‘LTE-diffusion approximation’ for arc calculations

Although many advances have been made in recent years in the modelling of electric arc and welding processes, improvements in modelling capabilities are still needed to make possible rapid three dimensional time-dependent calculations. This paper proposes the use of the local thermodynamic equilibrium (LTE) approximation for the electric arc, but with a particular use of the “Diffusion Length ” for the mesh size near the electrodes. This approximation overcomes the problem that the equilibrium electrical conductivity in the arc near the electrodes is almost zero, which makes accurate calculations using LTE impossible in the limit of small mesh size, as then voltages would tend towards infinity. Results are in approximate agreement with calculations made accounting for non-equilibrium electron densities in the arc region due to effects of ambipolar diffusion. 1. Introduction. In a previous papers [1-3] we have presented calculations of temperatures of free burning arcs and their electrodes for currents of the order of 200 A with an account of non-equilibrium electron