Plasma flow characteristics inside the supersonic d.c. plasma torch

A magnetohydrodynamic (MHD) model, which describes supersonic plasma flow inside the torch, is presented in this paper. It is a two-dimensional model but includes the K-epsilon model of turbulence, the gas viscous effects and compressible effects. The PHOENICS software is used for solving the governing equations, i.e. the conservation equations of mass, momentum, and energy together with the equations describing the K-epsilon model of turbulence. The calculated arc voltages and gas inflow rates are consistent with the experimental results when arc current and the working gas are the same as experiment. The plasma flow characteristics inside the supersonic plasma torch are analyzed in detail. Temperature, velocity, pressure and Mach number contours are presented to show the flow characteristics. Comparisons between turbulent and laminar models are made in detail also, and the results show the turbulent enhanced momentum and energy transport inside the supersonic plasma torch has little effect on the whole discharge area. The plasma flow inside the supersonic torch is mainly in the laminar state.