Three-Dimensional Simulation on Performance of Disk CCMHD Generator with Segmented Loading

Plasma structure and uid behavior in a segmented loading disk MHD generator have been investigated with time-dependent three-dimensional numerical simulation. The prticular attention is paid to the e ects of the increase in the downstream load resistance and the in uence of the middle electrode on the non-equilibrium plasma and uid ow. Furthermore, the feasibility of the improvement of generator performance by using segmented loading condition is investigated. It is shown that the increase in the downstream load resistance raises static pressure and decelerates working gas in the upstream region. This is because the increase in the static pressure and the development of boundary layer near the middle electrode have the same e ects as the change of the outlet boundary conditions for the upstream region. It is found that electron temperature is decreased rapidly on the middle electrode. Ionization degree of seed material is kept high near the optimum condition. This results from longer relaxation time of ion number density than that of electron temperature. Using segmented loading condition leads to improvement of enthalpy extraction ratio. Isentropic eAEciency, however, becomes somewhat lower under segmented loading codition. This is caused by high static pressure and low electrical eAEciency under high enthalpy extraction condition for the segmented loading.