Electrode processes in an open-cycle MHD generator

Basic results are presented on researches on combined electrodes and breakdown between electrodes performed jointly by the High-Temperature Institute, Academy of Sciences of the USSR, and the Institute of Electrodynamics, Academy of Sciences of the Ukrainian SSR, with the K-1 apparatus. The tests have indicated the optimum conditions for using electrodes in which the current-carrying surfaces are coated with materials based on zirconium dioxide (heat-flux range from faces are coated with materials based on zirconium dioxide (heat-flux range from 0.5 to 2 MW/m2, temperature up to 23000K, and current densities from 0.5 to 1.5x104 A/m2. The results are compared with data from the U--02 apparatus. These electrode types can be used in one half of the MGD ES-500 channel. The studies have shown that the Hall breakdown voltage increases appreciably as the gap widens from 2 to 10 mm, and with a safety factor on the electrical strength of 2--2.5, the working voltage correspondingly is from 30 to 60 V, and these values are below the Hall-arc extinction voltages. If the insulator is recessed into the electron gap, the electrical strength margin can be increased appreciably