EFFECTS OF EXTERNAL CONTROL-CIRCUIT ON COAL-FIRED SUPERSONIC DIAGONAL-TYPE MHD GENERATOR

The objective of this article is through numerical analyses to examine behavior of the coal-fired diagonal channel which suffers from the electrical nonuniformities caused by coal slag polarization. The channel is designed for a pilot-plant and is controlled with external circuits such as the master/slave current controller and a side-by-side power shuffling circuit. The MHD channel and external circuits are simultaneously analyzed. A two-dimensional equivalent circuit method is applied for electrodynamics, while the gasdynamical behavior is treated with time-dependent one-dimensional approximation. The following results are obtained: 1) the channel works well with the external circuits, although the supersonic channel suffers from shock when operated near open-circuit. The channel is dynamically stable without fluctuation when the load is changed: and 2) the external circuits can control interanode voltage and electrode current even when large electrical nonuniformities grow on cathode wall due to coal slag polarization. The loss due to slag leakage current becomes about 20% of power output at 10-MW scale.