Abstract
Effects of load resistance at nozzle on performance of disk MHD generator were investigated experimentally. Furthermore, a difference of electrical performances between a single load and segmented loads was studied. Experimental results indicated that an increase of static pressure at exit of the nozzle was not only due to Lorentz force in the nozzle but also to that in the MHD channel. This could be explained by the propagation of pressure increase at the MHD channel into the nozzle through boundary layer near walls. And it was found that load resistance at the nozzle affected Mach numbers, static pressures and Hall potentials at the inlet of the MHD channel. However, distributions of those values measured at middle-stream and downstream regions became almost the same. Therefore, influences of load resistance at the nozzle on enthalpy extractions remained small. When a single load was connected between the nozzle and the cathode, enthalpy extraction was reduced remarkably and this was due to a large Hall potential drop in the nozzle. Furthermore, it was found that there was a strong correlation between fluctuations of Hall currents in the nozzle and those in the MHD channel and that fluctuations of the currents in the nozzle were transmitted into the MHD channel by the flow. This suggests that non-uniformity of plasma in the nozzle affects strongly the uniformity of plasma in the MHD channel.
