An Interferometric Study of the Effects of Corona Discharge on the Temperature Profiles on a Flat, Uniform Temperature Plate in Forced Convection

摘要

The purpose of this thesis was to study the effects of corona discharge on flow past a flat plate at zero incidence. In a previous exploratory investigation into the effects of ionization on the gas in channel flow, interesting results were observed. Pressure drops and heat transfer coefficients were found to double. The velocity profile was distorted. In an attempt to explain the phenomenon, Velkoff hypothesized an induced electric field component in opposition to the flow. An analytical solution for laminar flow with a uniform charge density in the boundary layer was developed by extending the Rossow solution for MHD flows. The corona effect was predicted to retard the flow and thicken the boundary layer. An experimental program was initiated to study this phenomenon by observing changes in the temperature profiles on a flat, uniform temperature plate in forced convection with a Mach-Zender interferometer. A series of tests were run with a constant plate to ambient temperature difference but different free stream velocities and corona currents. At a 62.5 foot per second free stream velocity, a 1000 microns ampere corona current did not effect the flow. At lower velocities, the effects observed were opposite to those predicted. It was found that the boundary layer was turbulent at the 62.5 foot per second test. Also it was noted that 5.9 foot per second test with corona discharge was similar to the 62.5 foot per second test. The body force hypothesized by Velkoff does not appear to describe the corona effect. A possible mechanism that would account for the observed result is that the corona discharge induces an instability in the flow. (Author)