Boundary-layer profile measurements in a combustion driven MHD generator

Abstract

The velocity, temperature, and electron number density profiles were measured in the electrode wall boundary layer of a combustion driven MHD generator. Both subsonic and supersonic conditions were run. The experimental results are compared with predictions of a two-dimensional turbulent boundary-layer computation. For the subsonic condition, high levels of freestream turbulence were measured, about 10-12 percent. The measured velocity profile was fatter than that predicted, although the temperature and electron number density profiles were in agreement. This difference is tentatively ascribed to the high freestream turbulence levels. There was no measurable MHD effect for the subsonic case. For the supersonic condition, the measured velocity, temperature, and electron number density profiles fell under the predicted profiles. The discrepancy may be due to three-dimensional recirculation effects. There was a small amount of MHD interaction, the degree of which was in agreement with predictions. Electron number density nonequilibrium was not identified, but the degree of nonequilibrium predicted was small. Under the appropriate supersonic conditions, primarily at freestream temperatures below 2400K, ionization nonequilibrium is predicted to occur.