MODELLING OF HIGH INTENSITY ARCS INCLUDING A NON-EQUILIBRIUM DESCRIPTION OF THE CATHODE SHEATH

Abstract

An axisymetric model has been developed for prediction of high intensity electric arcs under atmospheric pressure. A set of thermodynamic and electromagnetic equations, including interaction terms (JOULE effect, LORENTZ forces) is solved using the orthogonal finite difference numerical code Mélodie. Conservation equations in the laminar arc column (mass, momentum, energy and current) are written according to the local thermodynamic equilibrium (L.T.E.) assumption and the OHM law approximation. The proper boundary condition at the cathode is derived from a one-dimensional description of non-equilibrium electrode boundary layer, coupled with full computation of heat transfer in solid region (conic cathode in tungsten). Numerical calculations performed for free burning and transferred argon arcs show a good agreement with experimental data