A Numerical Study of Leakage Current in A Coal-Fired MHD Generator

Characteristics of leakage current in a coal-fired MI-ID generator are studied by a two-dimensional time dependent numerical modeling, the method of which is based on a Finite Element Mathematics formulation for the generator electrodynamics. The analysis is directed at the study of electrical behavior near electrodes influenced by the slag coverage. The simulations have produced solutions which can explained the experimental results of the electric field and the current density for Component Development and Integration Facility 1A4 generator. The following observations are drawn from the analyses. High electrical conductivity of the slag and the Hall effect are the main factors to generate the leakage current and the arc current through the slag layers. It is clarified that the leakage current increases exponentially in the slag conductivity. The leakage current is one of the principal factors of the observed damages to both edges of the cathodes. A local blowout of the slag can be supported by the Fuse Theory where the slag is locally dissipated by leakage currents like a fuse.