Electrical effects of slag in a diffuse mode magnetohydrodynamic generator

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5582737

Nelson, R M

Since the performance of a magnetohydrodynamic (MHD) generator depends on the variation of electrical properties throughout the generator, and coal slag deposited on the generator walls can dramatically change the property distributions, it is important to investigate these effects. A high temperature (1900/sup 0/K) platinum-rhodium capped magnesia electrode was developed and successfully tested in a slagging MHD generator. Diffuse mode (non-arcing) operation of high temperature anodes was achieved at current densities up to 3 amps/cm/sup 2/. The problem of cathode shorting caused by the ionic nature of slag electrical conductivity (with iron as the major mobile species) was not substantially alleviated by high temperature operation. A computer code was developed which solves the governing electrical equations along with slag energy and thickness equations for a two-dimensional, periodic electrode pair in a slagging MHD generator. The numerical results compare favorably with the experimental results including cases with shorted cathode walls. The computer model was used to assess the effects of slag and other operating parameters on generator performance. Allowing axial current leakage was found to be the major effect of slag on MHD generator performance. Axial current leakage decreases and performance improves for smaller magnetic fields, less cathode shorting, larger channels, higher wall temperatures, and higher current densities. Using the most reasonable property models currently available, it appears that axial current leakage will be small for a well designed, large-scale, MHD generator.

• OSTI ID: 5582737
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
300102* -- MHD Generators-- Performance & Testing
COAL-FIRED MHD GENERATORS
COMPUTER CODES
DIRECT ENERGY CONVERTERS
ELECTRICAL PROPERTIES
ELECTRODES
MHD GENERATORS
NUMERICAL SOLUTION
PERFORMANCE
PHYSICAL PROPERTIES
SLAGS