In order to investigate the influence of changing electrode position on the characteristics of helium plasma jet at at -mospheric pressure , a plasma jet with needle -ring configuration is designed .In the experiment , the discharge process , dissi-pated power and jet length are studied through position changing of grounding electrode .Based on the experiment , the physical mechanism of the phenomenon is analyzed .The experiment results show that stable positive current "three pulses"and nega-tive "single pulse"can be realized with the rising of applied voltage when the distance between grounding electrode and nozzle is equal to D=28 mm.When D is reduced to 18, 8 mm, the positive can only appear "two pulses", and there is still only one negative current pulse , but the definition of the current pulse is more obvious .When the value of D separately equal to 28, 18 , 8 mm, the applied voltage makes pseudo glow into filamentous discharge mode is 6, 6.2 and 8 kV that is on the ris-ing, respectively.The dissipated power of the jet is almost unchanged though the variation of airflow under fixed voltage , but it decreased as D is increased .With the increasing of gas flow , the jet length will becomes longer at the first stage , then gets shorter, and a permanent length to the end .At the same time, the jet length becomes shorter with the increase of D.%为研究电极位置的改变对大气压氦气等离子体射流特性的影响,设计并制作了一种针-环结构的射流装置.通过实验研究了接地电极位置对放电发展、放电功率及射流长度的影响,在此基础上,对各现象的物理机理进行分析. 实验结果表明:随着外部电压的不断升高,且接地电极与喷口间距D为28 mm时,可以实现稳定的正向电流"三脉冲"、负向电流"单脉冲"放电,而当D值减小为18、8 mm时,在电流正向只能实现"两脉冲"放电,而负向依然只有一个电流脉冲,但电流脉冲的清晰度更为明显;当D值分别为28、18、8 mm时,放电由伪辉光进入丝状模式的电压分别为6、6.2、8 kV,呈上升趋势;在固定电压下,气流的变化对于APPJ的功率几乎没有影响,但随着D值的增大,功率却不断减小;在同一电压下,随着外部气流量的增加,射流长度首先上升至最大值,随后经一过渡阶段,最终趋于平稳长度,当D值增大时,射流长度呈现出减小趋势.
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