Design of multiple-anode and non-transferred laminar DC plasma torch

Abstract

DC plasma torch is the primary component of various industrial thermal plasma processes. Due to DC plasma torch has high energy density, it is widely used in the field of plasma spraying, metal cutting and welding, waste treatment, and gas production etc. This paper presents a new DC plasma torch structure with a high-frequency arc ignition circuit which is capable of generating laminar plasma flow. The plasma torch in this paper has multiple electrodes including a water-cooled cathode, a water-cooled middle electrode and two water-cooled anodes. For convenience, compressed air is chosen to be working gas. The air intake method is designed to be rotating to get a more compressed plasma flow. The diameter of electrodes gradually increases along the direction of the plasma jet. A new cathode structure is designed in this paper. The arc is ignited between the cathode and the middle electrode. After the compression of the first and second anode, the plasma jet is stable and laminar. Besides, a new arc ignition circuit is designed which can be coupled into the main power circuit in series connection. A high-voltage and high-frequency arc ignition circuit is designed to generate the arc. The designed working voltage is 100V and the working current is 50A which is the critical current of thermal plasma.