Influences of back pressure on discharge structure and performance of nonequilibrium disk MHD generator

Abstract

Influences of back pressure on the discharge structure and the performance of a He/Cs nonequilibrium disk MHD generator are investigated with time dependent r-Φ two-dimensional numerical simulations. For load resistances higher than the designed value, the discharge remains stable and uniform in the azimuthal direction even for high back pressures, while the electron temperature varies in the radial directions. In spite of the stable discharge, however the generator performance is deteriorated by the low gas velocity and high static pressure due to high back pressures. For low load resistances, the discharge structure becomes nonuniform and unsteady due to the ionization instability. In this case, the influence of the back pressure on the generator performance is masked because the performance strongly depends on the discharge structure. It is found that the increase in the back pressure can make the discharge stable for load resistances slightly lower than the designed value.