Three-dimensional simulation of nonequilibrium seeded plasma in closed cycle disk MHD generator

The three-dimensional (3-D) structure and behavior of nonequilibrium alkali metal seeded plasma in a supersonic disk closed cycle MHD (CCMHD) generator are simulated numerically. The simulation reveals the unsteady 3-D nonuniform plasma caused by the ionization instability. The plasma with low electron temperatures of ∼5000 K, corresponding to the fully ionized seed plasma, has spiral structure in the r-θ plane, and looks like a straight pillar between walls in r-z plane. The plasma flows repeatedly downstream in the generator, changing the shape unsteadily. For high load resistance, the nonuniform region is contracted near the inlet of the generator, and the plasma becomes steady and three-dimensionally uniform. The nonuniform structure does not appear in the regions between the faced anodes and between the faced cathodes, although the electron temperature is relatively low (∼3000 K) and the plasma is under the regime of a weakly ionized seed.