超声速气流中纳秒脉冲放电特性实验研究

产生超声速导电流体是开展磁流体（MHD）动力技术实验研究的前提，低温超声速条件下产生大体积均匀等离子体有效可行的方法之一是纳秒脉冲介质阻挡放电。介绍了基于马赫数为3吸气式双喉道风洞的超声速纳秒脉冲介质阻挡放电实验系统的基本组成、设计原理和运行情况，分别在静止和马赫数为3超声速条件下对气体电离，测量分析电压和电流波形。得到以下结论：风洞稳定工作时间约为16 s，满足超声速气体放电实验的可靠进行和数据的有效采集；实验条件下，纳秒脉冲介质阻挡放电气体击穿与电场强度值有关，而与电场强度变化率无关；实验条件下，着火电压大小受超声速气流密度波动影响显著，而受气流速度影响较小。另外，气体击穿后的放电状态受超声速气流影响小；气体击穿时刻的电流峰值受着火电压和实验环境中随机自由电子数共同影响。

Experimental Study of the Discharge Characteristic of Nanosecond Voltage Pulses in Supersonic Flow

Producing a supersonic conductive flow field is the foundation of the study of magnetohydrodynamics(MHD). Nanosecond pulsed dielectric barrier discharges is one effective method capable of producing large-scale and homogeneous plasmas in cold, supersonic air. An experimental system of ionizing supersonic air based on a double-throat tunnel is presented, and the data of voltage and current measured in static and supersonic air are analyzed respectively. Certain conclusions are drawn from the experiments. First, the stable working time of the wind tunnel is about 16 s, which is enough to guarantee the discharge experiments to work reliably and obtain effective measurements of the data. Second, for the nanosecond pulsed dielectric barrier discharges, the air breakdown is restricted by the value of the electric field strength, not its change rate. Third, in supersonic condition the breakdown voltage changes randomly with the density fluctuation of the flow field, while the velocity rarely influences it. In addition, after air breakdown, the supersonic flow field rarely influences the discharge. Fourth, the peak of the current during air breakdown is determined by the breakdown voltage and the number of free electrons in the experimental environment.