Transient phenomena in coal-fired MHD generators: electrical effects of slag in a diffuse-mode magnetohydrodynamic generator. Final report

Technical Report · Mon Mar 01 04:00:00 EST 1982

OSTI ID:5329453

Nelson, R M; Koester, J K; Eustis, R H

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 experimenal 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.

• Research Organization: Stanford Univ., CA (USA). Dept. of Mechanical Engineering
• OSTI ID: 5329453
• Report Number(s): EPRI-AP-2290; ON: DE82904376
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
300104* -- MHD Generators-- Duct Engineering & Fluid Dynamics
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BREAKDOWN
CHALCOGENIDES
COAL-FIRED MHD GENERATORS
COATINGS
COMPUTER CALCULATIONS
CURRENTS
DIRECT ENERGY CONVERTERS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
ELECTRODES
LEAKAGE CURRENT
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MHD CHANNELS
MHD GENERATORS
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
PHYSICAL PROPERTIES
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
PROTECTIVE COATINGS
RHODIUM ALLOYS
SLAGS
TRANSIENTS