increase obviously. The reason is that the decrease of the interval causes the electric intensity to increase and the average energy of electrons becomes high. When the electrons collide with gaseous particles more active particles can be generated and as a result the active particles promote the nitriding process.
243 Effect of discharge voltage on the nitrided layer Fig.5 shows the experimental curves when the voltage respectively equals 11.25kV, 6.25kV and the temperature equals 450 ~ and the nitriding time is 5 hours with the discharge interval 2mm. It can be seen that when the voltage arise from 6.25kV to 11.25kV, the depth of nitrided layer is increased from 115gm to 165gm. It resembles the mechanism of increasing electric intensity by reducing the interval.
Fig 5. Hardness in difference discharge voltage
Fig 6. Fig in difference processing time
Effect of the nitriding time on the nitride layer A larger amount of high-energy active N atom can supply in the N2-plasma, it can quicken the nitriding processing, but too long time would be result in roughness in the material, so 4~6 hours was selected in this experiment. As shown in Fig.6 (a)(b) are the pictures which are obtained for 5 hours and 6 hours with the same discharge condition. The thickness of the layer is 180gm and 200gm respectively. In the case of the same temperature and electric field the processing time has direct effect on the depth of the nitrided layer. In addition the hardness of the specimen with 6h processing is raised a little more than that with 5h processing. Orthogonal experimental results showed that the key for obtaining good nitriding layer was to choose the discharge voltage, discharge interval and nitriding temperature properly. Reducing discharge interval and increasing electric field intensity could increase the hardness and depth of nitriding layer markedly. CONCLUSION The authors have made many experiments using this system for surface modification of metal materials with DBD. According to the experiment results and various analyses the conclusion can be made as following: 1) Nonequilibrium plasma generated by DBD can reach the aim of surface modification for metal materials effectively. Meanwhile, this kind of surface modification has many advantages. For example, it has a very high nitriding speed, the temperature required is low and the hardness of the nitrided layer is great. 2) The electric intensity of DBD discharge has great effect on the nitriding. If the electric intensity is increased effectively the nitriding effect will be enhanced. 3) Temperature and time also have remarkable effect on the nitriding. The higher the temperature is, the greater the thickness and hardness of the nitrided layer is. REFERENCE 1. Pochner K, Neff W, Lebert R. Atmospheric pressure gas discharge for surface treatment [J]. Surf Coat Techno, 1995,74-~ 75:394-~ 398 2. Wang W, et al. Modification of Bearing Steel Surface by Nitrogen Plasma Source Ion Implantation for Corrosion Protection [J]. Surface and Coating Technology, 1999 (111): 97 - 102B. 3. Eliasson, "Nonequilibrium volume plasma chemical processing," IEEE Trans. Plasma Sci., 19(6): 1063-1077 4. Thyen R, Weber A, C.--P.Klages. Plasma-enhanced chemical-vapour- deposition of thin films by corona discharge at atmospheric pressure. Surface and Coating Technology, 1997, (97): 426~434 5. Segers.M. Thin film deposition using a dielectric barrier discharge. Journal of the Electrochemical Society, 1991, (138): 2741~2744. 6. Li Yan, Essential Patameters for Plasma Nitriding Technology under Atmospheric Pressure [J] materials protection 2002 35 34-37.
244 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on the Security of Electro-igniting Device in Long-term Storage Condition towards ESD* Guanghui Wei, Yazhou Chen, Lizhen Liu Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R. China
Abstract: JD-AA is a kind of typical electro-igniting device that ignites the medicament by electro-heating bridge. To evaluate the anti-electrostatic ability of rocket roundly, we choose JD-AA stored in standard condition for different years as samples to research its electrostatic sensitivity, according to true-electrostaticsensitivity test method. The distribution parameters and the secure limit of the electrostatic-igniting energy and the inherent anti-electrostatic power of JD-AA have been determined. Research result shows that 50% electrostatic-igniting energy of JD-AA which are manufactured in different age is a little different. But it is not sure that long-term storage has obvious influences on the JD-AA's electrostatic-igniting energy. The earlier production time leads to the bigger standard deviation of electrostatic-igniting energy distribution, which is likely caused by different production technology of different time. Keyword: electro-igniting device; electrostatic sensitivity; safety; deposit
Electro-igniting device is widely used in lighting of ammunition and explosive device for its high reliability and short-action time. But it is sensitive to static so that its electrostatic safety is caused wide attention. The electrostatic securities of many kinds of electro-igniting devices were test when they were new products during the past several years E~-31.But the electrostatic sensitivity of the electro-igniting device after long-term storage is not studied. To resolve the problem, we choose the JD-AA electroigniting devices stored in standard condition for a long period as samples to test its electrostatic safety, according to true-electrostatic-sensitivity test method.
ELECTROSTATIC SENSITIVITY TEST The electrostatic sensitivity of electro-igniting device is an important parameter that reflects the antielectrostatic ability of rocket. According to true-electrostatic-sensitivity test method, we test the electrostatic sensitivity of JD-AA to evaluate the anti-electrostatic ability for rocket. According to the electrostatic energy consumed by the tested samples, the 50% electrostatic igniting energy c50 and the standard deviation o'~ are got as the parameters which scales the electrostatic sensitivity of the tested samples [4]. Measure procedure of electrostatic sensitivity The JD-AA was sampled randomly which were disassembled from the ammunitions according to production date. After the bridge-thread resistance of the JD-AA is measured, the JD-AA is placed between the sample clamps of JGY-89 true-electrostatic-sensitivity test system to test its electrostatic * Project supported by theNSFC No. 50077024 and 50237040; Supported by foundation for university key teacher by ministry of education
245 sensitivity. According to up-and-down method [5], the voltage between the discharging capacitor is changed. The voltage u(t) between the sample and the current i(t) along the sample are recorded by data collecting and processing system during experimentation. The electrostatic energy consumed by the sample is"
e - if(t), u(t). dt
(1)
According to GJB377-87 up and down method and true electrostatic sensitivity data processing method [4] the relative electrostatic sensitivity and true electrostatic sensitivity are got respectively, and the distribution parameters of electrostatic igniting energy of JD-AA produced in different age are made sure. Test results of electrostatic sensitivity In experiment, the energy storage capacitor is chosen as 9.65nF. To ensure no heat loss during electrostatic discharge process, the discharge time constant should be less than 2gs E~1 and so the resistance to limit current should be about 150 f2. To ensure the estimation veracity, the upper limit 6 of variance coefficient of standard error is taken as 0.2. So the effective samples should be n'> 2(1.5/8)2=112.5 ts]. In fact, the samples are more than 120 and are set to 4 group. To overcome the shortcoming of up-and-down method that usually leads to low standard error, the revised method in GJB377-87 is adopted to calculated standard error. The test results are shown as Tab.l-3, in which /t v and /re are 50% igniting voltage and igniting energy of the test system respectively, and Sv is standard deviation of the test system igniting voltage,/t~ and S~ are 50% igniting energy and standard deviation of the energy consumed by the tested samples. Table 1 Electrostatic sensitivity of JD-AA deposited for 28 years Serial number 1
2 3
Relative electrostatic sensitivity //v/kV 6.08 6.50 6.44 6.41
illE/mJ 178 204 200 198
Sv/kV 0.45 0.43 0.72 0.75
Power coefficient
True electrostatic sensitivity
ni
ai
Hi
fie/mJ
SJmJ
16 16 16 15
0.948 0.952 0.924 0.922
1.679 1.661 2.026 2.071
2.15 2.44 2.39 2.21
0.32 0.33 0.53 0.52
Table 2 Electrostatic sensitivity of JD-AA deposited for 18 years Serial number 1
2 3 4
Relative electrostatic sensitivity
llv /kV
ll e /mJ
6.97 7.02 7.08 7.11
234 238 242 244
Sv/kV 0.92 0.50 0.34 0.52
Power coefficient ni
ai
16 15 15 15
0.915 1.003 1.070 0.938
Hi 2.260 1.388 1.277 1.786
True electrostatic sensitivity fie/mJ 2.61 2.62 2.62 2.68 , ,
SJmJ 0.69 0.37 0.25 0.39
Table 3 Electrostatic sensitivity of JD-AA deposited for 4 years Serial number 1
. . ,
2 3 4
Relative electrostatic sensitivity
/l v /kV 7.04 7.09 7.06 7.14
fie/mJ 239 242 240 246 .,.
Power coefficient
Sv/kV
ni
Gi
0.23
15 15 15 15
1.013 0.963 0.916 0.951
0.29 0.73 0.43
Hi 1.360 1.550 2.245 1.657
True electrostatic sensitivity
11e/mJ
SJmJ
2.57 2.54 2.48 2.53
0.17 0.21 0.51 0.30
246 The distribution parameters of electrostatic igniting energy of JD-AA According to test results in Tab. 1-3, the distribution parameters of electrostatic igniting energy of JD-AA stored for different years are got by statistic analyses (see Tab. 4). Table 4 Distribution parameters of electrostatic igniting energy of JD-AA Store time
Effective samples
28 year
Relative electrostatic sensitivity
True electrostatic sensitivity
ltv /kV
crv/kV
/6/mJ
~/rnJ
63
6.36
0.55
2.30
0.40
18 year
61
7.04
0.50
2.63
0.37
4 year
60
7.08
0.36
2.53
0.26
From Tab.4, it is shown that ge of JD-AA which are different for different store time has no obvious change rule with the store time. But tJe has direct proportion to store time. By analyzing the results, we can draw the following conclusion. The 50% igniting energy is different for different production. But long-time storage has no obvious influence on igniting performance of JD-AA. The earlier production time leads to the bigger standard deviation of electrostatic-igniting energy distribution, which is likely caused by different production technology of different time.
THE SECURE LIMIT OF THE ELECTROSTATIC-IGNITING ENERGY OF JD-AA Because of the stimulating energy is about 50% igniting energy every time, the little-probability igniting energy will lead to very great error when it is deduced from the experimental data according to up-anddown method. So, it is stated in GJB376-87 that the maximal reliability is 99.9% when data is deduced by using of up-and-down method. That is, only the igniting energy for 1%0 igniting probability can be deduced and be used as the minimum igniting energy Emin of the sample. If the critical igniting energy fits normal distribution, then ~'min -- fl/e --
(2)
3.090cr,
According to the Tab.4 and expression (2), the minimum electrostatic igniting energy of JD-AA stored for different years can be calculated as Tab.5. To ensure safety, we divide the lest igniting energy which leads to 1%0 igniting probability by a safety factor r=l.5, which is taken as the secure limit of the electrostatic-igniting energy for JD-AA. Tab.5 the secure limit of the electrostatic-igniting energy for JD-AA Store time
Effective samples
~-~min/mj
Secure limit el/mj
28 years
63
1.064
0.71
18 years
61
1.487
0.99
4 years
60
1.727
1.15
According to the above experiment and calculation, the electrostatic energy consumed by the JD-AA can't be more than 0.70mJ to ensure the safety of the rocket.
THE INHERENT ANTI- ELECTROSTATIC POWER OF JD-AA It is necessary to know ESD model and the energy secure limit of electro-igniting device and igniting circuit model of the rocket for analyzing the inherent anti-electrostatic performance. The igniting circuit of the rocket is relative simple. It can be expressed as a resistance with same value as the bridge thread of JD-AA. There are many kinds of ESD models to study the electrostatic harm to electric device and
247
circuitry [61. But
the electro-igniting device is a kind of different product. Taking into account the particularities of combustion and explosion, the human body ESD model and metal ESD model for exploded region were put forward [71. Mostly there are three characteristic parameters in the body ESD model: body to ground capacitance CB which implies the ability storing electrostatic energy of body; body resistance RB which represent the capacity consumed ESD energy by body, body inductance L which determines the current waveform of ESD from body. The human body ESD model for exploded region can be expressed as a CRL circuit in series (see fig.l). According to recent research results [v], the body to ground capacitance CB and body resistance RB are taken as 500pF and 100 f~, respectively. Metal ESD model for exploded region is similar to machine ESD model and furniture ESD model in electronic industry. For safety reason, the metal ESD model is composed of a capacitor with 200pF and a resistance with 3 f~. The equivalent circuit to calculate the secure voltage limit in different ESD incidents when discharge to rockets R L by direct-action is shown as Fig.1. The ESD model is , . ~,~-~-,,~-~ shown in dashed frame. The electro-igniting device is expressed as a resistance with the same value as its bridgeC thread. It has few heat loss in ESD incident for electroESD model igniting device because the course of ESD last very short r time less than microsecond Ill 9 The inductance doesn't _j.. assume the energy, but affect the discharge waveform. It is ................................................ - .................................... negligible when the electrostatic energy assumed by the Fig.1 equivalent circuit rocket is calculated. From the equivalent circuit, electrostatic energy absorbed by electro-igniting device is: ., ...................................................................................
e - CVZ r/(ZR + 2r)
(3)
To ensure the safety of rocket, it is required thatr < e L . So the secure limit of discharge voltage should be less than the following value" Vs - 4 2 e L ( R + r ) / r C
(4)
According to expression (4), human body ESD model and metal ESD model, the secure limit of JDAA can be calculated as following" The secure voltage limit is 11.3kV when body discharges to rockets directly. The secure voltage limit is 4.04kV when the metal object discharges to rockets directly.
REFERENCE 1. Wei Guanghui, The true electrostatic sensitivity test for JD-AA, Enginery industry secure technology(1992), 4 34--36 2. Wei Guanghui, Liu Shanghe, Xu Yigen, Effect on the Safety of Electro-explosive Initiators towards ESD. Initiators & Pyrotechnics(1996), 4 16~22 3.Wei Guanghui, Liu Shanghe, Chen Yazhou, et al. Research on Real Electrostatic Sensitivity Test for Conductive-powder Electro-explosive Device, The third international conference on applied electrostatics, Shanghai, China(1997) 322~325 4. Wei Guanghui, Fan Lisi, Lu Hongbin, The method for determine the threshold value on electrostatic safety, 5th International Symposium on Test and Measurement, Shenzhen, China(2003) 591~594 5. Liu Baoguang, Xie Gaodi, Ren Maosheng, et al. The up and down method for sensitivity tests, military standard press, Beijing, China (1998) 1~8 6. Owen J.McAteer, .Electrostatic discharge control, McGraw-Hill, New York, USA(1990) 169"---20 7. Wei Guanghui, Sun Yongwei, Tan Chaobin, Research on ESD model, Research on electrostatic foundation theory and applied technique. Nanhai press, Haikou, China (2002) 134-137
248 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on the Radiation Effects of F R E M P towards Radio Fuse* Guanghui Wei, Xing Zhou, Yazhou Chen Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R. China
Abstract: To evaluate the security and reliability of radio fuse under rigorous electromagnetic environment, the integrated circuit radio fuse is chosen as samples, and the samples are radiated under strong electromagnetic field with fast rise time (FREMP) in working condition and storage condition, respectively. The experiment shows that the FREMP field effect on the tested radio fuse is mainly caused by the electric field coupling to the samples, which can lead to false action for electronic modules and result in mistaken explosion of executing-device. Keywords: FREMP; radiation field; radio fuse; radiation effects; mechanism
Radio fuses, based on micro-electronics technology, are looked as terminal efficiency multiplier of weapon systems. But they are liable to be interfered and damaged by strong electromagnetic field ~1-21. U.S. Army has put forward the general requirements for the electromagnetic environmental effect in weapon systematic whole life in 1997, and firstly referred to that high-power electromagnetic radiation effects to weapon system should be considered, such as HPM and UWB E31.So, one type of integrated circuit radio fuses are chosen as samples, then radiation effects of FREMP to radio fuses are studied, and energy coupling approach and effect mechanism of EMP to radio fuses are researched. The radio fuses under test are composed of high frequency module, low frequency module and detonation-executing circuit. Its main technical parameters include emitting frequency, demodulation DC voltage, working current and ignition sensitivity. To evaluate the storage security and working reliability of radio fuse under rigorous EMP environment, radiation effects are studied when the sample is radiated by FREMP in different conditions. The electromagnetic field generated by FREMP radiation equipment is vertical polarized, and radiates along horizontal direction in test space. Its rise/fall time is about 0.3ns, and pulse width is about 4ns.
EXPERIMENTAL METHOD AND PROCEDURE (1) Experimental place should be chosen firstly, and FREMP source is started up. Using TEK TDS540A digital oscilloscope and E-field receiving antenna, radiation wave is tested and E-field strength at experimental place is calculated. Then FREMP source is stopped. (2) Radio fuse, that is numbered and connected with projectile body, are placed in experimental place. To find the best coupling direction, radio fuse is placed in vertical direction (when EUT is parallel to field polarized direction), horizontal direction (when EUT is vertical to radiation direction and polarized direction), and parallel direction (when EUT is parallel to radiation direction), respectively. (3) After radio fuse is powered and worked normally, (radio fuse is not shielded and not powered when tested in preparing condition), electric igniter is connected with igniting line of the tested radio fuse. Then radio fuse is radiated by single FREMP for three times, by EMP series with 20Hz repeat frequency for twice, and by EMP series with 100Hz repeat frequency for twice, respectively. If electric igniter is * Project supported by the NSFC No. 50077024 and 50237040; Supported by foundation for university key teacher by ministry of education
249 ignited after radiation, experimental results should be registered, and experiment is stopped. After replacing radio fuse and electric igniter, experimental procedure above is repeated. The number of tested radio fuses is ten at every experimental place and in every condition. (4) When radiation is over, each technical parameter should be tested, and compared with that of before experiment, so that the rules for radio fuses performances affected by FREMP radiation are studied. The rules for working security of radio fuses influenced by FREMP radiation are researched by using of the ignition probabilities. (5) Replacing the experimental place and direction of radio fuse, other experiments and researches will be done. To eliminate the influence of power supply interfere to experimental results, storage battery is placed in shield box surrounded by absorbing materials, and microwave cable is adopted to connect the tested radio fuse with battery. RADIATION EFFECTS OF FREMP TO RADIO FUSE IN PREPARING CONDITION The radio fuse and experimental equipment were placed in E-field which strength is 26kV/m in vertical direction, and radio fuse was not powered, that is, fuse was in preparing condition. In radiation experiments, no electric igniter was ignited by FREMP radiation, and technical parameters hadn't obvious change compared with that of before radiation. Then according to experimental procedure, radio fuse and equipment were placed in horizontal and parallel directions and radiated by FREMP, respectively, and experimental result didn't change. E-field strength is increased to 55kV/m by degrees, and experiments were done repeatedly, and results still had no change. This shows that FREMP field has no obvious influence on performances and security of fuses in preparing condition. It also shows that coupling energy from FREMP is not intense enough to ignite the electric igniter, when radio fuse is not powered. So the reason that igniters are ignited by mistake in following experiments is mistaken action of detonationexecuting circuit of radio fuse. RADIATION EFFECTS OF FREMP TO RADIO FUSE IN WORKING CONDITION EMP field can affect circuit reliability of radio fuse, and cause circuit performance to be changed or even cause hard damage. It also can affect security of radio fuse and result in early explosion [41. To approximately observe the radiation effects of FREMP to radio fuses in working condition, a radio fuse was placed in E-field with strength of 40kV/m in vertical direction. The radio fuse was powered and radiated for once, and electric igniter was ignited. This result shows that the intensity of E-field is intense enough to affect working security of the fuse. The following experiments start at low-intensity field and increase intensity by degrees. When E-field strength is 10kV/m at experimental place, all fuses didn't mistaken explode, and their technical parameters had no obvious change. Increasing E-field strength to 12kV/m, one fuse exploded when it was placed in vertical direction and radiated by EMP cluster with 100Hz repeat frequency, and few fuses' parameters changed much. The main change is that ignition sensitivity fall obviously. No hard damage occurred. Table 1 shows the fuses that had some obvious radiation effects. In this table, '~' expresses ignition and is followed the radiation condition, and 'A'expresses change of parameters.(These symbols will be adopted in following tables.) Experiment results show that radiation effects are more obvious when fuse is placed in vertical direction because fuse is parallel with polarized direction of Efield, and radiation effects are weak when fuse is placed in horizontal direction, and all the 10 tested fuses changed little in this direction. Table 1 Radiation effects when fuse is in working condition, E=12kV/m Working Current/mA Demodulation Voltage/V Sensitivity/cm Placing Radiation Direction Before After Radiation Before After Radiation Before After Radiation Effect Vertical 45 43 4.0 4.3 23 20 4 100Hz Vertical 45 42 4.5 4.9 58 18 A Vertical 40 40 3.4 4.0 25 10 A Parallel 43 42 4.3 4.1 20 11 A
250 When E-field strength is increased to 16kV/m, 3 fuses exploded by mistake when fuse was placed in vertical direction, and explosion ratio reached 30%. When fuse was placed in parallel direction, one fuse exploded by single EMP radiation, and a few fuses' parameters had changed obviously. No fuse was damaged. Table 2 shows the fuses that had some obvious radiation effects in this condition. Table 2 Radiation effects when fuse is in working condition, E=I 6kV/m Working Current/mA Demodulation Voltage/V Placing Sensitivity/cm Radiation Direction Before After Radiation Before After Radiation Before After Radiation Effect ...... Vertical 40 39 4.6 4.3 31 45 4 single Vertical 40 40 3.5 3.8 16 24 4 100Hz Vertical 39 38 4.3 3.7 42 28 4 100Hz Vertical 42 41 4.1 4.1 11 24 A Parallel 39 40 4.3 4.6 45 40 4 single Parallel 40 41 3.8 4.0 24 11 A Horizontal 41 40 4.0 11 26 3.7 A ,,
When E-field strength is increased to 38kV/m, radio fuses exploded by FREMP radiation are shown in Table 3. Mistaken explosion ratio is 80% when fuse was placed in vertical direction, much higher than that of other directions. Working current and demodulation dc voltage of some fuses changed, and sensitivity changed much. No hard damage occurred. Table 3 Radiation effects when fuse is in working condition, E=38kV/m Working Current/mA Demodulation Voltage/V Sensitivity/cm Placing Radiation Direction Before After Radiation Before After Radiation Before After Radiation Effect Vertical 42 2.4 2.4 100 100 4 single 40 100 Vertical 40 42 2.4 2.9 40 4 single 2.4 2.2 28 44 4 single Vertical 40 42 5.6 5.4 4 single Vertical 41 38 17 39 2.2 2.1 33 34 4 single Vertical 41 >50 24 32 2.9 3.0 4 single Vertical 41 >50 21 33 4 single Vertical 42 5.0 5.5 43 3.2 3.4 54 100 4 100Hz Vertical 43 39 4 20Hz 45 100 2.0 2.4 Parallel 40 39 4 20Hz 2.5 2.8 27 100 Horizontal 39 38 32 45 4 20Hz 2.1 2.0 Horizontal 39 38
EFFECT MECHANISM OF FREMP FIELD TO RADIO FUSE EMP energy can couple in the electric igniter by circuit connected to igniter, and fuse will mistaken explode when coupling energy is higher than threshold energy of igniter. In another aspect, external radiation can affect electronic module of fuse and lead to detonation-executing circuit mistaken action, and capacitance for ignition discharges to igniter, so fuse explodes. The difference between the two reasons is that, in the former, the energy causes ignition is supplied by external radiation, while in the latter the energy comes from capacitance of fuse's ignition circuit. But the radiation result of FREMP to fuses in preparing condition shows that the first reason can be excluded. To further analyze the action mechanism of FREMP to radio fuse, damaged radio fuses were contrastively studied by FREMP radiation experiment. The objects are, 7 fuses with damaged highfrequency module whose high-frequency oscillating signal disappeared, and 10 fuses whose highfrequency oscillating signal is normal but ignition sensitivity is zero. These fuses were placed in vertical direction and radiated by E-field with strength of 25kV/m, 37kV/m and 53kV/m, respectively. The obvious radiation effects are shown in Table 4. In this table, the symbol ' ~ ' expresses no obvious radiation effect. The fuses with damaged high-frequency module had no obvious effect in E-field with strength of 25kV/m, and in the field with strength of 37kV/m and 53kV/m, the result is that 2 fuses
251 mistaken exploded and other parameters had no obvious change. In the experiment of the other 10 fuses, 2 fuses exploded by radiation of E-field with strength of 25kV/m and 37kV/m, respectively, and another fuse exploded by radiation of EMP cluster of 20Hz repeat frequency with strength of 53kV/m. In the three intensities of radiation, the fuses that had mistaken explosion had no change, that is, the fuses that exploded in low-intensity field can explode repeatedly in high-intensity field. Table 4 Radiation effects of damaged radio fuses in working condition Working Demodulation Current/mA Voltage/V 50 0 >100 48 2.3 44 7.1 20 3.1 ,,,,
,,
,
High-fre. Oscillation damaged damaged normal normal normal
Sensitivity /cm
0 0 0
25kV/m Effect O O O 4 single 4 single
37kV/m Effect 4 20Hz 4 single ~ 4 single 4 single
53kV/m Effect 4 20Hz 4 single 4 20Hz 4 single 4 single
The result shows that the fuses with damaged high-frequency module still can explode by FREMP radiation. It proves that the important reason of mistaken explosion is that FREMP field directly acts on low-frequency circuit of fuse. In the 3 fuses that had normal high-frequency oscillating signal but no ignition sehsitivity, lowfrequency signal-processing circuit of fuse that has 20mA working current is damaged, at least. This infers that FREMP field can directly act on detonation-executing circuit and cause fuse explosion. A conclusion can be gained from above that FREMP field can directly act on low-frequency module of fuses and cause detonation-executing circuit mistaken action, and result in radio fuses explosion. CONCLUSION By analysis of all experiment results, some conclusions can be drawn as follows: (1) When projectile body and its radio fuse are placed parallel to polarized direction of FREMP field, radiation effects are most obvious, and mistaken explosion probability is higher than that of other directions, that is, FREMP field acts on radio fuses by electric field coupling. (2) FREMP can't lead to ignition by direct coupling to electric igniter even though the E-field strength is as high as 55kV/m. The reason of mistaken explosion is that FREMP field acts on electronic module and causes detonation-executing circuit mistaken action and result in explosion. (3) The threshold of E-field strength that causes fuse mistaken explosion is 10kV/m. Even the Efield strength is so high as 40kV/m, FREMP radiation can't cause fuses hard damage. (4) FREMP field can affect ignition sensitivity, working current and demodulation dc voltage of fuse, but affect emitting frequency little. REFERENCE 1. Lv Xianzai, Threat of electronic counterwork environment to fuses and countermeasures, Modem fuse.(1997), 1_:56~62. 2. Du Hanqing, Anti-jamming principles of radio fuse, Enginery industry press, Beijing, China (1989). 3. MIL-STD-464 Electromagnetic environment effects requirements for system, 1997.03 4. Sun Yongwei, Study on effect mechanism for intense EMP to radio fuses [doctoral dissertation], Shijiazhuang Mechanical Engineering College, Shijiazhuang, China(2003)
252 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research of Evolvable Hardware Technology in Improving the Reliability of VLSI Working in Extreme EMI Environment* Huicong Wu, Shanghe Liu, Qiang Zhaol, Guoqing Wang 1 Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping W.R, Shijiazhuang, Hebei, 050003, P.R.China lDepartment of Computer, Shijiazhuang Mechanical Engineering College, 97 Heping W.R, Shijiazhuang, Hebei, 050003, P.R.China
Abstract :In extreme EMI environment, VLSI with delicate electronics is being continuously bombarded by harmful radiation. This can cause local damage of the circuit and result in failure of the entire system. In this paper we introduced a new technology (EHW) to improve the anti-jamming capability of the system. EHW is a kind of hardware that can change its architecture and behavior dynamically and autonomously. The introducing of EHW technology can improve the VLSI system's reliability and self-repaired capability in extreme EMI environment. Keywords: space radiation, EHW, FPTA, reconfigurable VLSI architectures.
Because of the advantages of VLSI such as smaller size, higher density, and lower cost, its popularity continues to grow in many applications including space, military, and avionics. Space is a hash environment with radiation and temperature fluctuations making electronic equipment perform worse than optimal, and VLSI with delicate electronics is being continuously bombarded by harmful radiation, and there will be many electrical discharge damages such as SEU. As the limits of VLSI technology are pushed toward sub-micron levels to achieve higher levels of integration, devices become more vulnerable to radiation-induced errors. These radiation-induced errors can lead to system failure, and this failure can't be repaired directly by human interference because of the limit of working condition. What is more, once a system in space fails, any physical repairs can be very costly. Therefore special emphasis has been put on reliability of VLSI working in extreme EMI environments. One of the goals of future electronics is to design radiation-immune electronic components [ 1]. In this paper, EHW was introduced to improve the anti-jamming capability of the electronic devices. EHW refers to the self-reconfiguration of hardware to complete systems that could adapt to changing environments. It investigates the use of genetic algorithms to repair faults on FPTAs, a reconfigurable hardware platform.The paper is organized as follows. Section II is an introduce of the EHW technology. Section IIIpresents the FPTA which will be selected as a reconfigurable hardware platform for an EHW system. Section IV introduces the main steps of evolutionary synthesis. Following these, some key issues of EHW are discussed in Section V. Finally, the conclusion can be found in Section VI.
EVOLVABLE HARDWARE TECHNOLOGY EHW refers to hardware that can change its architecture and behaviour dynamically and autonomously by interacting with its environment such as high temperature, electromagnetic radiation etc [2]. EHW consists of a combination of Evolutionary Computation (EC) and hardware design. An evolutionary algorithm is used to evolve a design specification for an electronic circuit. The algorithm has Project supportedby the NSFC No. 50077024and 50237040
253 a population of data structures encoding these design specifications. Each individual design specification is the chromosome. The fitness of the individual circuits is determined by their behaviour. The individual circuits with good fitness get selected for genetic operations more often than the ones with bad. Genetic Algorithm (GA) is the most commonly used evolutionary algorithm in EHW. It's main genetic operations are crossover and mutation. Crossover is recombining parts of two parent chromosomes to a new chromosome. The offspring is a new and hopefully better design specification for the electronic circuit. The mutation operation alters chromosomes in the population to ensure diversity for further evolution. EHW can bring two main benefits. First it can generate new functions (more precisely new hardware configurations can be synthesized to provide required functionality) when needed. Second it can help preserving existing functions, in conditions where the hardware is subject to faults, aging, temperature drifts, radiation, etc. EHW is particularly suitable for applications requiting changes in task requirements and in the environment or faults, through its ability to reconfigure the hardware structure autonomously.
EVOLVING PLATFORM The evolving platform is the physical media that the EHW system is intended to evolve circuit specifications for. The FPTA is proposed as a flexible, versatile platform for EHW experiments. The FPTA idea was introduced first in [3]. The FPTA cell is an array of transistors interconnected by programmable switches implemented with transistors, acting as simple Tgate switches. The status of the switches (On or Off) determines a circuit topology and consequently a specific response. Thus, the topology can be considered as a function of the switch states, and can be represented by a binary sequence, e.g., $11 ~L. ~ _ _ i _ _ _ i _ - _ ............~!~ .. 515 "1011... ," where by convention 1 implies a switch tumed On and 0 implies a switch tumed Off. The FPTA architecture allows the implementation of bigger circuits by cascading FPTA cells. To offer sufficient flexibility the module has all transistor terminals connected via switches to expansion Figure 1 Module of the FPTA cell terminals (except those connected to power or ground). Further issues related to chip expandability are treated in [3]. Figure 1 is an example of FPTA cell consisting of 8 transistors and 24 programmable switches, the transistors P1-P4 are PMOS and N5-N8 are NMOS, and the switch-based connections are in sufficient number to allow a majority of meaningful topologies for the given transistor arrangement, and yet less than the total number of possible connections. Programming the switches On and Off defines a circuit. .
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MAIN STEPS FOR THE EVOLUTIONARY SYNTHESIS OF ELECTRONIC CIRCUITS The idea behind evolvable hardware (EHW) is to employ a genetic search/optimization algorithm that operates in the space of all possible circuits and determines solution circuits that satisfy imposed specifications. Figure 2 illustrates the main steps in evolutionary synthesis of electronic circuits.
254
Evolutionary Algorithm Genetic search on a population of chromosomes
Chromosomes 10101011010 01110101010 ~'-
Conversion to a circuitdescription
:::::::::::::::::::::: : Extrinsic ../" / 'I ! I evolution /.- / ~ !| , 9 . J " ~,~..nolo ~ I I " f" ,I /'" J o;c~re~i'tsi] ,IA 1
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Response evaluation and I ~ fitness assessment
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Intrinsic evolution Figure 2 Main steps for the evolutionary synthesis of electronic circuits
First, a population of chromosomes is randomly generated to represent a pool of circuit architectures. The chromosomes are converted into control bit strings, which are downloaded onto the programmable hardware. In the particular case of the FPTA cell, the chromosome has 24 bits that determine the state of the 24 switches (Figure 1). Second, circuit responses are compared against specifications of a target response using the rms error as the fitness criterion. The individuals are ranked based on their fitness. Preparation for a new iteration loop involves generating a new population of individuals from the pool of the best individuals in the previous generation. Third, individuals are selected probabilistically based on their fitness. Some are taken as they were and some others are modified by genetic operators, such as chromosome crossover (random swapping of parts of their chromosomes) and mutation (random flipping of chromosome bits). The process is repeated for several generations, resulting in individuals with increasingly better fitness. The search process is usually stopped after a number of generations or when closeness to the target response has reached a sufficient degree. One or several solutions may be found among the individuals of the last generation. EHW can be both extrinsic and intrinsic [4]. In intrinsic EHW the fitness evaluation of each phenotype is done in real hardware, the hardware design specification is decoded and loaded into a reconfigurable hardware circuit. In extrinsic EHW, the behaviour of the design specification is simulated by doing the run of the evolutionary algorithm. The best design specification is the result of the evolution and can be tested in hardware. In addition to the procedure described above (called intrinsic EHW), Figure 2 also shows an alternate way to carry on evolutionary circuit synthesis, by using simulators instead of reconfigurable chips (called intrinsic EHW). In this particular case, the chromosome is mapped into a SPICE circuit model, which will be simulated and evaluated.. KEY TECHNOLOGY OF EHW At present, the evolutionary speed is the main bottleneck in the application of EHW. Trying to improve the coding efficiency, the operation and fitness evaluation speed, and cooperate with the reconfigurable hardware structure, which is more suitable for evolving, is the key technology of EHW [2]. Coding efficiency The chromosome can be encoded in two ways, indirectly and directly. The former adopts the abstract expression way, regarding the tree or the grammar as the chromosome, the evolution result needs to be
255 decode before reconfigure the circuit. The latter regards the configuration bit string of the hardware as the chromosome, the evolution result can be used in the hardware reconfiguration directly. Fitness evaluation function The evaluation based on circuit model and software emulation is called Extrinsic EHW, which is time consuming and need large quantity of operation work, but not restricted by experiment platform, therefore it is flexible and the evolving result has universality. The evaluation based on actual circuit configuration is called Intrinsic EHW. Whose evaluation speed is very fast, it is adopted extensively. Hardware platform The structure of the reconfiguable hardware influences the coding efficiency and the fitness evaluation speed directly. XC6200 series FPGA, which can receive random configuration bit string and can partly construct again, has been widely used. But these series of FPGA has already stopped being produced now, present programming devices all have the disadvantage of minute granularity, complexity structure and difficult to program, it is not the best choice for EHW. Therefore, a lot of researchers are looking for the coding and evaluation method, reconfiguable hardware structure that is suitable for EHW.
CONCLUSION This paper has studied the use of evolvable hardware to improving the reliability of VLSI working in extreme EMI environment. EHW can adjust its inside structure real-timely, in order to meet the inside condition (such partly fault) and external environment condition (function requiring or physical condition) change. FPTA was employed as a platform for evolution and GA was used as a searching and optimizing tool to evolve a design specification for an electronic circuit. The introducing of EHW technology can improve the VLSI system's reliability and self-repaired capability without human interference. It is especially applicable to the microelectronics devices working in extreme EMI environment.
REFERENCE 1. Niranjan, S. and Frenzel, J. F., A comparison of fault-tolerant state machine architecture for space-bome electronics, IEEE Trans. Reliability(1996), 45, 109-113 2.Xin Yao, Promises and Challenges of Evolvable Hardware, Proc. of the First Intemational Conference on Evolvable Systems: from Biology to Hardware, (1996), 7-8 3. Stoica, A., Toward evolvable hardware chips: Experiments with a programmable transistor array, 7th Int. Conf. Microelectronics for Neural, Fuzzy, and Bio-Inspired Systems: IEEE Computer Society Press, (1999) 4. Ricardo S., Zebulum, Marco Aurelio Pacheco, Evolvable System: From Biology to Hardware, First International Conference, ICES, (1996), 1259
256 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Experimental Study on ESD Damage to 54 Series of Gate Circuits* Haiguang Guo, Zhiliang Tan, Jie Yang Electrostatic and Electromagnetic Protection Research Institute, Mechanical Engineering College 97 Heping West Road, Shijiazhuang, Hebei, 050003,P.R.China Abstract: In order to study the damage effect of ESD on IC, taking 54 series of gate circuits are selected as experiment objects, the injection experiments are made based on ESD HBM. The damage voltage and the sensitive part of 54 series of gate circuits are discussed, and the damage law is initiatively studied through the experimental results. Keywords: ESD, damage, IC, experiment study
INTRODUCTION ESD has the characteristic of high voltage peak value, short duration and steep rise edge. It can destroy electronic systems strongly [ 1]. ESD immunity of electron systems attracts more and more attention along with application of IC. Therefore, it is very important to study the ESD damage effect on IC.
EXPERIMENTAL PRINCIPLE AND METHOD ESD HBM is injected to gate circuits directly using ESS-200AX ESD simulator. The experimental frame was shown in Figure 1. Computer
ESD simulator
d H H
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II~
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,
HY4080+Online test set of IC
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~
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Figure1 Experimentframe of ESD damage experiment The GND of the gate circuit is linked with the earth, and ESD simulator discharge on a pin of the gate circuit directly, so it forms a discharge loop. Since the gate circuit has many complete circuits and ends, and every complete circuit also has many elements and devices, so the vulnerability is also not identical with different injection end. It generally thinks that the input end and the output end of the integrated circuit can easily be damaged, and the power end is not sensitive [2]. So the injection end pairs include the power end to the earth, the input end to the earth and the output to the earth, in order to find out sensitive part of the gate circuit. Firstly, putting one of the gate circuits on the offiine test box of HY4080+ online test set of IC, and measuring the normal parameters (including time sequential chart and *Project supported by the NSFC No. 50077024 and 50237040
257 V ~ I curve) of the gate circuit and recording it. Then ESD injection experiments are carried out under a certain voltage. After discharge is completed, we test its parameters and compare them with normal ones. If compared result isn't out of tolerance, increasing the injection voltage (step length not exceeding the 5% of last injection voltage) continuously to test. The times of discharge on one gate circuit are less than 5. The samples of every kind of the gate circuits are more than 5. When sequential chart arises mistake or pin-to-pin V-I curve compared result is out of tolerance, gate circuit damage is presumed. If the V-I curves of a certain pin to other some pins are all out of tolerance, it shows that this pin is damaged. The standard that pin-to-pin V-I curve compared is out of tolerance is that the difference exceeds 10% between tested parameters and normal ones.
EXPERIMENT RESULT AND ANALYSIS Damage voltage is an important character of ESD immunity. The scope of minimum damage voltage of some gate circuits is shown in table 1. According to table 1, the damage voltage of 54 series of gate circuits is the highest one when the injection pin is power end. They are all between 20.0kV and 30.0 kV. The damage voltage of 54 series of gate circuits when the injection end is input end is lower than that of the power one, and they are all between 15.0kV and 20.0kV. And the damage voltage is the lowest when injection end is output one, and they are all between 8.5 kV and 13.5 kV. Table 1 The value of damage voltage of the gate circuit Injection end
Name of the gate circuit
Power end Input end Output end
Minimum damage voltage/kV Minimum damage voltage/kV Minimum damage voltage/kV
54LS00
54LS02
22.0---25.0 26.0-'~30.0 15.5~ 18.0 17.0~-20.0 8.5~9.0 10.0-~ 11.0
54LS04 23.0~-27.0 15.0-~ 17.5 9.5"--11.5
54LS06
54LS30
24.0~--28.0 24.0~--28.0 16.0"-~20.0 15.0~ 19.5 10.5---13.5 11.0~ 12.5
The situation of exceeding measured by online test set of IC is shown in Figure3. In Figure3, (a), (b)and(c) represent the compared results of the curves of 8-12, 8-11 and 8-10. In (a) and (b), the curve whose slope is close to 0 is pin-to-pin V ~ I curve of normal gate circuit, and the other is the curve after gate circuit damaged. In (c), the curve whose slope is close to 0 is the one after gate circuit damaged, and the other is pin-to-pin V ~ I curve of normal gate circuit. According to Figure3, we know that V ~ I curve of 8-12, 8-11 and 8-10 is all out of tolerance. It shows that pin 8 is damaged (54LS30 has 8 input pins and 1 output pin, and pin 8 is its output pin), and it also shows that its output end is sensitive to ESD. It is similar to other gate circuits.
Figure 3 Pin-to-pin V n I curve of 54LS30
Based on internal circuit structure of the gate circuit, there is bigger capacitor between the power and the GND ends. So the power end of the gate circuit has stronger anti-static ability [3,4]. There is Schottky-barrier diode between the input and the GND ends, and there is Schottky-barrier dynatron between the output and the GND ends. The structural characteristic of Schottky-barrier transistor is that it has shallow PN junction, and mental can infiltrate PN junction, so it is sensitive to ESD. Therefore, the input end and the output end of the gate circuit are sensitive to ESD [4,5].
258
CONCLUSIONS According to the experiments, there is little difference in the damage voltages for different gate circuits when injection end is the same, but there is great difference when ESD injects into a same gate circuit from the input end, the output end and the power end. The damage voltage is the highest that injects from the power end, and the one injected from the input end is a little lower than that injected from the power end, and the damage voltage that is injected from the output end is the lowested.
REFERENCES 1. Minsheng Hou and Minghui Xu, Irradiation Effect Experiments of ESD EMP on Interface Circuit in A Certain Radar, Electronic Engineer (2003) 5 59-62 2. Zuwu Lai. Radiation Hardening ElectronicsmRadiation Effects and Hardening Techniques, Beijing: Publishing House of National Industry (1998) 214-215 3. Zhengyong Zhu, Semiconductor Integrated Circuit, 13eijing: Tsinghua University Publishing Press (2002) 71-79 4. Baoming Zhang and Wendi Lin. Electrostatic Protection Technology Hand Book, Beijing: Publishing House of Electronics Industry (2000) 118-120 5. Bihua Zhou, EMP and EMP Protection, Beijing: Publishing House of National Industry (2003) 143-145
259 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Experimental
study on ESD
sensitivity
of 8212 chips
Jie Yang, Zhiliang Tan, Haiguang Guo Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97Heping West Road, Shijiazhuang, Hebei, 050003,P.R.China Abstract: In the experiment, the Human Body Model (HBM) of electrostatic discharge (ESD) is used to simulate the real ESD events. The minimum damage voltage of the chip is found, and the most sensitive port is the controlend in 8212. And the row order of ESD sensitivity of control ends in 8212 has been carried out. Keyword: 8212 chips, minimum damage voltage, sensitive port
INTRODUCTION Integrated circuits (ICs) are the core of microelectronics technology. Those are the grain of electronic industry [1]. The output value of IC takes more than 80% in microelectronics industrial output. IC has been developed to ultra-large-scale, very large-scale and deep sub-micron ( 0.25 g m) precision. Millions of transistors can be integrated on one chip, even the entire electronic system [2]. Along with the demand and development of microelectronics technology, ESD is become a more and more serious problem on IC. It is particularly important to investigate the ESD susceptibility in IC [3]. 8212 chip is a kind of interface circuit which is regularly used in IC. This paper discusses the ESD susceptibility of 8212 chips, its antistatic ability has been tested, and the preliminary conclusion has been DSll [ 1 I Vcc obtained. At the same time, each pin in 8212 chip 23 I INT I queues up the susceptibility order on the foundation 22 DI1 I 13 I DI8 of studying its damage voltage. The structure of 8212 21 DOll [ 4 i DO8 chip and its block diagram of the effect test are DI2 I [ 5 20 I DI7 shown as Fig. 1. 19 DO21 [ 6 ! DO7 8212 DI31 [ 7 18 ! DI6 I EXPERIMENTAL PRINCIPLE AND METHOD DO31 I 8 17 I DO6 I 16 I 9 DI4 I !I l 1 DI5 The direct injection method is used in this experiment 1o 15 I DO5 DO4 1 I [4]. ESD pulse is injected into chips from each pin STBI I 11 14 1 CLR except ground end. ESD HBM (100pF, 1500[2) has GNDJ I 12 13 ! I DS2 been adopted [5]. The test has been carried out by I. i using the on-line testing instrument of IC and the offline testing box to check up the V-I curve between On-line Off-line each two pins. If the V-I curve is out of tolerance, the ESD testing testing box 8212 chip could be confirmed that it has been damaged. Simulator ..._.r instrument The V-I curve is shown by personal computer, and test results are recorded in it, too. Fig. 1 The structure of 8212 chip and block Because of individual differentia in 8212 pins, diagram of the effect test the V-I curve of each chip is tested and recorded before injecting voltage into it. It offers the basis of
24 I
Project supported by the NSFC No. 50077024 and 50237040
26O comparison to judge whether the V-I curve has changed or not after discharge. Then every time after ESD injection the chip is inserted in the off-line testing box, and tested again. Compared with the initial characteristics before the fist injection, if the V-I curve is not out of tolerance, the chip is injected again with the stepped voltage. What needs to be explained especially is that the total of the V-I curve, which is tested by the on-line testing instrument of IC, depends on the total number of the chip pins. There are 24 pins in a 8212 chip, so it gets (23+1)x23/2=276 V-I curves while testing. When carrying on functional test, the signal source in sine wave, 2000 Hz scanning frequency, and single folder continuous test mode have been set, and error option is moderate (the limit of tolerance is 10%). Through comparison, if the curve is not out of tolerance, the two groups of V-I curves, which are tested before and after injection, are superposed together. If some V-I curves are out of tolerance, the testing instrument may show both of the curves between the same two pins in one picture before and after injection. Fig.2 is the V-I curve between 12-14 pins in 8212 chip before injecting. Fig.3 is the compared result after the No. 1 chip has been injected with 1700V on the input end: an out of tolerance curve 12-14 is displayed. In Fig.3, when the voltage (abscissa axis) is over 5V, the slope of current curve at that point is not zero again. This case shows that this chip is damaged between 12-14 pins. The rest may be deduced by analogy.
Fig.2 The V-I curve between 12-14 pins in 8212 chip before ESD injection
Fig.3 Compared result of No. 1 8212 chip V-I curve after ESD injection
DAMAGE VOLTAGE OF 8212 CHIPS In this experiment the pins of 8212 chips are divided into three groups: Vcc, input pins and output pins combination. Input pins combination includes pins 1, 2, 3, 5, 7, 9, 11, 13, 14, 16, 18, 20, 22 and 23, which include all the data-input ends and control ends. Output pins combination includes pins 4, 6, 8, 10, 15, 17, 19 and 21, and those are data-output ends. According to experience, the damage voltage of Vcc -G is the highest. Different chip has a little different relationship on the damage voltage between input combination to ground (I-G) and output combination to ground (O-G). Therefore the injection order is Vcc-G, I-G and O-G. Each pin is stressed with 1000V by single ESD pulse. When a pin is injected, the other pins are opened. By using the on-line testing instrument of IC, the V-I curve is scanned and compared with the initial status while one combination has already been injected. If not damaged, discharge is continued on each combination by stepping voltage until damaged. 8 chips are selected in this test. Test data is specified in Table 1. The following results can be found out: For this kind of chip, the minimum damage voltage is 1450V (see Table 2). The source end Vcc is most non-sensitive to ESD. Usually 8212 chips will not be destroyed when injected on its source end [6]. Input pins combination is most sensitive to ESD. The susceptibility of output pins combination is a little higher than source end, but its minimum damage voltage is 10 times of that of input pins combination.
261
Table.1 Discharge voltage and damage conditions Pin No. 1
Injected port Vcc-G Vcc-G O-G
3
6 7 8
Vcc-G O-G Vcc-G O-G I-G O-G I-G I-G I-G I-G
Discharge voltage (kV) 2.00-~30.0,stepped by 1.00kV 30.0 20.0~22.0, 26.0~-27.0, stepped by 1.00kV 22.5~25.0, stepped by 0.50kV 30.0 25.0~26.5, stepped by 0.50kV 1.00~2.00, stepped by 0.50kV 1.30~ 1.70, stepped by 1.00kV 1.40~ 1.70, stepped by 1.00kV 1.40-'~ 1.70, stepped by 1.00kV 1.40,1.45
Damaged pins None None 15 None Output combination None None 12-14 None 14 3, output-22 14 14
Table.2 The damage voltage of each combination Injected combination Source pins Output pins Input pins
The maximum undamaged voltage (kV) 30.0 26.0
The minimum damage voltage (kV) None 26.5
1.40
1.45
STUDY ON THE SENSITIVE PORT IN 8212 CHIPS Above experimental data in Table.2 shows the most sensitive port is input pins combination (including control ends and data-input ends) to ground. Another two 8212 chips are selected. Control ends (1, 2, 11, 13, 14 and 23) and data-input ends (3, 5, 7, 9, 16, 18, 20 and 22) are respectively discharged. No.9 chip is injected on data-input ends, and No. 10 chip is on control ends. The discharge voltage is 1400V, and step length is 50V. Experimental results are shown in Table.3. Table.3 Damage condition while each pin is injected Chip No.
Discharge voltage (kV) 1.55 1.60 1.40 1.45
10
1.50 1.60 4.30 4.40
Injected ends Data-input ends Data-input ends Controlling ends Controlling ends Control ends except pin 14 Control ends except pins 13,14 Control ends except pins 11,13,14 Control ends except pins 2,11,13,14
Damaged pins None Data-input ends None 12-14 13 11 2 1
According to these experimental results in Table.3, the most easily damaged port is the pin of zero clearing (14). The row order of ESD sensitivity of the input pins combination in 8212 is" 14, 13, 11 (datainput end is coordinated), 2, 1, and 23 from high to low. Making reference to above experimental results (In Table.1 it can be found that the majority of damaged pin is 14. Damage voltage of control ends is minimum, and it is only 1450V.), we can affirm that the control end is most sensitive, but among all pins the zero-clearing end is the most sensitive pin.
262
CONCLUSIONS According to the experimental results of the ten 8212 chips, it can be confirmed that based on the ESD HBM the minimum damage voltage of 8212 chip is 1450 V. The most sensitive combination is the input pins. The most sensitive port is the control end to ground. The most sensitive pin is zero-cleating pin (14). Source end of 8212 chips is the most non-sensitive. Data-output ends take second place, and its maximum undamaged voltage reaches 26 kV. The damage voltage of both of them is ten times higher than datainput ends and control ends. Through above simple experiments, the susceptibility order of control ends may be (from high to low): 14, 13, 11, 2, 1, and 23.
REFERENCES [1] Lu Jianxia, Wang xiaopin, Su zhou. The Development Tendency and Prospect of Microelectronic Technology. Microprocessors, Feb., 1999. [2] Xia Hong. Electronic components invalid analysis and application. Feb., 1998. [3] Liu Shanghe, Tan Wei. Advance in Electrostatic Protection. Physics and High New Technology (1999) 304-307. [4] GB/T 17626.2-1998, Electromagnetic Compatibility Testing and Measurement Techniques Electrostatic Discharge Immunity Test. [5] IEC/PAS 62179. 2000.8,Electrostatic Discharge Sensitivity Testing Human Body Model. [6] Wang weimin, Sun yuhua. The Charater of Damage Caused by the ESD and the Protective Project. Electrical Measurement & Instrumenlation(2003).
263 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The ESD Effect Experiment of the Integrated DC-DC Transformer* Jie Yang, Zhancheng Wu, Shiliang Yang Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003,P.R.China
Abstract: Selected components were submitted to ESD-HBM, HMM and MM pulses. The ESD effect of the DC-DC transformer has been tested in the experiment. It is found that 1000V ESD could not make the component transform into catastrophic failures. A higher pulse is produced in the instantaneous output voltage/current with the ESD stress. By analyzing the data of experiment, the relationship between discharge voltage and the change of instantaneous output voltage/current of the transformer has been found. As a result, the anti-jamming property of this device needs further improvement. Keyword: integrated DC-DC transformer, discharge voltage, instantaneous output voltage/current
Electrostatic discharge (ESD) is the major factor in making electronic product invalid by getting the over electrical stress (EOS). It will cause electronic devices and circuit systems to form a kind of nonreversible mischief or make electronic products work abnormally [1 ]. Static electricity has become the most serious trouble in now electronic industry. Electrostatic control does not allow to be slacked [2]. This experiment studies the ESD effect of the certain type integrated DC-DC source module. Through data analysis the influence of ESD to this DC-DC transformer working state has been found, and the preliminary conclusions of ESD susceptibility have been confirmed.
EXPERIMENT SCHEME A certain type integrated DC-DC transformer is fixed Power supply] on a mold. Power is supplied continuously with the DC power supply TRADEX MPS302. This device tD I keeps in working state. Digital storage oscillograph I Load TDS680B is used to monitor the instantaneous output I current and voltage, while ESD pulse is injected. The e0 Ii Current probe small universal meter M890C is used to carry out the functional test of this device. When TRADEX MP302 offers 12.5V constant input voltage, under normal state, the output voltage of this DC-DC transformer should be 5 + 0. IV. Fig.1 the block schematic diagramof test circuit This experiment adopts three models" HBM (100pF, 1500f~) , HMM (150pF, 330f~) and MM (200pF, 0f~).The direct injection method is used through ESS-200 AX ESD simulator. [3] Any two of the three pins: input anode, input cathode and source, make pairs. All the six pairs of pins are respectively injected. The current probe uses Tek P6041 Project supportedby the NSFC No. 50077024 and 50237040
264 ( 5mV/mA, 25kHz-lGHz, matched resistance 5012). Tek P8139A is used as the voltage probe. The load is 1312. Test circuit is shown as Fig. 1.
EXPERIMENTAL RESULTS Tek Run: 250MS/s
Sample
[--T .....................................................................] The Influence of ESD Injection on Instantaneous Output Voltage/Current Before experiments, the modular carries out . . . . "; ....";i." .... ; .... ; .... ; .... i ....... C1 Pk-Pk 4.0g V functional tests. While the ESD pulse is injected, the output voltage and current waveform of the DC-DC C2 Pk-Pk iw, ei . . . . §. . . . . . 54.8 V source modular is being tested online. After discharge, the functional test has been carried out again to C1 Max ;'"~"+'"'~"+i 1.54 V definite the modular whether it is damaged or not. Experiment starts from 200V, and steps by 200V IB C2 Max until 1000V. Each discharge is single. 34.8 V By researching on the experimental data, it can be discovered that until 1000V the output voltage value that the small universal meter M890C shows 1.00VQ CI12 20.0V M 200rls Chl ./" 20mV 18 Dec 2003 11:22:39 keeps 4.95 + 0.01V. It meets the design requirement of this source modular. The phenomena can be Picture. 1 The instantaneous output voltage/current waveform explained that the device will not be caused perpetual damage by ESD. However, on the real time inspection by the oscillograph, a great pulse in the instantaneous output voltage and current has been discovered in the instant of simulator discharging. Picture. 1 is one of the waveforms. In that picture, C 1 is the current waveform, and C2 is the voltage waveform. Since what the oscillograph shows is voltage, the experimental data must be made conversion in recording the current data. The design standard of the current probe Tek P604 is 5mV/mA. So the current value is one fifths of the C1 value. Test data shows as table. 1 (do not consider the injected ports). .,,.
J
. . . . . . . . . . . . . . . . . . . . . .
.~. ~.
9
.
Table. 1 The instantaneous output voltage/current value while discharging without considering the injected pins Model Voltage(V) No discharge 200V 400V HBM 600V 800V 1000V 200V 400V HMM 600V 800V 1000V 200V 400V MM 600V 800V 1000V
Ip-p (output) 5mA 3 a.2mA 48mA 82.4mA 156mA 184mA 74.8mA 120mA 230mA 290mA 368mA 127.2mA 274mA 442mA 628mA 816mA
Imax (output) 2.8mA 13.6mA 23.2mA 41.6mA 80mA 94mA 19.2mA 25.6mA 54mA 60mA 92mA 39.2mA 100mA 150mA 224mA 308mA
Vp-p (output) 220mV 3.8V 4.96V 9.00V 16.1V 19.6V 7.32V 8.30V 16.0V 26.5V 42.0V 10.4V 17.9V 28.4V 36.0V 54.8V
Vmax (output) 5.06V 7.36V 7.80V 10.32V 14.7V 16.2V 8.28V 9.60V 14.9V 19.6V 22.6V 11.2V 12.6V 19.0V 20.8V 34.8V
,,
In Table.l, the peak-peak value equals to the maximum value minus the minimum value of the waveform. For the output current, because the minimum value is negative, the peak-peak value is larger than the maximum value. The more wide the amplitude is, the more the peak-peak value differs with the
265 maximum value. For the output voltage, when the amplitude is narrow, its minimum voltage is positive, so its peak-peak value is smaller than its maximum value; when the amplitude reaches a certain value, its minimum voltage is negative, then at that time the peak-peak value is larger than the maximum value like the output current. From above experimental data, it can be found that probably because of the problem on the circuit in the source modular, the instantaneous output voltage and current waveforms have already had some swings without injecting ESD, but the amplitude is small. No matter under which kind of models, as injecting voltage goes up, the amplitude of instantaneous output current/voltage increases gradually. In the same discharge voltage level, anti-jamming ability under HBM, HMM and MM are weakened in turn. It is most serious that the peak-peak current value of instantaneous output voltage can reach 816mA under MM model with the discharge voltage of 1000V. The Influence of ESD on Different Ports The ESD simulator is used to discharge on three ports: input+, input- and ground end (the shell). Any two of the three pins are selected. It can make 6 combinations (input+-~input-, input- ~ input+, input+'~ ground, ground-~input+, input- ~- ground and ground~-input-). While discharge, positive voltage is injected into input+ -'~ input-, input+ ~ ground, and input- -~-ground. On the other hand, negative voltage is injected into input+~input-,input+-~-ground, and input-~ground to simulate the injection into input -'~input+, ground~input+, and ground~input-. Under the same voltage level, by researching the influence of discharging on different ports, it will be found that no matter which model is being under, the law is basically consistent. Each combination is injected three times in the same voltage level. Data are recorded after each time. 3 groups data are got. Their average is taken down as the numerical value of the pulse voltage and current. Considering the precision of the oscillograph and the repeatability of the ESD simulator, the instantaneous voltage/current value under 800V are selected to be compared. Test data shows as following table.2 (under 800 V injecting voltage). It can reach as: 1) Under the same discharge voltage, the interference under MM is much more serious than under the other two models. 2) Usually, the interference produced by reversal injecting voltage is more serious. Table.2 The instantaneous output voltage/current value while discharge voltage is 800V Model
Voltage(V) input+~input. input- ~- input+ . HBM input+'~ground ....ground's'input+ input- "~ ground ' , ground'-s input- , input+~inputinput- "~ input+ , HMM ' i n p u t + ~ g r o u n d ' ground~-input+ input- ~ ground ground~inputinput+~input1 input-~-input+ input+~ground MM ground~input+ t input- ~ ground ground~-input- ,. |
|
i
!
i
!
!
!
Ip-p 63.6mA 65.]mA . i33.3mA 134.7mA [ 162.0mA ' 168.0mA ,,
Vp-p 11.8V ]3.0V 17.2V 18.8V 16'3V 17.3V 245.3mA ~ 22.2V 256.0mA 25.4V |
252.0mA
23.7V
281.3mA 28.8V 285.3mA 22.8V 320.0mA 29.7V 1.128A , 27.7V 1.181A i 32.3V 0.58271' 30.8V 0.6507A 32.1V 0.5027A 28.9V 0.6160A , 33.5V I
!
266 Susceptibility Rank of the DC-DC Transformer with HBM Passing above experiment, functional fault is not discovered by detections of this device. So the damage voltage test is carried out with HBM [4]. In this experiment the device is in power-off state, and discharged with no load. Single injection is adopted, and injected pins are input anode, input cathode, GND (the shell), output anode and cathode. Every two of those 5 pins make pairs to form 20 combinations. Under every testing voltage level, these combinations are respectively injected. Discharge voltage begins from 1000V, and step length is 500V. Functional test is carried out every time after discharging on all the combinations. The experiment is kept on if the device is not invalid. The experiment shows that up to 8000V ESD voltage, the modular is not damaged. It can be confirmed that the DC-DC source modular will not be caused hard-damage by ESD, and this device is non-sensitive to ESD.
CONCLUSIONS Through experiments, it can be discovered that: The DC-DC source modular has very weak isolation ability to ESD pulse. While 1000V ESD pulse is injected into GND and output cathode, its output current p-p value can reach 0.6160A, and the output voltage p-p value reaches 33.5 V. It is much higher than its normal value. So we know that ESD pulse can make the DC-DC source modular into great interference. But in the experiment this device is not in catastrophic failures while injected 8000V ESD. The antistatic hard-damage ability of this kind of devices is much strong. Usual this modular will not be made to occur perpetual damage by ESD. The anti-jamming ability of this device needs to be improved in the future.
REFERENCES [ 1] Wang weimin, Sun yuhua. The Charater of Damage Caused by the ESD and the Protective Project. Electrical Measurement & Instrumenlation(2003). [2] Xia Hong. Electronic components invalid analysis and application. 1998. [3] GB/T 17626.2-1998, Electromagnetic Compatibility Testing and Measurement Techniques Electrostatic Discharge Immunity Test. [4] IEC/PAS 62179. 2000.8,Electrostatic Discharge Sensitivity Testing Human Body Model.
267 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Analysis and measures of the Thunder Stroke Accident of the Hefeng Gas Station in Gaozhou Li Zhaodong Maoming lightning devices security test center, Guangdong Province, 525000, China
Abstract: The paper analyses in detail main causes that the Hefeng gas station was stroken by lightning, and provides some protection ideas. Keywords" Lightning Stroke; Down-conductor system; Equipotential bonding THE GAS STATION CONSTrIUTES ESSENTIALLY (Catch sight of the plan of Genzi gas station) The structure of the gas station The tank farm is at the west of the station, closing to the gas station. There are three storage tanks of 20m 3 inner the tank farm .It is four metres high to the breathing of the storage tank, but there is no firearm. Every storage tank has only one respected grounding. It is four metres high to the surface of the earth. The breastwork in oil storage is 24cm-thick brick wall. There are four reinforcing bar beton posts in the middle, and one ring of reinforcing bar beton beam on the top of the post. The surface of oil storage peak is beyond 1.0 meter to the surface of the earth. There is a reinforcing bar beton plank prefabricated on the top. The canopy is in the made of the reinforcing bar beton. There are three topping-up engines in the canopy, one 13.0 ms tall lightning rod is fixed in the peak, No thunder evading brings .An iron shelf covers between canopy and the living quarters. But no grounding. Lightning protecting facilities states On the basis of on-site measurement and the firsthand examination datum of GaoZhou lightning devices security test center, it is informed that the gas station is concealing the thunderbolt danger: 1) Power source string and the telephone line have not any measures, for example shielding, to against the lightning surge on incoming services. 2) The lightning rod and thunder evading brings is not enough, and the protection limitation is not defected. 3) Iron sheet roofing is not grounding. 4) It is not underway equipotential bounding between Lightning rod and composition reinforcing bar, and it is not underway equipotential bounding between lightning protecting grounding and the static electricity grounding yet. 5) Secure distance defect. Thunderbolt investigation At 4:15 on the moming of August 26th, 2000, the gas station was suffered the thunderbolt and fired. First of all, the tank farm district was on fire, and then the tanker is on fire. Three storage tanks and Tank farm peak were destroyed by fire. The Prefabricating plank bakes snapped, the breathing valve toppled, three tankers and one batch of else subsets were destroyed by fire moreover. Invariably economically decrease brief 20 thousand yuan of RMB. THE ANALYSIS OF THE THUNDERBOLT MISHAP On the basis of the on-site explore of the thunderbolt field and the mishap analyzing, When the lighting is coming, The lightning current goes to the ground by the way of the down conductor system. Rod happens
268 the thunder and lightning to join when going out of the way, The thunder and lightning runs along the down lead to adjust excretes when runing, The thunder and lightning runs to be living to part from 1 m that building composition reinforcing bar comes into being striking back the discharge spark, The petrol that the igniter electrode tank farm accumulated outside the pot catches fire. Analysis: When the lightning rod is struck by lightning, the current having ran the down conductor system is all of the lightning current, On the basis of formula U-- UR q- U L - IRi + L0 ~ hx
9
di
dt The lightning protecting unit high hx part potential may be requested out on the ground. At the same time also may be on the basis of formula di L o xh x x-S a l - ~I R i Jr
ER
dt
EL
Requests out the down lead parts from the secure distance of the building either metal matter that possesses the touch against such by safeguards of 1 m Chuju. Sa~-- Air middle distance. U - The lightning protecting unit high hx part potential on the ground. UR-- IR drop the when thunder and lightning has run the lightning protecting unit on the earthing device (KV). U L - The inductance pressure when thunder and lightning has run the lightning protecting unit on the down lead is drop (KV). R i " - E a r t h i n g device shock ground resistance O. d--L-- The thunder and lightning runs the gradient (KA/~t s). d, I - - The thunder and lightning runs the amplitude value (KA). E R ~ Resistance voltage drop air breakdown strength (KV/m) Geing such equals to 500 KV/M. EL-- Inductance voltage drop air breakdown strength KV/m. Foundation B u i l d i n g l i g h t n i n g p r o t e c t i n g d e s i g n c r i t e r i a Annex six attached list 6.1 ~ 6 . 3 . It is knowable that the attached list 6.3 reaches the picture I - 150KA R; - 3.5f~ L o - 1.5ld-1 / w h x - 1.0w di I 150 - - = - - = - - = 15KA/#s
d,
T1
10
,
EL -
600(1 + i ) - 600(1 +
E R - 5OOKV / m
1
- 660KV / m
The l m part potential of down lead is living on the ground is" di U - U R + U L - IR; + L o x h x x - d,
=150x3.5+l.5xl.0x15 = 547.5(KV) The 1m part of down lead is living on the ground adjust the striking back radius in vicinity being: dg L o XhxX-d~ /R i Sa I = =
ER
150•
+ EL +
1.5xl.0x15.0
660 500 -- 1.084 Beton breakdown strength is as against air breakdown strength.
269 Through calculation knowable, All metal conductors that on the ground 1 down lead of Mi Chu to such unit is living inner place 1.084 meters of limits wholly probably come into being the thunder and lightning and run to strike back, Through the thunderbolt field knowably, The distance between down lead together with the tank farm peak girth reinforcing bar is merely make an appointment with 5cm, The category is stroked back in the limit. THE STEP OUGHT TO BE ADJUST Equipotential bounding (All be getting near) By in the way of 40 between storage tank together with the storage tank 40 X 40, The galvanizing steel band joins reciprocally ; To the breathing valve, the petroleum pipeline is smaller than 5 flanges that the bolt joins in the way of 6 mm 2. The copper rush pith string is step to join. Be smaller than 100 to the clean distance inner place the petroleum pipeline road mmThe petroleum pipeline in the way of the metal string steps and joins. Lightning protecting grounding, Static electricity grounding, Electric grounding by means of the level terrestrial pole joins into employ the terrestrial pole in all. Iron sheet house metal shelf together with arrester equipment, the lightning-protecting unit joins against the metal matter inner place the building. General, Join and joins all metal matter and metal pipes and power lines inner place tank farm district and the topping-up awning against the lightning protecting unit. Equipotential bounding queen, Constitutes one and so on the potential part of the body, Remove potential difference, No potential difference does not there is not the striking back discharge. Grounding Grounding is leaved each other in two stops in the storage tank. Breathing valve by self grounding, Oil engine grounding. Bridging Original lightning rod down lead is living and joins the terrestrial pole away from the tank farm along 2 m along the iron sheet roofing, and adds a down lead. On the basis of the bridging rule, The per thunder and lightning that the down lead was pulled through runs in the interest of the 1/2 that complete thunder and lightning runs, In immediate future So abating the thunder and lightning enormously runs to strike back intensity. Shield Till lubricates the engine reaches else installations to be put on the steel tube and goes into with covering up in the way of the electricity power source string through the distribution house. CONCLUSION At the end of 2000, the peaceful and rich chief of gas station of Gaozhou source reconstructed the gas station after demolishing it, Being living in the reconstruction scheme accepts the lightning protecting that I propose to design the implementation scheme, In case picture, Do business safely much 2 years current, The directions scheme is feasible. REFERENCE 1. Buildinglightning protecting design criteria (GB50057--94) 2. Mineral oil together with mineral oil facilities thunder and lightning security norms (GB 15599--1995) 3. Design criteria of small-size mineral oil storehouse and motor vehicle gas station (Choose)(GB50156--92)
270 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on Electro-magnetic Shielded Packing Material Wang Wanlu, Liang Lihai, Yang Jianming, Yuan Zhongfu Jindong Chemical Group, Shanxi, CHINA, 045000
Abstract: The electro-magnetic environment in the modem high-tech war causes serious effect to the weapons & equipments. Upon analyzing of a.m. environment, the present paper mainly deals with the functioning principles, process, performance inspection and applications of the three electromagnetic shielded packing materials from our company. Key words: Electro-magnetic (EM) radiation, electro-magnetic shield, heat sealing, flexibility, fabric, packing material
INTRODUCTION In the modem high-tech war of sextuple space coveting ocean, ground, air, space, electro-magnetism and information, the electric technology has witnessed more applications in the weapons and equipments, greatly enhancing their automation, informatization, intelligence, integration and microminiaturization. "The impact of this technical progress is no less than that of the atom bomb in the forties of last century", as remarked by some authoritative persons from the Army. Following the rapid development and more application of the modem detection and control technologies, including radar, IR, laser and millimeter-wave in the weapons and equipments, the modem military radiation equipment such as radar, communication and navigation systems are characterized with increased power, broader frequency spectrum and more application. The military applications of the neutron bomb, HPM, VWB, EMB, NEMP and other equipments have improved the modem war with high-technology. Due to the severe electro-magnetic (EM) environment in the battlefield, the electronic components and devices within the equipments can be damaged at any case, causing serious consequences. Therefore, study and develop the multi-function protective packing materials, the relevant technical process are of great importance to improve their combat effectiveness and survivability of the weapons and equipments. Based on development of various materials of photo-chemical, concealed, conductive, and electrostatic proof compound/buffer, a comprehensive study on protective packing is badly needed, focusing on longer sealing storage, outdoor sealing storage, floating on the sea, air-drop, camouflage and other aspects. The attenuation ability of EM interference is a major technical datum of EM radiation-proof packing material, and is the most important topic in the current study. The comprehensive and in-depth study on the said packing material has been made in USA, Japan and other developed countries, and considerable results have been achieved. The said study started rather late in China, and there exists big gap as compared with the developed countries of above-mentioned. There have been stricter requirements to the performances of the EM shield following the technical progress in the field of weapons and equipments in recent years. Our company has involved in the study of EM shielded packing materials of compound high-molecular, heat-sealing, flexible and fabrics for the last ten years, and it has enjoyed wide application. COMPOUND HIGH-MOLECuLAR EM SHIELDED PACKING MATERIAL The compound high-molecular EM shielded material refers to the high-molecular plastic material with the property of EM shield after physical modification. Normally, conductive materials such as carbon black,
271 graphite powder/chips, metal powder and metal fiber are mixed with high-molecular material of polyolefm in a mixer, then blending, plasticizing, extruding and granulating are made in a twin-screw rod extruder, and furthermore, the said material is molded and shaped into the finished product. The fabric of stainless steel can be regarded as an EM wave absorbent in a certain degree. This is because that metal powder or thin wires can be served as the absorbent for the mono-layer EM-absorbing material besides the normal conductive carbon black or graphite. In Reference 6, a mono-layer absorbent is introduced, a solid adhesive with dielectric constant of about 1 is added with the EM-absorbing chaff (thin wire), and the incident wave can be weakened by the resistant consumption by the said thin wire. In current process, a certain percentage of metal fiber and other conductive medium are added into the polyolef'm, then subject to mixing, extruding, granulating before molding & shaping. As a conductive additive, due to the poor combination between the metal and polyolefin, the metal fiber is not well distributed in the material, and the length-diameter ratio is decreased with easily broken metal fiber. To ensure the large ratio as aforementioned, our process of compounding, extruding and granulating has improved constantly, the metal fiber is added at the spot of 3D before the discharging outlet, so as to avoid the high sheafing section of the equipment, and the material can be homogenized under enough pressure. Good results have been achieved for the EM shielding in many tests, refer Fig. 1, shielding reaches 77.6 dB within the range of 1 Fi~.l GHz'~ 10 GHz.
HEAT-SEALING, FLEXIBLE, ELECTRO-STATIC-PROOF, EM RADIATION-PROOF PACKING MATERIAL The present material is of multi-layer laminated material. According to the electro-magnetic theory and the principle of interaction between the material and EM wave, study the lamination rule, develop the lamination process with various material, and the packing material thus produced can enjoy good performances of absorbing & weakening of the EM wave. The polymer layer of conductive modified has higher tangent angle of power consumption, and the EM wave and radiation are weakened and absorbed by electronic, molecular or crosssection polarization, or by magnetic stagnant consumption, domain wall resonance and natural resonance consumption and other magnetic polarization system. With lamination of several different layers of conductive material, a laminated material of higher eddy current consumption is obtained, thus improving its absorption of EM wave in higher frequency band. Fig. 2 shows the attenuation curve of EM interference of the said packing material, of which the maximum shielding reaches 78.7 dB ng~ within the range of 1 GHz-~ 10 GHz.
STUDY ON EM RADIATION-PROOF FABRICS The EM radiation-proof fabrics refers to the one into which a certain percentage of conductive fiber is added, such as fibers of carbon, silicon carbide, stainless steel, and compound material of carbon fiber and silicon carbide, or the fabric is made from high-molecular fiber (polyester fiber) after electroplate treatment and transformed into a conductive material of low resistance rate, then processed with mixing, roving and spinning before weaving. Then the fabric thus produced is made into EM protective dress, articles, covering or laminated with multi-function compound material and become EM attenuation fabric for packing purpose. The polyester fiber is good for its high strength, heat/cold/oil/water proof, UV-
272 absorption, air-sealing and all-weather purpose. The stainless steel fiber of ~ 8 ~t is used as a conductor, and is compatible with polyester fiber during process. While reaching and penetrating into the surface of the conductive fabric, the high-frequency EM radiation wave would induce high-frequency alternating current within the conductive network of the metal fiber (see Fig. 4), the said current would excite a new current, of which the phase-position is reversal to that of the incident EM wave within the conductor, thus resulting a considerable eddy current consumption, eventually the overall EM field within the a.m. network is attenuated. "Penetrating depth" has close relation with the frequency of incident waveand the EM conductivity of the conductor, the higher the frequency, the higher the electric conductivity; the higher the magnetic conductivity, the less the penetrating depth. The penetrating depth of EM wave of about 1 MHz is just a few ~t within metals of A1, Cu, Fe, Ni and Co, it means very thin metal sheet/foil can withstand the a.m. wave. The ferro-magnetic material is both electric field and lowfrequency magnetic field shielded because of its high n~3 electric/magnetic conductivity. Weapons and ammunitions that packed with a.m. metal materials can withstand the interference from the surrounding high-frequency EM wave. Fabrics with metal fiber can protect the weapons and equipments from the risk of EM radiation. Fig. 3 shows that the fabric of EM radiation-proof, while within the range of 1 G H z ~ 10 GHz, the max. attenuation of 49.7 dB is observed from the curve. Fig. 4 shows the residue of the stainless steel fiber screen from the said fabric after burning. There is a long way to go as our study on the electromagnetic radiation-proof packing material is still in its initial stage. It is obvious that the multi-function, conductive, highng.~ molecular polyolefin and the conductive laminated material are superior for their EM radiation shielding. And the conductive high-molecular polyolefin material enjoys a rosy future in packing industry because of its good corrosion/penetration/water/vapor proof, light weight and easy processing.
REFERENCES 1. He Shuyun, Radio frequency-proof technology of weapons & equipments, Publishing house of National Defense Industry, Beijing, 1992 2. Shi Dongmei, Development of new EM shielded material, New Chemicals, 2001 (10) 3. Wang Zhenming, etc. Mechanics design, application and evaluation of compound materials and the structure, Publishing house of Peking University, Beijing, 1998 4. Zeng Xiangyun,Li Jiajun, Shi Chunsheng,Application of carbon fiber in EM compound material,Material Guide,1998,12(1) 5. He Yiyan, Du Shguo: Conductive, high-molecular packing material of EM radiation-proof, China Packing, 2002 (2) 6. Ganss A. A new type of EM absorbing coating | Ballistic Res.Lab. AD 117472
273 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Investigation on protection from ESD explosion of polyformaldehyde resin powder in pneumatic pipe Sun Keping, Yu Gefei Research Section of EMC and Electrostatics, Shanghai Maritime University 1550 Pudong Dadao Road, Shanghai, 20013 5, China, E-mail: [email protected]
Abstract: This paper presents the test result of powder resin specific charge in pneumatic pipe. We try to use a kind of improved active eliminators installed online to reduce the specific charge. Its eliminating effect is fine. Keywords: protection from ESD, electrostatic safety technology, powder statics, static explosion-proof
INTRODUCTION High insulation resin powder in pneumatic pipe can be charged highly. The mixture of powder-air in storage or silo may be ignited by ESD (electrostatic discharge). And the fire or explosion may be caused. This kind of accidents is reported by a lot of authors, such as T.B. Jones [ 1], M.Glor [2], etc. Maurer and Glor revealed some details of explosion in silo [3]. Britton and Kirby provided a fairly complete analysis of an explosion occurred in hopper [4]. A few of authors, however, reported the accidents that occurred in the pneumatic pipe. Two times of explosion accidents have occurred during last two years in a polyformaldehyde resin powder workshop of a plant in Shanghai. A report presented that it may be caused by ESD. In order to investigation the reason of the accidents, we measured the specific charge of polyformaldehyde resin powder in pipe. We find that the powder specific charge is high. We installed a kind of active eliminators in this pipe of the workshop. The data indicates that this kind of improved eliminator has a considerable effect.
MEASURING THE SPECIFIC CHARGE OF POLYFORMALDEHYDE RESIN POWDER IN PIPE The Faraday pail is the most fundamental electrostatic measure instrument. J.B.Gajewski provided a modification Faraday pail[5]. The pail is formed from two conducting co-axial cylinders. We used this kind of pails to test the specific charge of the polyformaldehyde resin powder in pneumatic pipe. The test results are shown in Table 1 and 2. The mass density of the powder is 0.5 • 103 kg/m 3, ~ r=3.8. Its resistivity is 1012 f~ .m. The quantity of feed powder is 300kg/h. The diameter of the pipe is 8 inches or 20.3 cm in Table 1, 10 inches or 25.4 cm in Table 2, respectively. Table 1 Recorded data of the specific charge of the resin powder in pneumatic pipe Temperature: 25.5 ~ Humidity" 55%; Pipe diameter: 20.3cm (8 inches) Specific charge ( ~t c/kg) 0.386 0.410 0.392 0.400 0.379 0.412 0.420 0.390
0.389 0.394
274 Table 2 Recorded data of the specific charge of the resin powder in pneumatic pipe ii
Temperature: 24.4 ~ Humidity" 55%; Pipe diameter: 25.4 cm (10 inches) Specific charge ( l~ c/kg) 0.520 0.603 0.510 0.590 0.600 0.533 0.655 0.640 0.510 0.540 i
ii
DISCUSSION Prof. T.B.Jones gives a guidance for assessment of ESD risks in powder [ 1]. Table 3 is quoted from the conference [1 ]. Table 3 Typical values for powder parameters used to assess ESD hazards Level of hazards Low Moderate High
specific charge (q / m, in la c/kg) < 10-3 10-3 ~ 10-1 > 10-l
From above tables we can see that the specific charge of the polyformaldehyde resin powder is higher than 1 • 10 -l v c/kg, that is, the polyformaldehyde resin powder is found to be highly charged. We also knew that there is some gas of petroleum ether inside the pipe in this plant for the reason of technology. We think that the two explosion accidents in the workshop of the plant in Shanghai may be caused by ESD. It may be ESD to ignite the ether gas and the resin powder inside pipe. The discharge mechanism, however, is not clear understanding to us. We think that the ESD in the pipe is not only difference from cone discharge inside silos (Maurer discharge), but also difference from the propagating brush discharge (because there is not any insulating liner in the pipe). We cannot also determine weather it is brush discharge or capacitive discharge or not. This is our next study project.
A MEASUREMENT OF REDUCING ESD RISKS In order to decrease the charge density of powder in pipe and reduce the ESD risks, we improved a kind of active eliminators we designed ten years ago [6]. It can be suitable for eliminating powder charge inside pipe. It is easily installed at online as flanges. This kind of eliminators has been used in practice. This device has operated for half year in the workshop. It has the following features: Its eliminating effect is high The specific charge of the powder had been reduced considerably after using this kind of eliminators. The results of test from the 10 inches pipe in the workshop are shown in Table 4. Table 4 contrast data of powder specific charge in 10 inches pipe using the eliminator or not Temperature" 24.4 ~ Humidity 955%; Pipe diameter: 25.4 cm (10 inches) Specific charge ( l~ c/kg) Not using the eliminator 0.610 0.583 0.592 0.542 0.655
Using the eliminator 0.085 0.072 0.075 0.082 0.095
ii
275 The test point is about downstream 20 cm from the eliminator. Table 4 is shown that its eliminating effect is considerable. Its safety is reliable The eliminator is with a certificate of explosion- proof by Chinese Authorities Concerned. Its basic circuits are safety and whole eliminator is with special safety measures. The designer is applying to a patent in China. It has an automatic control system It can be switched off by its relay and automatic control circuits when its electrical supply and pneumatic source do not work suddenly.
ACKNOWLEDGMENT This investigation is carried out with the support of Yang Tong, senior engineer and Lu Xinghai, engineer.
REFERENCES [ 1] Jones T.B., King J.L., Powder handling and Electrostatics, 1991, Lewis Publishers INC. [2] Glor M., et al, Discharge from bulked polymeric granules during the filling of silos, J.Electrostatics, 23(1989) 35-43 [3] Maurer B., Glor M., et al, Test rig for reproducible generation of discharges from bilked polymeric granules, J. Electrostatics, 23(1989) 25-34 [4] Britton L.G. and Kirby D.C., Analysis of a dust deflagration, Plant/Operation progress (AICHE) 8 (1089) 1770180 [5] Gajewski J.B., Inst. Phys. Conf.Ser., No. 143, 1995, pp311-314 [6] Sun Keping, Investigation on static explosion-proof of resin, proceedings of the 6th international colloquium on dust explosion, 1994, p420-425
276 Paper Pre,s'ented at the 5th h~ternational Confi;rence on Applied Electrostatic.s H(~)-IES'2()04), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-t,18-044584-5
Research on Dielectric Oxide Film Breakdown Mechanism of IC Device in Human Body Model* Sun Keping, Sun Zhiqiang Research Section of EMC and Electrostatics, Shanghai Maritime University, Shanghai, China Abstract: This paper, based on the physical model of dielectric oxide film breakdown in IC device, Discusses the breakdown mechanism of the film when ESD pulses in Human Body Model applied to oxide film. Keywords: oxide film breakdown, IC device, protection from ESD, dielectric breakdown
INTRODUCTION: The author has built physical model of dielectric oxide layer breakdown in IC device [1], put forward physical equation about capture hole charge density in the surface of medium with time changing. tox
Q+ (r)=e
Fc
~pdx=g ~dF= e (F c - - F a ) = ~ [ E o
c (~') -
E~(z)l
(1)
Fo
If above capture charge is beyond some critical value, then enough great electricity stress can latch up oxide layer. Suppose oxide layer thickness is t ox, average field strength is E ,then the relation equation between critical charge density and time 7: (7: is dimensionless time) can be presented by [1 ]" +
eO~o
Q 8z~=~tox e
-r (1-e)
(2)
(7"
The voltage added to oxide layer is fluctuation voltage in the electrostatic discharge in Human Body Model (abbreviated HBM) rather than constant voltage, and the electronic current J through oxide layer is not constant. Then dynamics characteristic must be taken into consideration under ESD pulse once more. This is what this paper focuses on.
OXIDE LAYER CAPTURE HOLE DENSITY UNDER HBM ESD PULSE Suppose series resistance is 1500 f2 between HBM circuit and the oxide layer, discharge capacitor capacitance 100pF. ESD pulse is added to capacitor. Then the circuit current flow from HBM simulator will flow through the oxide layer. Suppose active area of the oxide layer is A, the thickness is tox, and itself capacitance is C, and then voltage V(t) and instantaneous current I(t) through the layer that both are function of time t .Then the current equation about oxide layer is 9
*The research is sponsoredby Shanghai Education Foundation (No.03IZ01)
277 (3)
- c d--~V= I - A J dt
In virtue of current accumulation effect, the capture hole will also appear on the surface of oxide layer. Current density J is not constant any more, but it is a function related to t .Impact ionization on the oxide layer in the per unit length produces the number a of capture hole that is related to t. In such a case, capture hole density p on the oxide layer will not be the pattern in the [1] any more, and it must be supposed to be much more common pattern with relation to time. ' ~'(crd/e)dt" P (x, t) = 1 ~ core (4) e ~(crJ/e)dt'
e
Since the cr/e is constant, we use equation (3), and get the below equation" I(ffJ/e)dt' - ~
IJdt ' e
~ Idv eA
(5)
ESD pulse flows through the oxide layer, which produces trapped charge density on it will be changed to: Q+-
i ep(x, oo)dx - tox ~C fo Ere-(oC/eA)Vd V
(6)
V0 is the initial voltage of 100pF capacitor in the above equation. Because the index of equation (6) is much smaller compared than hundreds of V voltage, and it can be regard as approximate zero. Then the equation (6) will be simplified as the follow: Q+ - tog -~
c~lV - tog
In this equation, o~-
d V - (HC~z o)(tog / A)
e-'/Xdx
(7)
OCoe-H/F [1] and dimensionless field intensity E=F/H[1], and a 0 is the number
of capture hole in the per unit length on the oxide layer when t=0. According to the physical model of dielectric oxide layer breakdown put forward in the reference book [1 ], the medium will be breakdown when capture hole charge density Q+ rise to the critical value Q ~o, but the value is related to added field intensity, oxide trapped charge thickness and time. In the reference [1], several experiment results have been introduced in which thickness is more than 100A. As follows, it will discuss mainly about the relation between thinner oxide layer and the critical value. If suppose there to be some field intensity (For example if FBD =9.25 Mv/cm), and only to research on the relation between critical value of capture-hole charge density and oxide layer thickness, then it can be got from [ 1](attention: two sides of the equation have been got logarithm)"
L nQso + - -2.3 - 65 93 e -~176
(8)
From the equation above, the curve between the critical value of capture-hole charge density and oxide layer thickness can be got, as shown in the figure 1' It can be obviously found from the figure 1, the critical value of capture-hole charge density is about 0.1C/cm 2 when oxide layer thickness is close to 100A. The result is consistent with most results of [3][5]. The critical value will dramatically fall to about 0.002C/cm 2 when the thickness decreases to about 30A. Its sensitivity to ESD has been largely boosted up. In the mechanism of the much thinner oxide film breakdown, Q ~o is dramatically decreased, then ballistic tunneling effect may be important mechanism [6], and surface capture has played an important role, so the defensive performance is sharply deteriorated against ESD.
278
0.1
0.01
0.001 20
J
i
I
40
60
80
I
[
100 120
tox(A)
Figure 1" the curve between capture-hole charge density (critical value) and thickness
OXIDE LAYER BREAKDOWN UNDER HBM ESD PULSE Many investigators have made studies [2][3][4][5] to oxide layer breakdown under constant voltage effect, and drawn a series of important conclusions including the electricity field intensity will be about 20Mv/cm, which is more than 10-12Mv/cm when the oxide layer breakdown of medium thickness 100 ~t under constant voltage. And when oxide layer capture hole density Q § reaches to 0.1C/cm 2, the oxide layer will be immediately latched up. Universal curve of Capture hole c~ in per unit oxide layer length is a - 1.38 x 10 8e -72/F, c m -I
(9)
F's unit is still Mv/cm in the equation. And draw the curve with average free path 2, =7A, E~/eF2 - 5 or 6 .The voltage is not constant voltage added to oxide layer, but discharged pulse of HBM ESD, then breakdown mechanism and physical process will be not greatly same. Besides mentioned about ballistic tunneling effect above the paragraph (sensitivity of the critical value to the thickness will be greatly boosted up), electrostatic dimension effect will be also more obvious. This can be seen from the following paragraph about the important effect of breakdown voltage to the effective area of oxide layer. ] R1 [ " - ~ ~ S v
I R2 I
I Sample
Figure 2. The essential circuit of HBM model We adapt the HBM standard circuit (figure 2) of IEC479 (CO) 955 Standard. First, the power supply V charges to R l C, then discharge to sample by R 2C circuit. Thus, the voltage on the sample will not be constant voltage any longer, but a pulse voltage. In the figure 2, R 2 is 1.5K f2, C is 100pF,and they are both configured according to IEC standard. Watch whether oxide layer will be latched up in each of discharge. If not, then increase supply voltage, and make the experiment continuously until it is latched up. We make breakdown experiment with three kinds of oxide layer sample, of which thickness are all 400a.Besides their effective area are different from each other, and neither are their capacitance: According to the condition equation of medium breakdown [1 ]:
279
V~z ~ - F tox - H t o x /
(10)
In "c r i t
/
Additional two sorts of different intensity electric field (H=72Mv/cm, 180Mv/cm) on above three samples are provided here. Suppose critical constant is t ~ri,, then we can get corresponding voltage theoretical values of medium breakdown. Experiment values of breakdown voltage are listed right, in order to easily compare with. Table 1, oxide layer breakdown voltage under HBM ESD pulse Effective area of oxide layer (cm 2 )
Capacitance of oxide layer (pF)
Theoretical value of breakdown voltage (v)
Experiment value of breakdown (v)
10 -6
22
204
199
5.95 • 10 -6
14
177
174
5.25 • 10 -6
12
170
73
9.10 •
The result has shown the theoretical values and experiment values were wondrously consistent on the former two much wider active area of oxide layer. It shows the physical model is a p p r o p r i a t e that we have put forward. However, the consistency is not much good for the third smaller area of oxide layer. The possible reason is correlative with defect density variation put forward in [6] .The density variation change that will cause the smaller effective area of oxide layer prematurely latched up.
CONCLUSION 1. For the much thinner oxide layer thickness, the critical values of capture hole density change much sensitive with thickness. When thickness is decreased from 100A to 30A, the critical value of capture hole density is decreased from 0.1C/cm 2 to 0.002C/cm 2, Thus, the resistive capability sharply drop antiESD .So we must find much better technology countermeasure from the stratagem. 2. With the continual development of IC devices micromation, the active area and active width of oxide layer are reflect sensitively to ESD. This is possibly because density defect effect causes the oxide layer to be latched up prematurely.
REFERENCES 1.Sunkeping and so on, Research on ESD breakdown physical model in electronic devices oxide film. Shanghai Maritime University Transaction_,March, third ,2003,24(1),P56m59 2.E.A.Amerasekera and D. S. Campbell, ESD pulse and conditions voltage break down in MOS capacitor structures, EOS/ESDSymp.Proc, EOS-8, 1986,P208-213 3.M.J.Tunnicliffe, V.M.Dwyer and D.S.Campbell, Experimental and theoretical studies of EOS/ESD oxide breakdown in unprotected MOS structures, EOS/ESD proc., EOS-12, 1990,P162-168 4.P.P.Apte, T.Kubota and K.C.Saraswat, Constant current stress breakdown in ultrath sio2 films, J. Electrochem. Soc., 140(1993) P770-773 5.D.J.Dimaria, D.Arnold and E.Cartier, Impact ionization and positive charge formation in silicon dioxide films on silicon, Appl.Phy.Lett, 60(1992) P2118-2120 6.D.L.Lin and T.L.Welsher, From lighting to charged device model electrostatic discharges, EOS/ESD Symp.proc, EOS-14. 1992, P68-75
280 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Effects of High Voltage Prickle Electrostatic Field on the Expressions of the Surface Molecules on the T Lymphocytes and Antigen Presenting Ceils of Mice Sun YC I, Liu XD 2, Yang XL l Ye S l, Ma SM 2, Liu XC 2, Wang XL 1 ,
Department of Physics, Northeast Normal University, Changchun 130024, China 2.MH Radiobiology Research Unit, Jilin University. Changchun 130021, China
The objective was to observe the effects of high voltage prickle electrostatic field (HVPEF) on the expressions of the surface molecules on the T lymphocytes and antigen presenting cells (APCs). Kunming mice were selected and randomly grouped. Whole body treatment of HVPEF was performed. Flow cytometry (FCM) was adopted to detect the expression changes of surface molecules after different doses of HVPEF by dose-effect and time-course studies. The dose-effect results showed the opposite directions of the surface molecule expressions after HVPEF. The time-course results showed that the peak of expressions appeared at about 816h after 15kv HVPEF (P<0.001), and then recovered gradually. 24h saw the recovery to the baseline. The expressions decreased beginning from 2h and rapidly reaching their minimums after 35kv HVPEF, the lower level of expressions maintained up to 24h. The different doses of HVPEF might cause different changes of the surface molecule expressions on T lymphocytes and APCs, which suggested that HVPEF had potential immune-regulatory effects and changes of expressions might play important roles in immune modulation.
INTRODUCTION The immune system provides a highly sophisticated defense, surveillance and immunologic homeostasis function. Inter-cellular activated molecule (ICAM) involving in costimulatory molecules plays a crucial role for the intercellular linkage and participates in a series of physiological and pathologic processes of cell signal conduction and activation, growth and differentiation, extension and metastasis and so on [ 1]. Further, the participation of costimulatory molecules in the processes immune responses for the interaction between immunocytes or immunocytes and target cells is an important matter of recognitions and signaling cascades [2]. The recognition and conjunction of CD2/CD48 (the leukocyte functionassociated antigen-2 and -48) are essential matter as the second signal system in T cell activation [3]. The interaction of LFA- 1 (the leukocyte function-associated antigen- 1, CD 11 a/CD 18)/ICAM- 1 is a crucial matter inducing B cell apoptosis for the balance of the amount of B cell in bodies [4]. In addition, the recognition and conjunction of LFA-1/ICAM-1 provide costimulatory signal for T cell activation and being effect cell [5]. Recent studies have suggested that magnetic and electric fields affect human health and, in particular, that the incidence of certain types of cancer, depression, and miscarriage might increase among individuals living or working in environments exposed to such fields. Consequently, the impacts of such fields on human health are receiving increasing scientific interest and have become the subject of great public debate [6, 7]. Much more experiments showed that biological tissue is very sensitive for electricity and magnetism. There was a report that pulsed radio frequency electromagnetic fields did not have effects on Melatonin, Cortisol, and selected markers of the immune system in man [8]. No effects of extremely low frequency magnetic fields found on cytotoxic peripheral blood mononuclear cells in vitro was also reported [9]. Besides, some studies indicated power-frequency electric and magnetic fields and risk of
281 childhood leukemia [10]. Up to now, it is still unclear to the mechanism of the biological effects induced by electric and magnetic fields though many experiment results were reported. Therefore, the goal of the present study was to investigate how HVPEF affects surface molecule expressions of T cells and APCs.
MATERIALS AND METHODS Experimental device Figure 1 showed the device of HVPEF system in our experiments. The up plate with metal prickles of 1cm long and 4cm space in between is with positive change and is the square of 40cm• The low fiat plate in the same square is ground connection. 11.5cm distance is between up and low plates. The mice in an up-open, 15cm diameter plastic cylinder container with uniform small holes were placed in the center of plates. The electric field intensity in the container was considered uniform because the cross section of the container is much less than the area of the plates.
"1
I Figure 1 The device of HVPEF in the experiments (A: source of alternating current; B: the equipment producing high voltage electrostatics(HVE); C: output HVE; D: meter of liVE; E: needle of electric discharge; F: upper plate; G: lower plate.)
Animals and cells All experiments were performed using male Kunming mice, 5-6 weeks of age, 20-22g in body weight, obtained from the Department of Experimental Animals of Norman Bethune Medical Center, Jilin University, at room temperature and 40 __+5% relative humidity. The mice were fed with routine laboratory chow and water ad lib. The mice were randomly divided into 6 groups for each experiment, a sham-control and 5 experimental groups. 5 mice were in each group. The mice were sacrificed 16h after HVPEF. Thymocyte suspensions were prepared by grinding thymus tissue, the concentration was adjusted to 1x 107/ml. Peritoneal macrophages were drew from 5 mice abdominal cavities into which were injected 5ml PBS and softened slightly 5min by aseptic manipulation. FCM collected 10,000 cells for each sample. The FCM data was analyzed with the Celfit software. Main apparatuses and fluorescent antibodies HVPEF was made by Department of Physics, Northeast Normal University; High voltage electrostatic meter is 0-10kv in scale (Electric Meter Factory, Beijing); FCM (B-D Co, USA); anti-mouse-ICAM-1-PE and anti-mouse-CD48-PE (Burlingame CA, USA), anti-mouse-LFA-1- FITC and anti-mouse-CD2-FITC (PharMingen, USA). Treatment condition All experimental groups were treated 5d successively, 30min/d and the time interval after exposure between one after another was 24h. Detection of the surface molecule expressions 1x 106 cells for each sample were selected and washed with PBS 2 times, and then resuspended in PBS. Optimal concentrations of each antibody were determined in preliminary experiments. 501~ 1 (diluted with
282 PBS as 1:100)of anti-mouse LFA-1 or CD2 was added into tymocyte samples, and anti-mouse ICAM-1 or CD48 into peritoneal macrophage samples. All incubations were performed for 45min at 4~ followed by washes in PBS 2 times. Controls of specific labeling were prepared using isotype matched controls. Meanwhile, PBS replacing specific antibodies performed nonspecific control. Specific positive cell percentages of the data from FCM were calculated. Statistical analysis Arithmetic means and standard deviation were calculated. The Student's t-test was used to analyze the statistical meaning of the observed differences. Probability values (P) of 0.05 or less were considered significant.
RESULTS The dose-effect relationships The mice were irradiated after WBI with 0, 10, 20, 30, 35 and 40kv HVPEF. 5d later, they were sacrificed 16h after the last treatment. Thymocytes and peritoneal macrophages were obtained and detected by FCM after being labeled by CD2, CD48, LFA-1 and ICAM-1 fluorescent antibodies. Fig 2 and Fig 3 showed that the all experimental group expressions of CD2, CD48, LFA-1 and ICAM-1 were significantly higher or lower than the negative control after voltages <~ 20kv or >30kv (P<0.05, P<0.01 or P<0.001), respectively. The changes obviously showed in a dose-dependent manner.
--o-- CD2 --e-- CD48
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Figure 2 The effect-dose relationships of CD2 and CD48 expressions after different HVPEF.
283
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Figure 3 The effect-dose relationships of LFA-1 and ICAM-1 expressions after different HVPEF. The course-time relationships after 15kv HVPEF. The experimental results showed that the all experimental group expressions of CD2, CD48, LFA-1 and ICAM-1 were significantly higher than the negative control groups after voltages~ < 15kv (P<0.05, P<0.01 or P<0.001)(see Fig 4 and Fig 5). But they reached their expression peaks at different intervals after HVPEF. 24h saw the recovery of all expressions to baseline. --o-- C D 2
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Figure 4 The effect-time relationships of CD2 and CD48 expressions after 15kv HVPEF.
284
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Figure 5 The effect-time relationships of LFA-1 and ICAM-1 expressions after 15kv HVPEF. The course-time relationship after 35 kv HVPEF. The experimental results showed that the all experimental group expressions of CD2, CD48, LFA-1 and ICAM-1 were significantly lower than the negative control after voltages~<35kv (P<0.05, P<0.01 or P<0.001)(see Fig 6 and Fig 7). But they reached their expression minimums at different intervals after HVPEF. Furthermore, all expressions of experimental groups were lower than those of the shamirradiated groups in 24h after HVPEF. --o-- CD2 --a-- CD48
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DISCUSSION It is comprehesive biological phenomena that changes of immunologic functions are caused by physical factors. Adaptive immune responses depend on the surface of antigens by specific antigen receptors expressed on the surface of T and B cells. The processes of immune responses not only depend on recognitions and adhesions with immunologic cell subgroups, but also are modulated by humoral factors. Complex nets are formed from interactions and inter-coordination between imunologic cells and APCs. APCs present external antigens to T cells and activate T cells as effective cells by 3 couples of costimulatory molecules, those are B7/CD28, CD2/CD48/, LFA-1/ICAM-1, after CD4+ or CD8+ selections of T cells. CD2 and LFA-1 are two of the surface markers of T cells at different stages in T cell mature. CD48 and ICAM-1 are surface molecules of macrophages. CD48 is the ligand of CD2, and ICAM-1 is the ligand of LFA-1. Macrophages as the most common APCs interact with T cells to proceed immune responses of T cells. Mononuclear macrophages is immlunologic effector and regulatory cells. Static (nofunctional) macrophages are activated by external factors such as environments and pathogens and so on. Activated macrophages have potential functions to phagocytize pathogens, kill tumor cells, secret cytokines, and participate in immune responses. The conjunctions of CD2/CD48, LFA-1/ICAM-1 potentially increase the adhesion and recognition between T cells and APCs. Thus, increased immune responses more effectively protect the host organism from invading pathogens and altered cells (e.g., virus-infected and tumor cells). In the present study, we provide evidence that expressions of CD2, CD48, LFA-1, ICAM-1 of thymocytes and peritoneal macrophages emerged opposite directions after different doses of HVPEF. The surface molecule expressions both on thymocytes and peritoneal macrophages were increased after voltages~<20kv of HVPEF. Otherwise, the expressions were decreased after voltages>30kv of HVPEF. The results revealed effects of surface molecule expressions on T cells and APCs after HVPEF, suggested biological effects after static electric fields, and might provide a new application ideas for medical apparatus and instruments. ACKNOWLEDGMENT This work was carried out under the Project-sponsored by SRF for Ross, SEM, China(2002) and the program of science and technology development of Jinlin Province (20030543-3), China.
286
REFERENCES 1. Tuckwell DS, Weston SA, Humphries MJ, Integrins: a review of their structure and mechanisms of ligand binding. Symp Soc Exp Bio(1993), 47 107-136 2. Rolf Konig and Wenhong Zhou, Signal transduction in T helper cells: CD4 corecepors exert complex regulatory effects on T cell activation and function, Curr. Issues Mol Bio1(2004), _6 1-16 3. Germann T, Gately MK, Schoenhaut DS, et al, Interleukin-12/T cell stimulating factor, a cytokine with multiple effects on T helper type l(Thl) but not on Th2 cells, Eur J Immunol(1993), 23(8) 1762-1770 4. Wang J, Lenordo MJ. Essential lymphocyte function associated 1 (LFA-1): intercellular adhesion molecule interactions for T cell-mediated B cell apoptosis by Fas/APO-1/CD95, J Exp Med(1997), 186(7) 1171-1176 5. Van Seventer GA, Shimizu Y, Horgan KJ, et al, The LFA-1 ligand ICAM-1 provides an important costimulatory signal for T cell receptor-mediated activation of resting T cells, J Immunology(1990), 144(12) 4579-4586 6. Selmaoui B, Lambrozo J, Touitou Y, Endocrine functions in young men exposed for one night to a 50-Hz magnetic field; a circadian study of pituitary thyroid and adrenocortical hormones, Life Sci(1997), 61 (5) 473-486 7. Lino M, Effects of a homogeneous magnetic field on erythrocyte sedimentation and aggregation, Bioelectromagnetics(1997), 18 215-222 8. Radon K, Parera D, Rose DM, et al, No effects of pulsed radio frequency electromagnetic fields on Melatonin, Cortiso, and selected Markers of the immune system in man, Bioelectromagnetics(2001), 22 280-287 9. Keiichi Ikeda, Yasushi Shinmura, Hiroki Mizoe, et al, No effects of extremely low frequency magnetic fields on cytotoxic activities and cytokine production of human peripheral blood mononuclear cells in vitro, Bioelectromagnetics(2003), 24 2131 10. McBeide ML, Gallagher RP, Theriault G, et al, Power-frequency electric and magnetic fields and risk of childhood leukemia in Canada, Am J Epidemiol(1999), 149 831-842
287 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Effects of High Voltage Prick Electrostatic Field on Lewis Zhang Y, Sun YC Department of physics, Northeast Normal University, Changchun 130024, China
Cancer was the first enemy of the human beings, so there were more and more attentions to the therapy methods of it. In order to explore the biological effects of the high voltage prick electrostatic field on Lewis (murine tumor lung cancer cell) cells, minus high voltage prick electrostatic field was used in this work, and MTT assay method was also used to examine the proliferation of Lewis. The result showed that Lewis cells were restrained evidently at the voltage of 1500v. So we could conclude that some intensity of minus high voltage prick electrostatic field could restrain the growth of the tumor cells.
INTRODUCTION In the last several years, considerable evidence has been published demonstrating that non-thermal exposures of several in vitro biological systems to the high voltage electrostatic field (HVEF) can elicit cellular changes that might be relevant to in vivo biological systems [1-5]. HVEF has been shown to influence cell membrane signaling processes in variety of systems, including nervous system development. However, there are no references about high voltage prick electrostatic field (HVPEF) been seen, so the HVPEF is used in this work. The MTT 1 (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay is a simple colorimetric method to measure cytotoxicity, proliferation, or cell viability first developed by Mosmann in 1983 [6]. MTT is a yellow, water-soluble, tetrazolium salt. Metabolically active cells are able to convert this dye into a water-insoluble dark blue formazan by reductive cleavage of the tetrazolium ring [6]. Formazan crystals, then, can be dissolved and quantified by measuring the absorbance of the solution at 570 nm, and the resultant value is related to the number of living cells. By using96-well microtiter plates and a multiwell spectrophotometer this assay can be semiautomated to process a large number of samples and provide a rapid measurement of cell number. Therefore this method has been mainly used in the past decade for anticancer drug screening assays on human and mammalian cell lines [7,9]. The aim of this work was to develop a new method to therapy cancer.
MATERIALS AND METHODS Experiment apparatus The high voltage prick electrostatic field (HVPEF) apparatus was adopted. The high voltage prick electrostatic field (see Figure l) was made of two aluminum boards, whose distance was 20cm. The size of aluminum board was 45cm x 30cm, with pricks on the up one , whose length was l cm, and the distance of each other was 1cm, too. The plates were put in the center of the bottom aluminum board, we could ignore the verge effect, because the acreage of aluminum was much bigger than the plates'.
288
Iiii
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D
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,
-]-Figure 1 High voltage prick electrostatic field apparatus ( A: Homemade high voltage Power-supply; B" AC power-supply; C: voltammeter; D: discharge stick; E: Lewis tumor cells)
Chemicals and reagents All chemicals and cell culture reagents were obtained from the Sigma Chemical Co. unless otherwise stated. Cell lines were obtained from the department of medicine of JIL1N University. Maintenance of cells Lewis (murine tumor lung cancer cell) cells were grown in RPMI 1640 medium supplemented with 10% defined fetal bovine serum. They were maintained at 37~ in a humidified atmosphere containing 5% CO2.Cells were plated into 96-well plates with the density of 105/ml,, and after 24 h of incubation, required for cell adhesion, they were stimulated with anticancer drugs" Carboplatin (Car), whose final density was 40~g/ml, the equal vol. medium was use. Cells were put into high voltage prick electrostatic field after 2 h in the incubation box. Treatment condition Every treated group was into HVPEF for 4d, 15min/d, the interval was 24h. The control group was fake radicalized, 15min/d. Treatment condition: room temperature, comparative humidity:40%.The treatment voltage was 0v,1000v, 1500v, 2000v, 2500v. Cell proliferation assays The proliferation of cells was determined by MTT colorimetric assay. The MTT assay was performed as follow" the wells were washed three times with complete medium, then 180-~ 1 aliquots of medium and 20-~t 1 aliquots of MTT solution (5 mg/ml of PBS) were added to each well at the established time. After 2 h of incubation at 37~ and 5% CO2 for exponentially growing cells and 15 min for steady-state count cells, the media were removed and formazan crystals were solubilized with 175-~t 1 DMSO. The plates were then read on a Microplate reader Model 450 (Bio-Rad Laboratories, Hercules, CA, USA) at 570-nm wavelength. Statistics method Statisical significance of the difference between the control and treated groups is evaluated using Sl~dent's t-test.
RESULTS AND DISCUSSION The effects of HVPEF on cells without anticancer drugs. Cells proliferation was accelerated at the low voltage, because of the low dose radialization excitement effect, and was restrained at the higher voltage, such as 1500v. (fig.2) The comparative death ratio of the 1500v treated group was highest, and the OD value of live cells was the biggest one (p<0.001). (table.I) So we could know that some intensity HVPEF could restrain the growth of the tumor cells.
289
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Figure 2 The OD values of the live cells of the treated groups without anticancer drug Table 1 The OD value of the live cells and the comparative death ratio (CDR) of treated groups without anticancer drug Treated groups 0 1000 1500 2000
The OD value of live cells 0.5800__+ 0.03115 0.7050_ 0.02615 0.2083 + 0.02345 *** 0.4998 _ 0.05126 *
CDR -21.55% 64.09% 13.84%
2500
0.4563 + 0.02365 *
21.34% (*" p
The effect of H V P E F on cells with Car Cells proliferation was restrained evidently at 1500v cooperated with Car, the amount of alive cells of 1500v treated group was smaller 22.93% than that of control group. (fig.3) The comparative death ratio of 1500v treated group was lowest, which was consistent with the above results. (table.2) The result showed that HVPEF could choke back the proliferation of the tumor cells with the cooperation of anticancer drug. Table 2 The OD values of live cells and the comparative death ratio (CDR) of treated groups with anticancer drug (Car) Treated groups
The OD value of live cells
CDR
0 1000 1500 2000
0.8953 -+-0.04289 0.8050 -t- 0.04958 0.1605 _+0.02926 *** 0.5743 _ 0.04967 *
10.08% 82.07% 35.86%
2500
0.3288 + 0.03411 ***
63.27% (*" p<0.05; ***" p<0.001)
290
--m-- Control group - - e - - Treated group
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CONCLUSION Though the mechanisms of the high voltage prick electrostatic field on tumor cells had not been evidence, the remarkable restrain effect was gotten in this work, which could help us to exploiture the new method to therapy the cancer. ACKNOWLEDGMENTS This work was carried out under the Project-sponsored by SRF for Ross, SEM, China (2002) and the program of science and technology development of Jinlin Province (20030543-3), China.
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.
Cory Berkland. Biomaterials. (2004) 25 5649-5658. Alexey Peshkovsky, Ann E. McDermatt. Journal of Magnetic Resona.nce. (2000) 147 104-109. Hamdy F.M.Mohamed. Radiation Physics and Chemistry. (2003) 68 449-452. Behnom Farboud. Exp. Eye. Res. (2000) 7__0_0 667-673. T.Ward. Cancer Letter. (1996) 106 69-74. T. Mosmann, J. Immunol. Methods (1983) 65 55-63. F. Denizot, R. Lang, J. Immunol. Methods (1986) 89 271-277. J. Carmichael, W.G. DeGra., A.F. Gazdar, J.D. Minna, J.B. Mitchel, Cancer Res. (1987) 47 936-942. M.C. Alley, D.A. Scudiero, A. Monks, M.L. Hursey, M.J. Czerwinski, D.L. Fine, B.J. Abbott, J.G. Mayo, R.H. Shoemaker, M.R. Boyd, Cancer Res. (1988) 48 589-601.
291 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
High-quality Cucumber Production Improved by the High-tension Static Electricity Xiong Jianping, Hu Sumei, Xie Sheng Electrostatic Institute, Maoming University, Guangdong, P.R.CHINA, 525000 Abstract: This paper, having made a breakthrough toward the general seedhandling methods frequently used in the past 20 years, employs the physical technology of high-tension static electricity to handle the cucumber seeds. Through the comparative test between experimental and comparable groups, the paper looks chiefly into the optimized breeding scheme and its internal mechanism by way of high-tension static electricity. Key words: high-tension electrostatic field; cucumber; DNA technology
1. PREFACE During more than 20 years after the discovery of biological effect of electrostatic field, there have existed various physical and chemic methods, which can be used for induced mutation. However, the electromagnetic field as the new mutagen source has been more and more valued by people. In general, the yield of majority crops can be increased through electromagnetic technology, but mostly due to the lack of enough electromagnetic strength, genetic mutation of crops can hardly be attained. The reason lies in that the electromagnetic intensity of alternating-direct current and narrow-pulse high-voltage corona is limited by the critical breakdown force, and the criticality value is E
292 3. METHODOLOGIES We choose the improved cucumber seed imported from Japan by Guangdong improved variety import company. Firstly, immerse the seed into the warm water for 20 minutes at the temperature of 36~ and then dry it in a drying closet; secondly, classify the seeds into three groups and handle each group with static electricity at different length of time; thirdly, put the electrostatic-handled seeds and the un-handled seeds under management at the same level so as to observe their variations in terms of quality and production and then analyze their inner textures. 3.1 Data of electrostatic-handling seed obtained on April. 24th, 200.4 (.see table 1) Article name
Group number
Weight
Cucumber Cucumber Cucumber
1 2 3
20g 20g 20g
Indoor temperature 25~ 25~ 25~
Humidity
Voltage
Time length
Spacing distance
64 % 64 % 64 %
50KV 50 KV 50 KV
30s 60s 90s
3.00 cm 3.00 cm 3.00 cm
3.2. Dissemination
On April 24th, 2004, dissemination has been conducted in the fine variety breeding yard located in the city of Gaozhou. The 16 pieces of lands are divided into 4 groups with two disseminated lines in each piece of land. With the row spacing of 40cm and the pit spacing of 20cm, CK group (comparable group) is randomly inserted into other groups. 3.3 Sprouting data after high-tension electrostatic handling (see table 2) Root Stem Group length length number groupl 5.0 9.0 3.2 group2 8.8 April 27th afternoon 10.7 3.5 group3 7.4 2.7 CK group 5.2 10.8 group 1 12.5 5.0 group2 April 29th afternoon 15.0 6.0 group3 4.5 10.5 CK group 5.5 12.5 group 1 May 8th 14.5 4.5 group2 aftemoon 16.0 7.0 group3 CK group 10.5 5.0 From the above diagram, it may be perceived that the seeds in sprouting time, stem and root, especially those in group3. Date
Root width 1.0 2.0 2.5 0.6 3.0 3.0 3.5 2.5 4.5 5.0 6.0 4.5 groups 1,2 .
.
.
Number of Total length white roots 14.0 8 12.0 14.2 10 10.1 14 16.0 16 17.5 18 21.0 15.0 12 24 18.0 19.0 25 23.0 27 15.5 23 and3 grow very well in terms of .
.
.
.
, , ,
3.4 Data of fruit-bearing (see table 3)
~
erial number for cking First picking Second picking weight (kg) weight (kg) Group number Picking time June 11 June 17th CK group 1.45 2.80 group 1 1.80 2.97 group 2 3.65 4.12 group 3 2.35 3.03 Total for each picking 9.25 13.05 The average production is increased by 25.9 percent
Third picking Fourth picking weight (kg) weight (kg) June 23rd 2.92 2.81 2.49 3.74 11.14
July 3rd 1.3 1.4 1.75
1.91 6.36
Total for each group (kg)
8.47 8.97 12.01 11.01 40.46
293 4. EXTRACT AND PURIFY DNA OF CUCUMBER In order to probe the inner mechanism of the high-quality and high-yield cucumber by way of hightension static electricity, we resort to the CTAB to absorb and purify DNA of cucumber. E3I 1) put cucumber leaves (5g) in the cooled milling bowl together with some liquefied nitrogen to fragment cell. 2) add CTAB extract buffer solution (20ml) into the milling bowl and shake it evenly. 3) put the material in the milling bowl into the centrifugal tube and then heat it in the bain-marie kettle at the temperature of 65 ~ for about 60 minutes. 4) put it and the equal quantity of chloroform/octyl alcohol into the triangular bottle and extract for about 10 minutes. 5) rotate it in the centrifuge for 20 minutes (4000 rounds/minute), and the solution turns into 3 strata: the upper one shows the water solution containing DNA; the middle involves protein; the lower contains impurities. 6) suction the upper level (supematant)by proboscis and put it into another centrifugal tube. 7) add the equal volume of isopropanol into the tube, shake it evenly and then store it at-20~ for 2 hours. 8) rotate it in centrifuge for 15 minutes( 12000 rounds/minute). 9) clean the deposit by ethanol (concentration 75%) for 2-3 times. 10) rotate it in centrifuge for 10 minutes(12000 rounds/minute). 11)dissolve the deposit with TE buffer solution to obtain the crude DNA solution and store it into the refrigerator (-4 ~ for future use. 12) add some RNase solution of activated Dnase (kept warm in bain-mafie of 80 ~ for 10 minutes) into part of crude DNA solution, and store at 37~ for 30 minutes. 13) add chloroform/octyl to extract it for 10 minutes, and rotate it in centrifuge for 10 minutes(7000 rounds/min). 14) add ethanol into supematant to deposit DNA, rotate it in centrifuge for 15 minutes(12000 rounds/min) 15) clean the deposit by ethanol (concentration 75%) for 2-3 times, rotate it in centrifuge for 10 minutes (12000 rounds/min), and then dissolve the deposit with some TE buffer solution to obtain the pure DNA solution (storing it into the refrigerator of-20 ~ for future use).
5. ELECTROPHORESIS WITH AGAROSE GELATION Take 10ul of crude DNA and 10ul of pure DNA for electrophoresis by 1.2% agarose gelation for 2 hours. 6. RESULTS AND ANALYSIS To observe electrophoretic results by fluorescent ultraviolet analysis, the relevant pictures are taken as follows, Fro.rn the above pictures, we may perceive: 1)Compared with the spectrum of X -DNA, the DNA molecules of cucumber test groups 1,2,3 and CK group are about 23Kb; 2) RNA molecules may be observed in the spectrum of picture 1 instead of picture 2, which proves that RNA has been removed by RNase solution; 3) Compared with the spectrum of X-DNA, the concentration of DNA in cucumber test groups 1,2,3 is 250ng, while the concentration in CK group is comparatively low. To sum up, the innovative aspects for this research project may be conclude as follows: first of all, we apply the high-tension electrostatic field to seed breeding and employ the power of "sharp electrical scissors" to make seed gene fragmented, dislocated and mutated. This seed-handling method, by nature, means a breakthrough. What's more, we base this project on the fact that the production will be increased by about 30 percent to 40 percent when "satellite seed" is radiated by the high-pressure energetic cosmic rays. Especially
294 we imitate the strong electric field on the earth to achieve the same goal, so as to save the expenditure and improve the experimental feasibility. Finally, we attempt to control the biochemical indices in the process of seed sprouting and growing by controlling the parameters of the amplitude of electromagnetic field including the voltage, discharge time, direction and so on. No doubt, the processes of breeding and sprouting that are manipulated by manual work symbolize a sort of innovation as well.
Picture 1. electrophoretic spectrum with agarose 1--cucumber test group 1with RNase enzyme 2~cucumber test group 2 with RNase enzyme 3 ~ cucumber test group 3 with RNase enzyme 4--CK group with RNase enzyme 5 ~ X -DNA 6 ~ X -DNA 7mcucumber test group 1without RNase enzyme 8mcucumber test group 2 without RNase enzyme 9~cucumber test group 3 without RNase enzyme 10---CK group without RNase enzyme
Picture 2. electrophoretic spectrum with agarose 1-- x -DNA 2mcucumber test group 1with RNase enzyme 3mcucumber test group 2 with RNase enzyme 4roCK group with RNase enzyme 5 ~ X -DNA 10-- X -DNA 6~cucumber test group 1without RNase enzyme 7~cucumber test group 2 without RNase enzyme 8~cucumber test group 3 without RNase enzyme 9roCK group without RNase enzyme
REFERENCES 1. (3 $ - ~ . t ~ t I ~ ~ ~ ~ r c ~ : ~ J ~ . ~-~Jm_~,2002.4.7 2. YU LD,Phanchaisri B,Apavatjrut P,Anuntalabhochai S, Vilaithong T,Brown IG.Some Investigations of Ion Bombardment Effects on Plant Cell Wall Surfaces.Surface&Coatings Technology.2002.9 3. gl~m)l], ~ T J ~ , ~ DNA ~ I R . ~ . ~ ' ~ ' 1 ~ . 1 9 9 4 . 1 4. ~ - ~ . ~ : t , ~ g v J ~ ~ _ . ' - ~ / ~ l ~ i ) f ~ . ~ @ . 1 9 9 6 . 4 5. ~~-J~. NII ~ ~ ~ ~ ~)~A~)t:~j~,I~.1995 6. ~ ~ . ~'l'P,_,~-~(r~):l:~E~/~~l~/r]]:~. ( ( ~ ' ~ ~ ' ~ J ~ / i ] t : ~ ) ) .1998 7. ~ ~ ~ . ~ @ ~ ~ , 2 ~ , ~ ~ r ~ . ~ ~ ~ + , 2oo2 8. ~ ~ q ~ . J , ~ DNA 7]~i~'3~;~JJ~r ~(~)J:~gvJ]lS,~-~~ ~ ~ ~~. ~;~/~i~$:t:,2002.3 9. ~ _ ~ . S E ~ ' - ~ ~ ' ~ ~ ~ , . i N ~ / k l ~ $ : t : 1999, 188~210 10. ~ ~ , ~.~@~.~i~)ff~.~)C~~3~Tl~:.~L~:~-~.I.~~~, 1996 11. @ 1~~r @-~ ~_i~ r~ ~.~r @ ~ ~ ~~.~ ~ . 1987 12.~;~. ~@~~~@~~J3~~])~)~]J~[J]. ~@~. 1993(1) 13.~ ~.~@-]~ ~ . $ ' ~ / k l ~$_q:.1985 14 ~ ~ . ~~7~--~~)~]. ~I~~. 1984 15 - { . ~ - ~ . ~ ; , ~ . ~ ~ / @ ~ . :t~,~~~$:t:.1987 16. ~ ~ . ~~u d-I~/kl~,$:l:.1987 17 ~ , ~ , ~. ~5~:t:~J-~}~~t~~~~n~. ((~'-~@~)) .~]-~/-t~1~/~$:t:.1988 18. ~ ~ , ~ r , ~ ~ ~.~,~,,fq~~ ~ / ~ . ~ ~ : ~ ~ ~ ~$:t:, 1993 19. ,-@,~'~](~.~'.~ ~ ~ :~ ~'~'-,~.~ ~ ~ ~ ~ }~;~:t:.2004 20. ~ ~ . ~ @ : 1 : ~ _ ~ ) ~ ) ) .~~$~.1992
295 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Preliminary study on selecting the best treating dose of high static electric field by determining super-weak luminescence of germinating seed Hu Yucai, Bai Yaxiang School of Science, DalianFisheries University, Dalian 116023, China
Abstract: Dry seeds of beet and maize were treated with high voltage static electric field. The influence of treated dose for super~weak luminescence intensity of germinating seeds were observed, and if super-weak luminescence intensity could be as an index through which the best treating dose of static electric field is studied and determined. The results showed" high static electric field of different treating doses can all make the super~weak luminescence of germinating seeds stronger. Moreover, in the limits of treating dose the super~ weak luminescence intensity of germinating seeds is associated with the yield which has been proved in macro experiments, the treating dose of germinating seeds of the strongest super~weak luminescence is basically the same as the treating dose of the best yield which has been proved in the macro experiments. Keyword: high voltage static electric field, treating dose, super-weak luminescence, germinating seed
In recent years the biological effect of high voltage static electric field (HVSEF) has been attracting more and more attention, a great amount of work has been done on it by biologists and physicists, and a great deal of fruits have been reached. Many experiments results show that the HVSEF has obvious effect on the biology, especially the crops. For example, it was reported by Shen yang Agricultural University that the static electric fields (40kv/cm • 12h) can make the yield of cotton increase by 12.4%, the cotton length increase by l~2mm Ill. While Professor Liang Yun-zhang found that if the beet seeds were stimulated by HVSEF, then the amount of sugar of beet was enhanced by 0.6 degrees, the yield of mu by about 7% [21. At the same time many experiments demonstrated the yield of crop seed treated with HVSEF related with the dose of HVSEF, if the dose is lower the yield of crop increase little, while the dose is higher HVSEF can destroy the crop seed even decreased it's yield, so it is particularly important to choose the best treating dose. At present, the mainly mean to select the best dose is testing in field: which has some shortcomings such as test period is very long, and cost much etc. for example, it takes us 3-4years to find the best dose of beet seed, therefore, if we can find a faster, more accurate mean to select the best dose, the biological technique of HVSEF will be used more widely. Biological super~weak luminescence abbreviate as super~weak luminescence [3], which is a kind of low-level chemical luminescence, biological super~weak luminescence closelg related with its physiology, biochemistry and pathology course of the organism [4], therefore, it may be a very effective and accurate index to reflect the life state of the organism. In agriculture Production, some scholar taken biological super~weak luminescence as index to bear saline, alkaline, drought, heat, cold and disease [5-61. Wang Hong-pei and his co-worker demonstrated that under drought condition, the wheat seeds whose sprouting speed and super~weak luminescence intensity is higher are easier to stand drought, and through the convenient, effective and accurate method the seeds which are easier to stand drought can be selected [71. At the same time, some scholar found that under cold condition, super~weak luminescence intensity of the maize seeds which are apt to bear cold is higher, and super-weak luminescence could also be as an effective and accurate index, through which the seeds which are apt to stand cold can be selected [81. In addition, super~weak luminescence is also an effective and accurate index to judge the best dose
296 of chemical fertilizer and agriculture chemical used. In this paper, we firstly determine super--weak luminescence intensity of beet, maize and barely seed treated with HVSEF in different dose, and, compare it with the yield of seed treated with HVSEF in different dose, then, through comparing, we find in the limits of treating dose the super--weak luminescence of germinating seeds is in direct radio with the yield of seed treated with HVSEF in different dose, moreover, the group seed which super--weak luminescence intensity is highest has a highest yield.
MATERIALS AND METHODS Experimental crop seeds. The seeds of beet, maize and barley are plump and well selected. Methods The chosen seeds are similar in appearance. The seeds were divided into eleven groups at random with the similar numbers in each group. (One is the control group, others is experimental groups.) then the seeds were treated respectively by the following intensity of HVSEF: 100kv/m • 15minutes, 150kv/m • 15minutes, 200kv/m • 15minutes, 250kv/m • 15minutes, 300kv/m X 15minutes, 350kv/m X 15minutes, 400kv/m • 15minutes, 450kv/m • 15minutes, 500kv/m X 15minutes, 550kv/m X 15minutes. Measure of super--weak luminescence of germinating seeds The seed (control group and experimental group)was put in a thermostated container(the temperature is 20 4-1 ~ for x(maize" x=60, beet: x=72, barely: x=48)hours after soaked by distilled water, then, take out the germinating seeds and put it into measure device ,after an hour begin to determine the super--weak luminescence intensity of germinating seeds. In order to reduce error, every group is determined for 3 times, then, average it.
RESULTS AND ANALYSIS Results The results of super--weak luminescence intensity of beet, maize and barely germinating seeds are listed in table 1-3. Table 1 Effects of electrostatic fields on super--weak luminescence intensity of beet seeds ::::::::::
............
J~,llI~,~[
.....
:::::
:::::
: 'IlII
. . . . . . .
::::::
::
:-::
::
::::
::::
:.
:
:::
:::::::
"I I:
: --~
,
,
:::
" ::::::::::m~,I~,~,
:::::::::__:_:::::
::::
:
..
I I
Control group electrostatic 0 100 fields kv/m kv/m super--weak luminescence 9 6 7 3 9885 ..................:!ntensi~..........................................
.
.___I_____:::::
::::
:_ - : : : : : : : : : :
:::::::~
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Experimental groups 150 kv/m
200 kv/m
250 kv/m
300 kv/m
350 kv/m
400 kv/m
450 kv/m
500 kv/m
550 kv/m
10254 10625 10827 10942 11008 11967 11815 11076 11313
Table2 Effects of electrostatic fields on super--weak luminescence intensity of maize seeds Control Experimental group ............ gr~_o_up........................ 350 400 450 500 550 electrostatic 0 1O0 150 200 250 300 fields kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m super--weak luminescence 29555 29925 31768 33295 31765 34524 36159 39488 36252 34006 32404 .intens!.~
.................
...........................................................................
_ .................................................
_:_:~_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
297 Table3 Effects of electrostatic fields on super~weak luminescence intensity of barley seeds Control Experimental group __gro__uP 200 250 300 350 400 450 500 550 electrostatic 0 100 150 fields kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m kv/m k v / m kv/m super~weak luminescence 29889 41478 43594 51927 50364 39237 40888 44544 44948 42830 38836
Table l--~3 demonstrates that HVSEF increases super~weak luminescence intensity of germinating seeds, moreover, in the limits of treating dose the super~weak luminescence of germinating seeds is in direct radio with treating dose of HVSEF. Comparison of the yield with s u p e r ~ w e a k luminescence intensity Compare super~weak luminescence intensity with the yield of seeds treated with different dose of HVSEF, the results are listed in table 4-5 Table 4 the results of comparison super~weak luminescence intensity with the yield of Beet seeds treated with e HVSEF in different doses ~:::~=-:.......
~_.....~....~.~.:
..........
~:~_~_=~:~-~-~=:~-~-7--.~-~-=~=~_:~:
......
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Treating dose The yield ofmu was enhanced(%) The amount of sugar was enhanced(%) The super~weak luminescence intensity was e n h a n c e d ( % ) _ ~
Control group
150kv/m • 10min
::::
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
300kv/m • 10min
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
450kv/m • 10min
550kv/m • 10min
0
+4.55
+12.27
+16.62
+10.18
0
+0.17
+0.87
+0.95
+0.3
0
6.01
13.12
22.14
16.95
Table5 the results of comparison super~weak luminescence intensity with the yield of maize seeds treated with HVSEF in different doses Treating dose
Control group
150kv/m• 10min
400kv/m • 10min
550kv/m • 10min
The yield of mu was enhanced(%)
0
+10.01
+15.6
+12.7
The super~weak luminescence intensity was enhanced(%)
0
7.49
33.61
9.64
DISCUSSION Relation of super~weak luminescence intensity and treating dose of HVSEF According to Table 1-3, we find that HVSEF can increase s u p e r ~ w e a k luminescence intensity of beet, maize and barley germinating seeds within the range of certain dose, which proves HVSEF can accelerate crop seed's supersession and energy transform, moreover, the s u p e r ~ w e a k luminescence of germinating seeds is in direct radio with treating dose. Relation of s u p e r ~ w e a k luminescence intensity and the best treating dose From Table 4-5, we can find the seed's super~weak luminescence intensity is associated with the yield which has been proved in macro experiment, moreover, the group seed which super~weak luminescence intensity is highest has a highest yield, hence, we conclude the best dose of barley is 400-450 kv/m for 10 minutes by determining the s u p e r ~ w e a k luminescence intensity of barley seed, which need be verified in the future. According to experiment result, we preliminary consider we may select the best treating dose of HVSEF through determining Biological super~weak luminescence.
298 Because of many advantages such as the short testing time, less cost and not being effected by weather, land condition. If we can choose the best dose of HVSEF by determining super~weak luminescence intensity of germinating seeds, we will save a large amount of manpower, material resources, shorten cycle of selecting greatly, thus advance application of HVSEF in agricultural production. Because this experiment compares super~weak luminescence intensity with the yield of only two crop seeds, experimental result only can be regarded as a helpful try, in the future we need expand experiment rang further to prove this result.
REFERENCES 1. Liu Fu-quan, The effect of the static electric field on cotton, Journal of Dongbei Agriculture University, 1974, 1" 86. 2. Liang Yun-zhang, Biotic effects and application of HVSEF, Physics, 1995, 1:39. 3. Abeles F. B. ,Plant chemiluminescene Ann. Rev, plant physio,1986, 37: 49--72. 4. Shen Xun, Physics essence ofbiosystem's superuweak luminescence, Beijing, published by Beijing University, 1996: 46-69. 5. Yang Qi-jian, The relation of soybeans, wheat, maize's superuweak luminescence with its germinating under drought condition, Prog. Biochem. Biophys, 1989, 6: 452--454. 6. Nie Ju-yun, Peng Yun-sheng, super weak bio luminescence and its applied research, ACTA LSER BIOLOGY SINICA, 1998, 2:126--128. 7. Wang Hong-pei, Lu Jing-yin, preliminary study on selecting resist-drought wheat seed by determining super--weak luminescence of seed, Prog. Biochem. Biophys 1990, 5: 399--400. 8. Yang Qi-jian, The relation of several crop germinating seeds' supermweak luminescence with its resist-adverse circumstance, Prog. Biochem. Biophys, 1993, 4: 315m317.
299 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The transport character of water molecule on high voltage electric field in liquid biomaterials Ding C.J., Liang Y.Z*, Yang J.* College of Sciences of Inner Mongolia University of Technology, Hohhot 010021, P.R.China *Laboratory of Ions Beam and Static electricity Bioengineering of Inner Mongolia University, Hohhot 010021,P.R.China
The concentration experiments of sodium gluconate, pig bile, biology active ferment and immune foremilk whey were studied on the high voltage electric field. The results show that the concentration of liquid bio-materials is accelerated and efficient ingredients reminded of liquid bio-materials by high electric drying is more than that by oven drying. The mechanism of the transport character of water molecule on high electric field is firstly studied from force analysis of water molecule of interior and surface of the liquid materials and electrostatics theory. And it is thought that the drying mechanism on high electric field consists of the injecting of ion beam, the effect of uneven electric field and function of ion wind. And the elementary mechanism calculation is studied.
INTRODUCTION Drying technology now has been a tight part of industry and produces of agriculture, and has tight relation to human daily life. The traditional drying methods of drying heat sensitive materials increase materials' temperature by heat transfer to carry water out, assisting with wind and alternating heat. Lots of scholars have done many works about mechanism based on "heat transfer and mass transfer", and had set up all kinds of drying models; these models are greatly useful to make a mighty advance of dryingtechnology [1]. The concentration drying experiment of heat sensitive materials on the high voltage electric field is done for the first time. And the experimental results are satisfactory. In this paper, by using the data from experiments of concentration some materials such as solution of sodium gluconate, pig bile, biology active ferment and immune foremilk whey with high voltage electric field, we study the carrying process of water molecules and mechanism of high electric drying.
MATERIALS AND METHODS The pig bile was purchased at slaughterhouse, and the moisture is 89.1%; the specificity Immune Foremilk Whey was supplied by Dept. Food of Inner Mongolia Agriculture University, and the moisture of fresh whey is 87.6%, the moisture of concentrate whey I is 54%, the moisture of concentrate whey II is 65.3%; the Biology active ferment was obtained from Inner Mongolia light-industry academy, and the moisture is 95.56%. The equipment of high electric field drying is manufactured by the Department of Physics in Inner Mongolia University (type GXJ-2), the drying area is 3.2m 2, and the heated power is 1.5KW, the high voltage can be adjusted from 0KV to 50KV. There are other apparatus and equipments in the drying experiment such as Ultraviolet-visible Light Spectrophotometer(type:UV-250, made in Japan), Drying Oven(type" DG30h-J/HG202-1, made in China), Vacuum Freezing Drying Equipment(type" ALPHA I-5) etc.
300 Two disinfectant plastic trays filled with pig bile of the equality weight were separately put in the high electric field equipment and the drying oven. The temperature of the materials at the high electric field dryer was set at 40 ~ and at the drying oven it was set at 80~ drying experiment, the moisture is 6%, and we measured active principles of the pig bile by using Spectrophotometer, and the different results of oven drying and high electric drying can be showed. After the biology active ferment was concentrated 7 hours by high electric drying, its moisture content reaches 50%. Then it was dried with vacuum freezing drying. The temperature of the materials at the high electric field dryer was set at 40~ The parallel experiments with only using vacuum freezing drying were performed. After dried, the moisture is 6%. We compared the drying effect and determined the difference of number of live bacterium and enzyme liveliness. The specificity immune foremilk whey was split into two parts, and every part was split into three groups. The two parts were put into high electric drying and vacuum freezing drying separately. The temperature of the materials at the high electric field dryer was set at 35~ After dried, the moisture is 4.45%, and we measured IgG content (the diffusing method of unilateralist immunity [2]), and milk antibody agglutination titer (the method of test tube congealing and collecting [2]) and compared the influence of efficient ingredient with the two drying ways.
RESULTS AND DISCUSSION The remained efficient ingredient of the pig bile by high electric drying The drying time on high electric field is 420 minutes, while the drying time in drying oven is 480 minutes. This method can save 12.5% on total drying time. The experiment results (see Table 1) show that 10% of cholalic acid and bilirubin remained of the pig bile by high electric drying is more than that by oven drying. Table 1 active principle of saved by the two drying ways high electric drying
oven drying
cholalic acid(%)
13.06
11.67
bilirubin(%)
0.050
0.038
The retention of the efficient ingredient of the biology active ferment with high electric drying The drying time with high electric drying and vacuum freezing drying is 19 hours, but the drying time with only vacuum freezing drying is 25 hours. This method can save 28% of total drying time. Table 2 the results of drying by two ways determined item
high electric drying and vacuum freezing drying
vacuum freezing drying
The number of live bacterium (the hundred million/gram)
217
207
The enzyme liveliness(/gram)
7955
7424
The experiment results (see Table 2) show that 4.8% of the number of live bacterium and 7.15% of the enzyme liveliness with high electric drying and vacuum freezing drying is more than with only vacuum freezing drying. The remained efficient ingredient of immune foremilk whey with high electric drying The drying time with both high electric drying and vacuum freezing drying is 24 hours, has no difference. The results that we use t~proving to prove the data of Table 3 can show the active principles of dried immune foremilk whey by these two drying ways show no difference.
301 Table 3 the contrast data of dried immune foremilk whey materials flesh whey concentrate whey I concentrate whey II
The ingredient index IgG content of whey (%) antibody agglutination titer of whey IgG content of whey (%) antibody agglutination titer of whey IgG content of whey (%) antibody agglutination titer of whey
vacuum freezing drying 49.89 214
high electric drying
10.39 2~2
10.55 212
29.50 2~4
30.04 215
49.97 214
MECHANISM ANALYZING The mechanic character of electric field Calculation of Electric Field Intensity For electric field between fiat-electrode the electric field intensity is" -
U
E = --
(1)
d /~ is the electric field intensity, U is voltage, d is distance between electrodes. Electric field between needle electrode and flat-electrode is uneven electric field, if high-voltage is U , then every needle and flat-electrode form needle-flat electric field, l, equal to the distance from pin of needle i to surface of flat-electrode. Electric intensity E~ brings by needle i is" = - V U, - - 0___UU
(2)
al,
If the number of needles is n, then whole electric field E is overlapped by electric field of every needles: E=
E, = - U
(3) "= ~li
i=1
From equation (3) we can come to the conclusion that different position on fiat-electrode has different l,, then has different sum, so form uneven electric field in favor of dragging water molecules leave from liquid, and speed up drying rate. Relation of Electric Field and Carrying Process Water molecules in materials are carried out by electric field forces ft and f2 as follows" Electric field forces f~ acts on surface of materials. Any material in electric field will receive force of electric field; look drying unit as plate electriccapacity. A is the electrode area, H is distance between electrodes, h is the materials thickness, ~m is permittivity of materials, eg is permittivity of air. According to low of refraction: Eg Em=
Em
Eg
(4)
E m is electric intensity in materials and E m,Eg 9
Egh+Em(H-h)-U
Egis in air, there is the relation between voltage
U and (5)
From (4) and (5) can get" E g --
U~~
h(g m - 8g ) +
Heg
Then the capacitance is"
(6)
302 C = Q-Q-"-
EgEgAEm
--
(h(e m - F_,g) + H e g ) E g
U
EgAEm
(7)
h(em - eg) + Heg
Energy of capacitance is" 1 CU2 -2
W-
1 egemA )U 2 -2 ( h ( e m - 8_,g) + E g H
(8)
According to theory of virtual work, get the force acted on air eg 9 F = d__WW= 2U dh
dC = U 2
2
dh
e meg (eg - - e m )A
(9)
2 ( h ( e m - eg) + H e g ) 2
Put (6) into (9), get: 1
gg
2
(lo)
F - A 9- 9 9 Eg (Sg - e m ) 2 em
Then the force f~ act on surface of unit area of liquid materials is: f~
-
-
~
F
-
1
eg
2
em
- - e
A
Eg2 (em
9
Because of e m< eg,
_ ~,g )
(11)
fl <0, direction of fl is followed by the increase direction of h, it is said that
force f~ act on water molecules in the surface layer, the f~ direction is upward. This force f~ draws water molecules out of surface. Though (1 1) is deduced by flat electric field, differential cubage in uneven electric field always can be looked as even electric field. So (1 1) fits for any electric field. Water molecules in inner of materials can be drawn out by force of f2" Water molecule is polarity molecule, so we look upon it as dipole. In electric field, the force acts on dipoles in order to draw dipoles into the domain with major electric field intensity. Dipole moment is cl-fi = q d l , in electric field, the force equal to difference of forces act on anode and on cathode, it can be show: d F = qdE (1 2) Dipole moment dl can be showed as: (13) High electric drying adopts negative high voltage, electric intensity where negative electric charges existent is in excess of electric intensity where positive electric charges existent. The different isd[ = -{dx + ] d y + Kdz
-
dE
-{.OE x
OE~
•
=(Ox
fc . OE ~
Oy
dy +
OE ~
OE~
Oz
az) + ] (
OEy
c3Ey
ax + ~ a y Ox Oy
+
OEy
Oz
az) (14)
OE 2
+ (--g-~+ ~++
Oz..... dz)
The force act on dipoles can be written down as" dF = q[(dx 0' +dy 0 + d z cO)E~ + q j-( d x ~ + 0 dy az
+ q'2(ax 0
+dy
Ox
0
oy
+ dz
ax
0 + d z ~z )E oy
0
"
(15)
g)E
It can be known from vector analysis that" dx - 0- + d y
0+ d z
ax
-
Oy -
-
0
Oz
= (idx + jdy + kdz).(i
(16) - 0
-: O +f~
--~x + j 03,
c0)=(d.grad)
Oz
So the equation of d F can be reduced to" d F = q(dl . g r a d ) E = (d-~, g r a d ) E
(17~
303 Assume @ is dipole moment in differential cubage, and tum to the same direction in electric field, @ can be written down as Pdv, then
dF = (f' 9grad)Edv = z ( E 9grad)Edv = c o(em - 1)(/~ 9grad)Edv
( 18 )
And" -
-
(E 9grad)E
0
0 + Ez #)(~'Ex = (E x -2- + EY--~ oz + Ox
----~i(E o2V _-
~ + E
0%X,2 + ~,..,y
_ 02V - k (E~ ~
02V
F. 02V z
02V
ax
j(Ex O2V O2 )- ~+EyoyV+E~&oy
02V. ~-Oz )
(19)
O~V
Ey ~ . +
+
oxOz
J-/~y+ kE~ -- )
E~
-oz
Oz
)
And" 2
2
N+J
=--f(E x oZv
02V.
O2V
Ox + E , OxOy -
Oxoz
k(E~ o2V
32V
02V.
OxOz
@Oz
0-U )
~ + E y
_
2
+ ~ O ) ( E 2 + EY2 + E, )
grad E2 .
02V
&----~ +E,
32V
OZV
z)
(20)
Then dF can show: E2
dF - sg (G, - 1)grad(-~-)dv
(21)
Then the force f2 act on unit cubage of liquid materials is: E2
f2 - eg (c m -1)grad(-~)
(22)
The high electric field is a synthesis domino offect field. It has the function of the ion beam (the electron beam, negative ion beam that offer the electric charge and more free electron), radiation of the electromagnetism and the function of the invariableness electric field. The mechanism of the high electric drying as fallows' There are mostly three factors on the drying liquid bio-materials. Firstly, the liquid surface is a shallow layer with certain thickness; the thickness is equal to the effective distance that water molecules can attract each other, in this shallow layer, expulsive forces exceed attraction forces between water molecules that form tensile force that we called surface tension. This force makes it difficult for water molecules in liquid surface to come out. Secondly, in the inner of liquid, interaction between water molecules forms groups of molecules (HzO)n. The groups are dynamic unites that water molecules can uninterruptedly join and leave, which is (HzO)nr In the room temperature, the groups mostly consist of water molecules from 30 to 40. Finally, hydrogen bonds and hydroniums among water molecules and solutes in the liquid connect them together, so it is difficult for water molecules to move to surface. The injecting function of ion beam The act domino offect between the ion beam of the high electric field whose energy is low and materials consists of the domino offect of energy sediment, the domino offect of mass sediment and the domino offect of electric charge exchange[3]. Because the mass of the ion beam is low, the domino offect of mass sediment is neglect in the high electric drying. The process dried liquid bio-materials on the high electric field is that the ion beam aggrades the mass and exchanges the charge on the water molecules. On the one hand, after the ion beam carried energy enters into the liquid bio-materials, acts with the solute molecules, and gradually transfers kinetic energy to solute and water molecules, stops the materials until the kinetic energy of the ion beam is entirely dissipated. It is the mass transfer and sediment process. The process makes the water molecules' energy increase, speeds up the hydrogen bonds' disconnection, destroys the
304 surface tension of liquid materials; and makes the water groups single water molecule, decreases the volume of the groups; and makes water molecules separate from hydrophile substance in the materials, decreases the resistance when the water molecules emerge. On the other hand, the electric charge exchange process between the ion beam and water molecules makes schlepping ion capability of water molecules increase. In the electric field effect, the electric field force of water molecules increases. The two aspects make dynamic equation of the water groups rightwards develop, and make the water molecules move from inner to surface in materials. The ion has certain shot in materials. Water molecules accept energy and gradually divorce from the materials, as makes moisture content decrease and the water molecules beyond the shot transfer. It makes humidity gradient. The higher the energy of injected ion is, the farther the shot is, and the more the tangent water molecules of injected ion are. We assume that water molecules mostly absorb the ion's energy because the number of the solute molecules is low in liquid materials. The process makes more water molecules absorb energy and leave the materials, which accelerates the liquid materials drying. Drying effect of uneven electric field In high,voltage electric field, electric field engender two forces to act on water molecules in the surface layer and in the inside of liquid [4], these two forces break surface tension of surface layer, hydrogen bonds among molecules and groups of water molecules in the inner of liquid. By outside forces, water molecules overcome attraction force among water molecules and divorce from surface layer. By outside forces, water molecules and water groups move uninterruptedly from inside of the liquid to the surface layer and ion wind blow then away, so water molecules' moving process is increased. In the carrying process, water groups and single water molecules all can be drawn out of materials together, so latent heat of vaporization needs low energy. High electric drying technology is a low dissipation of energy drying technology.
.
.
.
.
.
Figure 1 force analysis Function of ion wind, blow away water molecules of surface With curvature of electric-conductor increasing, electric-charge density increases correspondingly. When electric-charge density comes to a certain degree, tip of electric-conductor will bring phenomenon of point discharge. During this process, needle-points of needle fiat-electrode engender point discharge; it ionizes molecules in the air and produces ions with positive and negative electric charges. Ion wind blows ions whose electrical property is opposition to needle electrode to the liquid surface under needle-points, then causes liquid surface fluctuating. The velocity of ion wind can reach 2.5m/s. When high-voltage increases, point discharge enhances, numbers of ions also increase. So moving velocity of water molecules in surface layer speeds up, decreases humidity of air on the liquid surface and increases moisture gradient. All these facts make it easy for water molecules to leave liquid. In the drying process, there is no obvious heat transmitting, which doesn't increase temperature of materials, and can be more remained active principle in the materials. The mechanism calculate The energy losing and gunshot of ions That the ions carried energy bombard materials is just like target practice. The ions are usually called "bomb", the materials are called "target"[3]. The ions which energy is E~ inject target, collide each other and loss energy. The solute molecules and water molecules in liquid bio-materials is "target". The water molecules accept energy in definite gunshot of ions, and gradually break away materials, which makes moisture drop. The water molecules beyond gunshot come in by osmosis. There are moisture grads.
305 We suppose that losing energy of the injected ions is dE~/~dx in unit distance along the depth direction. So in Ax distance losing energy of the injected ions is:
(23)
AE l - dEt Ax dx the ions' gunshot in target is: or dEl R, (E,) - - j _ (dE, /dx) El
(24)
Suppose N is body density of target molecules, Ax is thickness, A is area of irradiation from the ions. So NAx A is sum of target molecules from the ions' irradiation. Just as losing energy AEt lineal increase with Ax, the count of target molecules in unit area that is NAx lineal increase with Ax. Suppose that losing energy (dEy~dx ) A x is proportional to NAx, and define that proportional coefficient S (El) is preventive ability. So 9 1 dE l S(E,) =
(25)
Ndx
Because the value of dEledx is negative, right of formula above is negative.
Consider that the
injected ions 10ss energy by collided with solute molecules and water molecules, preventive ability S(El)Of target molecules to injected ions is summation of solute molecules' preventive ability St(El)and water molecules' preventive ability Ss(E1).Suppose because the ions collide with solute molecules and water molecules in dx, each ion's losing energy is - dE,. and - dE s , to get
1 (dE,) r Sr ( E' ) - - ' N
S, ( E, ) -
(26)
-~x
1 dE l ( ax
(27)
Total losing energy of each injected ion in unit distance in target is 9 dE)
dE)
(--'~X r 'dr" (--'~X
s -- N [ S r ( E, ) + S s ( E, )
El is energy of injected ions in target, so dEl = N[S r (E,) + S s (E l ) dx Put (29) into (24), total gunshot of injected ions is:
Rt =
(28)
(29)
1 o[ dE l N ~ S r ( E , ) + S~(E,)
(3o)
Projection gunshot Rpis gunshot's projection along injected direction. Total gunshot is: R t -- I 1 + l 2 + ......... -- ~ l~
(31)
i
So Projection gunshot Rp is: Rp - l I cos 0 i + l 2 cos 0 2 + ......... = ~ l i cos Oi
(32)
i
14 Injected ions
El=0
12 ll "~
Rp
~"1
Figure 2 Total gunshot and projection gunshot
306 From what we have said above we can see that the higher the energy of injected ions is, the farther the gunshot is, and the more the osculatory water molecules of injected ions. Because the number of solute molecules is low, we think that water molecules by and large absorbed the energy of ions. It accelerates concentration of moisture. Calculation of Electric Field Intensity From mechanic character of electric field we can see that: The force f~ act on surface of unit area of liquid materials is" f~
F A
1 Eg OEg2 (~Om__ Eg ) 2 ~'m
= - ~ = m o
(11)
The force f2 act on unit cubage of liquid materials is: E2
f2 - s (s --1)grad(--2--)
(22)
Force f2 acts on water molecules in inner of liquid, carries them from inside of liquid to surface layer, at the same time, force f2 acts on water molecules in surface layer too, carries water molecules from surface layer to air together with force f~. Because it is uneven electric field, electric field intensity is different at different positions. So forces f~ and f2 act on materials with different strength in correspondence with act of variable force, and in favor of carrying water molecules.
CONCLUSION In traditional heat drying, improving temperature of materials causes water molecules' irregular movement to accelerate, viz., speeding up vaporization. At the same time, it also destroys some ingredients in the materials, especially in heat sensitive materials, so heat drying has some limitation. High electric field drying technology using the injecting function of ion beam, function of ion wind, blow away water molecules of surface and electric field force to make water molecules move out of liquid, electric field force f~ and f2 draw water molecules out of surface layer successfully. During this process, water molecules' irregular movement becomes directional movement toward the direction that electric field intensity is increased. Kinetic energy of water molecules doesn't change, so temperature of materials doesn't increase either, and then active principle of materials can be remained. Mechanism of high electric field drying is physics process of 'mass transfer using electric field energy', completely different from any other traditional drying ways, and it is a brand-new drying technology. High-voltage electric field drying technology will bring into a new era in drying domain.
ACKNOWLEDGMENT This work was active support of NNSFC 59377327.
REFERENCES 1. Pan Y.K. Editor in chief, Modern Drying Technology, Beijing, Peking Chemical Industry Publishing Company, 1998, 821. 2. Xu Y.W. Immtmity Examination Technique. The Science Press. 1997, 3-4, 48-50. 3. Yu Z.L. The Theory of Ions Beam's Biology Technology, Anhui, Anhui Science and Technology Publish Corp.,1998,40-66. 4. Xie G.R. High-voltage Static Electric Field, ShangHai, ShangHai Science and Technology Publish Corp., 1964,377-384.
307 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Effect of ultraviolet radiation on charge storage stability of porous PTFE and nonporous PTFE electret Jiang Jian l, Cui Li-Li2, Wang Xiao-Ping l, Fang Ying l, Song Mao-Hai l, Li Ting 1 ~Department of Physics and Mathematics, Department of Basic Medicine, Second Military Medical University, Shanghai, 200433, China 2Department of Inorganic Chemistry, College of Pharmacy, Second Military Medical University, Shanghai, 200433, China
Abstract: Effects of ultraviolet (UV) radiation on charge storage stabilities of porous and non-porous polytetrafluoroethylene (PTFE) electrets were investigated by the isothermal surface potential decay measurements. The feasibility of UV radiation disinfection on medical products of PTFE electret was also studied. The results indicated that (1) UV radiation did not show any significant influence in the charge storage stability of two PTFE films under room temperature. (2) The charge storage stability of porous PTFE decreased slightly with the increasing of relative humidity (RH). (3) The medical electret products of PTFE could be disinfected by UV radiation. Keywords: polytetrafluoroethylene,porous film,electret,disinfection,ultraviolet
INTRODUCTION PTFE, an important biological electret material, is widely used as substitutes of human pathological organs for its excellent biological compatibility, extraordinary ability of negative charge storage and well ventilation, e.g. artificial blood vessel, artificial pulmonary organ, etc.. Besides, the statistic field and microcurrent, produced by PTFE electret, applied to biological body can improve the tissue microcirculation and accelerate the concrescence of fracture. The application of these kinds of biological effects have resulted in some electret medical treatment products in clinic [l3J. The commonly used disinfection methods for medical products are X-ray disinfection, alcohol immersing, scrub-up, high temperature and high humidity disinfection, radiation and chemical disinfection. Our previous studies indicated that the method of high temperature and low humidity was fitted for electret medical products, but only for laboratory use, not for industry production, because of its low disinfection efficiency L4' 51. In order to search for appropriate disinfection method and to provide gist for disinfection of PTFE medical products, a systematic study was carried out on the influence of UV radiation on charge storage stability of PTFE.
MATERIALS AND METHODS The electrets were made of 25gm thickness PTFE film and 40gm, 100gm porous PTFE films with the pore degree of 50% and aperture of 1-5gm (Shanghai plastic research institute, China). The samples were charged by means of constant voltage charging (CORoNATROL, Model 152A, Monroe Electronics Co., USA) with the point voltage -20kV, grid voltage -800V and charging time 10min. Then the sample was disinfected by UV radiation (length: 253.7nm, energy: 4.98eV) under natural state. The radiation intensity was measured by UV radiation meter (ZG-4A, Quartz-glass research institute, Architectural material academe of China). The surface voltage was measured using a Monroe Electronics Isoprobe Electrostatic
308 Voltmeter (Model 244, USA). V~o is the initial surface voltage. V~ was the surface voltage of sample measured after UV radiation. The environment humidity was measured by hygrometer. Statistical analysis was performed using the software of SAS system.
RESULTS AND DISCUSSION The influence of UV radiation to the charge storage stabilities of two PTFE electrets Fig.1 is the curves of surface potential decays of porous PTFE and non-porous PTFE electret after 900 gW/cm 2 UV radiation at different time, the electret being corona charged for 10min at RH=58%. The results indicated that after under 90 minute's UV radiation, both the electret samples could still hold 96.6% and 94.6% of their initial surface potential values, respectively, but 3% lower compared to corona charged at constant temperature and placed for 90min for these two electrets [51, which reflected that the UV radiation under the experimental condition did not have any significant influence on the charge storage abilities of the electrets. So this UV intensity can be used to preclinical disinfection on the medical products of porous PTFE electrets. From fig.1 we could also arrive that the charge storage stability of porous PTFE electret was better than that of the non-porous one, because of its larger interface, lower density and higher concentrated traps [5'6]. To make a further study of the influence of UV radiation on charge storage stability of porous PTFE, different radiation intensities and radiation time were used in the experiment. Fig.2 is the surface potential decay of the sample measured immediately after 30min UV radiation. There were 1.2%, 2.6% and 5.6% decreases of surface potential when the UV radiation intensities were 100, 750 and 1990gW/cm 2, respectively. It indicated that the sample had higher concentration traps in the body which made the electrons be difficult to detrap under 253.7nm and 4.98eV UV radiation. Therefore, the charge storage stability was greatly improved. Under the same radiation condition but stored for 24h, our experiment indicated that the surface potential decay were only 6.7%, 9.2%, 13.3% respectively. There was a little decrease of charge storage stability with the increasing of storage time and radiation intensity. The increasing of UV radiation intensity resulted in the same increasing of radiation sediment in the material, the increasing of radiation induced conductivity and delayed radiation induced conductivity. Therefore, the charge storage stability was decreased. What we can conclude now is that low intensity and long time of UV radiation is fitted for the disinfection of medical products of porous PTFE electret.
"~ o
O. 99 0.98
~> ~
o
~
0.97 0.96
~
0.95
t~
0.94
o
J_
0.96 0.94
.r.-~ 4-)
.~ =
v
0.98
0.92
p , -
o
~ ~
0.9
Z
O. 91 0
Z
..................................... 0 10 30 50 70 UV radiation time(min)
~
90
O. 88
L
~
l. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
200
UV r a d i a t i o n
750
1990
intensity(uW/cm2)
Fig. 1 Surface potential decays of porous PTFE and non- Fig.2 Surface potential decays of porous PTFE electret after UV radiation of different intensity porous PTFE electret after 900gW/cm2 UV radiation The influence of humidity to the charge storage ability of two PTFE electr.ets. Fig.3 is the surface potential decays of porous and non-porous PTFE electrets corona charged under 58%RH and 84% RH after 900gW/cm 2 UV radiation for different time. The results showed that relative humidity has little influence on the charge storage stability of non-porous PTFE. When RH increased from 58% to 84%, non-porous PTFE electrets still have respectively 94.6% and 93.3 of their initial surface potentials after 90min UV radiation. The decay of surface potential induced by relative humidity was less than 1%. However, the changes of RH showed larger effect on the surface potential of porous PTFE electret, and the electrets can only hold 96.6% and 71.4% of their initial surface potential under the
309 same condition as non-porous PTFE. With the increasing of relative humidity, the decays of surface potential reached even to 25%. It was further indicated in Fig.4 that RH had effect on the surface potential of non-porous electret with different thickness. Being UV radiated for 90min under RH=84%, the porous PTFE with the thickness of 40~m and 100~m can hold the surface potential respectively 71.4% and 86% of their initial values. Compared with non-porous PTFE, the porous PTFE had larger interface and absorbed m.ore water in the body with the increase of humidity. Then the absorbed water dissociated into H + and OH. The introduction of ions into the porous PTFE led to the increase of body conductivity and surface conductivity, the losing of stored charge in the body and on the surface. The larger humidity is, the more losing of charge of porous electret. Therefore, the humidity has large influence on charge storage stability of porous PTFE, and the alcohol, wiping or high temperature and humidity disinfection. are not suitable for medical product of electret. 1
0.9
~o. 9 ~0.8
"UI
.,--~
4.a
_~ PpTTF(RF~RHH:85~)
~
~ e,O. 7 0.6
--O--porous PTFE (RH=84%) --* porous PTFE (RH=58%) 1
10
40
~~ 0.7 o~ Z
70
Radiation timet (min) Fig.3 Surface potential decays of porous and non- porous electrets after 900~tW/cm 2 UV radiation under different RH
+ 2 5 u m PTFE 40um porous PTFE -100um porousPTFE 0.6 ............................................... 1
10
40
70
Radiation time(min) Fig.4 Surface potential decays of porous and nonporous electrets after 900~tW/cm 2 UV radiation when RH=84%
CONCLUSION According to the results, it seems that the UV radiation has little influence on the charge storage stabilities of the two PTFE electrets under normal condition. Therefore, the medical products of PTFE electrets can be disinfected by UV radiation. Nevertheless, the charge storage stability of the PTFE electrets decreases a bit with the increasing of environmental humidity. Hence, the environmental humidity has to be considered when the UV radiation is applied to disinfect the medical products of PTFE electrets.
REFERENCE 1. Xia ZF. Electret[M]. Beijing: Science Press. 2000, 191-194, 552-553. 2. Sessler GM. Electrets. Topics in Applied Phy[M]. 2nded. Vol.33. Berlin: Springer, 1987, 320-344. 3. Jiang J, Xia ZF, Wang ZZ et al. The study of Bioelectrets and their application in Medicine[J]. Aca. J. Sec. Military Med. Uni. (Chinese). 2001, 22(5):401-404. 4. Cui LL, Jiang J, Wang ZZ et al. The influence of NaC1 solution on charge storage stability of Teflon FEP.[J]. J. Med. Phy. of China (Chinese). 1996, 13(3):175-176. 5. Jiang J, Xia ZF, Cui LL et al. [J] 2000, 16(6): 127-129. 6. Xia ZF, Qiu XL, Zhang ZW et al. 2002, 51 (2):389-394.
310 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Charge Dynamic Characteristic in Hybrid Film Consisting of Porous PTFE and Teflon FEP with Negatively Corona-Charging Chen Gangjin l, Jin Guangyuan l, Li Qiaoling2, Ye Feipeng 3 ~Institute of Functional Material Research, Zhejiang University of Science and Technology, Hangzhou, China 310012 2Analysis and Test Center of Zhejiang University, Hangzhou, China 310028 3State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou, China 310027
In this work the hybrid film of porous PTFE and Teflon FEP is prepared by melting FEP into porous PTFE, their charge dynamics of injection, transport and trapping are investigated by means of corona charging, isothermally and thermally stimulated surface-potential decay measurement. The results indicate that the charge dynamics of storage and decay in the hybrid film are very different from single polymer film. When corona charging is performed through side PTFE (C-PTFE), the surface potentials increase at first and then decrease during thermal stimulating discharging. And when charging through side FEP (C-FEP), the surface potential decay only displays a slow change. The reason is interpreted by the assumption that corona charging will generate a large number of microscopic dipoles in the voids of porous PTFE and on interface of hybrid film. The depolarization of microscopic dipoles in the bulk of hybrid film is responsible for the measured change of the surface potentials during aging and storing after charged. The charges released due to thermal exciting run out across the porous PTFE.
INTRODUCTION It was known that the perfluoropolymer, e.g. porous polytetrafluoroethylene (PTFE) film, is a kind of excellent electret material. A lot of application has been proposed according to their excellent charge storage stability. Especially, since the high quasi-static and dynamic piezoelectric coefficients are reported in porous fluoropolymer sandwich system containing space-charge [1,2], soft~ard hybrid systems have become attractive for electret investigation[3]. But there are some problems still unsolved. For example, their high quasi-piezoelectric activity is corresponded to the space charge behavior of materials under loading, but the knowledge about their charge dynamics of storage and transport was very limited. In addition, negative charging is more stable than positive charging for the perfluoro-polymer such as Teflon FEP and PTFE, but the mechanism is not clear yet. Therefore, it is very important to investigate their charging and discharging behavior and to understand their electret mechanism. In this work the hybrid film consisting of porous PTFE and Teflon FEP is prepared by melting 50~tm FEP into 1601xm porous PTFE, and their charge behavior of injection, transport and decay are investigated by means of corona charging, isothermally and thermally stimulated surface-potential decay measurement, etc.. Charging Side MATERIALS AND EXPERIMENTAL METHODS Preparation of hybrid film consisting of teflon FEP and porous PTFE The arrangement of hybrid film is illustrated in Figure 1. The Teflon FEP of 50gin thickness is commercially available from Du Pont Co.
i FEP PTFE
''I PTFE
FEP
Aluminium
Aluminium
C-FEP
C-PTFE
Fig.1 Illustrationof hybridfilm
311 and the porous PTFE of~160~tm thickness ( ~50% porosity ) is obtained from Shanghai Plastic Institute, China. The hybrid film is prepared by melting 50~tm FEP into 1601xm porous PTFE. Firstly, FEP and PTFE film are tight stretched on a circular aluminum ring, respectively. Then, the two films are made to adhere to each other and to be put them into an oven. After heated for 20 min under 300 ~ a hybrid film was obtained. Corona charging at elevated temperature A circular aluminum electrode (100nm thickness) with diameter of 1.5 cm is evaporated on one side of the sample in vacuum. The charging of the hybrid film is performed through side FEP (for short CFEP)or side PTFE (C-PTFE) by means of a point-to-plane corona discharging in air under normal condition (ambient temperature of 298K, atmospheric pressure of 101.3 kPa, and relative humidity of 45%). The aluminized side of film is placed on a heated and electrically grounded metal plate. The air gap between the needle electrode and sample surface is 4cm so that the plasma near the needle tip can not affect the sample directly and the charged sample area is several centimeters in diameter. Unless specially pointed out, the charging condition is as follows: Needle electrode voltage is -12 kV, charging time is 5min, charging temperature is 100 ~ After charged, the samples are stored in small boxes to minimize charge decay by ions in the surroundings. Measurements of isothermally and thermally stimulating surface potentials decay The effective surface potentials are determined by means of non-contacting field-compensating electrostatic voltmeters (Model 344, TREK, USA). After charged at elevated temperature, the samples are immediately removed from charging chamber into a grounded metal plate for measuring surface potentials, so that the potential decay due to higher temperature is avoided. For the measurement of thermally stimulating surface potential decay, heating rate is 6 ~ 9min -~ and the surface potential is recorded at interval of 10 ~ from RT to 260 ~
EXPERIMENTAL RESULTS
A
-lOOOi
_m r
~-eoo
Isothermal surface potential decay no In order to investigate the charge storage stability of hybrid film ~-6oo after charged, the measurement of isothermal surface potential = C-FEP decay under 100 ~ is performed. The samples are charged with ~0 a control grid inserted between corona needle and sample plate. 0 1 2 3 4 5 .~ng "rime(hour) The grid voltage of 1 kV is responsible for the initial potentials Fig.2 Surface potential of hybrid film as a func~on of aging time of the sample. After charging for lh, the corona and grid voltage are turned off but the temperature of 100 ~ in sample chamber is still kept for 5h. Surface potential is measured at interval of l h. ~000 IL The results are shown in Fig.2. Although the initial surface -~ potential is higher in C-FEP sample than in C-PTFE, they \ = \ reached almost the same potential value after aged for 2h. When r8 aged for 5h, they still maintain more than 60% of the initial potential values. -400 For comparison, the results of single FEP and PTFE film 1 2 3 4 5 .~ing "hie (hour) under the same experimental conditions are shown in Fig. 3. The Fig.3 Surface potential of single film results indicate that is better than Teflon FEP. By comparing as a function of aging time Fig. 1 and Fig.2 it can be concluded that surface potential stability of the hybrid film and porous PTFE film are almost the same and even better than single FEP film. The good temporal stability of surface potentials for porous PTFE and C-PTFE film is predictable [4], and for C-FEP film the improvement of surface potential stability compared to single FEP is probably corresponded to the arrangment of hybrid film. The detailed discussion will be given below. (D
I=
u
,
I
|
I
,
i
,
!
,
n
- - m - - F~tOtlS [ r l ] ~ - - o .... T e n o n F E P
n
O
-e---
i
,
!
.......
,
o.
i
Thermal stimulating surface potential decay The result of thermally stimulating surface potential decay for hybrid film and single polymer film after charged for 5 days are presented in Fig.4. For the C-FEP sample, the decay start at about 75 ~ and cross
312 zero to inverse polarity at about 150 ~ then back to zero. It is intresting that the surface potentials for CPTFE sample first increase to 150% of initial value (at 150 ~ and then decrease to zero at about 250 ~ The single PTFE and FEP films have a common profile of surface potential decay, in which the decay displayes a slow decrease when temperature is below 200 ~ for FEP and 220 ~ for PTFE, and then drops greatly and reaches zero at ~250 ~ A direct comparison in Fig.4 demonstrates that the model of surface potential decay in hybrid film distinctly differs from that in single polymer film. For hybrid film, the charge stability is improved when corona charging is performed through side PTFE; while through side FEP the stability become poor. It is obvious that the interface characteristics between porous PTFE and Teflon FEP are resposible for these difference. This phenomenon has been observed by Wegener et.al. in the hybrid film of porous PTFE coated with Teflon| AF, which is related to the glass transition temperature of the Teflon | AF [5]. In order to further understand the distinguished --=-- C~FEP ~ -.. ----o--G P T F E characteristic of charge dynamics in hybrid film, the effect of .~ 1.2 ~ % --A__ Single FEp ~ \ --~--Single PTFE longer storing time on charge stability is investigated by means of the measurement of thermally stimulating surface o. potential decay. The samples are stored for 4 months after charged. Some of data are listed in Table 1. It is seen that g when charging time is 60s, surface potential o f - 5 kV can be measured. After prolonging charging time to 3h, however, the Temperature (~ surface potential of only-2.3 kV for C-FEP sample and-1.5 Rg.4 TS surface potential decay of hybrid filmfor 5 day after charged. charging condition: needle voltage -12 kV, time 10 rnin, T= 100 ~ kV for C-PTFE film are measured. This difference indicates that longer time charging leads to the surface potential 2.4 decreasing. The reason could originated from the charge - - " - - C-FEP1 ,t~-A-= - - o - - C-FEP2 AJ _m 2.0 spreading across the sample, which is the same as the effect of ....A-- C-PTFE1 ~" . . '\ /.v---v 'A 1.6 --v-- C-PTFE2 ~ v \ high charging temperature[6]. 13. 1.2 The results of thermally stimulating surface potential .... I . . '\ 0.8 decay are shown in Fig.5. As seen in Fig.4, with the raise of O9 0.4 temperature C-FEP sample only displays a general decay 0.0 course, and C-PTFE sample shows an increase at first, then E 0 50 100 150 200 250 300 z starts to decrease. Besides, for the C-FEP sample, the effect of Temperature (~ charging time is unobvious, and for the C-PTFE film the Fig.5 Thermally stimulating surface potential decay of hybrid film for 4 months after charged. charging time and aging time markedly affect the intensity of reverse peak. When a sample is charged by negative corona for 60s and then aged for 8h, its potential first increases to ~230% of initial value, and then decreases to zero at ~260 ~ and when charged for 3 h and aged for lh, the value increases only to ~ 180%. 1.6
_ e~e-e~ e
qK"
0..
\
0.8
0.4
o Z
50
100
150
200
250
300
l
r" O .,..,
0
,
"O
" o - o - o- 9
Table 1 Surface potentials of hybrid films after charged for 4 months Sample
C-FEP 1
C-FEP2
C-PTFE 1
C-PTFE2
Charging Time
60 s
3h
60 s
3h
Aging Time
lh
lh
8h
lh
Initial Value
-5000 V
-2300 V
-5000 V
-1500 V
Value after 4 months
-940 V
-468 V
-321 V
-459 V
C-FEP: charged throgh side FEP, C-PTFE: charged through side PTFE
DISCUSSION AND CONCLUSION Charge dynamics of storage and transport in fluoropolymers have been extensively investigated. For Teflon FEP, the investigation based on corona-charging samples has shown that the charges are initially trapped on the surface[7] and a very high surface potential can be obtained when corona charging without a control grid is adoptive, but the charge distribution is not uniform. Annealing at high temperature will lead to a charge spreading throughout the bulk and resulting in an uniform charge distribution. Sessler et.al, proposed that this spreading is due to drift of shallow-trapped holes from the sample volume to the surface-charge layer[8]. And for the porous PTFE, a large number of voids are expectable, which means
313 that a large number of charges are trapped at particular sites or in free volume beside surface charges. During corona charging the high electric fields can cause Paschen breakdown of the gas in the voids and form oriented microscopic dipoles in voids[9]. For the hybrid system consisting of porous PTFE and Teflon FEP, the interface between two kinds of film will become a very good site to store charges. Therefore, its electret behavior will depend not only on property of the single Teflon FEP or porous PTFE, but also on interface characteristics of hybrid film. When corona charging is performed through side PTFE (C-PTFE), the charging behavior of hybrid film is similar to that of porous PTFE. The charge carriers can be injected to the bulk of hybrid film through the voids in porous PTFE and directly deposite on the interface between porous PTFE and Teflon FEP. Airbreakdown occurring in the voids will generate a large number of microscopic dipoles and therefore cause a macroscopic polarization. In such a case, surface potential will firstly increase because the microscopic dipoles are depolarized and cause the charges in the bulk of hybrid film transfer to the PTFE surface when a hybrid film is heated, and then quickly decrease at higher temperature. When charging is through side FEP (C-FEP), the charge carriers can't be directly injected from surface of FEP to the bulk of hybrid film due to the absence of a free path comparable to the sample thickness, so that the charges will mainly reside on the FEP surface. The charge behavior in the bulk of hybrid film will mainly depend on the polarization due to surface electric field of FEP. In this case thermal exciting will make the interface charge run-away from rear electrode on porous PTFE. the charge stability will mainly lie on the property of FEP materials. As was summarized above, the hybrid film consisting of porous PTFE and Teflon FEP is prepared through melting FEP into porous PTFE. When corona charging is performed through side PTFE, the charge stability is improved, and when through side FEP the charge stability become poor. The reason is interpreted by the assumption that corona charging will generate a large number of microscopic dipoles in the voids of porous PTFE and on interface of hybrid film. The depolarization of microscopic dipoles in the bulk of hybrid film is responsible for the measured change of the surface potentials during aging and storing after charged. The charges released due to thermal exciting run out across the porous PTFE. ACKNOWLEDGEMENTS The authors are indebted to Dr. Rudi Danz for his help, and the German Federal Ministry for Education and Research for financial support in part. REFERENCE [ 1] Gerhard-Multhaupt,R., K/instler, W., G6me, T., weinhold, T., SeiB, M., Xia, Z., Wedel, A. and Danz, R., Porous PTFE Space-charge electrets for Piezoelectric Applications, IEEE Trans. Electr. Insul. (2000) 7480-488 [2] Neugschwandtner, G. S., Schw6diauer, R., Bauer-Gogonea, S., Bauer, S., Large Piezoelectric Effects in Charged Heterogeneous Fluoropolymer Electrets, Appl. Phys. A, (2000), 701-4 [3] Mellinger, A., Wegener, M., Wirges, W. and Gerhard-Multhaupt, R., Thermally stable dynamic piezoelectricity in sandwich films of porous and nonporous amorphous fluoropolymer, Appl. Phys. Lett., (2001), 7_? 1852-1854 [4] Xia, Z., Gerhard-Multhaupt, R., Kiinstler, W., High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures, ..J.Phys. D" Appl. Phys., (1999), 3__22L83-L85 [5] Wegener, M., Wirges, W., K/instler, W., Gerhard-Multhaupt, R., Elling, B., Pinnow, M., and Danz, R., Coating of porous polytetrafluoroethylene films with other polymers for electret applications, Conference on electrical insulation and dielectric phenomena, 2001 annual report, (2001) 100-103 [6] W. K/instler, Z. F Xia, T weinhold, A. Pucher, R Gerhard-Multhaupt, Piezoelectricity of porous polytetrafluoroethylene single- and multiple-film electrets containing high charge densities of both polarities Appl. Phys. (2000), 705-8 [7] Sessler G. M.and Yang, G. M., Evolution of charge distributions in polymers during annealing, 9th Intern. Symp. Electrets, Shanghai, China, (1996) 165-170 [8] Sessler, G. M., Alquir, C., and Lewiner, J., Charge distribution in Teflon FEP (fluoroethylenepropylene) negatively corona-charged to high potentials, J. Appl. Phys, (1992), 712280-2284 [9] Kressmann,R., Sessler, G. M. and Gtinther, P., Space-charge electrets, IEEE Trans. Electr. Insul., (1996), 3607-623
314 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Reduction of Braking Torque under the DC Electric Field Gajewski Juliusz B.*, Gtogowski Marek Department of Electrostatics and Electrothermal Engineering, Institute of Heat Engineering and Fluid Mechanics,Wroclaw University of Technology, Wybrzeze S.Wyspianskiego 27,50-370 Wroclaw,Poland
The paper presents some results of experiments on the tribocharging of different engine oils and lip seals and on its effect on the work of machines in which there are rotating parts such as shafts, crankshafts, etc. The research was especially aimed at the braking torque of metal rotating shafts sealed with a lip seal and a possibility of reduction of the torque under external DC electric fields. The DC voltage was applied between the stiffening ring of a lip seal tested and the rotating earthed shaft in the system: metal shaft-oil film-lip seal. The relationships of the braking torque to the DC voltage were established on the basis of measurements of the braking torque under steady conditions, that is for a constant oil temperature and shaft's angular velocity. In general, it was found that the positive and negative DC electric fields produced a negative effect on the braking torque depending on the sort of oils tested and on the material of which the lip seals were made. In only one case the braking torque decreased with the DC voltage applied.
INTRODUCTION Lip seals are used for sealing the rotating parts and protecting against the leakage of oil out of the engine interior and the penetration of impurities from the outside. During the work of a system: rotating shaftoil-lip seal intense friction and irreversible energy losses occur. The lip seals are still being improved through the modification of the shape of a lip and of the material of which the seal was produced [ 1, 2]. Moreover, the additives to oils are selected to reduce friction between a shaft, an oil film, and a seal [3]. The research, some results of which are presented here, was aimed at looking for the optimum combination of different lip seals and oils, as used in real engines, machines, and devices in which rotating parts occurred, for which the auxiliary external DC electric field could cause the braking torque of rotating shafts, crankshafts, etc. to be reduced. A decrease in the braking torque means the reduction of friction, energy losses, and finally operating expenses. The former research results [4] suggested the tribocharging in the oil film between a rotating shaft and a lip seal exert a rather significant influence on an increase in the braking torque. Also the authors found that an external DC electric field should play a role in the whole process and affect the work of the system. The natural tribocharging had the negative effect on the work of the system especially that the braking torque increased with the increasing level of electrification and temperature of the oils tested [4, 5]. The application of a DC voltage to compensate for the negative effect of a natural electric fields established between the rotating shaft and the lip seal and its earthed seating on the braking torque produced a negative, undesirable outcome. The DC electric field enhanced the negative effect in some cases. Only one lip seal used in the experiments and being in contact with all the oils tested revealed a positive, satisfactory, and promising result. While the metal shaft rotates, in the interfaces: shaft-oil film and oil film-lip seal and in the inside of the oil film some various types of charging occur at the same time and exert an influence on the whole process considered. Depending on the sort and quality [6] of oils used, the oil temperature, the material and the state of a surface (roughness) [7] of a shaft, the material of which a seal is made, the intensity and
315 way of contacts (friction) between the bodies, the different tribocharging of individual phases occurs since the contribution of each of the charging mechanisms to the total charging is different, as supposed. If the movement of the charged oil particles from the middle part of an oil film towards the interfaces is possible, it is interesting whether or not an external DC electric field could enhance this process and, if so, under which conditions. As supposed, under specific conditions an external electric field could act as a field that compensate for the natural one of the net charge in the space between the shaft and seal.
EXPERIMENTAL METHODS AND SET-UP Methods The various lip seals tested had stiffening tings and compression springs. The cross-section of such a typical lip seal is shown in Fig. 1. A stiffening ring was an electrode to measure the potential induced by the net charge of oil particles in the oil film between a rotating shaft and a lip seal. Also the ring served as another electrode to generate a DC electric field, that is the DC voltage UDC was applied between the same stiffening ring and the earthed rotating shaft to establish an external DC electric field across both interfaces. The braking torque of a rotating metal shaft was measured with a torquemeter under steady state conditions that is when a constant oil temperature T, a stable shaft's angular velocity n or a stable DC voltage UDC were reached. The braking torque MB was measured without any external DC electric field for the so-called natural tribocharging. After the DC voltage had been applied and the conditions had been stable the measurement of the braking torque MDC was being made. The both braking torques were measured as a function of the DC voltage UDC for all other things being equal, that is for the constant oil temperature and shaft's angular velocity. Figure 1. Cross-section of a lip s e a l .
Experimental set-up The experiments on the influence of the DC external electric fields on the braking torque of rotating shafts for different engine oils and lip seals were performed in the experimental set-up built on the basis of a model engine. The whole experimental facility is shown in Fig. 2 and was built for investigating the friction and testing the lip seals for sealing rotating parts of machines, engines and other devices. The schematic diagram (Fig. 2) shows the whole experimental facility which consists of: the housing of an oil chamber (1); a lip seal (2); the seal's stiffening ring (3); an oil tested (4); an air bearing (5); the sensor of a torquemeter (6); an electric engine (7); a steel shaft (8); a microprocessor-based system for controlling the angular velocity n and for measuring the braking torque M of the shaft and temperature T of oil (9); an oil heater (10), and a DC power supply (11). The chamber was filled with the oil tested up to a level just below the rotating shaft. The whole chamber was a model of the part of a real engine.
Figure 2. Schematic diagram of the model engine and experimental set-up
316 The DC power supply energized the stiffening ring of a lip seal to produce a DC electric field between this ring and a rotating shaft. The DC electric field of two polarities was expected to compensate the natural electric field of the net charge of oil particles to reduce the braking torque. RESULTS OF EXPERIMENTS Materials tested and experimental procedure The experiments were conducted for one shaft of the roughness Ra = 0.32 gm, the following fresh engine oils: ESSO SAE 30 and Polish LOTOS 15W40. Two fluorocarbon lip seals of 85 and 88 mm in diameter were tested which differed from each other in the contents and sort of additives, which were unknown. The measurements of the braking torque were made under steady state conditions to find its relationship with the DC voltage applied between the seal's stiffening ring and the earthed rotating shaft. The oil temperature T was 90~ while the angular velocity n was kept constant at 1500 rpm. The positive and negative DC voltage was applied whose value changed from 0 to 1800 V. _
Experimental results and discussion The braking torque M as a function of the DC voltage applied is shown in Fig. 3. The oil LOTOS 15W40 was used and a lip seal of 85 mm in diameter. The both braking torques are marked in all figures with the 0.50 symbols, which are different for the following DC voltages applied: MDC is marked with 9 and m for the negative and positive voltages, respectively while 0.48 MB ~ O for no DC voltage applied (UDC 0). The positive DC voltage UDC seems not to have Z 0.45 any influence on the braking torque for the oil and the 85-mm seal. The negative DC voltage has rather a negative influence on the braking torque. In the case 0.43 of LOTOS 15W40 the DC electric field causes the braking torque to increase with increasing DC voltage. 0.40 The many experiments carried out on many 0 300 600 900 1 2 0 0 1 5 0 0 1800 different oils and lip seals showed that in general the UDC[V] DC electric fields established between the rotating Figure 3. The braking torque as a function of the DC shafts and lip seals or other metal parts across the oil voltage for LOTOS 15W40 and the 85-mm lip seal. films had the negative influence on the braking torque namely the torque always increased with the 1.10 , . . . . increasing DC voltage applied regardless of the negative effect of the natural tribocharging in itself. 1.05 The overall trends of the braking torque with and without the external DC electric field and for different oils, lip seals and physical parameters were I ~.oo similar. The positive effect of the auxiliary DC electric 0.95 field on the reduction of the braking torque irrespective of the negative effect of the natural tribocharging is shown in the next two figures for the 0.90 0 300 600 900 1 2 0 0 1500 1 t00 lip seal of a diameter of 88 mm and two different oils UDC[V] used, namely LOTOS 15W40 and ESSO SAE 30. Fig. 4 illustrates how the braking torque Figure 4. The braking torque as a function of the DC decreases with the increasing DC voltage for the oil voltage for LOTOS 15W40 and the 88-mm lip seal. LOTOS 15W40 while the similar plots for ESSO SAE 30 are shown in Fig. 5. The relationship between the torque and the external DC electric field is promising since it suggests there is a possibility of decreasing the friction and the braking torque of rotating parts with the use of auxiliary external electric fields. The only limitation I
I
0.95
e-"n
Z 0.90
0.85 0
I
I
I
300
600
900
I
I
I
1200 1500 1800
UDC [V]
Figure 5. The braking torque as a fimction of the DC voltage for ESSO SAE 30 and the 88-mm lip seal.
317 here is the sort of oils and the type of lip seals used. Also the shafts used may play a role in the whole process. Out of many oils, lip seals, and shafts tested only for these, as presented here, the tendency to reduce the braking torque of a rotating shaft was observed for the DC voltage applied. It seems that the contents and sort of additives in the oils tested plays an important role in reducing the braking torque under an external DC electric field. There is a distinct difference between the Polish oil LOTOS 15W40 and ESSO SAE 30. In the case of the former the effect of the DC field on the braking torque reduction is stronger than for ESSO SAE 30 especially for the negative polarity of the DC voltage applied. The laboratory experiments were repeated many times during one experimental session and then also repeated after some time to find the repeatability of the results obtained. The repeatability was very good.
CONCLUDING REMARKS The experimental results show that the DC electric fields established between the rotating shaft and the seal's stiffening ring only in some cases can compensate for the negative "bad" effect of natural tribocharging of the different oils in contact with the rotating metal shaft and with different lip seals on the braking torque. It seems apparent that the positive effect of the DC electric field for only one lip seal tested is attributed to the contents and sort of additives used by manufacturers of the lip seals. Other experiments performed using other lip seals proved that only for a few of them the tendency of the external DC electric fields to reduce the shaft's braking torque was observed. For the majority of the lip seals and for the same engine oils used the braking torques tended to increase with the increasing values of the DC electric fields established across the oil films. The positive results obtained for only some lip seals are promising and it seems that there is a challenging possibility of the braking torque reduction in real engines, machines, and devices with rotating parts. The use of a properly selected lip seal and oil as used in car engines can reduce the friction and hence the braking torque of the rotating parts, e.g. shafts, crankshafts, etc., in various real machines. The application of the DC electric fields to the system: rotating shaft-oil film-lip seal can be promising to reduce friction and braking torques, and energy losses, and to simultaneously minimize operating expenses. Also, as a result, the lifetime of the lip seals can be prolonged. In the instance of the oils and seals tested the DC electric field only enhances that action, that is, the braking torque generally has a tendency to decrease with the increasing DC voltage applied to the system analysed. REFERENCES 1.Bock E., Vogt R., New radial shaft seal concepts for sealing hydraulic pumps and motors, Sealing Technol., vol. 11, pp. 6-10, Nov. 2003. 2. Gawlifiski M., On friction reduction in rubber lip seals for rotating shafts, Sealing Technol_., No. 40, pp. 8-11, 1997. 3. Wiehler K., Wollesen V., Additives in oil enhance sealing, Sealing Technol., vol. 63, pp. 8-9, Mar. 1999. 4. Gajewski J.B., Gtogowski M., Influence of tribocharging on the work of lip seals in a model engine, J. Electrostat., vol. 5152, pp. 124-130, May 2001 [9th Int. Conf. on Electrostatics ELECTROSTATICS 2001, Ko~cielisko-Zakopane, Poland, May 29-June 2, 2001 ]. 5. Gtogowski J.B., Gajewski J.B., Gawlifiski M., The DC electric field effect on braking torque in a model engine, accepted for presentation at the 4th Meeting of the French Electrostatic Society, 2-3 September 2004, Poitiers, France. 6. Harvey T.J., Wood R.J.K., Denuault G., Powrie H.E.G., Effect of oil quality on electrostatic charge generation and transport, J. Electrostat., vol. 55, pp. 1-23, 2002. 7. Harvey T.J., Wood R.J.K., Denuault G., Powrie H.E.G., Investigation of electrostatic charging mechanisms in oil lubricated tribo-contacts, .Tribology International, vol. 35, pp. 605-614, 2002.
318 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Experimental comparison of probes for air discharge measurements Paasi J., Salmela H., Kalliohaka T., Fast L.,* Smallwood J.+ VTT Technical Research Centre of Finland, P.O. Box 1306, FI-33101 Tampere, Finland SP - Electronics, P.O. Box 857, SE-50115 Borhs, Sweden + Electrostatic Solutions Ltd., 13 Redhill Crescent, Bassett, Southampton, SO 16 7BQ, UK
We have studied the performance of three different kinds of passive resistortransmission line probes intended for the measurement of electrostatic discharges (ESD)" an unshielded ball probe, a shielded ball probe with the ESD current collected on a coaxial wire tip, and a needle-like probe. We evaluated them for possible application in assessment of ignition hazards or ESD damage risks to electronic components. The results show that there is no single probe type that is ideal for all kinds of situations. There are significant differences between the probe responses in their ability to initiate ESD, charge transferred, and peak ESD current.
INTRODUCTION Rapid discharges of static electricity from insulating surfaces, metal objects and other materials are of concern in ignition of flammable materials and in the assessment of the risk of damage to electronic components and assemblies during manufacture and service maintenance. The nature of an electrostatic discharge (ESD) is determined by the electrostatic field distribution required to initiate a self-sustaining electron avalanche. The onset of discharge is governed by the electrical breakdown of the surrounding atmosphere. Accordingly, the waveform (peak current, duration, rise time, fall time, and charge transferred) of an ESD as well as the risks associated with the ESD depend on various factors, such as the amount and distribution of charge on the charged object, the conductivity of the charged surface, electrical and geometrical parameters of the discharging object, system geometry, etc. [ 1, 2]. A discharge between a charged surface and a discharging object is more likely to occur for short than long air gap lengths. Furthermore, at a fixed air gap, a discharge is more likely to occur to grounded needle than to a large grounded sphere. Different kinds of probes have been developed during the past years for the measurement of air discharges (spark and brash discharges, etc.) in order to evaluate the ESD risks, without the use of explosive atmospheres or destructive tests of electronics. In this work we have studied the performance of three different kinds of passive resistor-transmission line discharge probes: an unshielded ball probe developed at Physikalish-Technische Bundesansalt (PTB-probe) [3], a shielded ball probe having an earthed hemispherical shield with the ESD current collected on a coaxial wire tip, the probe developed at Electrostatics Solutions Ltd. (ESL-probe) [4], and a needle-like shielded probe developed at SP Swedish National Research and Testing Institute (SP-probe).
ELECTROSTATIC DISCHARGE PROBES Ideally a probe for ESD measurements should be uniquely designed for the situation it tries to mimic. For general purposes, a probe for a faithful ESD waveform measurement should be relatively small in comparison with the size of the charged body, the impedance of the probe circuit should be solely
319 resistive up to the highest rates of change of discharge current, and the value of the impedance should be small enough to avoid the generation of an excessive potential at the probe surface during the discharge [5]. For the measurement of ESD waveform (peak current, duration, rise and fall times) a passive resistortransmission line design is the most suitable one [5,6]. It is not limited to single discharges, but can measure also multiple discharges, and charge transferred in an ESD can be obtained by integration of the measured ESD waveform. In this work we focus on three different, passive resistor-transmission line discharge probe designs: PTB, ESL and SP types of ESD probes. The PTB probe is an unshielded ball probe with a 0.2 high frequency shunt resistance, connected to a rapid oscilloscope, in the earth line of a ball electrode of 25 mm in diameter, Fig. 1 (a). The shunt resistance is coaxially built of 10 high-frequency metal film resistors. The voltage developed across the shunt resistance is fed into a 50 transmission line cable terminated in a 50 input impedance of oscilloscope. See ref. [3] for more details of the PTB probe. The ESL probe is a shielded ball probe. The probe tip employs an earthed 20 mm hemispherical shield with the ESD current collected on a coaxial wire tip protruding about 1 mm from the shield centre, Fig. 1 (b). The aim of the shield is to ensure that the majority of the charge collected in the ESD event passes through the measurement circuit rather than being locally neutralised at the probe tip [5]. The ESD current passes into the sensing wire tip and through a 1 shunt resistor to the earthed hemispherical shield. The shunt is fabricated from a parallel array of 10 high-frequency carbon resistors. The voltage developed across the shunt resistance is fed into the oscilloscope through a 50 termination resistor and 50 transmission line cable. For more details of the ESL probe, see ref. [4]. The SP probe is a needle-like ESD probe having, in principle, much in common with the ESL probe, Fig. 1 (c). A major difference between the SP and ESL probes is the discharge tip which is a needle in the SP probe protruding 15 mm from the shield. The shield is not a hemisphere but simply a BNC terminal of coaxial wire. The shunt resistor of the SP probe has a value of 10, consisting of 7 carbon film resistors.
a)
E,D "
discharge
50 f2 cable
ESD<~
S
50Seriesf2resistor r--I
discharge ~~_~]shunt C~ 1.0 I
Oscilloscope 50 f~ cable
Probe shield _.L
c)
discharge
,
coax,a, shunt 10 ~
Probe shield
50f~
I
shunt 0.2 f~ J-~
b)
t~
'"'Oscilloscope
0 _1_
50~
Oscilloscope
b 50 f~ cable
~_
50 f~
Figure 1 Equivalent circuits of (a) PTB, (b) ESL, and (c) SP types of probes for ESD measurements.
RESULTS AND DISCUSSION The ESD probe comparison was done by measuring discharges from charged insulator surfaces (acrylic), metal plates, and from unearthed ESD protective fabrics. The objects were charged to potential levels from +3 kV to +40 kV by using corona discharge or by contact With a voltage source. The sample size was about 250 mm x 250 mm. A rapid oscilloscope with 1.5 Ghz bandwidth and 8 GSa/s sampling rate was used for the measurement. The results are averages of 5 discharges with the exception of ESD waveforms, which represent a typical ESD. We measured threshold of initiation of discharges from insulating surfaces for each probe for negative and positive polarities. These were: -16 kV and +17 kV for the PTB-probe, -7.2 kV and +6.5 kV for the ESL-probe, a n d - 7 . 2 kV and +3.8 kV for the SP-probe. Average discharge gap lengths for
320 discharges from insulator surface charged to -40 kV were 6 mm for the PTB-probe, 70 mm for the ESLprobe, and 130 mm for the SP-probe. The results clearly demonstrate the fact that for sharp discharge tips the electric breakdown field in the discharge gap is exceeded at a longer distance or at lower surface potential than for large spheres. The lower threshold potentials of ESL and SP probes for a positively charged object than for negatively charged object are consistent with documented lower breakdown voltages found with negative polarity electrodes giving a divergent field [7]. Typical examples of ESD waveforms are given in Fig. 2 for the discharges from charged insulator surface (a), charged metal plate (b), ESD protective fabric with stainless steel (SS) conductive fibres (c), and ESD protective fabric with surface conductive (SC) carbon fibres (d). The ESD protective fabrics are for protective clothing used in electronics manufacturing as well as in process industry, but similar characteristics would apply for fabrics used in fabrics for flexible intermediate bulk containers. Measured peak ESD currents and charge transferred in the cases of Fig. 2 are given in Table 1
Figure 2 Examples of air discharge current waveforms from (a) insulator surface charged to -40 kV, (b) metal plate charged to +3 kV, (c) ESD protective fabric with stainless steel (SS) conductive threads charged to-3 kV, and (d) ESD protective fabric with surface conductive (SC) carbon fibre threads charged to -4 kV. Measured peak ESD currents and charge transferred in the cases (a)-(d) are given in Table l.
Table 1 Measured peak ESD currents and charge transferred in the cases of Figure 2 for the different probes
Peak ESD current PTB ESL SP Charge anstransferred PTB ESL SP
Insulator -40 kV
Metal plate +3kV
ESDfabric,SSThreads,-3kV
ESD fabric SC-threads,-4 kV
-0.59 A -0.25 A -0.05 A
7.3 A 12.2 A 11.3 A
-3.0 A -7.5 A -7.3 A
-0.04 A -0.14 A -0.18 A
-44 nC -38 nC -5 nC
337 nC 359 nC 327 nC
-99 nC -133 nC -125 nC
-97 nC -111 nC -117 nC
From the experimental results of Fig 2 and Table 1 we can see that there are considerable differences in the performance of the probes. The ESL and SP probes, which are of shielded design, gave broadly
321 similar waveforms for ESD from fabrics and metal plate and higher peak current values than the PTB probe. The ESL and SP probes gave slightly larger values of charge transferred for the ESD from fabrics. For the discharges from insulator surfaces the situation is not straightforward. At high levels of charge, >1201kV, the PTB probe could be brought close to the charged surface before an ESD due to the large diameter of the electrode and, accordingly, a strong ESD was measured. The SP and ESL probes initiated discharges at a much greater distance from the surface, due to the presence of relatively sharp protusions from their tips. We note that the peak current is in inverse relationship to the distance at which discharge occurred, and we suggest that increased spark length, and hence spark channel resistance, may be a factor in this. In the case of the SP probe the charge transfer and peak current is about a factor of 10 lower than the PTB probe which shows that only a small fraction of the available discharge energy was transferred. So, the needle-like SP probe is not preferable for the estimation of ESD risks associated with highly charged insulators. On the other hand, the threshold potential of the PTB probe is relative high. At low charging levels of insulators (<1171kV) the ESL (or SP) probe can measure ESD that may not occur when the PTB probe is used. This may be important, for example when assessing the possible ignition risk to highly flammable gas mixtures from insulators charged to lower levels. The threshold of initiation of discharges, and ability to simulate ESD under the working conditions of interest are important considerations when assessing ESD risks. Peak ESD current is, from the electronic component failure point of view, the key parameter to control for most ESD sensitive electronic devices [8]. Charge transferred in a discharge, on the other hand, has been suggested as a key parameter to control in flammable atmospheres [3]. We can see that both charge transfer in the discharge and peak current varied with the type of probe used. This shows that the probe may well have influenced the discharge characteristics - we must be careful to select a probe that effectively produces as nearly as possible the conditions expected in the application. In electronics industry shielded ESD probes with small diameter discharge tips, imitating the small leads of electronic components, would be appropriate. In flammable atmospheres the discharge probe should have a large discharge electrode (either shielded or unshielded) with diameter about >15-20 mm in order to collect the maximum charge transferred to assess the risks. However for investigating ignition risks of highly flammable materials a different probe profile may be required in order to reliably initiate ESD at lower surface voltages. In conclusion, there is no single ESD probe type that is ideal for all kinds of situations where direct ESD measurements are used for the assessment of ESD threats due to charged objects. There are significant differences between probe responses in the threshold of initiation of discharges, charge transferred, and peak ESD current and the evidence suggests that the probe design influences these ESD characteristics. In electronics manufacturing environment, where the focus is in improperly or completely unearthed items charged to relatively low potentials, a small diameter discharge tip, shunted to ground through low-ohmic, high-frequency resistors, is the best choice. When assessing ignition risks related to highly charged insulators, the diameter of the grounded discharge electrode should be increased. There is some evidence for benefits of a shielded probe design at low charging levels for ESD from metals and fabrics, but less for ESD from highly charged insulator surface. REFERENCES 1. Cross, J.A., Electrostatics: Principles, Problems and Applications, Adam Hilger, Bristol (1987) 2. Davidson, J.L., Williams, T.J., Bailey, A.G., Stevens, R.P., Discharge energy available to grounded spheres approaching charged ground-backed insulators, J. Electrostatics (2003) 59 153-172 3. von Pidoll, U., Brzostek, E. and Froechtenigt, H.R., Determining the incendivity of electrostatic discharges without explosive gas mixtures, Proc. 2002 Industry Applications Conference, IEEE (2002) Vol. 1 277-283 4. Smallwood, J.M. and Heam, G.L., A wide bandwidth probe for electrostatic discharge measurements, Proc. Electrostatics 2003 Conference, Inst. Phys. Conf. Ser. No. 178 (2004) 125-130 5. Chubb, J.N. and Butterworth, G.J., Charge transfer and current flow measurements in electrostatic discharges, J_ Electrostatics (1982) 13 209-214 6. Smallwood, J., Simple passive transmission line probe for electrostatic discharge measurements, Proc. Electrostatics 1999 Conference, Inst. Phys. Conf. Ser. No. 163 (1999) 363-366 7. Meek, J.M. and Craggs, J. D., Electrical breakdown of gases, Clarendon, Oxford (1953) 8.Paasi, J., Salmela, H. and Smallwood, J., New methods for the assessment of ESD threats to electronic components, Proc. 2003 EOS/ESD Symposium, ESDA (2003) 151-160
322 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Measuring the Size and Charge of Dust Particles in the Martian Atmosphere C.I. Calle i, M.K. Mazumder 2, J.G. Mantovani 3, C.R. Buhler 4, D. Saini 2, A.S. Biris 2, A.W. Nowicki 4 ~NASA, Kennedy Space Center, FL, USA 2Univerisity of Arkansas at Little Rock, Little Rock, AR, USA 3 Florida Institute of Technology, Melbourne, FL, USA 4ASRC Aerospace, Kennedy Space Center, FL, USA
ABSTRACT Dust is airlifted into the atmosphere by frequent Martian dust devils as well as by the more infrequent regional and planet-wide dust storms. This phenomenon may compromise the duration of robotic and even future human missions to Mars, as it poses a serious problem for solar arrays, spacecraft, spacesuits and equipment. In spite of several successful landing missions to the planet, very little is known about the dust itself. It is believed to be comprised of particles with diameters less than 50 micrometers. In the presence of low moisture condition, this dust is also likely to be statically charged either triboelectrically, as particles collide with each other and the surface, and/or photoelectrically, by the incident UV irradiation. The presence of electrostatic charge on the dust particles has important consequences not only in terms of understanding the atmospheric phenomena on Mars, but also the methods for controlling the dust for future planetary missions. We present preliminary results particle size distributions and of charge-to-mass distributions of Martian simulants using a miniaturized prototype version of a commercially-available instrument originally developed by one of the authors at the University of Arkansas at Little Rock (UALR). This prototype, recently completed by UALR and the Kennedy Space Center, may be used to characterize the size and charge of dust particles suspended in the Martian atmosphere. Possible applications of this instrument for lunar missions will also be discussed.
323 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on Electrostatic Discharge Test Standard and Theory Models* Shanghe Liu, Ming Wei, Zhancheng Wu, Qiang Zhao, Liang Yuan Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, China
Abstract: In the electrostatic discharge electromagnetic effect experiment, it is found that different ESD simulators may yield inconsistent sensitivity test result for some EUT, though they both meet IEC61000-4-2 standard, Aimed at this phenomena, we found the difference was caused by different lead number of current. We suggest IEC standard should be modified. In the mean time, via research on ESD electromagnetic model, a new dipole model has been presented. These research results have been applied in practice. Key words: ESD, test standard, theory model, effect mechanism
Electrostatic discharge is widespread in dry environment. Electrostatic charge can gather to dangerous ESD source with more than 10 thousand voltages. Once discharge circuit forms, pulse current will exceed 10 ampere, even reach 100 ampere. The discharge procedure occurs with strong wide band EMI in nanosecond level. ESD releases energy not only via conducting, but also via radiating to equipments nearby and interfering or damage. In micro-electric area, the global loss is more than 10 billion US dollars. Therefore, developed countries attach importance to electrostatic protection research. In aspects of microelectric parts ESD protection, many theory models have been brought out early or late. IEC has also constituted check standards and experiment plate for micro-electric equipment and parts. But our research shows that all these models and standards are limited and need to be improved.
ESD MODEL AND LIMITATION OF EXPERIMENTAL METHOD&TEST PLATE DEFINED BY IEC61000-4-2 The main circuit of ESD simulator matching IEC standard contains R and C, which are discharge resistance and energy-storing capacitance [~-41.Considering the distributing parameters, model circuit will be more complex (see figure 1). In this situation, IEC defines standard current of human body ESD simulator as figure2. Table 1 shows the parameters of waveform. R4
I II~A
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,
f---- ................................. 4H
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Figure 1 ESD (human body model) equivalent circuit
Project supported by the NSFC No. 50077024 and 50237040
Figure 2 ESD (human body model) standard current
324 In the ESD effect experiment, we found that that ESD simulators may yield inconsistent sensitivity test results for some EUT, though they both meet IEC61000-4-2 standard. For a example, a single chip microprocessor circuit tested according to IEC standard showed different results obviously. Table shows the result. Table 1. ESD (human body model) standard current parameters Peak current/A(+ 10 %)
30ns current/A(+3 0
7.5
4
60ns current/A(+30 %)A 2
0.7~1
15
8
4
6
0.7~1
22.5
12
6
8
0.7~1
30
16
8
Discharge voltage/kV
Rise time
2
0.7"---1
ns
%)
, ,
4 .
In order to find the reason causing the Table 2. Radiating test result of different ESD simulators difference, we studied the output characteristics of the two ESD simulators. Figure 3 shows ESD Failure Simulator Threshold voltage/kV currents of Noisken ESS200AX and Schaffna 2.00~2.20 NSG435 ESD simulator measured by ESD ESS-200AX - 5.80 "~ - 6.00 Inner RAM simulator current verify device. Table 3 gives RONR7 error 2.50 ~ 2.70 the details. Compared with standard parameters NSG435 in table 1, both of the two simulators' current - 4.30~ - 4.50 parameters meet IEC standard. Though the two 1.10 "-~1.20 ESS-200AX simulators' currents are within 0.7ns- lns Exterior - 0.20~ - 0.30 defined by IEC, the front edges of currents are RAM content 3.10 "-'~3.20 not super- position (see figure4). The rising rate overwrite NSG435 can affect both the high frequency of radiation - 0.20 ~ - 0.30 field and experiment results. In addition, although the discharge current's peak values are similar, its derivative curves (di/dt) are different. Fig 5 shows 6kV discharge current's derivative curves of the two simulators. It can be seen that NSG435's current's derivative peak value is proximately 1.5 multiple of that of ESS-200A. Obviously, their radiation interference to electric devises are different. 7
7
6
6
ESS-200AX
5
4
~a
< v
3 2
2 1
1
0
0
-1
NSG-435
5
~,, 4
o~o
"50~On
t(s)
'"
;l'O0'.On
-1
" 010
. . . .
~"O0'.On
5010n
t(s)
Figure 3 Short cut currents of two simulators Table 3 Current parameters of the two simulators Discharge voltage/kV
ESS-200AX 30ns Peak current/A current/A 3.81 7.05
NSG435 30ns Peak 60ns Rise time/ps current/A current/A current/A 4.08 6.74 2.40 769
60ns current/A 2.67
2
Rise time/ps 883
4
923
14.35
8.11
4.39
734
13.38
8.03
5.01
6
896
21.66
12.32
6.73
743
20.00
12.42
8.07
907
29.33
16.35
9.00
733
26.94
16.66
10.25
325 We deem that this phenomena due to that the IEC standard current is not strict. This makes different results of different simulators. Therefore, we suggest IEC ESD verify standard should give more complete specifications for simulators. Besides current parameters, the front edge and derivative of current should be specified in order to minimize current oscillating. Only thus can reduce the difference. On the other hand, major of ESD if air discharge in the practice, instead of contact discharge. The air discharge current curve may affected by approach speed and environment factors. Although IEC standard specifies air discharge manner, there are no standard air discharge current curve and approach speed in the standard. Therefore, it is required to research the feature of air discharge and control the discharge manner and its test plate strictly. Our institute has produced air ESD test plate which can be seen in another article in this conference.
20
- - - - - ESS-200AX --o-- NSG435 ~~"N.
/
15
< 10 v m
5
-1 .'On
0:0
1.6n
t(s) Figure 4 Comparison of current front edges of ESD simulators
30
;. '~ ?,
20 "~> ~9
.... ~ I"1
= -10 -20-
-30 -2.0n t(s)
V' ,I /
a'l ,'~, , / t, / \1, ~ /
.
o
RESEARCH ON MODEL OF ESD RADIATION FIELD
ESS-200AX NSG435
'k/" I,
,,i
ESD model defined by IEC standard is applicable to EMS 0'.0 2.0n 4.0n test of all electric devices. But it only can represent the characteristics of ESD source without other information, Figure 5 comparison of current derivative especially radiation information. With the development of curves of two ESD simulators science and technology, it is found that ESD radiation field's hazard to micro-electric circuits becomes serious more and more. Therefore, many ESD radiation models have been brought out, such as long conductor model, dipole model, double source model and so on. Among these models, the dipole model by P.F. Wilson is the most famoustS7] o According to P. F. Wilson's hypothesis, ESD current is i (t), the length of discharge gap postpone force, P (z, r, r electromagnetic field of arbitrary space can be described:
_ dlk r [ Rja(t-R/c)] H(z,r,d~,t)-ar -~n ~ i ( t - R / c ) + ~ j=l Rj
-E(z,r,r
c
2 Rj
+ a~ 4 ~ 0 J-~
['
1
-1
Q(t-R/c) Ri
(z g z')2 1 Oi(t - R / c) +---------7--_ 1 Rj cZRj Ot
(1)
at
) + 3i(t-R/c) = -a r ~dl ~r(zlxz').[3Q(tzR/c -G 4Keo j=~ Rj L R~ cR2
dl, by
1 bi(t-R/c)] +
2
c Rj
i(t - R2 / C)
bt
(2)
}
In (1) and (2), ~0 is inductivity of air; c is light speed, i(t) is time-variable current. The direction of current is z axial. Q(t) is integer of current: Q ( t - R / c) = I o'fit '- R / c)dt '
When conductor discharges, spark near the surface. The distance of dipole and its mirror to the earth can be regarded as zero.
326 1
z'=0,
R j - R = ( z 2 +r2) ~
P. F. Wilson thought: as discharge conductor surface conductivity is rather low. Spark gap can't hold the current's charge as space dipole. So the current integral item can be ignored. EM field of point A(z, r, ~ , t) can be simplified as: -dl rz [ 3 i ( t - R / c) 1 ai(t - R / c) E ( z , r , q ) , t ) = ar 2---~o R---TL cR 2 + ~
at
c2R
+ a~
__
H(z,r,.,t)=a, ~
~
- 1
+
cR 2
--~--
1
J
(3)
c
at
(4)
i(t-R/c)+
j=l R j
c
at
The dipole described by equation(3) and(4)can be used to calculate electric field and magnetic field. But it does not represent static field variation in ESD process. As ESD hazard is the total effect of many related factors, the static field caused by static charge should be considered. After some approximate calculation, the express equation of electric field is" _ _ E(z,r,q),t) = ar ~
rZ
~oi(t'-R/c)dt'-
2r"r R2 [
-
dl ~ ( 3 z 2
+ a~ 2:r
R3 )~
[ ~ R2 - 1
3i(t
3Q0
-I
-
cR 2
'i(t'-R/c)dt'-Q~ o
R3
R/c)
1 ai(t
+ ~c2R
i(t-R/c) +
cR 2
-
R/c)
at
(5)
r E ai(t-R/c) _ c2R 3
at
Q is initial quantity of charge, other symbols are the same as P. F. Wilson's dipole model. Here we assume that all static charges are concentrated on the pole before discharge, although it is different to the fact. So the improved model is still need to be researched [4-5]. But this theory model can basically describe the near electromagnetic field and far field of ESD process. The new model considers not only radiation field in ESD process, but also static field. It is suitable to calculate both distribution of near field and that of far field. Based upon models above, we analyze the relationship of ESD EM field to temperature, air humility, shape of discharge pole, approaching speed, length of spark and discharge voltage. The calculation result shows that the near electric field is mainly static field exited by charge, the far field is mainly radiation field caused by differential current. Both of them increase with voltage. But with discharge voltage increases, the length of spark increases, front edge of pulse current will increase. But the radiation field will decrease. That is to say, The relationship of ESD EM field and discharge voltage is different in different frequency area. This conclusion is the same as M. Masugi's measurement via three antennas[6]. Part of experiment result proves our ESD theory model and calculation method are correct. Table 4 shows the comparison of the models mentioned above.
APPLICATION RESULTS We have studied theoretical model of ESD electromagnetic field energy coupling rules and aperture coupling by above research achievements. The ESD effect experiment objects include three typical mechanical electric devices, two GPS receive devices, two MPU and semiconductor parts. In the meantime, we use the research achievements to estimate electrostatic security and estimate methods. These achievements have been applied to estimating electrostatic security of Chinese airship Shenzhou No.5 and other important area.
327 Table 4 comparison of new ESD EM models and other models iiu
Name
]
Long conductor model tTl i
iii
iii
iii
i
. . . . . . . . . . . . . . . . . . . . . . . . . . .
Double ball model t81
Application
iiiii
iii
iii
ii
i
i
i i
i i
i
i
i
ttt0
Problem I Can't calculate far field and EgD fieid ].ex!ted by qu!ck c ~ e n t . . . . . . . . . . .
Long current channel in ESD i
t_u
iii
......
Near field calculation in ESD
I Ignore the effect of current and can't ...... I ca!cu!ate far field and m a ~ e t i c fie!d: ......
..... .......... ~ ~ Dipole model t~l
~ ~ Farfield CalCUlation in ESD. can be used to calculate electric field and magnetic field,
. . . . A.., t451 N~w u~ouc~ '
] Consider static charge and can caicuiate ] both near field and far filed.
Not consider static charge in ESD, can't calculate near field. i ]
..........................
.............................................
REFERENCES 1. Sheng Songlin, Tian Minghong, Liu Shanghe. Improved dipole model of ESD and calculation of electromagnetic field. High electric voltage. 2002, 28(10): 8~9 2. Sheng Songlin. Research on ESD electromagnetic field space-time distribution model and test technology. PhD thesis of electrostatic& electromagnetic protection institute. 2003:10~33 3. P. F. Wilson and M. T. Ma. Fields radiated by electrostatic discharges. IEEE Trans. on Electromagnetic Compatibility, 1991, 33(1)-10~18 4. S. Ishigami, R. Gokita, Y. Nishiyama, I. Yokoshima, and T. Iwasaki. Measurements of fast transient electric fields in the vicinity of short gap discharges. IEICE Trans. Commun. 1995, E78-,B(2): 199~206 5. S. Ishigami and T. Iwasaki. Two-source model of transient electromagnetic fields generated by electrostatic discharge. International Symposium on Electromagnetic Compatibility, Tokyo, 1999:130 ~ 133 6. M. Masugi, K. Murakawa, N. Knvabara, and F. Amemiya. Measurement and analysis of electromagnetic pulses caused by electrostatic discharge. IEEE International Symposium on Electromagnetic Compatibility, Anaheim, CA. USA, 1992: 361~365 7. D. Pommerenke. ESD: transient fields, arc simulation and rise time limit. Journal of Electrostatic. 1995, 36:31~54 8. Y. Tabata and H. Tomita. Malfunction of high impedance circuits caused by electrostatic discharges. Journal of Electrostatic, 1990, 24:155~166
328 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
An
Electrostatic Approach for Aerial Moving Object Detecting and Locating
Chen X., Cui ZZ., Xu LX., Bi JJ. School of Mechatronics Engineering, Beijing Institute of Technology, Beijing, 100081
A passive electrostatic detecting system is investigated in this paper to provide an effective approach for aerial moving object locating. The electrostatic detecting model of aerial moving object is proposed by using charge mirror method. The locating algorithm based on round array structure of electrostatic detecting system is derived, by which the range, pitch and azimuth angle of the object can be calculated. Monte Carlo simulating experiment is carried out to demonstrate the effectiveness of the proposed locating method; simulation result shows the proposed electrostatic detecting system can provide effective locating method for the aerial moving object.
MODELING ON PASSIVE GROUND ELECTROSTATIC DETECTION SYSTEM Aerial moving object can be charged electrically because of friction and inducting process, the electric charging of moving object causes an electric field which is transported by the moving object, this field can be measured by passive ground electrostatic detection system. If the assumption is made that the charged Q of the object is concentrated in one point P , the diagrammatic sketch of passive ground electrostatic detection system is shown in Figure 1. The electric field, which is transported by moving object, is influenced by the existence of electrode and ground. According to the charge mirror method, the supposed mirror charge ql on point /]1 ensures the invariant boundary condition of electrode, the corresponding quantity q ~ - - - r Q / d ~ ; a n d qo on point P0 ensures the invariant boundary condition of ground, the corresponding quantity qo -- ( e - e ' ) Q / ( e + e') , where e is the dielectric constant of air, and g' is that of ground; The distance between P~ and the center of the spherical I
I
I
Figure 1 Diagrammatic sketch of passive ground electrostatic
electrode O is b~, and the distance between P0' and O is d2; but the boundary condition of ground is disturbed by q~, and the boundary condition of electrode is disturbed by q0 SO qt and q2 are supposed; the rest may be deduced by analogy, inf'mite mirror charges are supposed, I
I
,
the quantity of inducting charge of the spherical electrode is the sum of all the mirror charge in the sphere. The mirror charges q~ (i =1,2,3-.-) are in the sphere, b~ (i =1,2,3--') are the distance between the corresponding charge to the center of the sphere, d~§z ( i =0,1,2,3---) are the distance between the corresponding charge out of the sphere and the center of the sphere, tg~+2 (i==0,1,2,3---) is the angle of horizontal line of the center sphere and the line which joins the corresponding mirror charge out of the
329 sphere and the sphere center, the angle above the horizontal line is supposed from 0 ~ to 90 ~ , the angle under the horizontal line is supposed from-90 ~ to 0~ According to the charge mirror method and the geometrical relation of the mirror charges, the expressions are derived after calculating, h-H
(1)
sinOl = ~
dl -h-H
(2)
sinO2 - ~
......
dE-
(3)
4dl 2 + 4Hh
(i =3,4,5.'.)
d~ - ~/b/_22+4H2 +4/~/_2 sin 0/_2 sin 0 i =
- 2 H - bi_ z sin Oi_2
(i =3,4,5-..)
(4) (5)
di r
2
bi- dj _ !-r)" q'
o
i-[ dzj_l "e + d "
(i =1,2,3...)
(i - 2 n - 1 n - 1,2,3"--) Q
j=l
_ <-r>"
qi
(6)
(7)
t
(i - 2n
n - 1,2,3"')
Hd2j e + j=!
The quantity of the inducting charge of the electrode sphere (i =1,2,3-'-)
q - ~-, qi
(8)
i
The expression (7) and (8) indicate the system model of passive ground electrostatic detection system, it cannot be use in locating calculating because of the iterative arithmetic of the model, it need to be reduced. When the electrode is placed near the ground, H = r , in the condition of h ? H , d E --d~, because r = d t and d2, b2 = b 1 = r ~ d l = 0 ,
namely, ql and qz are almost on the sphere center,
e' > e , 0 < k < 1, according to power series equation, ~tR
rQ I q = ' 7 - ( 7 - - I)In(I- k) = K Q dI d, /c
where
k =_____f_e E t d" E
1
K = r ( 7 - 1 ) ln(1- k). g
(9)
The expression (9) indicates the reduced system model of the passive electrostatic ground detecting system. From the reduced model, the quantity of the induction charge of the electrode is in inverse proportion to the distance between the object and the electrode; and in direct proportion to the quantity of the charge of the aerial moving object; the proportion coefficient K is related with the sphere radius and the dielectric constants of air and ground, this reduced model can be used in location calculating.
MEASUREMENTS A test is operated to prove the performance of the passive electrostatic ground detection system, the detection system is consisted of metallic electrode, measurement system and output instrument, the measurement system includes the weak current measurement circuit with low input impedance [~l, low pass filter and integrating device. The wave shown in Figure2 is the output of oscillograph when an aeromodelling is flying over the detecting electrode.
330
moving object ground
~
elec
.J measurement ] 11 system I
x./--
Figure 2 Diagrammatic sketch of measurement
LOCATING EQUATIONS The sketch of localization of aerial object by round detectors array is shown in Figure3. The detectors S, L S, (n is an even number) are placed on the circumference of round array, the detector So is placed on the center of the detection round array. P(p,o,~)
0
I I I I I
Pi
',h I ! ! I I
Figure 3 Sketch of localizationof aerial target by round array
The charge Q of the moving object is concentrated in one point P ,
the inducting charge
Qi (i-0,1,2,3"'n )of the correspondent detector are involved in the charge Q, the distance p , which is between P and the center detector, and the distance p~ ( i - 1 , 2 , 3 " - n ) o f P and the correspondent detector, R is the radius of the round array. Depending on the reduced system model,
KQ
Q0 - ~
(10)
P
KQ
Q~ - ~
( i - 1,2,3"-'n)
(11)
P~ Adopting the general form of plane round array [2], (12) can be obtained according to (10), (11) and the geometrical relationships of detectors shown in Figure 1.
K2Q2 K2Q2
~
=~+R Qi 2 Q02
2RKQ
2- ~
Q0
sin 0 cos((p- ~ )
( i - 1,2,3""n)
(12)
The location coordinate P , 0 and q9 of the object can be obtained by resolving simultaneous equations of (10) and (12). Only 4 detectors are needed to calculate the location coordinate P , 0 and (,oof
331 the object theoretically, the solutions of other equations are same as that, the location precision can be improved with increasing the detector number. Summing every equation of (12): K zQ2 nK 2Q2 2 2RKQ , -AS - ~ + nR - ~ sin OZ cos(q9 - qg~) i=1 Qi Q02 Q0 i-,
(13)
Because the arrangemem of the detectors is symmetrical, and n (the number of employed detectors) is an even number, it can be proved: ~ sin k(fp-fpi)-0 k - 1,2,3.
(14)
cos k(fp- qg/) - 0 (i=1
Using (14) to simplify (13), the distance calculating formula is R,f~ P-12tOo2
(15) _l)
i=1 ~" Qi 2
The calculating formula of pitch angle g and azimuth angle q9 of the object can be obtained by using minimum mean-square error method, the error of each corresponding equation of (13) e~ is KZ Q z KZ Q z R2 2RKQ ei = Q~2 Qo2 + Q0 sinOcos(~o-~) n
The mean-square error y - Ze~ 2
( i - 1,2,3-'-n)
(16) (17)
i=1
From (16) and (17), partial derivative~Oy/bg = O, by/~Oq9 = 0, the calculating formula of pitch angle g and azimuth angle q9 of the object can be obtained by calculating with trigonometric fimctions, Qo2 sinO -
~cos~p,
+ ~sinzfp,
,_, Q/'
/_,
In~(
Q,
(18)
Qo2 _l)
i=i ~"Qi 2
tan q~-
sin~.
i=l Qi 2
cos~. i=1
(19)
O//2
The location coordinate P and 0 of the object can be calculated by (15) and (18). Because the range of the azimuth fp is 0" 360 ~ , so the quadrant, which the object is in need be determined firstly by using the method of comparing the outputs of the detectors, then the unique solution of angle ~o can be obtained by using (19).
SIMULATING EXPERIMENT Monte Carlo simulating experiment is carried out to demonstrate the effectiveness of the proposed locating method. In the process of the simulating experiment, firstly the truth-value of the inducting charge of every detector is given by detecting system model with the truth coordinate of the object known, the simulating value of the detector output is gained by adding the truth-value a random error which is generated by computer and the measurement error; secondly the computing result of the object coordinate is computed by using locating formulas; thirdly statistical processing is carried out, finally the location error is gained.
332 The simulating results are shown in Figure4 and Figure5. The curve of ranging error varying with the azimuth angle of the object when the distance between the object and the center detector is 500m and 1000m is shown in Figure4; the curve of pitch angle error varying with the azimuth angle of the object is shown in Figure5.
Figure 4 Curve of range error with azimuth angle of the object.
Figure 5 Curve of pitch angle error with azimuth angle of the object.
CONCLUSIONS The investigations about moving object demonstrate that it can be successful to detect the aerial flying object the by using electrostatic ground detecting system. The results of simulating experiment show that the proposed electrostatic detecting system can provide effective locating method to derive the coordinate, which is the range, pitch and azimuth angle of the object by using locating algorithm based on round array structure of electrostatic detecting system for the aerial flying object. Further investigation are ongoing to extend the maximum range by improving the measurement system, and improve the location precision by optimizing the arrangement of detection system round array.
REFERENCE 1. Chen, X. Cui, ZZ. Bi, JJ., Research on Low Input Impedance Measuring System in Electrostatic Field Measurement, ISTM/2003 5th International Symposium on Test and Measurement, Vol 1.53--56 2. Zhu, LS., Research on Passive Acoustic Localization Techniques, Nanjing University of Science and Technology, 1998. 57-,72.
333 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES"2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on Input Impedance of Measuring Circuit in Electrostatic Measurement System B i JJ., Cui ZZ., Xu LX., Chen X. School of Mechatronics Engineering, Beijing Institute of Technology, Beijing, 100081
In this paper, a thorough analysis is made about the input impedance of the amplification circuit in non-contact electrostatic measurement system. Firstly, two kinds of measuring amplification circuits with operational amplifiers are investigated by using the circuit node analysis theory. Then a model of capacitance-resistance equivalent circuit is established according to the characteristic of non-contact electrostatic field measurement. By analyzing the gain and the frequency band of the circuit, the conclusion is obtained and proved by laboratory tests that not only high but also low input impedance measurement circuit can be used for measuring electrostatic field.
ANALYSIS OF SIGNAL AMPLIFICATION CIRCUIT It is a new application field of electrostatic measuring to detect the charged flying object and acquire the distance and azimuth. Non-contact measurement method is obviously suitable for most of measurements [4,5]. In general, high input impedance circuit is used for this kind of non-contact measurement system; the low impedance circuit is another way of the solution. A thorough analysis is carried out about the input impedance of the non-contact electrostatic detecting system in this paper. Analysis of high input impedance circuit The whole circuit is composed of measuring electrode, signal amplification circuit and posterior signal processing circuit. The schematic diagram of this measurement system with high input impedance is shown in Figure 1. The parts those compose the signal amplification circuit are in dashed frame. i i !
Measuring electrode , ~.... " Signal Amplification Circuit
R1 Ul
"i,,, ' ~OPAiP", ,' I
R2
..... R4
D2
......... U R5 N . . . . .
i ~
..J,.. P
R3
"~! .... .:.~- |
=o=
]
L.._
i
"-'-o
i
PosteriorSignal Processing Circuit
Figure 1 High Input Impedance Circuit Using For Electrostatic Field Measurement The signal amplification circuit is composed of two connected amplifiers in series in figure 1,and its input impedance is equal to that of first stage amplifier. Equivalent circuit of first stage amplifier including integration operation amplifier is shown in figure 2. [6] Where Ria is the equivalent input impedance of integration operation amplifier, Aa is open loop gain of integration operation amplifier, Ro is equivalent output impedance of integration operation amplifier, U+ is potential of positive pin, and U_ is potential of negative pin.
334
ui
o----------L~
u+l +!
A
a
(u+-u_)
Ui
.....VO
U+
o
+
U.
"VWr-_
.....
Rid
.~Uo
~Ro
Ad (U+-U.) "-'~"
0
Figure 2 equivalent electric circuit of first stage amplifier of high input impedance circuit Simultaneous equations acquired by circuit node analysis theory are as follows"
(1
1
+
1
(2.1)
Aa(U + - U _ )
Ro)Vo
-
Ro
(2.2)
v§ u_=uo From 2.1 ~2.3:
(2.3) Uo =
Aa R~d + Ro
U~
(2.4)
AdR~d + R o + R~d
where Rid is usually more than 10 l~ f~, Ad can reach 120dB, Ro is less than several hundred ohms usually. 2.4:can be simplified and written as Uo =
AdRid Ui Ad Rid + R o Ui = AdRid + R o + Rid (Ad + 1)Rid
=
Ui
(2.5)
According to def'mition of input impedance, the input impedance of this circuit is: Ui i
(2.6)
where,
(2.7)
Ri= i - U~ - U o R~d
From 2.4, 2.6 and 2.7"
R~ - ( A d + 1)R~d + R o = ( A d + 1)Rid
(2.8)
According to 2.8, Ri, the input impedance of this circuit, is fearfully high. It can reach 1016f2 theoretically while Ad, the open loop gain of integration operation amplifier, is 120dB and Rid is 10 ~~f~. Analysis of low input impedance circuit A kind of circuit for measuring electrostatic field with low input impedance is shown in figure 3. It also includes measuring electrode, signal amplification circuit and posterior signal processing circuit. Equivalent circuit of signal amplification circuit is shown in figure 4. [6] J
Measunng Pole :
Signal Amplifi- ~ cation Circuit
',
R1
! ..... ~ I
*l---'t~/OPAMP
}
I R5
R2
i ~ ~v---n;_ L ~L: [ ',
Posterior Signal Processing Circuit
I
'=0
Figure 3 Low input impedance circuits using for electrostatic field measurement
335
R1
R2
i
i UAR1 Us Ra 9~ .... ~ ] ~ .... ]Uo
----" o 9o
R3
Rid
-
Rid - U-
Uo
]
U+ r R2
U+
R5
{Ro
<~Ad(U+- u_)
Ad(U+-U)
R5
-2-':'2-0 "~o
Figure 4 Equivalents signal amplification circuit in low input impedance circuit UA, Us and Uo are supposed nodes potential in figure 4. Simultaneous equations acquired by circuit node analysis theory are as follows: (1__
Ri
+
1 Rid + R s
).U A -1.U
Rl
s -O.U o -i (2.9)
1 1 _ _ _1 .UA+ ( 1 + 1 + ).U B.U o - 0 R3 R~ R 1 R 2 R3 O.UA_
(2.10)
1 Aa(U + - U _ ) 1 1 .U s + ( + )'Uo = Ro R3 Ro R3
(2.11)
U = UA + Rid + R-5 R5
(2.12)
U_ - U .
(2.13)
The solutions are as follows: ( R 2 -t- R 3 + R o ) R 1 -t- R2R o -t- R2R3)(Rid -I- R 5)
g A-
i
(2.14)
(R 2 + R 3 + R o)(R1 + R 5 + Rid)+ AaR2Ria + R2R 3 + R2R o Uo - -
(AdRidR2 + AdRidR3)R1 + AdRidR2R3 - R2R~ (Rid + R5)
i
(2.15)
( R 2 .-I-R3 + Ro ) R 1 + ( R 3 -I-R o .-I-R2)R 5 -.I-(R3 + A d R 2 + R o + R2 )Rid + R2R 3 -~-R2R ~
The input impedance is: u. _
Ri " - ' ~ ~
i
+
+ Ro)& + R Ro +
+ R,)
(R 2 + R 3 + R o)(R, + R 5 + R~a ) + AdRzRid + R2R 3 + R2R o
(2.16)
When Rid is up to 10 l~ Q and Aa is up to 120dB and R o is far less than RI and R2, 2.14,2.15 and 2.16 can be predigested. 2.14, 2.15 and 2.16 can be simplified and written as. U o = - R1Rz + R1R3 + R2R3 9i
(2.17)
R2 U A = RIR2 + RIR3 + R2R3 9i R2Ad R, -- R'R2 + R'R3 + RER3. 1 R2
(2.18)
(2.19)
Aa
Supposing R 1 - 10kf~, R 2 - lkf~, R 3 - 100kQ, A a - 120dB, from 2.17 and 2.19" U o =-1.1•
R i = 1.1~
6.i
(2.20) (2.21)
336 ANALYSIS OF EQUIVALENT CIRCUIT OF NON-CONTACT MEASUREMENT SYSTEM Potential signal is induced on the measuring electrode by charged object while non-contact electrostatic measurement is done. This signal is exported in propriety form after it is amplified and processed. The measurement systems shown in figure 1 and figure 3 have equivalent circuit shown in figure 5. Suppose Cl is the capacitance between charged A B object and ground, and Q is the quantity of electric charge on charged object, then U/ is the voltage charged between charged object and ground. object So: U i - - O / C1. Suppose Ca is the capacitance between charged ~0 object and electrode, and Ca is the capacitance Figure 5 Equivalent circuit of measuring circuit between ground and electrode. In figure 5, voltage source is equivalent of charged object, and its output voltage equals to Ui, node B is equivalent of electrode, load resistance RL equals to input impedance of signal amplification circuit. Voltage Uo on RL is as following according to Ohm's law: ui=g
Ug =
C3 PRL
o
C2 + C3 pRL
where Ugo a n d Ugi are phasors. If
1
C2
g
1
Ui
(3.1)
C3 + C 2 _ J ~ caR L
- C 3 + C 2 then Ug~ =
caR L
C 2
g
U,
C3 + C 2
g
Suppose A, is gain of whole circuit, and co- 2Icf" g
g
Uo
C2
Ui
C3 + Cz - J 2 ~ f . R L
A, = --y-=
1
(3.2)
g
Following is the amplitude of A u : g
/i 3
IA I =
1
+1)2+
(3.3)
(2Jr f . R LC 2)2
~[ C z
I f f --~ oo, then: g
C 2
I Au I "--)'
g
-- I td~u Im ax
(3.4)
C 3 -I- C 2
where
[A]maxiSthe maximum of[A.[. If ]A~ico)[- - ~1 . g
g
f-fL
-
g
]A~[max' then: 1
2n'R L(C 3 + C2)
(3.5)
whcre fL is the lower limit cut-off frequency of equivalent circuit. Suppose: C3 = 50pF, C2 =100pF, and fL >0.016Hz, from 3.5" 1 = 6.631 • 101~f~ (3.6) RL > 2~(100 + 50) • 10-~2 x 0.016 Therefore, the input impedance of measurement system must be very high if the measurement system is used for non-contact electrostatic measurement. However, the lower limit cut-off frequency is not the most important determinant factor for choosing Re, C3 and C2 when a circuit which input voltage range is less than 100 V is used to measure charged object with tens of thousands potential. According to 3.2, If RLand f are small enough, then:
337 g
(3.7)
A~ = j 2 x f . RLC2 g So:
g
g
g
U o - A u U i - j2~f
(3.8)
. R L C 2 9U , g g
g
o Then iR," , current in R~., is as following: iR," = U = j 2 x f . C z . U R~.
According to3.5, if C3>>C2, then: f - fL =
1
g
~
(3.9) (3.10)
2~RLC 3
Therefore, low input impedance circuit still can be used to measuring electrostatic signal on the condition of propriety circuit parameters. The left graph in Figure 6 shows the potential variety of electrode while a charged object passes over the electrode by using high impedance measurement circuit; the fight one shows the potential variety of electrode when a charged metal ball discharges near to the electrode by using low impedance measurement circuit
Figure 6 Test results from different m e a ~ e n t
system
CONCLUSIONS Generally, high input impedance is used in non-contact electrostatic measurement system. The reason is that lower-cut-off frequency of this system can be extremely low, and the potential signal on detecting electrode is strong enough. According to the analysis about the model of capacitance-resistance equivalent circuit of this kind of system, the transmission bands of measurement system with low input impedance can also meet the requirements when the parameters of the circuit is selected correctly, as the potential signal on detecting electrode is very weak, so posterior signal processing circuits is needed to improve the gain of the measurement system.
REFERENCE 1. Liu SH., Electrostatic Theory and Protection, Ordnance Industry Press, 1999.1. 2. Sun KP., Industrial Electrostatics, Petrochemical Press of China,1994.8. 3. Bai YX., Modeling and Analyzing on Electrostatic Fuze, Journal of Detection and Control, Vol.24 No.2 2002.02 4. Li YL., Passive Electrostatic Fuze Detection Technology and Information Processing, Beijing Institute of Technology, 2000.08 5. Dai FZ., Research on Passive Electrostatic Detection Technology Based on Electrode Scanning Theory, Beijing Institute of Technology, 2004.02 6. Qian GF., The Theory and Application of Integrated Operation Amplifier, Shanghai Jiaotong University Press, 1992.
338 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on Vector M e a s u r e m e n t Method of Electrostatic Field Xu LX., B i JJ., Cui ZZ., Chen X. School of Mechatronics Engineering, Beijing Institute of Technology, Beijing, 100081
A vector measurement method of field intensity is investigated in this paper to determine the orientation of electrically charged object. Firstly the vector measurement method and formula of determining the orientation of a point charge is deduced in two-dimensional space. Then the model of uniform line charge that is the approximation of charged object is analyzed, the formula of determining the orientation of line charge is gained, and proved by simulating experiment. The influence factors on the measurement method of electrostatic vector are analyzed based on the simulating experiment.
The condition of electric field, which is transported by the charged object, can be obtained by detecting the electrostatic field intensity around the object. The general method in non-contact measurement is measuring potential to gain the information of the charged object. Measuring the potential of one certain point is not enough to know the electrostatic field intensity, because the electrostatic field intensity is a vector with magnitude and orientation. The vector measurement method of electrostatic field is deduced by analyzing point charge and line charge in this paper.
VECTOR MEASUREMENT METHOD OF POINT CHARGE ELECTROSTATIC FIELD The electrostatic field which is generated by the point charge can be considered as uniform field in the sufficient small area M round the zero, the orientation is shown as in figure 1. Two pairs of parallel plate electrode AA' and BB' are placed in js M sI area M shown as in figure 1, r > 0 . The distance ss between the zero of coordinate and a point charge in /fl in P XOY plane is R shown in figure 1, the quantity of the charge is -q. according to the electrostatic field theory, the electric field intensity of area M
r,21:'
r
E=
4
q 7[EOs R
r 2 aR
r
(1 1) 1
where a R is the unit vector of E . The potential difference between AA' and B B' due to the electrostatic field U ~ , - E- AA' 1
(1.2)
tlUU
UBB, : E" B B '
Form 1.1,1.2 and 1.3:
(1.3)
I-
Ir.
~x
~I
Figure 1 Schematic diagram of vector measurement of electrostatic field of point charge
339 UAA, =
q r matt 4~eoe~R2 a R 9A A '
(1.4) (1.5)
So
UAA,=
rq COS0 4~teoe~R 2
(1 6)
rq sinO UBB, = 4~.oe~R ~_
(1.7)
with e 0 :the dielectric constant of air, e~" the dielectric constant of the medium around the point charge. The quantity and orientation of the electrostatic field intensity of area M are gained by measuring U,u, and UBB, 0 = arctan UBB'
UAA,
E-
(1.8)
~UAB2 + Uc~ r
(1.9)
Obviously, when R ? r , the electrostatic field of area M can be regarded as the field with uniform electric field intensity. The quadrant in which the angle 8 is can be determined by judging whether U~, and UB~, is positive or negative, in the condition of figure 1. Table 1 the relation of the quadrant which the angle 0 belongs to and the sign symbols of Uaa, and UBB,
UBB, >0
UAA,>0
UAA, <0
The first quadrant
The second qua&ant
UBB,<0
The third quadrant The forth quadrant Note: the point charge with negative polarity
VECTOR MEASUREMENT METHOD OF LINE CHARGE ELECTROSTATIC FIELD The charged object can be regarded concentrating in one point when it is far from the detector; the electrostatic field intensity generated by the charged object can be measured using 1.8 and 1.9. However, it is different when the object is near to the detector. The following research is based on the approximation of charged object as a line charge. The charge density of line charge in plane XOY shown in figure 2 is - 9 , one endpoint coordinate is (x0,y0), the angle of the line and the horizontal axis is the 0, the length of it is m, the angle of the horizontal axis and the joined line of the center D of the line and the coordinate zero is 13, the position of the detector electrode is same as that in figure 1.
-p
s
(xo, Yo)
.."
11jsSSt
r/2 _!.
_7
-r/2 A
I I
0 -r/2
A'
I
r
U
X
B
Figure 2 schematic diagram of vector measurement of electrostatic field of line charge
340 The electrostatic field intensity of the coordinate zero Ut
Ut
Ut
E = Ex + Er
(2.1) U
U
Where the electric field intensity distribution of X-axis Ex and the distribution of Y-axis Er X 2 + y2
4y.t~oEr (X 2 + y 2 )
_ ~ncosO+xO
X
.
pdx
4X 2 + (X- xO)" tan 0 + yO) 2 4~oe r (X 2 + ((X -- xO)" tan 0 + yO) 2 ) cos 0
dxO
(2.2)
.
4;W.oe`(x 2 +
X 2 + y2
= [m~o~O+xO
(X -- xO)"
y2)
tan 0 +
yO
pdx
JX 2 + ((x - xO). tan 0 + y0) 2 4~rs r (x 2 + ((x - x0). tan 0 + y0) 2) cos 0
~0
(2.3)
Followings are gained by deducing[3]: 2
2
P(Yo 4x~ + Yo + m sin 8 4 x ~ + Yo - Y o " exa) EX ~"
(2.4)
4~EoEr ( - Y o COS 0 + X0 sin O) . exa . 4X2o + y~
Ey
- P ( X o 4 X ~ + y3 + m c o s O 4 x ~ + y3 - x o 9exa)
(2.5)
2
4~0er (-Yo cos 0 + x 0 sin O).exa. 4x~ + Yo
where exa - 4x~ + 2Xom cos 0 + m 2 + y~ + 2Yom sin 0 From (1.8): fl
--
arctan Ey -- arctan ~E y ' r = arctan ~UBB. Ex E x .r UAA,
E - 4E~ 2 + Ey 2 =
4(E~ .r) 2 +(Ey .r) 2
=
(2.6)
4UAB 2 +Uco 2
r
r
(2.7) THE CALCULATION SIMULATING OF LINE CHARGE The calculation simulating is carried out in the condition of the length of the line charge is 1.5m, the charge density of the line is 5e-5C/m, the angle of the line and the X-axis is -10 ~ the extent of the distance between the zero of the coordinate and the center of the line charge is 2.5m to 61.5m. the dash dot line in the figure 3 is the truth value of angle fl of the D O and X-axis, the solid line is the calculating value of that. The simulating result indicates that the difference of the calculating value of and the truth value is decreasing with the distance of the zero of the coordinate and the line charge increasing, it can be regarded that the approximate accurate value o f t can be gained by using the method mentioned above.
CONCLISION The research in the paper indicates that charged object, which is approximated as a point charge or a line charge, can be measured by using vector characteristics of the electrostatic field, in the condition of that it is far from detector electrode, or the distance is great more than the electrode space; the electric field
341 intensity and the orientation of the charged object to the detector can be obtained by the measurement of the electric potential difference of the electrode plates. 35 30 25 20
<
15
10
0
0
10
20
30
40
50
60
70
Length of line segment OD (m) Figure 3 the comparing of the truth-value and the calculating value
REFERENCE 1. Lin.S., Ranging and Directing of Electrostatic Target and Its Signal Processing Research, Beijing Institute of Technology, 2002 2. Bai Y., Modeling and Analyses on electrostatic Fuze Detection, Journal of Detection and Control, Vol.24 No.2 2002.2 p4548 p53 3. Zhang ZY., Mastery on Matlab 5.3, Beihang University Press. 2000.8. 4. Bi junjian, Research on Measuring Electrostatic Field of Three-Dimension, ISTM 2003 5th International Academic Publishers World Publishing Corporation
342 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Automation design of the ion stream generation device Qing Li, Wenjie Zhou, Zhiqiang Liu, Zisheng Zhang Electrostatic Research Institute of Hebei University 071002
In industry such as chemical industry, textile industry and so on, the ion stream generation device is mainly applied to dispel the static occurred with rolling and high speed spurt. At present sign and intensity of static occurred in industrial scene is mainly measured by artificial measurement. Then different ion stream generation device is adopted according to specific situation. This paper presents an automation design propose which can detect the static parameter of scene and create ions of different polarity and density automatically.
SUMMARY Dangers caused by static in industry and life get more and more regard of people, so it is always an important subject for research of static field to eliminate static and prevent dangers from static. But existing methods of measurement can't meet with the demand of modem industry any more. In this paper, a set of adaptive design plans based on PID control is presented. And it can detect the static parameter of scene and create ions of different density automatically in order to eliminate dangers from static.
GENERAL STRUCTURE OF SYSTEM Hardware Structure Single chip computer 80C52, operational amplifier OPAl28, chip CAC24C021, DAC1210 and so on are adopted in the core of the system. Overall block diagram of the system is shown as Fig 1[ 1]. static detection
module
12 bits A/D transition chip
89C52 singlechip
12 bits D/A transition chip
Pulsed module
high frequency transformer
Figure. 1 Total block diagram of the system
Static detection module Static detection module is mainly made up of chip OPAl28 allocated corresponding outside circuit. Chip OPAl28 is a monolithic operational amplifier ultra-low with ultra-low bias current. Low bias current and high impedance character of it has attained or even exceeded the character of "electrometer amplifier" which is specially made up of hybrid integrated circuit because it applied dielectric isolation MOSFET and the geometry of its input stage is the newest. So OPAl28 can be called electrometer magnitude amplifier. Low noise common source of the input stage enables OPAl28 to treat faint signals and its flicker noise is very low, at the mean time offset voltage and drift characteristics attain a very high level too. OPA 128 is very suitable for various applied occasions with high-impedance, so shielding measurement
343 must be taken seriously to reduce as much as possible AC interference on the incoming line. Leakage current occurred along printed circuit board is quite considerable compared to ultra-low bias current of OPAl28. Electromagnetism compatibility must be considered thoroughly on circuit design, so signal input line of OPAl28 is connected to PTFE support frame. If the signal input line is welded on the circuit board directly, parallel printed board must be used for wiring. At the same time in order to prevent the cable of the input end of the amplifier from producing the static because of rubbing, the signal source should be weld on the input end of the amplifier directly by the line which is short and hard, and this can dispel the noise. Wiring and shielding ring are set up as Fig.2.
---t
IN
I
I- I....
f :
i
i
i
I OUT
i ......
Figure.20PA128wiring diagram
"Watchdog" Function and its Anti-interference Measures In order to increase dependability of the system and improve anti-interference ability, power noise filter and switch regulated power supply are adopted in the power supply in this system. It is proved through factory practices that it can suppress interference caused by power noise such as electric welder, AC contactor, crane and so on effectively. In order to improve the dependability further, "watchdog" is added especially, i.e. chip CAT24C02 l is added. It is a RAM which integrated "watchdog" function in it. If the program is running regularly, it will send out a pulse to "watchdog" at regular intervals, and make the output can't upset. If it isn't running regularly or the interval of pulse is too long, the output will upset. Then the single chip computer will reset and work again from the place cut off controlled by software. Software Structure PID control is a control law which is used most extensively. It is the association of three kinds of regulation laws: proportion, differential and integral and the function of each control law is different. When the function of proportion control is strengthened, movements of the system are sensitive, and speed of it is accelerated; When the function is partially great, the shaking frequency will increase, and time spent on regulation will extend; But when the function too heavy, the system will be unstable; when the function is too little, movements of the system will be too slow. At the situation that the system is stable, increase of proportion control can reduce the steady-state error, improve the control precision, but it can't dispel the static error totally. Integral control makes the stability of the system decline. But it can dispel the static error of the system and improve control precision of the control system; Differential control can improve the dynamic characteristic of the system (such as inducing overshoot and shortening time of adjustment), reduce static error of the system and improve the control precision. Choice of control parameter Critical proportioning method is suit for controlled object with self-equilibrating ability and it doesn't need to determine mathematic model of the object. At first the controller is chose as proportion control only. Then the proportion coefficient Pi is changed from small to large, until the step response of system sustains vibrating 4-5 times. At this moment, the system is considered that it has already reached the critical vibration state. The proportion coefficient at this time is noted as critical proportion coefficient Pj. Time from a climax of the vibration to the next one is noted as oscillating period Ti. Then the control parameter of PID controller is determined by data stored in CAT24C021, and the data is calculated through Ziegler-Nichols empirical equation. The flowchart is shown as Fig 3.[2]
344
Proportional control sampling period T
Increase the scale coefficient
~
N
Record Tj, pj I
Choose control parameter I Test run, and correct the parameters
Figure.3 PID control flow
CONCLUSIONS Through experiment and practical application, it is known that the ion stream generation device presented in this paper have better adaptivity, because the PID intellectual control algorithm is adopted in it. So the voltage accumulated is treated to the range of safe voltage. And automaticity is improved greatly and the time of adjustment is reduced.
REFERENCES 1. Chuanshuo C. Exactly making the method of PID control parameter. Institute's Journal of Post and Telecommunications of Changchun. (1994) 2. Peimin F. The integrated circuit uses the guide. Electronic Industry Press.(1996)
345 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The Development of ESD Radiated Field Measurement System" Changqing Zhu, Shanghe Liu The Institute of Electrostatic and Electromagnetic Protection, Shijiazhuang Mechanical Engineering College, Heping West Road 97#, Shijiazhuang, Hebei Province, P.R.China Phone (86) 0311-7993886, Fax (86) 0311-7994981, e-mail" zhuneil@ 163.com
For making certain the bandwidth of measurement system, the bandwidth of ESD radiated field has been estimated by analyzing the frequency spectrum of the standard ESD current. The relative technology with the measurement system, the design of the antenna circuit, electro optical modulation, photoelectric receiver, and so on, are analyzed in detail. Based on theoretical analysis, the ESD radiated field measurement system has been developed successfully, the measurement bandwidth is 6.5Hz~970MHz (within___ 1.5db), the measurable dynamic range is more than 60db, the minimum of measurable E-field strength is lmV/m, and the experimental results are given. Key Words: ESD, Radiated field, Bandwidth, Measurement system
INTRODUCTION With the development of micro-electronic technology and information technology (IT), the electronic sets are interfering by ESD radiation, more and more badly. Electromagnetic radiation by ESD has become one of the main harm sources of electronic sets. In research of EMC and ESD protection, in order to investigate the effect mechanism of ESD radiated field, it is very important to measure accurately the radiated field by ESD. Although people has putted forward several test & measurement method and carried out experiment successfully, so far, the known measurement sets cannot meet the practical need in bandwidth and sensitivity because the ESD radiated field has a great wide spectrum and dynamic range. Based on the need of practice, authors have developed a set of measurement system of which measurement bandwidth is 6.5Hz~-970MHz, dynamic range 60db, sensitivity lmV/m. So far, there are mostly two ways to measure E-field, direct induction and electro-optical modulation. Generally, the measurement system is composed of the probe and the signal-processing unit to carry out amplifying, transmitting, recording. Direct induction measurement uses an antenna as probe to induce the E-field signal, and depends on a coaxial line for the long-distance transmission of the signal. Therefore, the transmission distance and bandwidth is limited, and the transmission line is likely to interfere the measured field. The antenna is the key part of the measurement system. In reference [1 ], the performance of many antennas is introduced. By comparing, electrically small pole antenna is preferred measurement antenna because that has a fiat frequency response, and shorter the pole is, wider the measurement bandwidth, but lower the sensitivity. In order to come over the disadvantage of transmission line, electro-optical modulation was putted forward, which changes electrical signal into light signal by modulating laser with the field signal, and uses of optical fiber to realize the long-distance transmission of the signal, then the modulated laser is resumed original measured field signal by photoelectric receiver' In accordance with the way of modulation, there are direct electro-optical modulation and external electro-optical modulation. Direct electro-optical modulation means using of the field signal received by antenna, after amplified, to Project supported by the NSFC, Grant No. 50077024, 50237040
346 modulate the driving current of laser diode directly, and realizes the intensity modulation of laser. The bandwidth of the measurement system depends on antenna, the driving circuit of the laser diode and the photoelectric receiver. Normally, the sensitivity of the meastirement system could be enough high to meet the practical need. External electro-optical modulation uses of the characteristic of some crystal of which the reflective index is sensitive to the electrical field. When a beam of polarized laser gets across the crystal, the phase of the polarized laser will change with the strength of the E-field, and a phasemodulated laser is got, if which gets across an analyzer again, then a intensity-modulated is got. Generally, external electro-optical modulation needs a high E-field strength because that the electro-optical coefficient of the known crystal is too small. In order to measure the weak E-field, people has tested M-Z optical waveguide modulator and modulator with dipole antenna, which is analyzed in detail in references [2] [3]. Although External electro-optical modulation has obvious advantage of the size and no interference to measured E-field because of no conductive material, its performance, bandwidth and sensitivity in particular, is limited because many factors that include the time through the crystal by the laser, the length of antenna, linear modulation range, the electro-optical coefficient of the crystal and so on. So far, there is no report about applied measurement set.
THE BANDWITH ESTIMATE OF ESD RADIATED FIELD In research of ESD radiated field, Y.Tabata and Tomita putted forward spherical electrode model [8], David Pommerenke has long conductor model [4], and F.Wilson has dipole model [7]. In terms of these models, the E-field strength in near-field zone, where just is measured zone, is direct ratio with ESD current. Therefore, the bandwidth of ESD radiated field is approximately the bandwidth of ESD current. So that, the bandwidth of ESD radiated field can be estimated by analyzing the typical ESD current waveform specified in IEC61000-4-2 standard. For that, in first, the conception of signal bandwidth must be defined. The bandwidth and energy of signal It is not perfect to express the bandwidth of ESD radiated field in traditional 3db bandwidth.Taken for the human body model of ESD as example, the discharge potential is U, then the discharge voltage pulse is u ( t ) - Ue -~
(1)
- U e -~'
and the corresponding amplitude of spectrum is lu(j
o)l -
+
By calculating, the 3db bandwidth is B W = 1/2~ra~, and the energy within the 3db bandwidth is
1 flu(jO.))12do)__
1 cg
(3)
2
which is only 50 percent of the all energy
89
2.
Therefore, it is necessary to take into account the
relation between the bandwidth and the energy. In addition, the dynamic range of a measurement system always is limited. In above all, the bandwidth of a signal should be defined under the condition that 1) the signal's energy within the bandwidth should hardly be the all of the signal's energy, which may be stipulated as 95 or 99 percent. 2) The amplitude of the ~ignal's spectrum within the bandwidth should be hold within a certain range for ensuring the measurement valid. The bandwidth of ESD current The ESD current specified in IEC61000-4-2 only is a typical waveform but a function expression. The function mentioned in references [4] or [5] are capable of simulating approximately the ESD current, and the error is relatively small but obvious different from the typical waveform. In reference [6], authors had proposed a method to express the waveform by computation, which can completely simulate the typical waveform and relative error is less than 2%0. There still uses of the method mentioned in reference [6] to compute and get the ESD current waveform showed as real line in Fig. 1a, then the spectrum of the ESD current is computed by Fast Fourier Transform (FFT) and showed as the real line in Fig.lb, the energy
347 distributed curve of the ESD current is given by integrating the spectrum curve of which and showed as real line in Fig. 1c. In terms of Fig. 1, it is known that the energy within 300MHz has been already 99.5 percent of the all of the ESD current's energy. In order to measure ESD radiated field as accurately as possible, based on feasibility of measurement, maybe take 55db dynamic range of the signal into account to stipulate the signal's bandwidth, correspondingly, there is 890MHz. There are two peaks on the waveform of the ESD current, and the rising time of the signal depends on the first peak, similarly, the high frequency part of the signal mostly comes from also the first peak. Considering some ESD events have possibly shorter rising time, a probable waveform is simulated under the condition of unchanging the parameters but the rising time changed from 0.83ns to 0.54ns, as shown as the dashed in Fig. la. The dashed shown in Fig.lb and Fig.lc are correspondingly its spectrum and energy distribution, respectively. At the same time, the most part of signal's energy still concentrates within 300MHz, but the 55db bandwidth has enlarged to 1060MHz. Owing to the minimum of the rising time in IEC61000-4-2 is 0.7ns, based on above analysis, it is reasonable that the estimate of the bandwidth of ESD radiated field is 1GHz. In addition, Fig. 1 makes out that the obvious change of the rising time (35%) only has resulted in a less enlargement of the signal's bandwidth(19%).So that, the additive rising time caused of 1GHz measurement system may be neglected.
THE DESIGN OF THE MEASUREMENT SYSTEM In terms of the above analysis, the project using of direct electro-optical modulation is selected. The measurement system is composed of antenna, electro-optical modulator, photoelectric receiver and oscilloscope. The radiated field signal received by antenna, after amplified, drives the laser diode directly, and get intensity-modulated laser. Being transmitted to photoelectric receiver by optical fiber, the modulated laser is demodulated to get the original field signal, then use of an oscilloscope to complete the display, record and measurement of the field signal.
.............................................................
l
tr=0.83ns
o|
]
tr=0.83ns
'+j
l
' i
.
............i ..................! .................~.................i ..................i................ i
~o -.<
l
8
..........
4
i.
!................~.................!..................i.................
! ................
~
-3o
~..................i ................i..................i..................i.................t .................i........
.~
.+o
+s ........ ~::.........~................... i......................i.......................i......................!......................
+o
m ....... i ...........i ......................+......................i......................: ...................... +......................
-
0
10
20
30
40
50
60
70
0
200
400
600
800
1000
1200
1400
0
50
l~X)
/ MHz
I ns
(a)
Figure
9~ ...................... ! .....................i ! 1 5 : ......... i....... ____L_' t r = 0 . 8 3 n s
(b)
1 The
waveform,
energy
distribution
and
150
200
250
300
/ MHz (c)
spectrum
of
ESD
current
specified
in IEC61000--4--2 as the effect from rising time as well The antenna A single pole antenna is selected as measurement antenna. The received voltage is
VL( f )
_
(f)E, (U)Z L( f ) ZL(f)+Zo(f )
h e
(4)
There, he(f) is the effective length of the antenna, Er ( f ) is the E-field strength measured, Z 0( f ) is the input impedance of the antenna, Z L( f ) is the load impedance of the antenna. Every the parameters, includes VL( f ) , is the function of frequency f . If the length of the antenna h meets the relation flh << 1 ( ] 3 - 2 ~ r / 2 , called wave number, 2 is the wavelength of the signal received by antenna), then the effective length of the antenna is given by [ 1]
he -
h(o~- 1) a - 2 + In 4 and the input impedance of the antenna Z o( f ) is
(5)
348 6O
(6)
Zo ( f ) - - j - - - ~ ( c r - 2 - 1 n 4) .
a is the radius of the antenna. It is obvious that the input impedance of the Here, or-21n(2h/a), antenna given by (6) is purely capacitive. Therefore, the equivalent input circuit of the measurement system may be as fig.2. Where U, - h e ( f ) E i ( f ) , t h e equivalent capacitance of the antenna is given by (6) h
q
(7)
60c ( a - 2 - In 4) \
Ca
I
/
and c is the propagation velocity of the E-field. The input voltage of the measurement system is
27cfeif aUa --
VL ~l.al_[2Ti~fRi ( Ca .al-Ci - )]2
(8)
Ua
~
Ci
VL
Ri O
o
Figure 2 the equivalent input circuit
Here R i is the input impedance of the measurement system. In terms of formula (8), the-3db frequency, i.e. the low terminal frequency of the input circuit is f L - 1/ 2rcR i (C o + C i ). (9) Owing to the input stage of the measurement system is a field effect transistor (FET) of which input impedance is more than 109 f~ , when (C,--~.C i ) is equal to
Figure 3 the direct electro-optical modulator
100pF, then the low terminal frequency of the input circuit may be as low as 1.59Hz, and the upper terminal frequency of the input circuit only is limited by the condition of flh << 1, i.e. 2~rfH h << 1.
(10)
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The electro-optical modulator Figure 3 is the schematic diagram of the electro-optical modulator. The signal received by antenna, after being amplified by amplifier composed of FET, drives directly the laser diode to get intensity-modulated laser. Figure 4 the photograph of electro optical The shell of the electro-optical modulator is a columnmodulator form copper plating steel shell, of which external size is 100 x 30 1Tlrll 3 and 5mm thickness. Therefore, one hand the shell has excellent shield performance; on the other hand, the upper circular plane of the shell is also the plane of reflection of the single pole antenna. The key of circuit design is high input impedance, ultra wideband and deep modulation with a large linearity range. The circuit of the electro-optical modulator mainly includes an ultra wideband low noise amplifier, a high stabilization linear laser and temperature compensation circuit as well as the power circuit. Figure 4 is its reality photograph. The photoelectric rece~ye..r The photoelectric receiver is composed of high linearity InGaAs plane PIN detector, high gain ultra wideband amplifier, detection and display circuit of optical power as well as power source circuit. The schematic diagram of photoelectric receiver is showed as figure 5, and figure 6 is its actual photograph. The PIN detector converts the intensity-modulated laser into current. The current is parted into two ways" one is converted into voltage signal by a load resistance, and it is the signal of measured field. After amplified, the signal is connected to an oscilloscope by which displays and records the measured field signal, and it is completed to measure the E-field strength of ESD radiated field; and the other way of the current enters optical power detection and display circuit by which the average optical power into PIN detector is detected and displayed by LED.
349 The output impedance of the photoelectric receiver is 300 f2. For ensuring 1GHz bandwidth, the oscilloscope must have 1.5GHz analogue bandwidth and 1M f2 input impedance.
THE EXPERIMENT By test and measurement, the main characteristics of the ESD radiated field measurement system have been got, they include that the system gain is more than 17db, the non-distortion output range is 2.5V and the measurable signal dynamic range is 60db. Figure 7 is the actual frequency characteristic curve of the measurement system, which was got by a network analyzer (AV3618, made in 44th institute of CETC, measurable frequency ranges 40GHz from 50MHz, accuracy is __+1% ). It is obvious that the upper terminal frequency of the measurement system is 970MHz (within ___1.5db). The low terminal frequency is 6.5Hz, which is measured by universal dot-by-dot measurement method.
Figure 5 the schematic diagram of the photoelectric receiver
Figure 6 the photograph of the photoelectric receiver
CONCLUSION A set of ultra wideband ESD radiated field measurement system has been developed successfully, of which the bandwidth ranges 970MHz from 6.5Hz within _ 1.5db, and the minimum of the measurable E-field is l mV/m. If a capacitance is parallel connected to the input terminal of the antenna, which not only make the measurement system be capable of measuring high electromagnetic pulse field, but also can lower the low terminal frequency of the measurement system.
Figure 7 the frequency response curve of the measurement system
REFERENCES 1. Motohisa Kanda. Standard probes for electromagnetic field measurements. IEEE Trans. on antennas and propagation, Vol.41, No.10, OCT (1993) 1349~-1364 2.Masamitsu, Nobuo KUWABARA. Recent Progress in Fiber Optic Antennas for EMC Measurement. IEICE TRANS. COMMUN.,Vol.E75-B, No.3 Mar (1992) 107-113 3.Nobuo Kuwabara, Kimihiro Jajima, Ryuichi Kobayashi, etc. Development and Analysis of Electric Field Sensor Using LiNbO3 Optical Modulator. IEEE Trans. On EMC, Vol.34, No.4, Nov (1992) 391-396 4. Kai Wang, David Pommerenke, Ramachandran Chundrce,et al. Numerical Modeling of Electrostatic Diischarge Generators [J]. !EEE Trans. On EMC, Vo145, No.2 (2003)5 258-271 5. Sheng S L. Study on theoretical model and test technology of electromagnetic fields generated by ESD. Doctor dissertation. Shijiazhuang: Ordnance engineering college (2003) 6.Zhu Changqing, Liu Shanghe. A study on the radiated field by ESD. Proceedings of Asia-Pacific conference on Environmental electromagnetics (2003) 209-212 7. Perry F. Wilson, M.T.Ma. Field radiated by electrostatic discharges. IEEE Trans. On electromagnetic compatibility, Vol.33, No.l,Feb (1991) 10-18 8. Y.Tabata, Tomita. Malfunctions of high impedance circuits caused by electrostatic discharge. Journal of Electrostatic (1990) 24 155-166
350 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on 300kV Electrostatic Sensitivity Test for EED Qingmei Feng, Wei He, Tuan Zhao State key Laboratory of Applied Physics-Chemistry, The 213th Research Institute of China Ordnance Industry, Xi' an 710061,China Abstract: In this the paper, by setting up the test systems composed of 300kV, 1000pF, 1 f~ and so on, that the simulating test about electrostatic discharge of helicopter air supplying is mainly discussed. In this system, it is six levels of electrostatic sensitivity for fuse (which do not bear passing-explode tubes and expanding drug) and for EED (electro-explosive devices), with charging voltage from 50kV to 300kV including positive polarity and negative polarity that may be tested. At present, the related testing research on calibrated resistance of 100 f~ has been made. Key words: EED; electrostatic discharge; test
INTRODUCTION EEDs are not only absolutely necessary igniting and blasting components in special power, but also the most dangerous and susceptive subsystems in weapon systems. They are widely used not only in the fuse of engine of rocket, missile and roll booster impetus but in spreading of two-double's wing, self-damage setting and explosive bolt and so on. The safety and reliability of whole weapon's system are directly decided by the safety and the reliability of EED. The research on anti-electrostatic technology of EED is in the demand of development of science and technology of military affairs, and is the important part of improving safety and the reliability of weapon system. So it is attached important to home and abroad. With the development of science of military affairs, in the future, the war will be in the capacious field of solid. Because electron antagonism, electromagnetic interference, microwave weapon etc Will make the electromagnetic field of astrospace become more and more strong. At the same time, with the change appearance of the transportation and the logistic safeguard of weapon ElI, the highly insulted materials and the costume of chemical fiber are also indispensable for the weapon equipment and the persons attending a war. In order to ensure that the EED are immune to danger of electromagnetic and to avoid invalidation and improper action, the simulative test of EED against electromagnetic environment hazard is of importance, of which, the simulative electrostatic sensitivity test for EED is more vital, which insure the safety and the reliability of EED against electromagnetic environment hazard
DEVELOPMENT HOME AND ABRORD Development abroad In nineteen seventies', in U.S.A., the susceptive instrument of electrostatic, listed in MIL-STD-1512 t21, had been used in the EEDs and their components. In this test, the electrostatic sensitivity was only confined to simulating static of human body. That is, human body is equivalent to the circuit of resistance of 5k ~ and capacitance of 500pF. When the capacitance is charged up by high voltage of 25kV, the electrostatic sensitivity of EED to the circuit is tested. In the course of test, if no EED under test was fired, the EEDs are up to quality, on the contrary, if only one or more of EEDs under test was fired, the EEDs are not up to quality. With this testing equipment, the 50 percent of electrostatic sensitivity of EED may
351 be tested. The test about electrostatic sensitivity of powder was listed in MIL-STD-1576 E31.In this test, if no one of 20 samples is fired under quantitative energy, they are believed up to quality. If there is one sample of powder is fired, then the energy should be reduced by voltage of 500V, till end in voltage of 2500V. At the same time, with a capacitance of lower value, then the test is continued until there is no one fired. Finally, the sequence of electrostatic sensitivity of powder is arranged. The result of this test may be referred to assess the ability of powder against electrostatic. Because of the change appearance of transportation and logistic safeguard of weapon, the test of electrostatic sensitivity confined to simulating static of human body does not meet the demand of actual war, especially, in aerial transportation of weapon. With the speed of transportation growing up, and the conveyances charged up by atmosphere or thundercloud in interspaces, the new hazard of electrostatic power to EED appears. So, the test that simulate electrostatic of aerial transportation of weapon will be new one subject. The conditions of electrostatic of aerial supply were added in revised MIL-STD-331B [4], which are as follows" the capacitance of 1000pF, the resistance of 1 f~ ,charged voltage of six levels from 50kV to 300kV with positive polarity and negative polarity. Development home In our nation, since seventies' of last century, such special apparatuses as instrument of electrostatic sensitivity of EED, instrument of electrostatic sensitivity of powder and instrument of electrostatic accumulating of powder have been completely manufactured. At the same time, the test of electrostatic sensitivity of EED has been developed, the test with the capacitance of 500 __+25pF having voltage charged of 2500kV, the serial resistance of 5000 +__250 f~. In the test, the electrostatic sensitivity of EED's leg-leg or leg-shell may be tested by Bruceton method. Then, according to the result of test, the electrostatic sensitivity of EED, namely the firing average voltage and criterion may be calculated. In later of eighties' of last century, GJB736.11-90 [51 (method of EED test, EED determining electrostatic sensitivity), WJ1869-89 (method of EED test, powder determining electrostatic sensitivity), JGB737.389(method of EED test, column of powder and surface resistance determining electrostatic sensitivity) and WJ2018-91 (method of EED test, powder accumulating electrostatic sensitivity) are successfully set down. Such methods have met the demand of hazard of electrostatic from human body to EED but not in the demand of hazard of electrostatic from aerial supply to EED.
ELECTROSTATIC DISCHARGE TEST OF AERIAL SUPPLY TO FUSE'S SYSTEM In the nineties' of last century, the test simulating electrostatic discharge of helicopter was brought forward, whose character with capacitance of 1000pF, discharging resistance of 1 f~, maximal inductance of 20 la H and maximal testing voltage charged of 300kV. If packed fuse under the test, its electrostatic sensitivity is tested. Then the safety of fuse against electrostatic discharge is further assessed. If bare fuse under the test, the reliability may be evaluated. According to above figure, the testing equipment of 300kV electrostatic discharge of aerial supply to fuse's system including EED, with maximal Voltage of 300 kV, Capacitance of 1000pF and Maximal resistance of 1 ~, was successfully manufactured by us. As is shown in following Fig. 1 In the simulating circuit, the capacitance of capacitor is 1000pF, and other parameters are referred to table 1. When tested, rising maximal voltage, rising time and pulse width passing calibrated resistance will be gotten. By comparing the result of test with indexes of MIL-STD-331B, as is shown in table 1, we can come to conclusion that, given the same rising maximal voltage, rising time and pulse width (halfheight width of pulse) passing the calibrated resistance in MIL-STD-331B is respectively 180ns and 300ns, but in our test, which is respectively 50ns and 150ns. At the same time, the dissipation of energy in calibrated resistance in MIL-STD-331B accounts for 88.8 percent of total energy of capacitor but in our test 95.9 percent. The graph as is respectively shown in Fig.2 and Fig.3.
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353
Fig.4: the curve of current and voltage of calibrated resistance with capacitor charged valtage of 200kV. Chunnell is curve of current; chunnel 2 is curve of voltage.
Fig.5: the curve of current and voltage of calibrated resistance with capacitor charged valtage of 300kV. chunnel 1 is curve of current; chunnel 2 is curve of voltage.
CONCLUTION According to above analyzing, the testing performance of electrostatic discharge of aerial supply to fuse's system manufactured by us is superior to that of MIL-STD-33 lB. For example, the 95.9 percent of energy dissipation in calibrated resistance in our test is higher than that of MIL-STD-331B In above 300kV electrostatic discharge testing system for EED, there is a isolated circuit, which has following function: when the capacitor is charged by power of high voltage, the discharge circuit will be isolated; in turn, when the capacitor is discharged toward sample, the charge circuit will be isolated. Most of all, in this systems, six levels of electrostatic discharge for fuse or for EED, with charging voltage from 50kV to 300kV including positive polarity and negative polarity, may be tested. So this testing systems supply a gap in our nation.
REFERENCES [ 1] LIU Shanghe, WEI Guanghui, LIU Zhicheng. The Theory and Safety of Electrostatic. Publishing House of Ordnance Industry, 1999 [2] MIL-STD-1512. Electroexplosive Subsystems, Electrically Initiated, Design Requirements and Test Methods, 1976 [3] MIL-STD-1576. Electroexplosive Subsystems Safety Requirements and Test Methods for Space Systems, 1984 [4] MIL-STD-33 lB. Fuze and Fuze Components Environment and Performance Test for, 1989.2 [5] GJB736. 11-90. Test Method of Initiating Explosive Device, Electrostatic Sensitivity Test for Electric Initiating Explosive Device, 1991.6
354 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Test Method Study on Correlation of Electromagnetic Radiation and Injection for Microelectronic Devices* Xing Zhou, Guanghui Wei, Shiliang Yang, Haiguang Guo Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R. China
Abstract: General procedure and method on correlation test of electromagnetic radiation and injection for microelectronic devices are put forward in this paper, and devices choosing, working circuit designing, radiation test methods and relational parameters testing, and correlation evaluating are introduced and analyzed in detail. Key words" correlation, radiation, injection, electromagnetic pulse (EMP)
With the rapid development of integrated circuits (ICs) producing technology, the integrated densities of ICs are higher and higher, and lines in electronic devices are thinner and thinner. This causes a little heat and over voltage can lead to burn or short circuit, so ICs are more and more sensitive to all kinds of EMP. Economic loss caused by electromagnetic harm is increasing year by year. So, enhancing EMP immunity for microelectronic equipments is all along emphasized by developed countries [1-3]. In the past, direct injection method has been used for assessment of the susceptibility of electronic devices to EMP [4-51,that is, ESD pulse, rectangular pulse, or damped sinusoid is injected into sensitive pins of isolated devices to evaluate the damage threshold of voltage. In injection method, devices are commonly in non-working condition, but in fact, devices are interfered or damaged by EMP field when devices are in working condition. Some research results show that devices in working condition are much more sensitive to EMP than that of non-working condition [2],[61. So, studying correlation of direct injection and radiation coupling is very important to evaluate EMP radiation immunity of devices in working condition and further study EMP protection technology.
GENERAL METHOD AND PROCEDURE In the experiments, some representative devices should be chosen as studying objects firstly, and simple circuits are designed to make devices under test (DUT) work. Then printed circuit boards (PCBs) with DUT and working circuits are radiated by different EMP field respectively. Voltages and currents between sensitive pins are tested, and the strength of electric field and magnetic field are tested also by broad band antennas. According to the effects of interference and damage of DUT, sensitive type of DUT is analyzed, such as voltage sensitive type, power sensitive type, or energy sensitive type. Numerical relation of electromagnetic field and sensitive parameters is established according to sensitive type of DUT. To study correlation of injection and radiation when devices in working condition and non-working condition, experiments are done in two conditions. In non-working condition, the main aim is to gain correlation of damage threshold of field strength and voltage by different EMP. If the field strength is not intensity enough to cause hard damage on DUT, numerical relation of field strength and sensitive parameter should be gained, and correlation is analyzed according to the results. In working condition, the * Project supported by the NSFC No. 50077024 and 50237040; Supported by foundation for university key teacher by ministry of education
355 main aim is to confirm sensitive pin combinations, gain interference or damage threshold of different EMP field, and analyze correlation of injection and radiation.
CHOOSING DEVICES AND DESIGNING CIRCUITS Electromagnetic waves radiated from EMP sources are picked up by PCB traces or device pins, which act as unwanted receiving antennas. Such disturbances reach IC terminals in form of voltages or currents. To comparatively study the receiving capabilities of different ICs, which have different internal structures and different input impedances, the chosen devices are consisted of several sorts, and each sort of devices have the same or similar function. The devices should include digital devices and analog devices. The test ports of ICs can be divided into three kinds, the power supply ports, input ports and output ports. According to practical conditions, the external circuits of test port are designed in different shape, such as loop circuit, conducting wires with different length and different loads, etc. The external circuit of test port acts receiving antenna, and induces voltages or currents to test port. Other circuits should be as simple as possible to reduce undesired interference. To quantitatively analyze radiation results, the same sort of devices should have the same external circuits.
RADIATION TESTING In this section, radiation test method is introduced firstly, and according to experimental procedure, some parameters should be tested. The parameters include E-field strength, M-field strength, induced voltage and current. Radiation test method There are many methods for radiation test [7],[8], such as microwave anechoic chamber method, TEM cell method, GTEM cell method, reverberating chamber method, open-area test method, etc. Each method has its own applicable conditions, and tabletop based method and TEM/GTEM method are suitable for EMP radiation test of PCBs. The tabletop based method is adopted by IEC standard 61000-4-2 for ESD immunity test. A typical ESD laboratory test setup for table-top equipments is Generator . VCP shown in Figure 1. Using this method, discharges to HCP objects placed or installed near the EUT can be simulated by applying the discharges of the ESD generator to horizontal coupling plane (HCP) or vertical coupling plane (VCP), in the contact discharge mode. The setup of this method is very simple, and because EMP field strength is attenuated quickly in distance, the field generally does little harm to peoples and equipment nearby. But the electromagnetic field in space is inhomogeneous, the actual testing of field strength in small space is difficult, and the relation of field and induced voltage ~Ground reference plane or current can't be confirmed. So this method isn't suitable for correlation testing. Figure 1 Test setup for table-top equipment TEM cells are useful for EMC measurements from DC up to a few hundred MHz or even 1GHz, and electromagnetic distribution in TEM cell is homogeneous, so field strength testing can be realized. The GTEM cell is a hybrid between an anechoic chamber and a TEM cell, and can be used for EMC measurements over a wide frequency range. The resonance and reflected coefficient of GTEM cell are small, and a closed outer conductor serves as an effective shield to isolate the electromagnetic environment inside the cell from the electromagnetic environment outside of the cell, so TEM/GTEM
356 cells are suitable for EMP test with high intensity. So, the TEM/GTEM method is adopted for correlation testing. The test setup of TEM method is shown in Figure 2. By changing direction of PCB in the TEM cell or GTEM cell, the coupling of field to PCB traces or field to IC pins and lead frame can be tested. In the Power Test Figure 2, PCB is parallel to septum, and IC pins and Supply Monitor lead frame are parallel to E-field polarized direction, Susceptibility so the radiation coupling on pins and frame shall be Test PCB ~ . ~ studied. When the PCB is vertical to septum and parallel to propagating direction of EM waves in cell, Load ~DUT L the coupling of magnetic field to loop circuit on PCB can be tested. And when PCB is vertical to septum, v-1 I Source p~ , the coupling of E-field to horizontal traces or vertical traces on PCB can be studied, respectively, by changing PCB directions. Figure 2 Test setup of the TEM method i
4
E-field testing A broad-band E-field testing instrument is adopted in the experiment. The testing instrument includes two parts, the receiving and conversion part, and the optical receiver part. The former part, which is placed in the TEM/GTEM cell, is consisted of antenna, preamplifier with very-high input resistance and optical-toelectricity conversion circuit. They are shielded by a shield box excluding the antenna. The optical signals, which are modulated by testing signals, are transmitted to optical receiver outside of the cell by optical fibers, and the optical power is linear changing with testing signal. The optical signals are converted to electric signals by optical receiver, and the testing E-field waves are displayed by digital oscilloscope. M-field testing M-field testing instrument is composed of magnetic small loop sensor, acquisition card, and computer. Different magnetic sensors shall be adopted to adapt different intensity and frequency band of M-field. Acquisition card is inserted into computer, and fulfills analog-to-digital conversion. Processing and displaying of signals are done by computer. Voltage and current testing When field frequency and input impedance of ICs are not very high, the induced voltage can be tested by existing voltage probe and oscilloscope, and when input impedance of IC is very high, the impedance of voltage probe maybe influence receiving capability of IC, so special probe with very-high impedance and high shield performance should be developed. When field frequency is too high, the influences of field to voltage probes can't be neglected, and using existing probes can't achieve actual testing of induced voltages. In this instance, one approach is to develop special high-shielded probes to achieve actual testing, and another approach is choosing ICs with low damage thresholds, and studying correlation by damage experiments. To reduce testing difficulty, experiments should start with low frequency, and extend to high frequency. The induced current can be tested by current probe and oscilloscope.
EVALUATION OF CORRELATION The sensitive parameters are different when the tested devices, experimental EMP sources, or experimental methods are different. Interference and damage of devices are dependent on the EMP energy, induced or injected voltage peak values, induced or injected ports, and pulse width. According to internal structure and characteristic of devices, sensitive types are tested firstly by radiation method or injection method, and related sensitive parameters are confirmed. And correlation can be discussed according to sensitive parameters. For voltage sensitive devices, the numerical relations of E-field and voltage or M-field and voltage can be gained from experimental results. For power sensitive devices, the numerical relation of field and power can be gained. And for energy sensitive devices, the relation of field and energy can be gained.
357 Then according to the results, the rules and relations of these numerical curves for the same sort of devices are concluded, and therefore correlation is evaluated. And interference thresholds and damage thresholds are gained from radiation experiments, so it will be found that if the devices, which are in the same damage threshold level by injection method, have the same EMP immunity in the same radiation conditions, that is, devices have the same external circuits and are in the same electromagnetic environment.
DISCUSSION In the past, injection method is adopted to evaluate damage thresholds of devices, and EMP immunity levels are classed by injection voltages. But in fact the interferences and damages of devices are not only related with conduction coupling, but also radiation coupling. Different devices with the same or similar functions and the same external circuits maybe have different induced voltages and currents in the same electromagnetic environment, because of different internal structures and impedances of devices. Whether can the EMP immunity assessed by injection method represent EMP radiation immunity of devices in working conditions is an important topic concerned by electromagnetic protection workers, and conclusion will be gained by correlation study discussed in this paper. But this paper only studies the correlation testing method, the further experiments and study need to be done.
REFERENCES 1. Schreier, L. A., Electrostatic Damage Susceptibility of Semiconductor Devices, Proc. 16th Annu. IEEE Reliability Physics Symp. (1978) 151-53 2. Ricktts, L.W., Bridges, J.E., Miletta, J., EMP Radiation and Protective Techniques, John Wiley and Sons, Inc (1976) 3. Ghose, R. N., EMP Environment and System Hardness, Don White Consultants, Inc (1984) 4. IEC 61340-3-1, Methods for simulation of electrostatic effects-Human body model-Component testing(2002) 5. IEC 61340-3-2, Methods for simulation of electrostatic effects-Machine model-Component testing(2002) 6. Changhe Wang, Study on Radiation Effects and Reinforcement of Electronic Devices, Protection against Nucleus and Reinforcement (1997) 6 55-65 7. IEC 61000-4-2, Testing and measurement techniques, Electrostatic discharge immunity test (2001) 8. IEC 62132, Integrated circuit, Measurements of electromagnetic immunity in the range of 150 kHz-1 GHz (2001)
358 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
I n v e s t i g a t i o n o f the A n t i s t a t i c A b i l i t y of L o w - n o i s e M i c r o w a v e Device* Shiliang Yang, Zhancheng Wu, Jie Yang, Xijun Zhang Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R.China
Abstract: The electrostatic susceptibility of low-noise, high frequency triodes has been investigated with the electrostatic simulator of HBM. Threshold value and threshold model have been confirmed. Damage mechanism of the component has been fimher investigated by using failure analyze instruments. Through testing to discover, the most sensitive port of this type device is cb p-n junctions. It is different with normal (Normally the most sensitive port is eb p-n junction). This paper carry out helpful discuss on this kind of phenomenon. The foundation has been made to improve technology and raise the ESD Threshold Level. Keywords: antistatic ability; microwave device
INTRODUCTION Electrostatic discharge (ESD) is an event of electrical overstress that transfers a finite amount of charge between two objects at different potentials.ESD can cause direct, indirect, and latent failure in electronic devices. Such an event accounts for more than 25% of the failures throughout the electronic components life, starting from wafer fabrication, extending to assembly and testing, and finally ending at the user's site [ 1]. And, as electronic devices became faster and smaller, their sensitivity to ESD increased. So ESD component level stress testing continues to be a critical step in the qualification process of electronic products like integrated circuits(ICs).It is very important to investigate the antistatic ability of the low-noise, high frequency triodes with narrow base width and shallow junction depth.
EXPERIMENTAL METHOD AND INFRASTRUCTURE A charge injection test method using the human body model (HBM) is adopted in the experiment, which, is used for the case where a human body, charged by triboelectrification, approaches an electronic device which may be either floating or grounded. Figure 1 is a block diagram of equipment used to take the typical ESD injection experiment. The test system utilized an ESS-200AX ESD simulator, a TDS680B transient digital oscilloscope, a Tektronix Tek P6041 current probe with frequency range from 25kHz to 1GHz and a QT2 transistor curve tracer.
I EUT
,
I , Current
I Oscilloscope
I Figure 1 Block diagram of equipment of injection experiment
Project supported by the NSFC No. 50077024 and 50237040
359 A certain model of six low- noises, high frequency triodes produced in the same batch were selected as samples for the experiment, they were marked respectively. Before testing, all the samples of the component were tested to all specified static data sheet parameters.
EXPERIMENTAL RESULTS AND ANALYSIS ESD susceptibility contrast of pin combinations ESD stress test was performed at room temperature in accordance with the procedure called step-stress method. It must be remembered that the sort of ESD testing is destructive to the component, even if no component failure occurs. The ESD pulse of 600 volts accounted for 80 percent of the guesstimating threshold value was injected into all pin combinations. Then the component was tested to full static data sheet parameters and the result was recorded perfectly. If there being no damage to the electrical component, increments of 50 volts was added until a failure occurred. The voltage injected just now was designated as the ESD damage voltage, while the voltage injected before was regarded as the ESD withstand voltage [2]. A component is considered an ESD failure if it fails the data sheet parameters as follows: BVebo>38V/10].tA, BVceo>27~30V/101.tA, BVebo>38V/101.tA. The gained data cannot to be valid if the electronic component is failure for the first time ESD pulse injected into. Damage voltages and withstand voltages are shown in table 1. Table 1 Damage voltages and withstand voltage Bin combinations
Damage voltage(V)
Withstand voltage(V)
bc
1250
1200
cb
1100
994
ec
1300
1250
ce
1300
1250
be
1300
1250
eb
1300
1250
Table 1 shows that the most sensitive pin combinations is reverse cb p - n junctions instead of reverse eb p-n junctions. One of the reasons is that the damage mechanism of p - n junction differ from each other. The explicit explanation for the case will be proposed subsequently. Change trend of the sensitive parameters The sensitive parameters of the electronic component were tested once the ESD pulse had been injected into the pin combinations. The BV character of the component was measured with the QT2 transistor curve tracer. The sensitive parameters, which include BVcbo and BVceo, would change to some extent when the component had been damaged. But the change degree of sensitive parameter vary from each other. When the component was damaged severely, all the sensitive parameters changed. But if the damage to the component is trivial, only the most sensitive parameter (BVeeo) changes. The value of the BVebohad been kept invariability all through the process. Analysis of the damage mechanism ESD damages in electronic component can be characterized as catastrophic failure, i.e., hard failure, and latent failure, i.e., soft failure. Typical hard failures are associated with either thermal damages in metal interconnects, contacts/vias, and silicon, or dielectric ruptures. Latent ESD failure is normally defmed as the kind ESD damages, often invisible, which lead to noticeable, however, still within the specification, electrical parameter deterioration after lower-level ESD stresses.
360 After its encapsulation being opened, the triode was examined with a 1000• microscope. The metal stripe was found integrity, while the p - n junction was damaged to some extent. The effect of an ESD-pulse on a microwave device depends on the pulse height (breakdown power), rise-time and energy (developed heat). The character of the damages varies with the parameters mentioned above. Through intensive analysis, we thought that the damage was connected with the thermal secondary breakdown. There are two kind of different theory on thermal secondary breakdown including thermal instability theory (called thermal model) and avalanche degradation theory (called current model). Scarlett et al. [3] reported that the secondary breakdown occurs as a result of hot inside the structure. The reason for the formation of a hot lies in the instability of the thermoelectric system of the device structure [4]. The breakdown of a transistor causes the current density to increase, which raises the temperature at the base-collector junction. The rise in temperature may result in the formation of a hot spot, which is unstable and leads to secondary breakdown. It is proposed in the latter that the thermal secondary breakdown is related to the transient current density and the field strength in a spot of the collector junction. Once the injected current density approaches the collector space-charge modulation and the field strength reaches the critical value, the thermal secondary breakdown occurs. It is found that the thermal secondary breakdown occurring in the eb p - n junction is thermal model, while what happens in another two p - n junction is current model. The transient power of the current model is more significant than that of the thermal mode, as a result, the cb p - n junction is more sensitive than the eb p-n junction when ESD damage occurs.
CONCLUSION The low-noise high frequencies transistors are extensively applied in electrical industry, which are confirmed as level one sensitive component according to their HBM ESD withstand voltage. On the base of the above analysis, some conclusion can be drawn: the most sensitive pin combinations are cb p - n junctions and the mbst sensitive parameter is BVceo accordingly, there is no explicit relation between the injection sequence and the susceptibility of the pin combinations.
REFERENCES 1. Duvvury, C.and Amerasekera, A., ESD: A pervasive reliability concern for IC technologies, IEEE Proc (1993) 81690-702 GJB 538-88, Testing methods for electromagnetic pulse damage threshold of semiconductor devices 3. Scarlett, R. M. and Schockley, W., Thermal instabilities and hot spots in junction transistors, Phys. Failure Electron (1963) 194-203 4. Steffe, W. and Le Gall, J., Thermal switchback in high ft epitaxial transistors, IEEE Trans. Electron Devices (1966)13 635638 2.
361 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on Electrostatic Discharge Radiation Field Simulating Technology* Lizhen Liu, Guanghui Wei, Lisi Fan Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Rord, Shijiazhuang, 050003,China
Abstract: On the basis of analyzing characteristics of electrostatic discharge electromagnetic pulse (EMP), an ESD radiating field simulator is studied in this paper that is composed of pulse voltage generator, transmission cell and matched load resistance. The influences to the output waveform are discussed, such as pulse voltage generator's capacity, discharge switch, circuit loop inductance and charging voltage. Key words: ESD, FREMP, radiation field, GTEM cell, simulate
With the development of science and technology, density of integrated circuit of semiconductor is increasingly improved, but power consumption is lower and lower. Working frequency of circuit is advanced. These reason lead to electronic device is extreme sensitive to EMP. The loss resulted from EMP is growing year by year. To reduce these damages, we must understand fully mechanism of action of EMP to microelectronic device. For this reason the real electromagnetism environment must be simulated. The old version specified rise time of nuclear electromagnetism pulse (NEMP) produced upper air nuclear explosion is less than 10ns and pulse duration is approximately several hundreds of nanoseconds, while the new version American army standard MIL-STD-464 (1997 version)[1] specified that HEMP rise time is about 2-3ns and impulse half-height duration is about 25ns.However electrostatic discharge is a complex variable procedure. The electrostatic discharge can not only yield that a high-current pulse, which rise time is extreme fast and duration time is extreme short but also produce strong electromagnetic radiation. So far accurate simulation means is yet designed. In order to evaluate ESD radiation immunity of electronic device in IEC 61000-4-2, the personnel applied a method of discharge to horizontal coupling plane and vertical coupling plane. But due to some important parameters such as field waveform and homogeneous degree is not specified, experiment results quite differ. In order to solve this question, electrostatic discharge simulator is badly developed. It is well known that the faster the rise time of pulse is, the broader spectrum is. But EMI is easily caused. Due to electrostatic discharge pulse with a rise time 0.7-1ns, it is faster than HEMP. So simulating is more difficult. In order to simulate electrostatic discharge radiation field, this paper adopt Pspice simulating and numeric value calculating to analyze the important parameter of high-voltage pulse power influence to electrostatic discharge waveform. A method that better output waveform and reduce the rise time is put forward.
PRINCIPLE AND COMPOSITION Electromagnetic pulse simulating device" consists of high-voltage pulse power, control switch, antenna or field transmission device [2]. Because the rise time of pulse produced electrostatic discharge is fast, duration is short and frequency is relative high, utilizing wide radiation antenna (gain up to 5-10 dB), which can gain higher field strength at the condition of pulse power output voltage is appropriate, But Project supported by the NSFC No. 50077024 and 50237040
362 developing broad-band radiation antenna is difficult. So this paper adopt field transmission device at the beginning of research. RI G High-voltage pulse power is the foundation of simulating o technology. According to initial energy storage means pulse discharge circuit is divided into capacity storage and induction L storage .due to high induction of induction storage circuit, current waveform rise time is slower. When the fast rise time is needed, capacity storage discharge circuit is applied [3]. Because typical electrostatic discharge waveform is double exponential, we may apply simple RLC circuit. Its primary principle is showed in Figure 1.After storage energy capacity is Figure 1 the principle diagram of charged, storage capacity discharge through close switch to the circuit resistance R. When induction value is low, the produced double exponential pulse is applied to load resistance R0. As simulating environment electric field is complex, the charged means of storage capacity C is diversity. When storage energy capacity C operating voltage is less than 80kV, direct charging do not produce strong corona discharge. Due to using direct current high voltage power through currentlimiting resistance charging capacity C the cost is cheap and waveform parameter is easily controlled. EMI is weaker [4]. Storage energy capacity C operating voltage is above 100kV, direct charging will lead to strong corona discharging and increase power load and decrease safety. Marx power should be adopted in place of storage energy capacity C. Its character with parallel charging and series discharging will inhibit corona discharge. This simulating device will work at the under of 50kV. Control switch include high-pressure gas switch, high-pressure mercury relay switch, mercury film electric pole discharging tube, pseudospark switch, laser triggering switch, photoconductive switch. Mercury film electric pole discharging tube is usually applied as impulse trigger switch. Pseudospark operating voltage is low, it switch working voltage is not above 2kV at home. Only high-pressure gas switch and high-pressure mercury is still developing, laser triggered switch is used as triggering. Photoconductive relay of ESD simulator is applied in this experiment. Field transmission device has many ways such as parallel plate transmission, TEM cell and GTEM cell. Due to parallel plate transmission working at the under of 300MHz,it cannot be applied in simulating fast rise time pulse. TEM cell and GTEM cell can work at the under of several hundreds of GHz. but GTEM cell frequent character is good but economize space. So we developed electrostatic discharge radiation field simulator should apply GTEM cell as transmission device.
D
THE INFLUENCE OF CIRCUIT PARAMETER TO WAVEFORM According to Fig. 1, the expression for the circuit can be written as: u C -
L -di- + dt
R i
i = - C du dt
(1) (2)
according to the above two equation, the below equation can be drawn: LCd2i RCd i + ~ + dt 2 dt
i- 0
(3)
L is the inductance of the capacitor C itself and i is the current of the circuit. Equation (3) characteristic root 2~, 2 2can be written as follows"
363 (4)
tC An expression for i (t), which is derived from equation (1), is
(5)
i ( t ) = A l e ;qt + A z e &t
Substituting the initial value i(0) = 0 and di / dt 1,=0- Uo / L into equation (5),we can obtain t
R wt
(6)
i(t) -- U o (e Rc _ e L ) / ~[R 2 _ 4 L / C
So, the rise time
tr ~
2.2L/R
and half height duration time t h - 0 . 6 9 R C .
Substitute the value
L=20nH, R=50 f~, give t r = 0.88ns ,we can see that the rise time is less Ins. The voltage waveform of the road R simulated by Pspice is shown in Figure 2. Because the electric field in GTEM cell is approximate homogeneous and its expression is E= U/d, we may take place of electric field waveform with simulated voltage waveform. Modifying the parameters, the rise time will change. As is shown in Tablel, Table2 and Table3. Theoretical calculation value greatly differs from the simulated value by comparing. This result maybe be caused by the different approximate process.
Table 1 Influence of capacity value to the rise time
....
R/~ 50 50 50 50 50 50 50 50
L/nil 20 20 20 20 20 20 20 20
C/pF 10 50 100 150 500 1000 1500 2000
rise time/ns oscillation 0.52 0.59 0.64 0.75 0.79 0.80 duration> 100ns
Table 3 Influence of inductance value to rise time R/~ 50 50 5O 50 50 50 50
L/nil 15 20 30 40 60 80 100
C/pF 150 150 150 150 150 150 150
~}l~w aSkv
0v On.5
Ins
2ns
:Ins
4n.5
5ns
6ns
7ns
9n.s
8ns
t imc
Figure 2 the voltage waveform of the load Table 2 Influence of load value to the rise time R/~
L/nil
C/pF
rise time/ns
25 30 40 45 50 55 ,, 65 80
20 20 20 20 20 20 20 20
150 150 150 150 150 150 150 150
0.96 0.88 0.74 0.69 0.64 0.60 0.54 0.45
gl
G
rise time/ns 0.51 0.64 0.90 1.12 1.53 1.90 2.24
LR
Figure 3 the equivalent circuit
364 Due to the influence of the capacity and inductance impedance of resistance itself, the circuit is changed partly. As is shown in Figure 3. The parameter value is given R =50 f2, C = 150pF, L = 20nil, LR= 20nil, and CR =10pF. The voltage waveform of the R0 is shown in Figure 4. In the simulating test, we found that only the value of inductance L~ is changed, the rise time is also influenced largely. But the higher the value LR is, the faster the rise time is. Regardless of the capacity impedance of the matched resistance, the waveform of the voltage R is shown in Figure 5. The parameters are given R=50 f~, L=20nH,C=150pF and LR---10nil. 30-
30
25 20 > " 15 Z)
~.~ 20 Z)
15
10
10
0
0
5
10
1~i
2()
Time/ns
Figure 4 the voltage waveform of the load
0
-
2 |
9
i'
4
9
6 |
9
13
-
Time/ns
10
12
1~1
'.
16
Figure 5 the voltage waveform of the load (regardless of the capacity impedance of R )
Above figures show that the waveforms are approximate double exponential waves and the rise time are about Ins. The above waveforms are gained under ideal conditions Tand different from the real waveforms because of the influences of the switch conduction resistance, power consumption on transmission line and the loop capacity and induction.
CONCLUSION From the simulating test, the conclusion will be drawn that the inductance value of the charging capacity itself is the main reason of effecting the rise time. So to steepenthe rise time must reduce the value of the inductance. Secondly the induction of the circuit must be reduced. Thus the circuit must be arranged compactly. But if the load is not matched, the rise time may be effected.
REFERENCE 1. Department of Defense Interface Standard. MIL-STD-464, Electromagnetic Environmental Effects Requirement for Systems., (1997) 2. Ying Wang, High Power Pulse Resour.ce, Atomic Energy Press, Beijing, China (1991) 3. Ji Liu, Yuanji He and Jiaxiang Yang, Numeric Analysis on Discharging Circuit of Capacity Storage Ener_~_ for High-current Pulse, Harbin Industry College transaction 4 91-94 4. Guanghui Wei, Yongwei Sun and Minghong Tian, Theoretical Calculation and Simulation Technique of LEMP Field, Safety and EMC (2003) 3 36-38
365 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
T h e I n f l u e n c e o f E U T to C h a r a c t e r i s t i c I m p e d a n c e in G T E M Cell* Lisi Fan, Xijun Zhang, Lizhen Liu Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping W.R. Shijiazhuang Hebei. 050003,P.R.China
Abstract: The influence of EUT to characteristic impedance in GTEM cell twodimensional cross section is calculated using finite element method (FEM). The variations of the characteristic impedance in GTEM cell induced by grounding and un-grounding metal EUT are compared. The relation between the characteristic impedance and the EUT relative size is discussed, when the EUT is dielectric material. The useful references are presented in this paper for GTEM cell design and application. Key words: GTEM cell, characteristic impedance, finite element method
The GTEM cell is a 50 f~ tapered rectangular coaxial transmission line with an offset center septum. Although the structure of the GTEM cell is complex, the characteristic impedance should be calculated in order to determine the maximum size of the acceptable EUT, in other word, calculate the maximum available measurement space of the GTEM cell. In the paper, the characteristic impedance of the GTEM cell is calculated, the calculation relational curve between the characteristic impedance and section dimension is provided, which provide the evidence to evaluate the uncertainty of the measurement using GTEM cell, and the maximum size of the EUT can be determined according to the curves when the characteristic impedance without significantly descent.
THE CALCULATION METHOD FOR CHARACTERISTIC IMPEDANCE In general the GTEM cell is considered as the rectangular coaxial Y~I, transmission line, it is difficult to solve the characteristic impedance d using traditional analysis and semi-analysis method. In this paper, h finite element method is applied to calculate the characteristic impedance of the GTEM cell. For a rectangular coaxial transmission line shown in figure 1, According to the theory of lossless transmission line, the characteristic impedance can be written as [ 1] 1 Zo=~ (1) 0 CoC -a/2 -w/2 .............
4
/0
tn i !
EU
!
x
X
!
w/2 a/2"
Fig. 1 Cross section of GTEM cell
Where, co is the velocity of light in the free space, c0~-3.0 X 108m/s. C is the unit capacitance of the transmission line. So the problem to calculate the characteristic impedance can be generalize to solve the unit capacitance of the GTEM cell. The capacitance storage-energy formula can be expressed as W-
-1CV2 2
lit
Project supported by the NSFC No. 50077024 and 50237040
(2)
366 Thus
C - 2W V2
=
eo I[E( x, y)l dxdy
(3)
V2
If the mode of propagation in the GTEM cell is considered as an ideal TEM mode, the filed pattern of TEM mode can be calculated as electrostatic case [2,3]. The potential distribution rp(x, y)in the cross section satisfying the Laplace function, ~2 rp(x, y) ~gx2
+
~2 rp(x, y) ~gy2
=0
(4)
The potential distribution in the cross section is calculated by FEM with triangular unit mesh. The electric-field intensity at the point of each gird can be obtained by differentiating to the potential [4].
(5)
bT(x, y) - E, (x, y)i + Ey (x, y ) j where" E
X
1 [(yj _ym)(igi+(Ym--Yi)(tgj +(Yi--Yj)(ffm]
2A
--
Ey
(6)
- - - -1 [(Xm __ Xj)~O i -t" (X m -- X j ) ~ j -I- (X m -- Xj)(sOm ] 2A
Here xi, xj, Xm, y~, yj, Ym are the coordinates at the three nodes of i, j, m. (ffi, (ffj' (ffmis the potential respectively at each vertex./~ is the area of the triangular mesh. l
1 r
A = ~ [(yj --ym)(Xi --Xm)--(Ym --Yi)(Xm --X j)]
(7)
2
The electric field distribution in the cross section of the GTEM cell can be calculated by FEM program in term of equ. (5), (6). Substituting equ.(5) into equ.(2), the distributed capacitance per unit length is rewritten as [5] n0
f[E(x,y)[2dxdy
C
_
,
V2
Z ~ o (Ex 2 -.I-Ey2)Si =
,=o
(8)
V2
Where, no is the sum of the mesh, Exi, Eyi is respectively the electric component in x and y direction, at the grid index as i, si is the area of the i th grid calculated by equ.(7). Substituting equ.(8) into equ.(1), the characteristic impedance of the GTEM cell is obtainable.
THE INFLUENCE OF EUT TO CHARACTERISTIC IMPEDANCE General requirement for characteristic impedance is that the reduce is no greater than 2 f~ when EUT is placed into the testing region. The analysis by FEM in two dimension cross section are applied to determine the maximum EUT size and placed position which conform to the characteristic impedance requirement The influence of ungrounding EUT to characteristic impedance In practice testing process, the EUT is placed on the insulating testing plate, and then the metal EUT becomes a floating conductor in the GTEM cell. In order to simplify calculation, It is assumed that the voltage on the septum is IV, and the EUT is good conductor which width and height is respectively denoted by x and y. The EUT is placed at the center of the testing zone, and the characteristic impedance of the GTEM cell is 50 f~ when no EUT is placed. The relation between the characteristic impedance of the GTEM cell and the relative width of the EUT is shown as figure 2.
367 From figure 2, a conclusion can be obtained that characteristic impedance decreases with the increment of the EUT size. If the size of the EUT is not larger than the one-third of the testing region, the decrease of the characteristic impedance can be approximately ignore. The influence of grounding EUT to characteristic impedance In some testing process, The EUT is metal instrument on earthing state. From the field distribution point of view, the earthed EUT distorted the field distribution in the GTEM cell; from the structure point of view, the earthed EUT changes the cross section structure, so the unit capacitance is changed by the structure variation. The characteristic impedance is significantly decreased by the earthed EUT in GTEM cell.
50
=
r o
48
50
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
E 46
~
4442
E
9-u
~
/
3
..a
o -~ 9
i
44 42 40
y/h=1/2
i i
i
',', i ,,
i, , ,,
/3
40
r
~ h = 1 / 2
38
i i
36 0.0
010 01~ 012 o:a 014 01~ 016 017 0:8 ,.
.
(x/a)
Relative width
. . . 012 014 Relative width (x/a)
016
018
Figure 3 The influence of the earthed EUT placed at the center of testing zone to characteristic impedance
Figure 2 The infulence of the ungrounding EUT to characteristic impedance
The relations between the characteristic impedance and the size of the EUT are shown as figure 3, which earthed metal EUT is placed at the center of the testing zone. The figure 4 shows the relation that the EUT is placed on the bottom plate. When the earthed metal EUT is placed in the GTEM cell at the center of the testing zone, the characteristic impedance decreases rapidly with the increment of the width and height of the EUT. If the earthed EUT which relative height is less than 1/6 and the relative width is less than 1/10 of the testing zone, the characteristic impedance of the GTEM cell is larger than 48 f~, and the size of the EUT larger than that the decrease of characteristic impedance is larger than 2 f~, that is to say the characteristic impedance of the GTEM cell significant decrease has happened in the GTEM cell. But if the earthed EUT placed on the bottom plate, even the size of the EUT that relative height is lager than 1/3 and relative width is larger than 4/5, the characteristic impedance is still larger than 48 f~. 50.5
50
cl r
~ylh= 116
Ci 49.550"0 ~ ~ ~ ................................................ _ _ - ~
49
E
~
r
r 48
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
49.0
.
E
.~_, 48.0 ---
E
:.-:-
.,...
~9
47
~
46.
45 0.0
~
.._......~ylh=ll2
~ rJ
"
012
" 0'.4 " 016 Relative width (x/a)
'
0'.8
Figure 4 The influence of the earthed EUT placed on the center of the bottom board to characteristic impedance
46.5 46.0
0.0
0.2
0.4 0.6 Relative width (x/a)
0.8
Fig.5 The influence of the earthed EUT placed on the center of the bottom board to characteristic impedance
To compare the figure 3 and figure 4, a conclusion can be derived that the influence to the characteristic impedance of the GTEM cell with earthed EUT placed on the bottom board is less than that EUT placed at the center of testing zone. It is because that the shielding effect of the metal EUT at the center of the testing zone, the electric-field intensity above the EUT is enhanced, the electric-field intensity below the EUT is weakened, the field distribution is strongly distorted in the cross section, the
368 unit capacitance of the cross section increases largely, so the characteristic impedance of the GTEM cell is reduced rapidly. In the testing process, the earthed metal EUT should be placed on center of the bottom board, so that can less the influence of the EUT to the characteristic impedance of the GTEM cell. The influence of the dielectric EUT to characteristic impedance The relative width of the dielectric EUT influence to characteristic impedance is shown as figure 5, the EUT is the dielectric material with relative permittivity as 3. A conclusion can be obtained from figure 5 that the influence is weaken to the characteristic impedance, if the EUT is dielectric material with small relative permittivity. The reason is that the influence of the dielectric EUT to the distribution capacitance is small, so there is weaken effect to the characteristic impedance. Consider the field uniformity in the GTEM cell the dielectric EUT should be placed at the center of the testing zone. The characteristic impedance of the is larger than 48 Q, if the relative height of the dielectric EUT is less than 1/2, and the relative width is less than 1/3, in other word, there is no significant drop of the characteristic impedance if the EUT less than that.
CONCLUSIONS The calculation results show that the decrease of the characteristic impedance can be ignored, if the ungrounding metal EUT, which is no larger than one-third of testing zone. The influence to the characteristic impedance of the GTEM cell with earthed EUT placed on the bottom board is less than that EUT placed at the center of testing zone. In the testing process, the earthed metal EUT should be placed on center of the bottom board, if the earthed EUT placed on the bottom board and not larger than onethird of the testing zone, the characteristic impedance of the GTEM cell can be ignored. If the EUT is dielectric material with small relative permittivity, which the relative height of the dielectric EUT is less than 1/2 and the relative width is less than 1/3, there is no significant drop of the characteristic impedance.
REFERENCES [ 1] Clemens Ichelen. The construction and application of a GTEM cell[D]. Technical University of Hamburg-Harburg, 1995. [2] Huang Zhixun, He Tao. Theory and computation method of the GTEM[J]. Jou.rnal of Astronautic Metrology and Measurement, 1992, (5):29~40. [3] Huang Zhixun, He Tao. The quasi-static analysis and computation of the characteristic impedance on TEM transmission cell and gigahertz TEM cell [J]. ACTA METROLOGICA SINICA, 1994, 15(3): 167~174. [4] Ni Jian-hong. Electromagnetic field numeric analysis. BeiJing: Science Publishing House, 1984 [5] Lu Xin-hua, Jiang Quan-xing. Calculation characteristic impedance of TEM and GTEM cell using auto- -gird FEM. Security & EMC, 1997(2)" 21~33.
369 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Study on Mechanism and Protective Technology of Electromagnetic Harm to Microelectronic Equipment Chaobin Tan, Jianzheng Yi Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R. China
Abstract: In order to gain some methods of electromagnetic protection and designing principles to enhance the capability of anti electromagnetic harm of the micro-electronic equipment, the mechanism of the micro-electronic equipment electromagnetic harms are analyzed theoretically. Practices and test show that those methods and principles are very efficient in microelectronic equipment electromagnetic protection. Keywords: micro-electronic equipment, harm, electromagnetic protection
INTRODUCTION With the development of electronic technology, large scale integrated micro-electronic equipment is wide used in industrial, military and space field for its little volume, low power consumption and intelligent control. Under the modem serious electromagnetic environmental, the electromagnetic harm of microelectronic equipment is also increasing seriously. The electromagnetic interfere can not only disturb communication system, but also deviate missile course and cause space flight fail. And it causes one hundred million dollars loss every year [1]. The study on the mechanism and protective technology of electromagnetic harm to the Micro-electronic Equipment is very important.
ELECTROMAGNETIC HARM TO MICRO-ELECTRONIC EQUIPMENT Radio station and radar do work on sending and receiving electromagnetic wave. All of electronic equipments radiate electromagnetic wave at different level when they are in their work. Therefore, in space, there is fill with the electromagnetic wave of different frequency. The inutility electromagnetic wave and electromagnetic energy can cause disturb and do hazards to the micro-electronic equipment. From Maxwell equations, we know that electromagnetic wave is aroused mutually by electric field and magnetic field. Current density J and charge density o act on electromagnetic wave with certain forms [ 2 ]. So, the electromagnetic harm to micro-electronic equipment can be divided into the harm of electric field and the harm of magnetic field. The harm of electric field to micro-electronic equipment The electric field E can form an additional potential in micro-electronic loop. AU-
IE.dl
If E is even electric field in the loop, the voltage between load R is U R - e + A U - e + f E , . dl + f E 2 9dl - ( e + U ) - ( 0 + U) - e (a, b are two points of the loop)
Therefore, even electric field does not do hazard to the loop. If E is not even electric field, ~he voltage between load R in microelectronics loop is
370
AU - ~E.dl - ~ E i .dl + ~ E 2 .dl r A additional voltage A U is add to e. In strong electric field, A U may be very high. If e + A U exceeds the threshold voltage of the load R ,some hazards to the micro-electronic equipment will be caused by electric field. The harm of magnetic field to micro-electronic equipment Magnetic field can do harm to the optical-electric equipment (such as display, TV, CRT). In magnetic field of B, the electrified particles that have vertical sport velocity will do circular motion with radius R - m V / q B , under the affect of the Lorenz force. The original movement orbit of the electronic or electrified particle will be changed. So the harm to electronic equipment is caused by magnetic field. Therefore, the electronic equipment, which has electron gun or cathode ray, should be far away from magnetic field in order to avoid disturbed. Magnetic field will not influence the current in loop directly. The kinetic energy of free electrons in conductor is not as high as the level to make electronics release from the conductor's surface. And the force of magnetic field ( F = q-V • B ) does not do work to the electrons. Therefore the kinetic energy of free electrons will not increase for the force of magnetic field. And magnetic field will not influence the current in loop. Alternative electric field influences the current of the loop through its induce voltage. Set up the area of a loop is S. The voltage that induced by the alternative electric field is
e=~B.ds dt A additional voltage e ' is added to the loop. And a wave voltage disturb to the load R is formed. If e + e ' is larger than the threshold voltage of the load R , R will be burned out or damaged. Electromagnetic pulse (EMP) can affect the logic gate in integrate circuit to produce misoperation. This will cause abnormal result or work failure and forms software damage. So, the miseode and information lost of computer are caused for this reason and invaluable lost is caused every year [3]. Therefore, we can know that the mechanism of electromagnetic harms has 3 kinds: a. The voltage of electric field or the induce voltage of magnetic field cause harm to the loop. b. The influence of magnetic field to cathode ray, electron gun and electrified particle bundle. c. Electromagnetic pulse disturb to micro-electronic equipment and the software.
MEASURES OF ELECTROMAGNETIC PROTECTION OF MICRO-ELECTRONIC EQUIPMENT Shield The free electronics of conductor will redistribute under the affection of the outer constant electric field. Another constant electric field, which is as strong as the original electric field but reverse in orientation, will be formed in interior of the conductor. And the outer constant electric field is shielded. The strength of electric field in interior of the conductor is 0v/m. According to this principle, we can use material of high electrical conductivity to shield constant electric field. Coveting the micro-electronic equipment and grounding the shield, the outer constant electric field will be shielded completely. The bigger the electrical conductivity of material is, the more the effect of the shield to the constant electric field is. And the thickness of the material is little in the identical shield effect. Therefore, the material with great electrical conductivity frequently is selected to shield the constant electric field. General material we used often are" Copper, silver and aluminum alloy. Constant magnetic field can be shielded by use the high magnetic conductivity material just like shield constant electric field. The resistance of high magnetic conductivity material is much lower than that of the space and it gives constant magnetic field a shortcut to pass. Constant magnetic field will not go through the inside space of the shield. The surface of the shield is an identical-magnetic -potential surface. There is no constant magnetic field in the inside space of the shield. Thus constant magnetic field of outer space is shielded. The magnetic conductivity of the highest magnetic conductivity material is not high enough to shield magnetic field completely. A part of magnetic field can get into the inside of the shield. It is difficult to
371 shield magnetic field and the shield has a little thickness and the shield effect is not as far as the constant electric field does. Completely shield constant magnetic field is harder than constant electric field [4]. Electromagnetic wave is a matter that arouse mutually by electric field and magnetic field. Internal electronics will form the conduction current under the affection of the alternative electric field. The electromagnetic wave on the surface of the conductor is reflected and transmitted separately. Joule heat is produced by the conduction current and the transmitted electromagnetic wave is attenuated. Eddy current in the shield, which produced by the alternative magnetic field, consumes the energy of magnetic field and makes the original magnetic field attenuated. The magnetic field that produced by the eddy current is reverse to the original magnetic field and the affection of the original magnetic field becomes weaken. The attenuation formulas of electromagnetic wave with co frequency, which vertical incidence to a conductor with cr electrical conductivity and/z magnetic conductivity, are as follows [2]: E(x,t) = Eo e-~~e ~(p~-~) B(x,t) = Bo e-~x e ~(p~-~) Cr --
" ( attenuation constant ) fl = " (phase constant) 2 2 The thickness of the shield, which attenuates the electric field E or magnetic field B to l/e, is Of
O"
The calculated shield thickness of 20db, 40db, 60db attenuation of the electromagnetic wave are as follow: 2.30 8 4.61 8 6.91 8. Now we know that the greater the electrical conductivity and the magnetic conductivity are, the thicker the thickness of shield is. We can choose the material with big electrical conductivity and magnetic conductivity to shield electromagnetic wave. General material we used often are copper, silver and aluminum alloy. Superconductor technology prevent electromagnetic hazard to micro-electric equipment The electrical conductivity and the magnetic conductivity of superconductor are both tend to infinite. Therefore, the superconductor shield is able to completely shielded electric field and magnetic field. According to Meissner Effect, the strength of magnetic field B is 0A/m in the inner of the superconductor when the superconductor is in super conduct condition [2]. n-(B 2 - B , ) - 0 n x ( H 2 - H I) -- 0 B2 = / / o H 2
H2t
H2n
=
/.to Htt
]1 Hin
Bl" =//J-/l
~0
Under the affection of the outside magnetic field, superconduction current will be produced on the surface of the superconductor. The magnetic field, which aroused by superconduction current, offsets the affection of the original magnetic field to the inside of the shield. The outside magnetic field can only go through the superconductor's surface. And this makes the strength of magnetic field B is 0A/m in the inner of the superconductor. The superconductor shield is able to completely shield electric field and magnetic field both. The superconductor technology of high temperature is still immature, although it has a considerable prospect. The equipment of superconductor is very huge and with a very high cost. The project application of superconductor under high temperature condition has its difficulties. Optimization designation, enhance ability of the micro-electron equipment to anti electroma~aetic disturb The additional electric potential that produced by electric field is A U - I E. dl - ~ E - d l + ~ E. dl
We know, in order to reduce A U and enhance the ability of the micro-electron equipment to antis electromagnetic disturb, the length of the loop L should be designed as short as possible.
372
A U - I E . d l - ~Ed/cosO+ ~Edlcos0 If the orientation of the electric field E is certain, in order to reduce cosO and/kU, the line should be vertically to the orientation of electric field. The induced electric potential of the alternative magnetic field is
~ ' = ~ B . d s - ~ BdscosO dt dt The area of the loop S and the length of the line L should be reduced in order to reduce the induced electric potential of the alternative magnetic field. If the orientation of the magnetic field B is certain, in order to reduce cos O and s ', the line should be parallel to the orientation of magnetic field. The loop with counter symmetrical structure can produced contrary voltage and reduces electromagnetic harm. For a loop (area is S), which has a pair of counter symmetrical loop (the area are s l, s2 and s l =-s2), voltage of the loop that induced by the alternative magnetic field is s ' = s l' +' s 2=~-) d~ d ~ B.ds2=O - B.ds t+-~ From this, we know that the counter symmetrical structure can make the induced electric potential offset and enhance the ability of the micro-electron equipment to anti electromagnetic harm. Filter Suitable frequency band filter should be designed in micro-electronic equipment circuit in order to decrease the electromagnetic pulse disturb and guarantee the software of the system. The forms of filter are as follow, R-C, R-L and R-L-C [3]. Protective circuit Protective circuit is very important to micro-electronic equipment. Protective circuit can discharge the disaster energy of the sudden electromagnetic pulse disturb and protect the hard ware of the microelectronic equipment. Ground We must remember to ground the circuit when we design the PCB of micro-electronic equipment. The circuit must be reliable grounded nearby. Analog circuit, digital circuit, power circuit and signal circuit should be grounded separately. Only grounding the circuit, the shield, the filter and protective circuit do work reliable. So, we can prevent the electromagnetic harm of the outer and inner.
CONCLUDING REMARKS The mechanisms of electromagnetic harm to micro-electronic equipment are theoretically analysis above. And some methods of electromagnetic harm protection and some designing principles to enhance the capability of anti electromagnetic harm of the micro-electronic equipment are gained. Practices and test show that those methods and principles are very efficient in micro-electronic equipment electromagnetic harm protection. However, electromagnetic protection is a technology with deep theoretical and practical basic. How to shield electric field and magnetic field completely at the same time and filter electromagnetic wave both in height frequency and low frequency need discuss and study further.
REFERENCES 1. Shanghe Liu. Theory and Protection of Electrostatic. Beijing: Weapon industrial press, China (1997). 2. Shuohong Guo. Electrodynamics. Higher educational press, China (1978). 3. Zh.L Tan, Sh.H Liu, G.H. Wei. Electromagnetic Pulse with Protection Technology.Mechanical Eng. College,China (1999) 4. Renyu Zhang. High Voltage Experiment Technoloffy. TsinghuaUniversity press, China(1982).
373 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Analysis and Design of Electro-magnetic Compatibility (EMC) in Pulse Power System Dong Qi, Ninghui Wang Institute of Electrostatics, Dalian University of Technology, Dalian 116024, ER.China
Abstract: This paper analyzed the effect of pulsed power on control system, based on the basic theory of electromagnetic interference (EMI). The aim is to solve the EMI problem appeared in the study of the pulsed-bias arc ion plating thin film deposition technology. Several methods were put forward against interference in the aspects of system reliability, circuit design and manufacture technology. The experimental results show that these methods are very effective on restraining interference, and make the stability of the pulsed power systems improved.
INTRODUCTION Pulsed-bias arc ion plating (PBAIP) is an advanced plating technology emerged in the late 20 centuries, which has broad application perspective in modification of material surface, especially in synthesis of high quality membranes. But the stability of manufacture technology is not very good. So high stability of control circuit is required in order to improve the stability of PBAIP. Also the electromagnetic compatibility of the system is highly important for the high voltage pulse mode of the main circuit and the low voltage mode of the control circuit.
CONSTRUCTION AND OPERATIING PRINCIPLE OF THE SYSTEM As shown in Figure 1, the negative pulse-biased arc ion plating voltage power supply is composed of five parts and it's operation process can be described briefly as follows 9Output DC voltage about 500V is generated after filter and rectification of threee-phase industrial frequency power supply; then the continuously adjustable DC volatage is output after chop and adjustment of the 500 V DC voltage; high voltage and high frequency output is generated after the invert, and is the input of the high volatage pulse gengerating unit; the frequency-and-duty-ratio-adjustable high voltage pulse is the output; at last, the high voltage pulse and the DC base volatage are superimposed and the output is the pulsed negative high voltage which supply the arc ion plating load with the pulsed negative biased voltage.
AC Voltage Input 1 (Thr )_.~__DI_ Pha ~ - -~- ~ f-
2 ~~i
3 ~[~
5 --I4 -T" l " ~ ' i " ~ ' " ' - ~ ~ ,..... PulSeoutput
i...................,...,,....................................... 1.Reetifieationand filterunit: 2.Chopand adjustunit: 3.Invertand step-upunit; 4.Highvoltagepulsegeneratingunit: 5.DCbasevoltageunit Fig. 1" the structure map of arc ion plating pulsed negative bias power
374 THE INFLUENCE OF HIGH VOLTAGE PULSE POWER SUPPLY ON THE CONTROL SYSTEM Zl
As stated above, PBAIP is composed of two partsthe low voltage part (control system) and the high "'.. y voltage part (pulse power supply, etc). The high voltage part, is the source of serious " ' - . ~ I ~ . --''- I A electromagnetic interference, especially the pulse ""~p'~x.y) power supply whose load features resistance and o capacitance and it's fast variation of load b "-I impedance cause the fast rate of change of the voltage as well as the current of the power supply Figure 2 Illustration of influence of conducting wire over other closed loops loop t~l. According to the electromagnetic induction principle, magnetic field is induced around the wire conducting current and varies with the change of the current. The varying magnetic filed induces the induced potential and the induced current in a closed loop, as shown in Figure 2. The magnetic flux density at any point P(x, y) is :
"'d
B= where sin (at =
(1)
~t~ (sin ~/91+ sin (P2) 4n(R + a - y)
Ll + x , sinqg2= L2-x 4(/I + x) 2 + (R + a - y)2 4(L2 - x) 2 + (R + a - y)2
The magnetic flux of area marked by points O , A , B and C is 9
~-~a~~
g01 (sin (pt + sin ~o2 )dxdy 4n(R + a - y)
9
The magnetic flux rate of change is 9 dedt
d dt
~a ~~ dxd y
~a ~b
~ oI 41t(R + a - y)
(sin (pi + sin (p 2 ) dx dy
= ; ;Bdxdy = ; ; 4n(RlX~ a - y) (sin (,oI + sin (,02)dxdy
(2)
The reliability and the stability of operation of control system is influenced by the comparatively high induced voltage because of the existence of distributed inductance and high rate of change of loop current of the pulse power supply. We can draw conclusion form formula (1) and (2) that the larger R is, the smaller d~/dt is and the smaller of active area of closed loop is, the smaller dcb/dt is. So the distance between control circuit and the power supply main circuit and the position of the control panel should be considered. So does the coupling of high voltage to the low voltage loop for the distributed capacitance between wires and the comparatively high rate of change of high voltage.
ANTI-INTERFERENCE MEASURES OF CONTROL SYSTEM Any electromagnetic interference is derived from the combination of three elements, interference source, interference receiver and transmission channel as shown in Figure 3. Measures to suppress the EMI should also start from these three elements accordingly. Interference source
Channel (coupling mechanism)
Interference receiver (susceptible
Figure 3 9Model of electromagnetic interference According to the EMC basic theory, factors that affect the EMC of control system are given as follows"
N(co) - G(m) . C(co)/ I(co)
(3)
375 Where N(co) -the influence of the interference over the control system, G(co) -strength of interference, C(co)-coupling function of interference transmission, I(co)-anti-interference ability of interference receiver(control system). Mathematic model of formula (3) reveals the principle of enhancing the anti-interference ability of system: @cutting the interference source, namely to decrease G(o). (~) reducing coupling, namely to decrease C(o). @raising the lower limit of susceptibility ,namely to increase I( o ). According to the electromagnetic condition of control system of PBAIP, following main measures are taken to prevent EMI. Shielded floating Grounding and shielding are important measures to suppress EMI and hence enhance the system anti-interference ability, o Z12 ] Proper grounding can not only suppress the influence of EMI but also prevent the devices from emitting interferences, UN2 Zi otherwise, severe interference will be introduced. The earth uN~ soil is different from metals and its specific conductance is 1 _l.. Go between conductor and insulator. The grounding impedance under impact current is very different from that of industrial ? frequency. Both earth connection's distributed capacitance . .Go ..... Io, and inductance affect the impact impedance, including earth connection's resistance and conductance and the effect Figure 4 : Shielded floating circuit depend on the structure of earth connection, electrical characteristics of soil and the frequency band and amplitude of impact current. In the PBAIP system, the fluctuating of ground voltage caused by the sudden change of current is coupled to the control circuit through distributed capacitance, which causes severe common mode interference to control system. So we choose the floating shielding and it's assistant measures to make control system less susceptible to the common mode interference and the control system's anti-interference ability is improved. The key of floating shielding is to increase the common mode loop's impedance while reducing the common mode input current. And advantage of floating shielding is that system-to-ground impedance is large while distributed capacitance is small, thus making the interference current flowing into circuit caused by common mode interference small. The principle is illustrated in Figure 4. Shielding is added between control circuit and external device's casement, Z10 is the impedance between control circuit and shielding and Z20 between shielding and device's metal casement. The interference voltage, namely UN2, coupled to the control circuit, can be calculated as follows:
I
•
tC2o
UN2----UN1Zi/(ZI2+Zi+ZN) Where Zl2=l/(coCl2), ZN=l/(coCo), Co=CloC20/(Clo+C20. In control system, the resistances component of complex impedance Zlo, Z20 are insulation resistances which may be more than 108f2 , and impedances of Zlo and Z20 are decided by distributed capacitance Clo and C20. So distributed capacitance Co between control circuit and measure ground G1 is series of Clo and 6'20, which increases the impedance of common mode circuit thus decreasing UN2, common mode voltage drop on Zi. This wiring mode compared with non-shield floating mode further improves ohmic leakage and common-mode rejection ability by controlling the distribute parameters of control system, prevent the decrease of CMRR when the signal frequency is increased within a wide frequency band, thus suppresses common mode interference very well. Isolation Isolation is to cut or reduce the electromagnetic coupling of interfering circuit and other circuits by isolating them from each other in a distance. It's principle and method are 9
376 1) interfering wiring should not be parallel with other wirings as much as possible .If parallel is needed, proportion of space between wirings L to the diameter of wirings D should not be less than 40 and L should be as long as possible while the parallel part as short as possible. 2) the space between susceptible wiring and general wiring should be longer than 50mm if parallel positioned. 3) Power supply feedback wires and signal wires should be isolated, if parallel positioned ,the space should be more than 50mm. Other measures Other technical measures are also taken to improve the reliability and stability of control system including the shielded floating and isolation. For example, analog circuit and digital circuit are isolated, put in separate shielded cases and powered independently. Control circuit controls operation of main circuit through optical-electrical coupling, which effectively suppresses the interference between strong signals and weak signals.
CONCLUSIONS The influence of pulse power supply over the stability of control system is analyzed aiming at the problems confronted while researching on the pulsed-bias arc ion plating and anit-interference measures are taken accordingly.Experiments show that these technical measures have obviously supressed the interference and improved the stability of pulse power system. So conclusions are as follows: (1)The arc ion plating load is plasma load of resitance-capacitance characteristics and EMI are caused to control system for the high rate of change of voltage and current, dv/dt and di/dt, under the pulse biased voltage power supply. (2) Shielded floating is a practically feasible also effective measure to enhance the control system's anti-interference ability and its effectiveness depends largely on the actual floating extent. (3) In order to guarantee the stable operation of control system in given electromagnetic conditions, anti-interference measures should be considered from the design stage and different measures such as shielding, grounding, isolation and filter be chosen accordingly while focusing on the circuit design, choice of devices, framework layout as well as the characteristics of interferences.
REFEREBCE 1. Dong Qi. Study on the pulse negative bias power supply [J]. Metal Heat Treating, 2002, 27(12):56--59. 2. Pengwang Cheng. Electromagnetic Theory [M]. Beijing : People's Education Press, 1978. 3.ZHENG Qiong-lin, HAO Rong-tai. 50kVA IGBT Inverter Design For Locomotive In Consideration Of EMS [J] .China Electrical Engineering Journal, 2000, 20(5): 34~36, 41.
377 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
The T M R Fault-Tolerant based on E H W Under Single Event Upset Guoqing Wang, Qiang Zhao, Liang Yuan, Shanghe Liu*, Huicong Wu* Department of Computer *Electrostatic and Electromagnetic Protection Research Institute Shijiazhuang Mechanical Engineering College, 97 Heping W.R, Shijiazhuang, Hebei, 050003, China
Abstract: In extreme ESD, EMI environment, the circuit system is bombarded by harmful radiation and will be damaged by many electrical discharges. The SEU is transient radiation electromagnetic pulse The SRAM cells configuration upset by SEU may result in a device functional upset. This could also lead to destruction of the system. System resources may be damaged by SEU. Although traditional Fault-Tolerance based on Triple Modular Redundancy methods cannot deal well Single Event Upset with the recovery requirement. But it can not recovery system function with Fault-Tolerance under Single Event Upset. EHW is an alternative method for logic design and EHW can change its architecture and behavior dynamically and autonomously according to the outer environment. The paper looks for ways of increasing the circuit's reliability with the help of evolutionary techniques and proposes the use of EHW in the TMR fault-tolerant circuit design to achieve Evolutionary Fault Repair TMR fault-tolerance circuit. Key word: Evolvable Hardware, ,Single Event Upset, EMI, ESD
INTRODUCTION Designing for electromagnetic radiation need not be limited to space-bound systems. Even on Earth, where most of the cosmic radiation is absorbed by the atmosphere, radiation tolerance is very important. For example, in certain military applications, in atomic power plants, or on aircraft, equipment has to function even under the highest radiation levels. Further, the semiconductor industry's move to decrease device structure sizes, reduce power requirements and increase speed, has lead to increased radiation sensitivity for all applications. Thus, a radiation-induced device failure could become a major problem, even at sea level. Radiation comes in many forms. The material forms include high-energy neutrons, protons and heavy ions along with alpha (helium nucleus) and beta (electron or positron) particles, all of which can cause ionization currents in the materials they strike,or dirrectly damage them. This paper reflects fault tolerance in this application and introduces some ideas from the author on how to apply evolution to existing fault tolerance schemes. Because of FPGAs inherent time-to-market, low NRE, and flexibility advantages over ASICs their popularity continues to grow in many applications including space, military, and avionics. The extensive use of FPGAs in these applications underscores the importance of understanding the different effects on FPGAs of ionizing radiation components like neutrons, protons and heavy ions. We examines the cause and effects of SEU and the Single Event Upset (SEU) susceptibility. It also examines SEU mitigation techniques. Our paper also discusses the susceptibility of SRAM-based FPGAs to SEUs. Finally, we looks for ways of increasing the circuit's reliability with the help of evolutionary techniques and proposes the use of EHW in the Triple Modular Redundancy (TMR) fault-tolerant circuit
378 design to achieve Evolutionary Fault Repair TMR fault-tolerance circuit, and illustrate the immunity of FPGA devices to SEU effects. SINGLE EVENT UPSET SEU is defined by NASA as radiation-induced errors in microelectronic circuits caused when charged particles (usually from the radiation belts or from cosmic rays) lose energy by ionizing the medium through which they pass, leaving behind a wake of electron-hole pairs. These are collected at the source and drain the transistor, producing a current pulse. This pulse can be large enough to change the state of a node from logic 1 to logic 0 and vice versa. Thus memories can become corrupted and lead to data errors. For example, in a space computer, a bit flip could randomly corrupt critical data, randomly change the program, or confuse the processor to the point that it crashes. While the upset causes a data error, the circuit itself is undamaged. This type of event is called a "soft error." A reset or rewriting of the device results in normal behavior.
SEU IN SRAM-BASED FPGAs As mentioned earlier, the major concern for SEUs are in RAMs because they contain the largest number of bits susceptible to upset. SRAM-based FPGAs use 6-transistor SRAM cells to store device information. The function of the FPGA is determined when the bitstream is downloaded to the device during device configuration. If any of the SRAM cells used for configuration are affected by SEU the function of the device is changed. Therefore, a device configuration upset may result in a device functional upset. This could also lead to destruction of the system. System resources may be damaged by loss of control of tristate busses or by initiating critical system events.
GENETICS AND EVOLVABLE HARDWARE In artificial evolution, a binary string describes the system. This system is either described directly or is described through some form of embryological development. The system is then assessed within the environment to find its fitness relative to the other individuals. This measure can then used to weight the probability of reproduction so that through many generations, good genes survive and bad genes die out. A further extension to the domain of evolutionary techniques is Evolvable Hardware (EHW), EHW can be viewed as a combination of Evolutionary Algorithms (e.g. Genetic Algorithms) with reconfigurable hardware (e.g. FPGAs). Shortly: EHW =EAs + FPGA. EHW coming after the creation of Field Programmable Gate Array (FPGA) devices and Programmable Logic Devices (PLD), since these can be programmed using a binary string or by coding a binary logic tree. EHW is adaptive at different levels, such as adaptation to changing requirements, changing operational environment, adaptation to partial hardware failure, and fabrication defect adaptation. These unusual properties open a possibility of fault-tolerant, high-performance and high-availability circuit system. The electronic circuits can be evaluated either electronically, to compare their outputs with the required output (intrinsic EHW), or in simulation (extrinsic EHW) to create some measure of the fitness [2].
FAULT TOLERANCE Fault tolerance is a technique used in the design and implementation of dependable circuit systems. With the increase in complexity of systems, complete fault coverage at the testing phase of the design cycle is very difficult to achieve. In addition, environmental effects such as Radio Frequency (RF) and ElectroMagnetic (EM) interference make faults occur in systems continuously. These faults will cause errors and if left untreated, could cause system failure. The role of fault tolerance is to deal with errors caused by faults, before they lead to failure.
379 TRADITIONAL TRIPLE MODULAR REDUNDANCY (TMR) FAULT-TOLERANCE The basic principle behind fault-tolerance is redundancy, that is, providing the system with additional resources, beyond the minimum required for its operation. Redundancy can take various forms (hardware, software, timing, etc). A common approach to hardware fault-tolerance is to use multiple copies of the same hardware module and a voter mechanism. In particular, Triple Modular Redundancy (TMR) is widely used to implement majority voting-based fault-tolerance system. It consists of three identical replicas of the same module and a voter mechanism, which outputs a majority value. A module can occur at any system level, from gates to processing units.
APPLICATION OF EHW IN FAULT-TOLERANT DESIGN Because of their low manufacturing cost and In-t-~ in-system programmability, there is an ever growing interest in the use of FPGAs, and it makes fault-tolerant implementation Nr possible. The fault tolerance perspective of FPGAs can be explained in two aspects" tolerance for permanent faults and tolerance for transient faults. First, for permanent faults in FPGAs, once the locations of faulty CLBs or routing resources are diagnosed, rt,~o ~--~ ' the FPGA can be reconfigured to avoid these faulty parts in the mapped circuit. These ' ~ CROSS-CHECK faulty parts can be replaced with previously & ,~ R~ONFIGUR~TIOb' unused resources in the same FPGA hardware. In this way, the system can still operate in the presence of faulty parts, and dependability is improved with very small hardware redundancy. Recovery from multiple (sequential) faults on different devices can be achieved at zero outage time, provided that the individual devices have sufficient reconfiguration capabilities, and that the time necessary to perform diagnosis and reconfiguration is lower than the minimum time interval between two subsequent faults. As previously introduced, the methodology to implement fault-tolerant FPGA-based systems here proposed is based Figure 1 on the use of Triple Modular Redundancy, with triplicate voting scheme. Our main objective is the design of highly available systems, that is, systems ensuring a continuous operation even in the case of faults. To achieve this goal we consider a whole FPGA as the basic module (to be triplicated according to the TMR general technique), so that the three replicas are to be implemented on three different FPGAs. When a fault occurs in one of the replicas, the faulty FPGA can be switched off, while the others go on with their normal operation. Moreover(see Figure 6), the FPGA reconfiguration capabilities are exploited to concurrently execute some diagnosis and repair procedure, so as to re-arrange the internal logic and interconnection of the faulty FPGA, thus isolating its faulty components. Each FPGA contains a functional module (F) with k inputs (11 ........Ik) and n outputs (O1 ......Ok), together with the corresponding outputs of the replicas, is given to the input of a majority block (MJB). _
IL
. . . .
t
. . . . . . .
,.+
_
380 For simplicity, the n outputs of each block Fj are represented by single lines; similarly, the n necessary MJBs are represented by a single block. Each MJB gives at its output the majority value ( M V ) among its inputs, as well as three additional bits (failed line codes: FL_0, FL_I, FL_2) suitably encoded so as to allow us to determine the possibly erroneous input to the voter which is different from the majority. The used code is reported in the truth table shown in Table 1. The set of MV/values represent the actual primary outputs of the j-th FPGA device, while the failed line codes from all the MJBs are collected as a single 3-bit bus; therefore, each MJB/contributes in determining the global FLj code for the j-th FPGA, which is actually a logical "OR" of the failed line codes from all the MJBs. The bus values are made available for a cross-check with the corresponding replicated buses so as to verify the accordance among the three replicas. The Cross-check & Reconfiguration module contains two functions: i) verify the accordance in the behaviour of the replicated functional modules (Cross-check module). ii) control the execution of the diagnosis and reconfiguration procedure (Reconfiguration module) for the faulty device. All the majority values (MV/j i=l,...,n and j=l,...,3) are evaluated by means of n majority value encoders that produce a 3-bit codeword in the pointing out the device giving an incorrect value through the J-tag Boundary Scan bus. Each tern of input values is also given to the input of a majority voter that produces the majority correct output vales (OUTi, i=l,..., n). It is not necessary to distinguish between a fault in the module (F) within a given functional module and a fault in one of the majority blocks within the same FPGA, since both conditions require that the same FPGA be switched off. During a diagnosis phase the Reconfiguration module checks continuously the failed line codes value. If it switches to another error code (it means that a further fault has been detected), a global system error condition is set, and the whole system stops and undergoes a global diagnosis procedure. In case of faults within the Cross-check &Reconfiguration module, the whole system stops and undergoes a global diagnosis procedure. When a fault is detected within a given device, the Reconfiguration module will disable that device and generate new configurations according to the principle of GA and EHW, then load the best new construction configuration data into the FPGA module through the J-tag Boundary Scan bus. Thus, the function of the fault FPGA module will be recovered.
REFERENCES 1. J.H. Holland.Adaptation in Natural and Artificial Systems. University of Michigan Press, 1975. 2. X. Yao and T. Higuchi. Promises and challenges of evolvable hardware. In International Conference on Evolvable Systems" From Biology to Hardware. Springer, 1996...1 3. A. Thompson. Evolutionary techniques for fault tolerance. UKACC International Conference on Control, 1996.
381 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghai, 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
A Double Short Pulse High-Voltage Power-Supply Based On DSP Xu Dapeng, Wu Yan, Liang Ping, Li Guofeng Institute of Electrostatics&Special Power, Dalian University of Technology, Dalian, China, 116023
This paper describes a new double short pulse power-supply based on DSP (Digital Signal Processor). The power-supply system is composed of a positive and a negative DC high-voltage power-supply and a RSGS (rotating spark-gap switch). The RSGS is used to control charge and discharge of pulse forming capacitances. The DC high-voltage power-supply employs full-bridge inversion techniques and LCC resonant techniques to realize miniaturization. DSP is the controlling core of the whole power-supply system, which regulates pulse amplitude and pulse frequency of power-supply based on the feedback information of interior parameter of the load. This power-supply system has been applied to discharge in water for dye wastewater treatment.
INTRODUCTION With the pollution is gradually severe, the quality of water deteriorates badly. So traditional ways of wastewater treatment is being challenged. Recently many researchers paid attention to a kind of way of wastewater treatment by high-voltage discharge in water. Single pole short pulse and AC high-voltage power-supply are most commonly used for generating this kind of discharge. But there are no research results of double short pulse high-voltage power-supply reported. In this paper, we designed a double short pulse high-voltage power-supply system, which can output high peak voltage, short voltage rise time, and high frequency. Mostly importantly, it can be applied on DBD (dielectric barrier discharge) wastewater treatment reactor to decrease energy consumption. Double DC High-Voltage (positive&negative) .....
lT
!I
DSP control unit
J Formof '1 pulse
J"!
J eactor I
DC motor
T 1.Voltage regulation 2.Speed regulation
3.Frequency regulatin of pulse 4.Voltage/Frequency feedback
Figure 1 the block diagram of power-supply system The double short pulse power-supply system comprises two sectors. One sector is DC high-voltage power-supply; the other sector controls RSGS by DC motor so that it can produce short pulse by charge and discharge of capacitances. In the first sector, traditional high-power power-supply and medium-power power-supply also use 50Hz transformer to boost voltage, this kind of way has some disadvantages such as low frequency and big bulk, furthermore its ripple coefficient and stability can not be satisfied. In this
382 power-supply system the full-bridge inverter is used to increase frequency, so bulk and weight of the power-supply will be reduced obviously. The using of the double loop controlling (the voltage loop and the current loop) can reduce the ripple coefficient and advance the stability. The second sector has two emphases. One emphasis is controlling rotating speed of DC motor accurately, the other is capacitances match of discharge loop. DSP is the controlling core of whole power-supply system, which regulates pulse amplitude and pulse frequency of power-supply based on the feedback information of interior parameter of the load. Figure 1 shows the block diagram of system.
DSP CONTROLLING SYSTEM The controlling core of this power-supply is a DSP chip, TMS320LF2407. The ability of processing data of DSP is very strong so that it can complete all kinds of complicated jobs rapidly. TMS320LF2407 has two event manager modules, each module comprises eight 16 bits PWM channels. So we can control BUCK DC-DC circuit and full-bridge inverter (fixed frequency) and rotating speed regulation of motor only by the chip. In addition, this chip has sixteen A/D conversion channels. So it can accept all kinds of signals simultaneity such as voltage, current, feedback parameter of the load and so on. The frequency of sampling signal is 20K Hz. Realization functions in this power-supply by DSP are as follows" 1) Regulating BUCK circuit of DC high-voltage power-supply based on interior parameter of the load. Then we can regulate voltage of DC high-voltage power-supply, namely, voltage amplitude of double short pulse power-supply. 2) Realization soft-switching technology of full-bridge inverter. 3) Controlling rotating speed of DC motor based on interior parameter of the load.. Then we can regulate speed of charge and discharge of capacitances, namely, frequency of double short pulse powersupply. 4) Over-current and over-voltage and under-voltage protection.. 5) Improving the stability of system by closed loop regulation of output high-voltage and frequency.
DC HIGH-VOLTAGE POWER-SUPPLY Structure of DC high-voltage power-supply
[
220V/50Hz~ : ~
~~ 3 ~ 10 PWM
7 I
I
1. EMC 2. Rectifier + Filter 3. BUCKcircuit 4. Full-bridge Inverter
4 ~
5 ~::~
6 ~DC(HV)
t
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v~> 5. Step-up Transformer 6. Multiple voltage rectifier 7. Auxiliary power supply 8. DSP control unit
::M(to !C motor) 9. Voltage divider 10. Current feedback ll. Keyboard/Display 12. Voltage feedback
Figure 2 The block diagram of DC high-voltage power-supply The forming of the double short pulse needs two DC high-voltage power supplies (the positive powersupply and the negative supply). Figure 2 shows the block diagram of the positive DC high-voltage power-supply. The structure of the negative DC high-voltage power-supply is identified with the structure of the positive DC high-voltage power-supply. Input is 220V AC (50Hz). After rectifier and filter, output is about 300V DC. Because output of this power-supply is high voltage and low current signal, and the load is capacitance load, so it's difficulty to regulate voltage in the full-bridge inverter. This power-supply employs BUCK circuit to regulate DC voltage so that amplitude of high-voltage output can be controlled. PWM signals for BUCK circuit and full-bridge inverter are also produced by DSP. High frequency AC signals can be got by full-bridge inversion. It can become DC high-voltage through step-up transformer
383 and multiple voltage rectifier. With experiment, we can know parameters of this power-supply. Output is adjustable from 0 to 50KV; ripple coefficient is 1%; stabilized voltage coefficient is 1%. These parameters are all satisfied. Realization soft-switching by LCC resonant circuit In the inverter, application of soft-switching has two advantages. The first advantage is reducing loss of switch, then frequency of power-supply can be heightened much more. The second advantage is solving EMC problem of power-switching circuit. Because of the particularity of power-supply for wastewater treatment (charge and discharge of the capacitances), so change of the load is greatly. We choose LCC series-parallel resonant circuit. This kind of resonant circuit has advantages of series resonant circuit and parallel resonant circuit, and overcome their disadvantages (LC series resonant series load circuit can not be open circuit; LC series resonant parallel load circuit can not be short circuit). Hence, we use it to realize soft-switching of full-bridge inverter. Figure 3 shows sketch of the circuit.
Figure 3 The circuit of LCC resonant
Figure 4 VDS(A) and ILl(B)
In the design of this power-supply, we use a kind of way [2] to make sure component parameter of the LCC resonant circuit generally. The way get state trajectory of the LCC resonant circuit through coordinate conversion, and make use of geometric relation of the state trajectory to conclude math relation of component parameter. We simulate the circuit using PSIM, and get concrete parameters combined with simulation results. L1 =480uF;C 1=94.4nF;C2=78.6nF. Figure 4 shows simulation waveform. The waveform displays Vds and current through L 1. From the waveform we can see realization of zero-current switching.
FORMING OF DOUBLE SHORT PULSE Figure 5 shows forming of double short pulse. It comprises DC high-voltage power-supply, energy storage capacitances Cs, pulse forming capacitances Cp and a RSGS. In this paper, we only analyze single pulse circuit. When G1 is breakover and G2 is breaking, Cp charges by Cs; When G2 is breakover and G1 is breaking, the load discharges by Cp. While voltage surpasses visual critical voltage, gas-liquid mixture in the reactor can corona discharge. The pulse frequency of the system is controlled by switch of RSGS. In addition, we can make sure Figure 5 The circuit of form of double short pulse capacitance parameter value based on all kinds of experiment demands. Cs=33nF; Cp=4nF.
384 This power-supply use DC motor to control rotating of spark-gap. So we must control rotating speed of motor, in that way, we can control rotating speed of spark-gap so as to control pulse frequency of double short pulse power-supply. This motor speed regulating system employs DC-DC BUCK circuit to adjust armature voltage of DC motor. The field current is fixed. Namely, we make use of separately excited mode to regulate rotating speed of DC motor. For improving accuracy and stability, chopping circuit adopts double loop(current loop and voltage loop)controlling mode. Closed-loop controlling is controlled by PWM wave from DSP.
EXPERIMENT RESULT AND CONCLUSION This paper designs a double short pulse power-supply based on DSP. DSP is core of the power-supply The whole power-supply system realizes closed-loop control by DSP. We use LCC resonant circuit to realize soft-switching in the full-bridge inverter of the DC high-voltage power-supply. Experiment result reach expected effect. The power of this powersupply is 800W; output of DC high-voltage power-supply is from 0 to 50KV; rise time of the double short pulse is from 50nS to 100nS; pulse width is from 200nS to 500nS. These parameters are very satisfied with the demands of wastewater treatment by discharge. Figure 6 shows typical waveforms of voltage and discharge current of the double short pulse ~ i g ~ 6 trpi~l ,~,,~.~o~m~of , , o l t ~ ~a ai~h~g~ r power-supply. (The experimental conditions: Vp=15kV f=50Hz (p=0.75m3/h Cp=10nF IC solution V: voltage I: discharge current)
REFERENCES 1. Robert.W and Erickson,Fundamentals of pow..erelectronics, New York,Chapman&Hall(1997) 2. Ashoka K S Bhat, Analysis and design of a series parallel resonant converter with capacitive output filter, IEEE Trans. on Ind. Appl.(1991)27(3) 523 - 529 3. Texas Instruments TMS320LF LC240xADSP Controllers System and Peripherals Reference Guide (Rev. B) (2001)
385 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on the Technology of Anti-electrostatic Interference for Radio Microwave FM Fuze Zhang Wanjun, Cui Zhanzhong, Li Wenying, Cheng Fang School of Mechatronics Engineering, Beijing Institute of Technology, Beijing, China
Abstract: The principles, influences and hazards of causes of static electricity and electrostatic discharge (ESD) are researched on the design of the radio microwave FM fuze. The importance of the electrostatic prevention and the electrostatic prevention measure is mainly put forward in the practical design. These researches have great significance to the improvement of the performance of the radio microwave FM fuze, the effective reduction of the exploded ahead rate and the research of the technology of anti-electrostatic interference. Keywords: microwave FM fuze; electrostatic interference; ESD; electrostatic prevention
INTRODUCTION Radio microwave FM Fuze used by rockets, missiles and general projectile is to a certain extent in the environment of electrostatic interference, during the period of development, production, launch and the radio fuze moves along the ballistic trajectory. For the new microstrip antenna and microstrip circuit design are introduced, this fuze has some advantages such as high frequency, wide frequency band, small volume and light weight, etc. Meanwhile, it has some disadvantages such as high loss, low power capacity and the effect of electrostatic interference, etc. In the paper, the principles of the causes of electrostatic electricity and ESD are analyzed, then, the influences of ESD on the microstrip antenna, microwave microstrip circuit and electric detonator are researched. Especially, the electrostatic prevention measure is put forth in the practical design.
ANALYSIS OF THE PRINCIPLES OF THE CAUSES OF STATIC ELECTRICITY AND ESD Because of the potential gradient in atmosphere, radio microwave FM fuze will be affected by the electrostatic field under conditions of the changes of environment, situation and height, during the period handle and launch processes, and then, fuze body is induced to cause static electricity, In addition, when fuze moves along the ballistic trajectory to encounter cloud and fog, dust, water drip or ice particles, fuze body can sharply be electficized to high voltage under the effect of contact, high speed friction and separation. For example, a certain rocket can be electricized to more than 100 kV within 0.5s ill. Fuze body is easy to cause electrostatic breakdown, and then, ESD phenomenon occurs, which has high discharge current amplitude and sharp rise edge. Therefore, electromagnetic field with high intensity and wide frequency spectrum is induced near the discharge current. It is obvious that ESD is a process of high voltage, strong electric field and instantaneous pulse current. Through research, it is proved that the typical radiant field of ESD is attenuation sine wave, which continues about 500ns and reaches peak value of field intensity of about 150V/m, the power spectrum magnitude of frequency is mainly fastened within 0Hz~250Hz and center frequency of several MHz-~several GHz. As a result, radio microwave FM fuze antenna, circuit and electric detonator are interfered in. ESD has many modalities, but the access of energy coupling in fuze has three kind of master modality: straight conduction, capacitance coupling and inductance coupling. The principles o f ESD interference of radio microwave FM fuze is shown in Figure 1.
386 Straight conduction means that ESD current directly acts on microwave microstrip antenna or microstrip circuit and so on. Usually, the route with minimal impedance is chosen to discharge, then, the charge is accumulated on the microstrip antenna surface, this result in that the electrostatic interference effect arises by reason of asymmetry of charge distributing. At one time, MMIC or microwave component is destroyed. In the result, the failures occur in the operation of fuze. Capacitance and inductance coupling mean that electromagnetic field by ESD current couple in microwave circuit through autoecious capacitance or inductance and distributing Fuse body parameter component. Especially, the joints of Electromagnetic field caused by ESD ~ _.~l I"T-"--"'fuze head and fuze body, fuze body and projectile body, the stage of rocket have gaps or ..... p' ~,~ f l ~ ] ] ] Mic~!owave L_~-~:~'~[.__~explosive II ~ . ~ holes, then, conductive discontinuous nodes . , , ~ ( ~ ~ r o s m p r . - ~ - _ . ~ ,. 71-I'I series II _~ " ~ ~ t_..._z:.:zz:_ I I ~, ~, form and strong electromagnetic field arises. - - ~ , l ~ c u i t l ~- 2. ~ - ~ ~ ~ ~ ' . ~ . . . ~ ' . , ~ ..... projectile ] ] ~ Accordingly, electric detonator and microwave Fuse "r body ~" circuit are interfered in, and some severe accidents such as accidental detonation of rocket, route selected by current short circuit exploded ahead and dud of fuze occur. This device Figure 1 The principles of ESD interference of radio microwave FM fuze shows that design of the electrostatic prevention on microwave FM fuze is highly significant.
ELECTROSTATIC PREVENTION MEASURES OF MICROWAVE FM FUZE When the principle of ESD interference is considered, some main measures of electrostatic prevention design of microwave FM fuze are put forward as follows" Electrostatic prevention design of microstrip antenna Microwave power, transmission system fall short of high power, so the emission performance of microwave FM fuze and the directionality of antenna should be better, so as to avail anti-electrostatic interference. In addition, in order to prevent asymmetry distributing of surface charge on microstrip antenna, in the paper, the antistatic film is used to cover on the antenna surface. In result, ESD can be avoided. TO conductive film is introduced in practical design. It has the property of conduction and antielectrostatic interference; moreover, it can be penetrated by microwave. According to description above, the compatible performance between electrostatic prevention measures and transmission performance of microwave is the key of the design, that is to say, transmission performance of microwave can not be weakened because electrostatic prevention measures are considered. Based on microwave theory, the intensity I of the plane electromagnetic wave transmitted in certain direction through microstrip antenna is damped as distance according to exponential rule. Namely: I - I 0 9e -2K'
(1)
where, I 0 :incidence wave intensity in section start; K~ :transmission damped coefficient. And then, according to the performance demand of wave-transparent materials, when microwave frequency is within 0.3 ~ 3 0 0 G H z and intensity(I) decay is less than 0 . 2 d B , wave-transparent materials have ideal wave-transparent property and smaller insertion loss. For TO conductive film, when the operation frequency of fuze is 3 G H z and the thickness of conductive film is 20 n m , we have: 1/1 o - 0.99 -- 1
(2)
From this, it can be seen that transmission loss of TO conductive film on microwave can be neglected. In addition, it is the same as the choice of microstrip antenna bottom. Thus, some bottom materials such as polyurethane amine or polytetrafluoroethylene are selected in order to reduce microwave loss and improve the antistatic performance. Electrostatic prevention design of microstrip lines circuit
387 Microwave FM fuze by varactor FM VCO of microstrip lines has been designed. It has higher oscillating frequency and the circuit transmission means is based on microstrip lines, that is, electromagnetic wave is transmitted from one end of circuit to another end. Microstrip lines transmission means is quasi-TEM model, so various higher-order model can also be transmitted by microstrip lines under conditions of higher microwave frequency, namely dispersive model. In order to prevent transmit electrostatic and electrostatic interference, microstrip lines conductive band width W , transmission medium layer thickness h and dielectric constant e~ should be exactly chosen when microstrip lines are designed. Consequently, microstrip lines are assured to operate in quasi-TEM single model to avoid other dispersive model. For example, W is selected as cut-off condition of TE model in microstrip lines, that is" f <
1
1
4l"10~0 2W4~ r
(3)
Where f " microstrip lines operating frequency; e0,/t 0 9dielectric constant and magnetic permeability of transmission medium in vacuum. In addition, affecting factors of microwave transmission Loss, coupling frequency of microwave and electrostatic field, characteristic impedance and transmission constant are all considered when microstrip lines geometrical parameters are confirmed. At one time, the improvement of the surface slick degree of microstrip conductor and medium substrate can reduce ohm loss of microstrip transmission and prevent distributing asymmetry of surface charge as a result of ESD. The choose principle on microwave components is that microwave nesistor has high gain, antistatic, better voltage & current -withstanding performance. Microwave MESFET and MOSFET have high efficiency, low noise coefficient, high input impedance, high operating frequency, but it is not as good as nesistor in antistatic, voltage & current withstanding performance and gain characteristic, so electrostatic prevention should be designed. Electrostatic prevention design of electric detonator Electric detonator used by fuze is terminal tache that carry out detonation function of fuze, thus it is extreme significant to electrostatic prevention design of electric detonator. In order to effectively prevent accident of rocket projectile caused static electricity, the most effective method is that electrostatic short circuit device are adopted in the joint of between the two sections of rocket projectile or fuze body and projectile body. If accidental current and static electricity act on rocket or fuze, a majority of current will be effectively shunting by the device, so as to lead the energy of electric detonator fall short of minimum required in ignition. Therefore, the antistatic performance of rocket or fuze is improved. Micro-resistance short circuit device designed in practice should contain ESD with 200 pF capacitance to charge 100KV. Equivalent coupling circuit model of ESD and rocket projectile or fuze body is shown in the figure.2. Where, C1 is equivalent deposited energy capacitance of the joint, R1, R2, R 3 , R4 is arc chopping resistance, connection resistance, electric detonator bridge-wire resistance and short circuit micro-resistance designed, respectively; L~ is down-lead inductance, which influences discharge current wave shape, does not energy loss. Accordingly, R4 can protect electric detonator to avoid electrostatic hazard through depressurization and shunting. When capacitor deposited energy voltage is U . In order to Figure.2Equivalent circuit model of ESD and ensure electrostatic security of electric detonator, and projectile body projectile electrostatic energy absorbed E is required less than EL, viz, E<E L
here, E L is security energy limit of electric detonator.
(4)
388 Thus, according to equivalent model, as R 2 << R~, R 2 << (R 2 + R 3), we have: R 4 -< 42R, (R2 + R3) 2EL/(C, U2R3)
(5)
if E~.= 1.28mJ , we will have R 4 < 80mf~. So micro-resistance short circuit material can be chose, such as, A1 and Mg alloy, Beryllium Bronze and stainless steel, etc. Therefore, rigidity stainless steel is used in design; it has easy pressing moulding, better antiseptic, mechanical and conductive performance.
CONCLUSION Microstrip antenna, microstrip lines circuit, microwave component and electric detonator of microwave FM fuze are severely destroyed by the electrostatic interference, which causes to a large extent, to be dud, exploded ahead or unstable operation of fuze. Therefore, ESD should be carefully considered when microwave FM fuze is designed and tested. In this way, accidents and losses can be reduced as long as possible. Accordingly, the operation performance of fuze will be improved.
REFERENCES 1. Zhang Xiu cun, The Theory and Provention of Static Electricity, China ordnance indistry press,1999 2. Wei Ming, Static Electricity and Electromagnetism Provention Technique, Ordnance Engineering CoUge,2002 3. Wang Qing bin, Liu Ping, Electromagnetism Interference and Electromagnetism Compatible Technique, China Machine Press ,2003 4. Advanced Design System Fundamentals,Agilent Technologies.Innovatingthe HP Way.2002 5.Guillermo Gonzalez, Microwave Transistor Amplifiers Analysis and Design, Prentic Hall,Inc.,1997
389 Paper Presented at the 5th International Conference on Appfied Electrostatics (ICAES'2004), ShanghaL 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Research on the Effect of Digital Circuit under the Influence of LEMP* Yongwei Sun, B ihua Zhou, Guanghui Wei, Ming Wei Electrostatic and Electromagnetic Protection Research Institute, Shijiazhuang Mechanical Engineering College, 97 Heping West Road, Shijiazhuang, 050003, P.R.China
Abstract: On base of the experimental results of LEMP to circuit, and the analysis of the coupling ways, it is concluded that the earth potential level of circuits can be fluctuated by LEMP and the output state of the gate also can be changed, which will cause digital unit or system overturn in wrong way. Key words: LEMP, digital circuits, interference
INTRODUCTION Lightning electromagnetic pulse-LEMP is producing with the suddenly changing of electrical current and electromagnetic. Radiation it is the second effect, the peak value of field strength is high, the waveform is raising quickly, the over -voltage, over-current and the electromagnetic radiation will damage or interfere the sensitive electronic circuit around. There are two causations of LEMP damage digital circuits, one is the surge transmitting to mains input of electronic equipment from out side power cord, at the output, there are damping concussion, cuspate impulse, and a series of impulse; the other is the area where digital circuits locate at are full of electromagnetic pulse, the circle of power source and the circle of earth cable will get transient induced voltage (or current). The lightning precaution engineering is commonly used to reinforce the electric source; the output voltage wave motion can be reduced, so the electromagnetic induction is the principle cause of the LEMP disturbing the digital circuit.
EARTH-CURRENT AND DEVICE-EARTH Except for bringing a function to the digital circuit to eventuate correspondence error code and device latch or destruction by heat through receiving wire or generalization wire in the foi'm of information disturbance or energy disturbance, thunderbolt electromagnetic pulse can make a transient state earthcurrent in the ground wire loop or the ground plate of the digital circuit by conduction coupling or radiation coupling. The transient state earth-current can bring transient fluctuation of the earth potential. This is the important reason that LEMP makes the digital circuit defective or work mistakenly. Under the function of the impulse magnetic field, ground wire loop circuit of the printed wiring plate has induced current in it, Therefore, under the raying of the electromagnetic pulse, the potential difference between the points of the loop circuit arise, the earth potential difference of each IC in the electric circuit arise too. So we suggest that the foot electric potential Vss (Gnd) be defined device earth or IC earth. When having no disturbance, IC earth is equipotential with signal earth. The transient potential difference between digital IC device earth of the circuit plate is the principal causation that makes the whole digital electric circuit working mistakenly. The change of the digital IC device earth may bring instabiliW to the digital electric circuit, and affects the input state of the next electric circuit. Therefore, the same lightning is a high current course; its Ill
Project supported by the NSFC No. 50077024 and 50237040
390 radiation field has a high magnetic field character. The voltage fluctuation brought by the electromagnetic induction is the important form that LEMP damage the digital electric circuit. We select negator and multi-vibrator circuit cell as the experiment object, and make the IC earth generate potential fluctuation by inductance coupling, test the reaction to the over voltage and lack of voltage about the digital electric circuits. The purpose of the experiment is analyzing the influence of the working state of the typical digital electric circuit cell produced by the device earth.
EQUIPMENT EXPERIMENT EQUIPMENT The figure 1 is the model figure of the experiment equipment, we use LSG8015 lightning surge as the current generator, take short-circuit current between SURGEOUT and SURGEG to drive promoting coil, so we can get impulse of magnetic field. Lightning surge can be set to single manual control manner. The inductive coil and is spooled on a 5 cm diameter organic glass cylinder, adjusting the coil distance and the electric current direction may change the amplitude value and polarity of the induced voltage. The incentive coil connects in series with a 1000A: 1V special electric current ....................k... /J - . T probe, the output connects with an oscilloscope in order to measure the incentive electric current. We use four 1.2V Ni-Cd rechargeable batteries as the I :L?_iT::~ o n ~ ~" oscope Input power source of the electric circuit. This equipment simulates the fluctuant state of the device earth when the circuit Figure I Expedmt,. +equipment outline map board is radiated.
I
THE EXPERIMENT OF THE AFFECTING THE NEGATOR
DEVICE-EARTH
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ELECTRIC
POTENTIAL
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The experiment uses 741s04 74HCT04 74AHC04 CD4069 produced by Texas Instnnnent, take one negator of them. The normal power value is 5.14v. Testing condition: positing LSG8015 surge voltage as 650v, incentive electric current as 290A. Over-voltage function For individual IC, the electrical potential fluctuation of device earth is equal to the voltage variation of the power source. Fig.2(a) is a power voltage waveform of CD4069; Fig.2(b) is its fan-out voltage waveform.
Figure 2 response to over voltage surge of the negator unit (top)and power voltage waveform.
Figure 3 response of the negator to the not enough voltage and IC power voltage waveform
391 We can see from the figure that the output of the negator changes following the power voltage, both waveforms are similar. Functions of not enough voltage. Changing the current direction of the incentive coil is alternating the discharge voltage polarity of lighting surge generator, do the experiment again. Figure 3(b) is power voltage waveform of CD4096; Figure 3(a) is its output voltage waveform. Testing conditions: we can suppose that the surge voltage is 650V, and the incentive electric current is 290A. Experiment conclusion For the IC power source, different type negator circuit has different load current and load impedance, 741s04 is low power TTL electric circuit; 74AHC04 is advanced high velocity CMOS electric circuit; 74HCT is TTL level input CMOS circuit; CD4096 is normal CMOS circuit. In the circumstance of unchanging of incentive current, the output of inductive coil mainly depend on its load impedance; the greater the load impedance is, the greater the power voltage varying quantity is. The experiment result is determined by power load characteristic of forenamed four kinds of IC. The experiment result explains a fact: for the single negator, no matter device-earth potential is overvoltage or not enough voltage, both of them can change delivery end voltage, so LEMP may change the state of single gate circuit by affecting the stability of device-earth potential.
THE EXPERIMENT OF DEVICE-EARTH ASTABLE MULTIVIBRATOR UNIT
POTENTIAL
FLUCTUAION
AFFECTING
THE
The objective of the experiment is to analyze the experiment that device-earth potential fluctuation affects the digital unit that contains many gate circuits. The astable multivibrator that is consisted of three negators is a commonly square wave source. The astable multivibrator is linked to the experiment equipment.
Figure 4 over-voltage affects the working condition of astable multivibrator
Figure 5 not enough voltage affects the working condition of astable multivibrator
The amplitude value and polarity of device-earth fluctuation can be changed by adjust the discharge voltage and surge polarity of the surge generator. Because the lighting surge generator is controlled by manual control, it can not be controlled precisely to discharge in freewill instance of multi-vibrator cycle. We discharge repeatedly and register its waveform. In order to precisely analyze the circuit unit influence brought by the device-earth potential fluctuation, it can be divided into two conditions: over voltage and not enough voltage .the electric circuit is experimented by over voltage manner and not enough voltage manner. Finally, we select four representative error overturn waveform from lots of experiment register, see Figure 4 and Figure 5. The experiment explains the following questions: the fluctuation of the power voltage may be reacted on the output state, the output state of the three negator can not be controlled by power voltage changing, it is controlled by synthetical factors such as RC discharging time constant, the over voltage surge of the Figure 4(right) shows up in high level time, it is mainly influenced by output gator, the peak arise in the top of the square wave; In the Figure 5(right), the voltage surge arise in the low level time, it makes the circuit turn over mistakenly, this forms a little time cycle pulse; Figure 5 (left) is a critical turnover state, the not enough voltage arises in the high level time, but its peak value is lesser; Figure 6
392 (right) shows that the not enough voltage shows up in square wave high level time, the circuit turns mistakenly to a low level. The experiment result explains that the voltage surge works mainly in highlevel time of the square wave; the not enough voltage surge works mainly in low level time of the square wave.
THE CONCLUSION OF THIS PAPER This paper gives a device-earth conception by analyzing the energy coupling form between the lighting magnetic wave and digital circuit. The chapter considers that the fluctuation of the device earth voltage is the important reason that magnetic field interferes the digital circuit. For the digital IC, the change of the IC direct current power supply voltage represents the potential fluctuation of the device- earth. The experiment result proves that no matter the change of the direct current supply voltage is over-voltage form or the not enough voltage form, both of them may change state of the digital circuit unit. However, which form of error turnover and order disturbance may be represented, it is mainly determined by work state of the digital circuit when surge happens. At the same time, the range of the fluctuation of the device-earth has the same affect. Solving the voltage fluctuation is the key to improve the ability that resists disturbance degree. The capability that the power source prevents the LEMP has an important effect to the whole digital electric circuit. First of all, the power source must be reinforced of preventing surge.
REFERENCES 1. Vernon Cooray. Calculating lighming-induced over-voltages in power lines: a comparison of two coupling models. IEEE Trans. on EMC, 1994, 36(3): 179~182 2. P Ratnamahilan, P Hoole. Modeling the lightning earth flash return stroke for studying its effects on engineer system. IEEE Trans. on Magnetics, 1993,29(2): 1839~1844 3. Hidetaka Satoh. Study on increasing the surge capability of a lightning surge protection semiconductor device. IEEE Trans. on EMC, 1993,35(2): 311~315 4. Marcos Rubinstein, Martin A Uman, Pedro J Medelius, etc. Measurements of the voltage induced on an overhead power line 20m from triggered lightning. IEEE Tran. On EMC, 1994,36(2): 134~140 5. Reinald P. Handbook of Electromagnetic Compatibility. San Diego:AcdemicPress,Inc..1995.32~79 6. MIL-STD-464. Electromagnetic environment effects, requirements for systems.1997 7. MIL-STD-461D. Requirements for control of Electromagnetic interference emission and susceptility.1993
393 Paper Presented at the 5th International Conference on Applied Electrostatics (ICAES'2004), Shanghag 2-5 November 2004 Elsevier, ISBN 0-08-044584-5
Computer System Disaster Recovery for Electromagnetic Interference Haitao Sun, Qiang Zhao, Guoqing Wang, Jianwei Zhang, Kaiyan Chen Department of Computer, Shijiazhuang Mechanical Engineering College 97 Heping W.R, Shijiazhuang, Hebei, 050003, P.R.China
Abstract :Nowadays, more and more computer used bring a new problem. With the effects of software damages, such as network attacks, virus, and hardware damages caused by EMI and ESD, disaster recovery becomes a new challenge to us. In this paper, we introduce two kinds of commercial-off-theshelf software to achieve the target. It is especially applicable to our daily use. Key word :EMI, disaster recovery, Undo
INTRODUCTION Today's Intemet-driven e-business economy, with its global, round-the-clock requirements, is raising a whole new set of disaster recovery challenges. Hacker intrusions, network attacks, viruses, spamming, Electromagnetic Interference(EMI), Electrostatic Discharge(ESD), and line failures now can pose greater risks to Information Technology(IT) operations than hurricanes, floods, power outages, and the like. And recovery can depend more on restoring applications than on fixing hardware. Ensuring the continuity or recovery of IT-supported business processes, in the face of disaster, is essential. We are not simply seeing a revival of the old mainframe model of computing. Especially, to prevent EMI destroy the system of computer. With today's network-delivered services targeting new classes of information users and devices, under new usage models encouraging outsourcing and service composition across corporate boundaries, and on hardware platforms optimized for cost and peak performance at the expense of traditional mainframe virtues like reliability and serviceability. In spite of these, more atrocious-environment equipment come to rely on commercial-off-theshelf(COTS)equipment for the computing needs. One disadvantage of using COTS hardware components is their susceptibility to EMI or ESD etc. In the event of an EMI or ESD,a fault-tolerant system can mitigate the effects and continue to process on the remote system from the same last known correct system state. In this new service-oriented world, the need for a dependable computing infrastructure has never been more urgent.
BACKUP MANAGEMENT USING COTS Motivated by the pressing need for increased dependability ~in corporate and Intemet services and by the perspective that effective recovery can improve dependability as much or more than avoiding failures, we introduce a novel recovery mechanism that gives human system operators the power of system-wide undo. System-wide undo allows operators to roll back erroneous changes to a service's state without losing enduser data or updates, to make retroactive repairs in the historical timeline of the service system, and thereby to quickly recover from catastrophic state corruption, operator error, failed upgrades, and external attacks, even when the root cause of the catastrophe is unknown.
394 Low availability, high cost, and poor performance of radiation hardened equipment has driven the market to rely on commercial-off-the-shelf(COTS) equipment for the computer needs. Now, we introduce two COTS software to achieve our revival target. We use Power Quest Drive Image which is the most popular system disaster recovery software overseas to achieve the backup task. In addition, we develop a remote backup system. Without it, we can not revive hardware disaster caused by EMI and ESD. Power Quest Drive Image 2002 is a disaster recovery and backup solution. Wizards guide you through creating an exact copy, or image, of your hard disk. The image includes the operating system, applications, and data from your hard disk.
You can use wizards or the Disk Operations feature within Drive Image 2002 to create a new backup location to store images on your hard disk. In addition to saving images on your hard disk (as shown above), Drive Image can save images to a network directory or external media, such as a CD.
If you want to return your system to the state it was in when you created the image, you can restore a backup image.Drive Image includes Boot Disk Builder, which enables you to access network drives from within Drive Image when creating or restoring images that include the system partition. (The system partition, usually C', includes the operating system.) If you are not saving images to a network drive, you do not need to run Boot Disk Builder.
395 ImageExplorer, also included with Drive Image, lets you manipulate images and restore individual files from within an image. If, for example, you deleted a single data file by accident but had a backup image that included that file, you could use ImageExplorer to restore the file from within your backup image, without restoring the whole backup image. If you want to move the contents of a hard disk quickly without creating an image, you can copy drives.
REMOTE BACKUP AND RECOVERY TO EMI USING SYSTEM UNDO Remote backup For the effects caused by EMI and ESD always bring catastrophic damages to the computer hardware, local backup cut no ice in this occasion. So we introduce the remote backup system. The remote backup system work in base of TCP/IP protocol, it can use in LANS, WANS and telephony. The Imageconsole can create a new backup location on a remote computer, and store the image on it. It would mostly avoid the effect bring from the hardware damages caused by electromagnetic.
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System-wide undo We describe an implementation of our system-wide undo framework for standalone services with human end-users. With a recovery-oriented approach to human operator error as our target, we must devise techniques that will allow service infrastructures to accept and compensate for the inevitable weaknesses of their human operators. Recovery-oriented service systems should recover easily from operator mistakes, give the operator an environment in which trial-and-error reasoning is possible, and harness the unique human capacity for hindsight by allowing retroactive repairs once problems have been manifested. There is a recovery mechanism that has these properties, and it is one that we use every day in our productivity applications like word processors and spreadsheets: undo. Undo recognizes that humans will make mistakes and offers recovery from those mistakes by providing a way to roll back their effects.
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396 Take the commercial software Goback as an example. GoBack is the missing piece of the operating system. It is a remarkable tool that integrates itself into the operating system to protect you from data loss. This includes the everyday "oops" that occur from user error or software problems, file recoveries of deleted or overwritten files, virus attacks, problems from software installation, and even system crashes. With GoBack enabled, as you use your computer, GoBack keeps track of every move you make that affects your hard disk, allowing you to go back in time. You can retrieve specific files or entirely restore your hard disk. The amount of hard disk space that you set-aside on your computer for GoBack determines how far back in time GoBack is able to retrieve information. GoBack is not just another backup product because, unlike a traditional backup product, GoBack does not involve copying data to a separate tape or disk. Thus there is no specific point in time where you must stop and make a backup. Your system does not even need to be operational in order to restore data. Therefore, mistakes can be corrected without having made a backup.
CONCLUTION Just as a system development project responds to user needs, a disaster recovery project responds to an organization's needs for survival and business resumption in the wake of a disaster. With the threat of hacker intrusions, network attacks, viruses, EMI and ESD, our system manager should pay great attention to disaster recovery. This paper introduces some approach in reviving. Especially, the effect caused by EMI and ESD is a new challenge for us. As a routine backup method can not play its role, we develop a remote backup one. This net-based method overcomes the influence brought by hardware damage. In addition, we describe a new product Goback, which unlike a traditional backup product, to deal with operators' error.
REFERENCES 1. Jon.William.Toigo_Disaster Recovery planning Prentice Hall PTR 2. Aaron.Brown A Recovery-Oriented Approach to Dependable Services: Repairing Past Errors with System-Wide Undo from EECS Computer Science Division University of California, Berkeley
397
Author Index
A Adamiak K
29,37
Amirov R H
108
Annadurai G
104
B Bai M D
212,216,225
Bai M D
216,220
Bai X Y
212,216,220,225,230,241
Bai Y X
295
BiHT
25
BiJJ
328,333,338
BiZJ
92
Ding Ch J
299
Dong B Y
136
Dong G Y
234
F Fan L S
41,45,361,365
FanS D
241
Fang Y
307
Fast L
318
Feng Q M
350
Filimonova E A
108
Floryan J M FuGS
37 237
Futamura S
104
Biffs A S
322
BredinA
199
Brocilo D
100
Gajewski J B
Buhler C R
322
Gao B Q
52
Gao B
77
C Cai W j Calle C I Cao J Castle G S P
145,150 322 55 6
G 314
GaoQ J GeZL
207
Glogowski M
314
Grace J R GuJL
58 25 230
Chae J O
116,120
Guan Z C
77
Chang J S
96,100
Guo H G
256,259,354
Chen G J
310
Chen H Chen KY Chen X Chen Y Zh
154 393 328,333,338 244,248
H Han Li Han S
234 124
HeW Hensel K
350 128
Cheng F Chi J H
385 158
Choi I C
120
HuSM
291
Cui L L
307
HuYP
241
73
HuYC
295
328,333,338
Huang L
154
385
Hui H X
55
234,237
Ikezaki K
33
Dang X Q
158
Inculet I I
6
Dekowski J
100
Itoh M
Cui X Cui Z Z Cui Z Zh
HuH
96
D Dai X H
Demidiouk V I
116,120
96
398
J Jiang J
M
J iang X L
307 234
M a N Sh MaSM
Jin G Y
310
Jojima E
33
Mantovani J G Marquard A
58 280 322 199
Matsui Y
128
Mazumder M K
322
K Kalliohaka T
318
Mehrani P
Kang Y M
158
Meyer J
199
Kasper G
Miao J S
52
Katsura S
199 128
Koyamoto I
128
Mizuno A
L
Mizeraczyk J
25
100 128
N
Lee H K
195
Lee T S
10
Nishimori K
21
Lei L
48
Nishimura R
21
LiD
61
Nowicki A W
322
LiGF
61,69,132,136,141,381
LiHL
81
Li H Sh LiJW LiJ
176,179 145,150 61,69,136,141,203
LiLF
81
LiMF
65
Li Q L
310
Li Q
162,165,167,169,172,182,192,342
Li T
307
LiWY LiXT LiXW LiXW LiZD Liang L H Liang P Liang X D Liang Y Zh Liu H B Liu Li Zh Liu R J Liu Sh H
385 81 234,237 84 267 270 203,381 77 299 77 244,361,365 234,237 48,92,252,323,345,377
Nair S A
112
O Obara S Oda T Ouyang J T
96 1,124 52,55
P Paasi J
318
Pang D X
167
Pemen A J M
112
Peng Z W Podlinski J
167,169 100
O Oi D
373
R Ravi V R uan X F
120 45
S Saini D
322
Salmela H
318 128
Liu W P
96
Sawada J
Liu X C
280
Shang K F
Liu X D
280
Smallwood J
318
Liu X W
220
SoMH
195
Song Mao Hai
307
SuP
154
Sun H Tao
393
Liu Y Liu Zh Q Lv B
73 162,165,167,169,172,192,342 203
61,141
Xu Y Xu Y Xue X H
Sun K P Sun M SunYH SunY C Sun Y W Sun Zh Q
Takashima K Tan Ch B Tan Zh L Tang Sh P Tang X Tatsuo T Tong X Y
Urashima K
van Heesch E J M
Wang F M Wang G Q Wang H J Wang J Q Wang N H Wang N H Wang W Wang W L Wang X L Wang X P Wei G H Wei M Winands G J J WuHC WuXD Wu Y wu Y Wu Z C
X Xie S Xiong J P XuDP Xu D X XuLX XuM H
96,100
112
Yamashita K Yan Ch G Yan K Yan Li Yang B Yang J M Yang J P Yang J Yang J Yang S P Yang S L Yang X L Yang Y D Ye F P Ye S Yeulash N M Yi J Z YuGF Yuan L Yuan Z F
Zeng H H Zhan K P Zhang D M Zhang J W Zhang M Zhang Q A Zhang Q C Zhang R X Zhang R B Zhang W J Zhang X J Zhang Y Zhang Z X Zhang Z T Zhang Z Ha Zhang Z S Zhao L Zhao Q Zhao T Zhao X M Zhou B H Zhou W J
400
Zhou X Zhou Y X Zhou Z G Zhu C Q Zhu J Zhu X H Zhu Y
