Three-dimensional current distribution in coal-fired MHD channels

Abstract

Slagging effects on theoretical three dimensional current and potential distributions are presented for one frame of the UTSI 60/sup 0/DCW channel. The electrodynamic problem is solved with imposed gasdynamic and slag layer solutions. A three-dimensional finite element method is applied to solve for the electrical potential. The location of current concentration calculated on anode sidebar wall coincides with wear pattern observed in experiments. Without considering slag polarization, the leakage resistance calculated lies between 5 to 7 ..cap omega.., which gives the upper bound of slag layer leakage resistance. Next, the effects of slag polarization on electrodes and the sidewall configuration on generator performance are investigated experimentally and analytically in the UTSI channel. An analysis of the voltage-current characteristics between two generator frames measured during the operation of the TP40-07 experiment is presented along with the examination of nonuniformities of interframe voltage. Experimental data reveals that the polarization effect reduces about three percent of the overall electrical performance of the UTSI 60/sup 0/ Diagonal Conducting Wall (DCW) channel. A moderate increase of conductivity in the vicinity near the cathode-side frame gives a calculated leakage resistance which approximates the value derived experimentally. The polarization effect results in a large change of themore » potential and current distributions near the frame but has a small effect on the overall electrical performance. Alternate sidewall/electrode configurations are considered analytically.« less