Boundary layer effects in He and Ar driven disk MHD generators

Abstract

A two-dimensional compressible turbulent boundary layer model is adopted to predict the boundary layer characteristics of the 100 MW thermal input supersonic disk MHD generator walls for helium and argon under various enthalpy extraction conditions. The results show that the boundary layer thickness increases downstream in the channel for both argon and helium, and for helium, there occurs a boundary layer separation under high enthalpy extraction conditions. A slow variation of the Faraday current is observed through the boundary layer, while the Hall current decreases sharply, and the direction of the Hall current gets reversed in the vicinity of the insulator wall at the channel downstream end. This effect is observed to be more prominent for helium than for argon. The percentage of pressure loss through friction is found to be more for argon than for helium, while the heat loss is observed to be more for helium than for argon.