Numerical simulation of a stationary 3D direct current plasma torch

Summary form only given. Electric arcs used in plasma torches are found in many practical applications, such as thermal spraying or waste treatment. To get a better understanding of phenomena occurring inside a torch, a number of numerical studies first considered mainly 2D configurations. In recent years, the increased available computer power allowed researchers to progress towards simulations of electric arcs in fully 3D configurations, such as arcs in a cross-flow or DC plasma torches. A 3D code was developed, starting from a Navier-Stokes CFD code (Vos et al., 1998) implementing the finite volume method, to which a Poisson equation for the electrical potential was added. The fluid and electric parts are linked through ohmic heating and Lorentz force source terms and electric conductivity, which depends on the state of the fluid. The code was first tested for arcs in a crossflow in a simple geometry as described in the experimental study of Benenson et al. (1970). Results were consistent with similar simulations by Kelkar et al. (2000). Here we present simulations of an arc in the geometry of a Sulzer-Metco F4 torch operated in steady-mode conditions (600 A, 30 SLPM argon). Early runs revealed numerical problems originating in the evaluation of gradients not present in Vos et al.'s work. Recently we have found a second-order method for gradient evaluations based on an isoparametric transformation that retains its accuracy even on highly distorted meshes. Steady state computational solutions for the F4 torch using this new method will be presented.