Influences of coal slag on electrical characteristics of a Faraday MHD generator

Abstract

In order to clarify the influence of coal slag on the electrical characteristics of a large scale Faraday MHD generator, numerical analysis by a new equivalent circuit method is performed. At first, an equivalent circuit for a space element in the Faraday channel and a slag layer element are derived. Next, the numerical results are compared with the experimental ones obtained from the ETL Mark VII. The results are: (1) when the thickness, the conductivity, etc. of the slag are nonuniform, distributions of not only the load voltage, but also the voltage between adjacent electrodes becomes nonuniform, and the latter may cause interelectrode breakdown; (2) when the shortings over several cathodes occur, a typical distribution of the load voltage appears near the shorted region, in which, at first, the load voltage rises a little, then decreases gradually, and finally, recovers rapidly to the normal voltage along the gas flow. By the above short-circuit, the distribution of the voltage between adjacent electrodes is made remarkably nonuniform, and this may lead to another inter-electrode breakdown.