Three-dimensional simulation on performance of a nonequilibrium disk MHD generator under subsonic flow condition

The performance of a nonequilibrium disk magnetohydrodynamic (MHD) generator under subsonic flow condition is examined with time-dependent τ-θ-z three-dimensional numerical simulation for the first time. The uniform plasma structure and proper fluid flow are realized for the optimal working condition. For low-load resistance, however, the flow chokes at the throat, and shock waves and boundary layer separation are observed in the generator channel. For high-load resistance, on the other hand, the subsonic flow is maintained, although the boundary layer becomes considerably thick. When the plasma with low electron temperature flows into the generator, ionization instability takes place, which markedly reduces the enthalpy extraction ratio and isentropic efficiency. This suggests that some way to raise the electron temperature in the upstream region, for example, a pre-ionization, is needed