MHD発電機の隣接陽極間絶縁材のアーク損傷特性

Abstract

The inter-anode arc caused by a Hall field is driven by a magnetic field into the anode wall in an MHD generator, which limits the lifetime and performance of the generator. The arc damage to inter-anode insulators of an MHD generator has been studied experimentally to obtain basic data for the design of the inter-anode insulation. The experiment was conducted using a pair of electrodes with an insulator between them. Arc currents were supplied from a dc power source and magnetic field was applied perpendicularly to the arc current. Experimental parameters are the insulator thickness, arc current, magnetic field and insulator materials. Quartz glass, boron nitride, magnesia, alumina, silicon carbide, silicon nitride, etc., were tested and evaluated. The following conclusions are evident from the experiments. Boron nitride and quartz glass are the most promising inter-anode insulators. Boron nitride has a higher arc voltage and longer cutting time than quartz glass, and it is the best material. The cutting time is approximately proportional to the −0.4th power of the magnetic field. The loss of insulator is approximately proportional to the 0.7th power of the arc current. The arc voltage increases linearly with the inter-anode gap length. Also, it increases with magnetic field, but decreases with increase of arc current. An equation which approximates to such relations of arc voltage versus inter-anode gap length, arc current and magnetic field has been obtained. The standard deviation of the error of this equation is 12 percent for boron nitride and 15 percent for quartz glass.