Numerical Study of Plasma-Electrode Interaction During Arc Discharge in a DC Plasma Torch

Energy transfer within an arc is of crucial importance in numerous applications, such as thermal spraying and electric propulsion (arcjet and magnetoplasmadynamic thruster). Its control will frequently determine the viability of a process or a device. However, a lot of numerical works done to model arc discharge using finite volume or finite element method consider the arc core only, while the near-electrode layers are ignored and replaced by a presumed boundary condition. This greatly limits the reliability of the simulation model. The goal of this paper is to make the bulk plasma coupled with electrode regions, where the special space charge layer (sheath) on cathode is taken into account. This is achieved by a simplified 1-D sheath model developed in this paper, which is then applied on a nontransferred dc plasma torch to study the thermodynamic and electromagnetic interaction between plasma and electrodes. The simulated results in electrode and plasma regions are presented, the predicted temporal evolution of electric potential with sheath model is in good agreement with the experimental measurements.