Limiting Mechanisms in MHD Generator Performance.
Final rept. 15 Nov 71-15 May 75,
STANFORD UNIV CALIF HIGH TEMPERATURE GASDYNAMICS LAB
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Experimental and analytical studies were undertaken to investigate loss mechanisms in MHD generators associated with the boundary layers and the electrodes. Measurements were made of the electrode boundary layer profiles of velocity, static temperature, and electron number density in an operating MHD generator for both subsonic and supersonic flows. Good agreement with a theory which included MHD effects was obtained for subsonic flow and somewhat less satisfactory agreement for supersonic flow where three-dimensional effects were thought to be significant. A theory was developed for predicting boundary layer parameters on the insulating wall of an MHD generator. It was shown that for high power density application of interest to the Air Force, separation may occur as a result of the non-uniform current distribution in the magnetic field direction. The Hall field breakdown between adjacent electrodes was investigated and the importance of the interelectrode gap width was demonstrated. Voltages considerably in excess of the standard 40 volts per electrode pair or per centimeter were obtained for the larger gaps and the importance of the insulator in the breakdown mechanism was postulated. Transient start-up performance of MHD generators was modelled analytically and it was shown that by suitably controlling the design and thermal capacitance of the electrodes, the generator power response can be tailored to meet the requirements for the pulsed operation studied.
- Electric Power Production and Distribution
- Plasma Physics and Magnetohydrodynamics