MHD flow simulation in subsonic disk MHD generator driven by a shock tube facility

摘要

The MHD flow behavior and the performance of an experimental nonequilibrium subsonic disk MHD generator driven by a shock-tube facility have been examined with time-dependent r-z two-dimensional and r-θ-z three-dimensional Large Eddy Simulation for the first time. The calculation region is extended and covers a hot duct through a downstream duct including the subsonic MHD generator with two throats. For optimal and high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. The discharge structure is uniform in the θ direction, and suitable fluid flow is realized in the generator channel, although the large boundary layer separations and eddies are observed behind the downstream throat. For low load operations, the flow chokes at the upstream throat and the flow becomes supersonic, where pseudo-shock waves and large eddies are observed in the generator channel and the downstream duct. The ionization instability in the r-θ plane occurs in the generator channel, which deteriorates the generator performance. Asymmetric flow at the generator inlet, which is attributed to the change of flow direction from the hot duct, seems not to be significant for the generator performance.