Joule heating effects in MHD generator boundary layers
Experimental measurements were performed of temperature and electron number density profiles on a laboratory-scale MHD generator. Comparisons between calculations from a two-dimensional theory and measurements for cases without current generally showed good agreement when the turbulence model properly accounted for the effects of freestream turbulence, although small discrepancies were observed between theory and experiments for the overall profile shape, Comparisons of experimental temperature profiles without current to profiles with current showed a marked temperature increase in the boundary layer due to Joule heating. The magnitude of the increase was well predicted by the two-dimensional boundary-layer theory. Measured temperature profiles with current and magnetic field did not agree with predictions. The predicted profile in the inner region of the boundary layer for a case with current and magnetic field was above a similar case without current, whereas measurements for anode boundary layers were below control profiles without current. A cathode boundary layer behaved oppositely to the anode boundary layers. Three-dimensional recirculation induced by nonuniformities in axial current could explain the discrepancies.