A Non‐equilibrium Treatment for Free Burning High Current Arcs.

Abstract

ABSTRACT: A two‐temperature variable‐density treatment has been developed for description of high current free burning arcs, including departures from thermodynamic and chemical equilibrium in the plasma. The treatment includes the arc and the electrodes, and considers the separate energy balance of the electrons and the heavy particles, together with the continuity equations for these species throughout the plasma. For a 200 A arc in pure argon at 1 atm, we calculate large differences between the temperatures of the electrons and the heavy particles in the plasma region near the cathode tip. In the main body of the arc, at high plasma temperatures, we predict minor differences between the temperatures of the electrons and the heavy particles. However, we predict large departures from local chemical equilibrium throughout the plasma, due to overpopulation of the ground state level of the neutral atoms caused by the injection into the arc core of a large mass flow of cold gas, resulting from the arc constriction at the tip of the cathode.