Experimental Study of the Discharge Characteristics of a Magnetically Stabilized Double-Chamber Arc Plasma Torch

The double-chamber arc plasma torch (DCAPT) is a promising arc source due to its high energy efficiency and low erosion rate. It has been widely used in various fields including coal powder ignition, boiler heavy oil-free ignition, and production of sheet-shaped carbon materials, among others, but research on its micro-discharge characteristics is still insufficient. In this work, a magnetically-stabilized DCAPT with a quartz window on the inner electrode is designed and studied, in order to investigate the effects of magnetic field position and intensity, discharge current, gas flow rate, electrode diameter, and electrode polarity on its discharge characteristics. Results show that both the volt-ampere characteristics and thermal efficiency of DCAPT exhibit a strictly decreasing trend, and both of them can be accurately predicted using similar theoretical approaches. The discharge characteristics of DCAPT differ significantly for different polarities. When in reverse polarity, the outer cathode arc root attaches to the outlet, resulting in an increased arc length and greater randomness in the arc-root fluctuations. As a result, the arc length, voltage, thermal efficiency, and voltage fluctuations are all greater than with normal polarity. Within the experimental range of the parameters, the thermal efficiency of DCAPT is between 40 and 74%. Due to the cathode's “easily mobility” characteristic, the rotation speed of the cathode arc root is always greater than that of the anode, resulting in higher thermal losses for the cathode than for the anode. This is the primary source of thermal loss and the main factor contributing to the rapid erosion of the cathode in the DCAPT. This study reveals the correlation between the volt-ampere characteristics, thermal characteristics, and dynamic evolution of the DCAPT. The research findings have significance for guiding the structural design, parameter selection, and choice of application of this type of plasma torch.