Influence of the inlet gas velocity components on the survival of the vertex of gas in the plasma torch

Abstract

The vortex gas injection into plasma torch is considered as a method for reducing electrodes erosion. In order to investigate the effects of vortex gas injection on plasma structure, as well as the effect of gas viscosity on the rate of rotation, a threedimensional nonequilibrium and time-dependent non-transferred DC plasma torch model has been simulated. Viewing the general characteristics of the plasma shows that the model works well. The results have shown that if the components of the inlet gas velocity are not properly selected, it is possible that the rotary effects of the gas are greatly depleted even before the gas reaches the cathode tip and plasma formation. In this case, only the change in the axial component of the gas causes changes in the structure of the plasma. Vortex reduction is also observed during the movement of cold gases. It is observed that the change in viscosity of gas has significant effects on the rate of the vortex.

Predicted Anode Arc Attachment by LTE (Local Thermodynamic Equilibrium) and 2-T (Two-Temperature) Arc Models in a Cascaded-Anode DC Plasma Spray Torch

“…1). However, the radial profile of electric current density calculated by the 2-T model is wider, with a lower current density at the cathode center (4.3910 7 A/m 2 instead of 5.8910 7 A/m 2 in the LTE model). It also has a much lower peak at the edge of the flat part of the cathode tip (3.4910 7 A/m 2 instead of 8.0910 7 A/m 2 in the LTE model).…”

“…However, the radial profile of electric current density calculated by the 2-T model is wider, with a lower current density at the cathode center (4.3910 7 A/m 2 instead of 5.8910 7 A/m 2 in the LTE model). It also has a much lower peak at the edge of the flat part of the cathode tip (3.4910 7 A/m 2 instead of 8.0910 7 A/m 2 in the LTE model). In the 2-T model, the rate of heat transfer to the cathode tip is 1.9 kW (1.1 kW by the electric current, 0.6 kW by heat diffusion and 0.2 kW by radiation) while it is 1.7 kW in the LTE model (1.2 kW by the electric current, 0.1 kW by heat diffusion and 0.4 kW by radiation).…”

Effect of vortex gas on the anode arc attachment behaviour inside the plasma torch: Numerical study

“…The incoming gas at inlet has the velocity profile of a fully developed laminar flow through a pipe. The heat transfer coefficient (ℎ ) at the anode wall is equal to 10 5 W 2 −1 (and approximates the convective heat transfer due to turbulent flow in a pipe [2]). The heat from the anode wall is ejected into a thermal sink of temperature ( ) 500 K. A flat profile of current density is imposed on the cathode tip to ensure the integration of current density over the cathode tip area equal to applied arc current.…”

“…Several researchers have investigated the effect of vortex formation on the arc behavior and plasma movements inside the torch [1][2][3]. Moon et al [3] investigated the influence of fluid rotation on plasma structure by varying the angle of gas injection to create gas swirl.…”

“…They have deduced an optimized angle where the low flow resistance due to the wall effects are minimized. Gharaeinia et al [2] have used a non-equilibrium plasma model to investigate the variation of velocity component (axial and tangential) by induced swirl at a fixed total velocity. Their simulation shows that the mean temperature of the plasma jet is reduced by imposed gas swirl and that the extent temperature reduction is directly proportional to fluid rotation intensity.…”