Modeling of the near-electrode regions of arcjets. I - Coupling of the flowfield to the non-equilibrium boundary layers

Abstract

A model for arc attachment at an anode in contact with a flowing thermal plasma is described. Current limitations are identified which arise when the convective transport of ions into the electrical, thermal and hydrodynamic boundary layers is incapable of supplying the loss of ions through three-body recombination in the volume, and catalytic recombination on the electrode surface. It is shown that the anode current where this condition is achieved can be exceeded provided there is a significant Joule heating in the boundary layer. The saturation current (current density above which the anode must emit ions) is found to substantially increase with increasing free stream velocity and anode temperature.