EHD 電液體動力泵被視為是傳統風扇的可能替代品，雖然其涉及的電壓很高，但過程產生的電流很小，這使得系統功耗非常微小，且沒有移動部件因此維護要求低。本實驗將運用單/雙級圓管EHD模型之設置，因為在方管EHD於六根電極所產生的流量與效率較佳，因此採用六根電極模組進行比較，且將電極排列設為連續半圓周，考量的操作電壓為24、26和28KV。圓管與方管之差異為前者摩擦阻力較小，與方管相比可產生更高的流速，因此圓管在相同電壓之流量皆最高，而流場呈現高低差及明顯波浪狀；但方管在提升電壓之時其流量明顯提升，反觀圓管之流量僅提升10%以下，而 EHD泵提高電壓會增加30%功耗，因此當電壓為28KV時，圓管EHD反而會造成額外能量損耗而降低效率。另外在方管相鄰雙面因相互垂直，故兩面夾角處最靠近的兩根電極會有電場與流場相互影響，從流場分佈可發現已影響到總流量，從此現象可觀察非等距與等距之電極配置的影響差異，故將此模組延用於圓管EHD以評估其對流量與效率影響，也觀察與雙級平行雙面之方管EHD性能差異。
雙級與單級之EHD性能趨勢不同，雙級系統包括同面式與交錯式搭配進行實驗，從結果得知同面與交錯擺放對實驗結果有決定性作用，同面安置針對電極下游可提供高於交錯系統之風速，但產生之離子風貼近壁面而無法帶動其它空氣流動，因此整體流量低於交錯系統；交錯系點為上下級電極交錯排列，電極位置均勻分佈於整個圓周，故產生離子風面積大而提供較大流量。上述數據與雙級方管兩種電級配置進行比較，可發現圓管半圓周與方管相鄰雙面此種連續電級配置，更適合應用在交錯系統，且圓管能提供更高之流量、風速與效率因子，此特性可在未來應用提供合適選擇方式。

Due to the lesser power consumption and no moving component, the electrohydrodynamic (EHD) pump is considered as a potential alternative for the conventional fan and become the topic of this thesis. This experimental study examines the performance characteristics of the one-stage and two-stage EHD gas pumps fitted in a circular channel, which owns a smaller friction drag compared to the square channel. In addition, as suggested in the previous square-duct EHD reports [18、19], six emitting electrodes flush mounted on the wall are uniformly installed over the half circumference for a superior performance. Also, the in-alignment and the offset arrangements are evaluated for the two-stage circular-channel EHD. The proposed devices are examined for their effectiveness in enhancing flow-pattern uniformity and the flow rate as well as reducing the power requirement. Under all operating voltages, the experimental results indicate that the one-stage circular EHD delivers a bigger flow rate with a more uniform velocity distribution, which is different from the obvious high-low velocity patterns observed from the parallel and the adjacent two-surface-electrode arrangements of the square EHDs. Also, a minor 16% flowrate (from 4.88 to 5.67 LPS) increase from 24 to 28 kV implies that the circular EHD generates good flowrate at the 24kV input in an efficient manner.
Regards the two-stage models, the forementioned advantages induced by the circular channel become distinct and insignificant since the two-stage arrangement has a dominant influence on the EHD characteristics, especially on the generated flow patterns. As expected, all two-stage EHD yield a higher flowrate compared to their corresponding one-stage EHD. Also, regarding the in-alignment two-stage EHD, the circular EHD still maintains the flow-pattern uniformity while the performance superiority is vanished, especially compared to the square EHD with electrodes mounted on the two opposite walls facing each other. However, the offset two-stage circular EHD can enhance the velocity uniformity further and deliver a bigger flow rate with a higher efficiency over the entire 24-26 kV operating range. In conclusion, the one-stage and two-stage EHDs fitted in the circular channel do generate more flow rate and velocity uniformity under the low-to-medium-voltage operation, which also results in an energy-saving consequence. Also, the offset arrangement for a two-stage circular EHD is appropriate for its performance features. Moreover, through the performance assessment, the present results can provide useful information for practical applications of EHD gas pumps.

參考文獻
[1] Mujumdar, A. S. Drying Fundamental. in C. G. J. Baker (Ed.), “Industrial Drying of Foods.” London: Blackie, pp. 8–31, 1997.
[2] Yang, J., Ding, C. J., Bai, A. Z., and Liang, Y. Z. “An Application of Drying Technology with High-Voltage Electric Fields on Bioproducts,” Acta Scientiarum Naturalium Universitatis NeMongol, Vol. 35, No. 5, pp. 510–511, 2004.
[3] Moreau, E. “Airflow Control by Non-thermal Plasma Actuators,” Journal of Physics D: Applied Physics, Vol. 40, pp. 605-636, 2007.
[4] Leger, L., Moreau, E., and Touchard, G. G. "Effect of a DC Corona Electrical Discharge on Airflow along a Flat Plate," IEEE Transactions on Industry Applications, Vol. 38, No. 6, pp. 1478-1485, 2002.
[5] Futrzynski, R. “Drag Reduction Using Plasma Actuators,” KTH Royal Institute of Technology, Ph.D. Thesis, pp. 10-52, 2015.
[6] Laroussi, M. “Low-Temperature Plasmas for Medicine,” IEEE Transactions on Plasma Science, Vol. 37, No. 6, pp. 714-725, 2007.
[7] Fridman, G., Friedman, G., Gutsol, A., Shekhter, A. B., Vasilet, N. V., and Fridman, A. “Applied Plasma Medicine,” Special Issue on Plasma Medicine, Vol. 5, No. 6, pp. 503-553, 2008.
[8] 賴建霖，"以微粒影像測速儀探討二階靜電集塵器內之充電微粒軌跡"，台灣科技大學機械工程系碩士論文，2019年。
[9] Tian, C. P., Lin, S. C., and Lai, F. C. “Experimental Study of EHD Pump in Square Channel with Asymmetric Electrodes,” Journal of Electrostatics, Volume 107, Article 103482, 2019.
[10] Bondar, H. and Bastien, F. “Effect of Neutral Fluid Velocity on Direct Conversion from Electrical to Fluid Kinetic Energy in an Electro-Fluid-Dynamics(EFD) Device,” Journal of Physics D: Applied Physics, Vol. 19, pp. 1657-1663, 1986.
[11] Hyun, K. T. and Chun, C. H. "The Wake Flow Control behind a Circular Cylinder Using Ion Wind," Experiments in Fluids, Vol. 35, pp. 541-552, 2003.
[12] Magnier, P., Hong, D., Chesneau, A. L., Pouvesle, J. M., and Hureau, J. “A DC Corona Discharge on a Flat Plate to Induce Air Movement,” Journal of Electrostatics, Vol. 65, pp. 655-659, 2007.
[13] Zhang, J. and Lai, F. C. "Effect of Emitting Electrode Number on the Performance of EHD Gas Pump in a Rectangular Channel," Journal of Electrostatics, Vol. 69, No. 6, pp. 486-493, 2011.
[14] Brown, N. M. and Lai, F. C. "Electrohydrodynamic Gas Pump in a Vertical Tube," Journal of Electrostatics, Vol. 67, No. 4, pp. 709-714, 2009.
[15] Moreau, E. and Touchard, G. "Enhancing the Mechanical Efficiency of Electric Wind in Corona Discharges," Journal of Electrostatics, Vol. 66, No. 1–2, pp. 39-44, 2008.
[16] Birhane, Y. T., Lin, S. C., and Lai, F. C. "Flow Characteristics of a Single Stage EHD Gas Pump in Circular Pipe," Journal of Electrostatics, Vol. 76, pp. 8–17, 2015.
[17] Lin, S. C., Chang, Y.J., Wu, C., and Lai, F. C. ”Electrohydrodynamic Pump in a Channel with Electrodes Mounted on Two Parallel Walls,” Journal of Thermophysics and Heat Transfer, Vol. 36, No. 3, pp. 500-506, 2022.
[18] Lin, S. C., Wu, C. Y., Chang, Y. J., and Lai, F. C. “A Two-Stage EHD Gas Pump in a Square Channel with Electrodes Mounted on Two Opposite Facing Walls,” IEEE Transactions on Industry Applications, Vol. 58, No. 4, pp. 5292-5300, 2022.
[19] Lin, S.C., Huang, B.L., Liou, S., and Lai, F.C. ”Electrohydrodynamic Swirl-Flow Generators for Application in Thermal Management,” AIAA Journal of Thermophysics and Heat Transfer, Vol. 37, No. 4, pp. 500-506, 2023.
[20] Maskell, B. R. "The Effect of Humidity on a Corona Discharge in Air," Royal Aircraft Establishment, Farnborough (UK), Technical Report 70106, 1970.
[21] Chang, J. S., Lawlwss, P. A., and Yamamoto, T. "Corona Discharge Processes," IEEE Transactions on Plasma Science, Vol. 19, No. 6, pp. 1152-1166, 1991.
[22] Zhang, T. Y., Ji, Q., Li, B., and Ouyang, J. "Characteristics and Underlying Physics of Ionic Wind in DC Corona Discharge under Different Polarities," Chinese Physics B, Vol. 28, No. 7, Article 075202, 2001.
[23] Castellanos, A. Electrohydrodynamics, New York: Springer Wien, 1998.
[24] Birhane, Y. T., Lin, S. C., and Lai, F. C. "Flow Characteristics of a Single Stage EHD Gas Pump in Circular Pipe," Journal of Electrostatics, Vol. 76, pp. 8-17, 2015.