一种针-环结构大气压氦气等离子体射流特性研究

Research on Helium Plasma Jet Characteristics at Atmospheric Pressure for Needle-ring Configuration

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 k V,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。

In order to investigate the influence of changing electrode position on the characteristics of helium plasma jet at atmospheric pressure,a plasma jet with needle- ring configuration is designed. In the experiment,the discharge process,dissipated 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 negative ＂ 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 to28,18,8 mm,the applied voltage makes pseudo glow into filamentous discharge mode is 6,6. 2 and 8 k V that is on the rising,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.