Experimental and Theoretical Study of Hall Field Limitations in MHD Generators

Abstract

Experimental and theoretical results pertaining to the Hall field behavior in combustion-driven MHD generators using clean fuel are presented. MHD generators are subject to Hall field breakdown as a result of electrical-thermal instabilities within the interelectrode plasma region and the interelectrode insulator. Interelectrode breakdown within the insulator typically occurs at a lower threshold voltage than breakdown of the plasma itself. As a result, experiments have been carried out to study the effect on the insulator initiated breakdown threshold of interelectrode insulator cooling. Experiments have also been carried out to study the dependence of the breakdown threshold on the electrode boundary-layer Joule heating, insulator width, and magnetic field. A two-dimensional computer model of the plasma and insulator regions has been developed. Theoretical results based on this model are compared with experimental data. The comparisons indicate both qualitative and quantitative agreement between experiment and theory. 12 references.