Instability evaluation of a dual-jet DC arc plasma based on the visible image treatment

In order to ensure the safe operation of plasma equipment, to promote the application of plasma in material processing, and to guide the design and optimization of plasma generation systems, we proposed a method for diagnosing the discharge stability of dual-jet DC arc plasmas through collecting and analyzing the visible images and the discharge voltage of dual-jet DC arc plasmas. The visible images and the discharging voltage were recorded simultaneously at a preset time interval on a dual-jet plasma experimental platform. By introducing the eight-direction Freeman chain codes for image procession, we defined four parameters including perimeter, area, correlation coefficient in time domain, and the FFT amplitude in frequency domain. Using these four parameters and the discharge voltage, we quantitatively analyzed the discharge stability in the plasma arc-jet region. The results show that the perimeter and the area determine the geometrical sizes of the arc-jet boundaries, the correlation coefficient describes the boundary differences, and the FFT amplitude reflects the boundary smoothness of the arc-jet region.