Numerical simulation of plasma and fluid flow in a shock-tube-driven disk MHD generator

Three-dimensional numerical simulations have been carried out in order to explain the experimental results with a shock-tube-driven disk magnetohydrodynamics (MHD) generator with inlet swirl for the first time. The numerical results agree well with the experimental results especially in the enthalpy extraction ratio. The isentropic efficiency obtained numerically is higher than that in the experiment, for seed fractions lower than the optimum value. There may exist some additional mechanism causing a total pressure loss which cannot be, included in the present numerical model. The radial component of Mach number becomes less than unity for high seed fractions. This decrease in Mach number is not so steep but moderate, and seems to be different from that attributed to a shock wave observed in a fluid flow without MHD interaction. The plasma structure is almost uniform in the θ direction near the optimum conditions. Under the condition far from the optimum value, however, a nonuniform and unsteady plasma structure owing to the partial ionization of seed material is observed