中規模非平衡亜音速ディスク形MHD発電機内の電磁流体挙動と発電性能(熱工学,内燃機関,動力など)

MHD flow behavior and the performance of a middle scale nonequilibrium subsonic disk MHD generator have been examined with time-dependent r-z two- and r-θ-z three-dimensional numerical simulations. The generator performance, such as the enthalpy extraction ratio and the isentropic efficiency, can be varied time-dependently because the boundary layer separation occurs and the fluid flow fluctuates in the diffuser. However a mean enthalpy extraction ratio of 23% and a mean isentropic efficiency of 83% are achieved for the optimal load resistance under the inlet stagnation pressure of 0.75atm. This performance is almost high enough for the commercial generator. When the low electron temperature plasma flows into the generator channel, the ionization instability occurs and the discharge structure becomes nonumiform in θ-direction, which deteriorates the generator performance considerably. This fact indicates the importance to produce the proper plasma for the power generation by optimizing the generator channel or utilizing the preionization.