双环电极大气压氦气等离子体射流的特性及其影响因素

Characteristics and Their Influencing Factors of Double-wrapped Electrode Induced Atmospheric Pressure Helium Plasma Jet

大气压等离子体射流(APPJ)具有极强的应用前景,近年来在国际上引起了重大关注,成为气体放电领域的重要研究课题。为了进一步掌握其射流特性及影响因素,设计并制作了外表面双环电极氦气等离子体射流装置,通过实验研究了电极宽度、电极与喷口距离对射流功率及射流长度的影响,并在实验的基础上,分析了放电的发展过程以及各现象的物理机理。实验结果表明:随着外加电压的不断升高,APPJ半周期内的放电电流脉冲个数从1个逐步升至2个、3个,随后放电电流出现不规则丝状,直至2个电极间沿外表面击穿;增大高压电极的宽度或缩短高压电极离喷口的距离,都有利于APPJ放电功率的提升;2个电极间距越大、高压电极离喷口越远,最大射流长度越长,而初始的射流长度由高压电极宽度决定;随着氦气流量的增加,APPJ的射流长度先增长,然后下降,最终趋于平稳,在射流长度的下降阶段会出现长度多波峰现象。

In recent years,atmospheric pressure plasma jet（APPJ） has received considerable attention for its application potential.In order to further understand the characteristics of APPJ and its influencing factors,we designed and manufactured a device with double wrapped electrodes for porducing helium plasma jet.Using the device,we experimentally researched the influencing factors on dissipated power and jet length,including the width of electrode and the distance between electrode and nozzle.Then,we analyzed the discharge processes and physical mechanisms of different discharge phenomenon.The experimental results show that the number of current pulses in every half cycle of the applied voltage increases from one to two,and to three gradually as the applied external voltage rises;if the applied external voltage keeps increasing,there will be filamentary discharges of no regulation till the breakdown between the two electrodes.Adding the width of the power electrode and shortening the distance between power electrode and nozzle are both beneficial for improving the dissipated power;the longer the gap between the two electrodes is,or the farther distance from the power electrode to the nozzle is,the longer maximum jet length is;meanwhile,the initial jet length is decided by the width of power electrode.With the increasing of gas flow,the jet length increases at first,then it gets smaller before stopping at a permanent value till the end;during the period of the jet length getting shorter,the multi-peaks phenomenon of APPJ appeared.