磁驱动旋转电弧运动图像及弧电压脉动的实验研究

Experimental study on arc images and voltage fluctuation of magnetically driven arcs

磁驱动旋转电弧产生扩散电弧等离子体过程中有许多有趣的物理现象。本文利用高速摄影技术研究了大气压条件下、非均匀磁场中、大尺度磁驱动旋转氩电弧的电弧结构;在一定的弧电流和外磁场条件下,电弧的平面形状表现为不断发展和增长的螺旋结构,电弧螺旋结构的破裂往往产生于阴极附近的等离子体射流。采用图像分析的方法计算了外部磁场作用下阳极斑点沿弧室内壁的移动频率,分析了磁驱动旋转电弧运动过程中的弧电压脉动现象。结合电弧图像分析和电弧电压脉动及其FFT分析得出:电弧电压的大幅波动与多层电弧螺旋结构破裂和重建相关,而电弧电压的小幅波动则是弧根小幅跳动引起电弧拉长和收缩的结果。

There are many interesting physics phenomena in producing diffusing arc plasma by magnetically driven rotating arc. The large-scale arc hollow electrode plasma generator with an outer magnetic filed is designed and a photogrammetry is built to investigate the arc structure and arc movements in the argon under the atmospheric pressure with the aid of a high-speed digital camera. Typical arc structure, under arc currents and external magnetic field, is a developing and increasing spiral one, which breaks and new arc column is re-constructed as plasma jets towards the anode appearing nearby the cathode. The rotating frequency of anode spot of the arc is analyzed with statistics mean. The arc voltage fluctuation frequency resulting from arc movement is obtained by using the Fast Fourier Transform （FFT） method. The analysis results show that large voltage drop is attributed to the breaking and reconstruction of multiple layer spiral structure of the arc, and small voltage fluctuations are probably caused by arc lengthening and shortening during the arc root jumping on the anode.