大气压直流氩等离子体射流工作特性研究

Characterization of DC argon plasma jet at atmospheric pressure

介绍了一种新型大气压直流双阳极等离子喷枪,并对其电特性参数和发射光谱进行了测量.通过对氩等离子体射流的电信号进行时域和频域分析,研究了载气流量和弧电流的变化对射流脉动的影响,结果表明氩等离子体电弧的伏安特性呈上升趋势,射流脉动属于接管模式,电源特性中的交流分量引起的电压波动是影响氩等离子体射流脉动的主要因素.通过光谱法测量了氩等离子体射流在弧室内和弧室出口的发射光谱,利用玻尔兹曼曲线斜率法计算了射流的激发温度,根据ArI谱线的斯塔克展宽得到了射流的电子密度,并对等离子体射流满足局域热力学平衡(LTE)状态的判定标准进行了分析,在本实验条件下大气压直流氩等离子体射流达到了局域热力学平衡.

An original DC double anode plasma torch operating with argon at atmospheric pressure which provides a long time and highly stable plasma jet is analysed through its electrical and optical signals. Effects of gas flow rate and current intensity on the arc dyrnamics hehaviour are studied using standard diagnostic tools such as FFT and correlation function. An increasing current- voltage characteristic is reported for different argon flow rates. It is noted that the takeover mode is characteristic for argon plasma jet and arc fluctuations in our case are mainly induced by the undulation of torch power supply. Furthermore, the excitation temperatures and electron densities of the plasma jet inside and outside the arc chamber have been determined by means of optical emission spectroscopy （OES）. The criteria for the existence of local thermodynamic equilibrium （LTE） in plasma is then discussed. The results show that argon plasma jet at atmospheric pressure under our experimental conditions is close to LTE.