Ionizational and Thermal Nonequilibrium in MHD Boundary Layers

Abstract

Abstract : The effects of thermal nonequilibrium (elevated electron temperature) and ionizational nonequilibrium (finite-rate recombination) are studied in the insulator boundary layer of a potassium-seeded nitrogen MHD accelerator flow. The nonsimilar, compressible boundary layer is assumed steady, laminar, and two- dimensional. A collisionless sheath is assumed and matched with the boundary layer equations, which are solved numerically for a core flow Hall-neutralized Faraday accelerator. The relative importance of the various terms in the electron energy equation are assessed, and the overall effect of the nonequilibrium phenomena on the boundary layer parameters is described. It is concluded that thermal nonequilibrium can lead to significant B-wall shorting in long channels and that Hall effects should not be neglected but that operation is not noticeably affected by ionizational nonequilibrium or the physics of the electrostatic sheath.