Numerical analysis of non-equilibrium plasma property in anode boundary layer of argon Gas Tungsten Arc

Although the LTE assumption is effective to evaluate high temperature region in the arc column in Gas Tungsten Arc (GTA) which is a kind of a transfer-type plasma torch, it is difficult to apply it to low temperature region such as the fringe of the arc column or an electrical sheath due to decrease of collision frequency. Especially, in order to consider the effect of chemical reaction between the arc plasma and the surface of the anode material, non-equilibrium property of the arc plasma should be considered without the LTE assumption, since it is required to understand precise property of the arc plasma close to the anode surface. Therefore, we have developed non-equilibrium simulation model of GTA. In this paper, the reliability of the model was confirmed for comparing the simulation result with the experimental result. Furthermore, it was found that the thickness of non-equilibrium region in case of 150 A is approximately 0.3 mm near the anode surface and that in case of 50 A exceeds 1 mm.