Working Gas Oscillation in Open-Cycle Faraday MHD Generator

Abstract

A theoretical study based on time-dependent quasi-one-dimensional approximation has been carried out to estimate the interaction between combustor noise and working gas oscillations in a magnetohydrodynamic (MHD) generator, and also to gain information on the behavior of shock waves induced by fault affecting some of the DC-AC inverters. The MHD generator considered here is an open-cycle Faraday-type 25 MW-class generator fueled with heavy oil.
The results of calculation indicate that relatively high frequency components of combustor noise (say above 10 kHz) would be conveniently attenuated through the MHD channel, but that low-frequency components would be transmitted along the channel, and this would, in turn, produce standing pressure waves of a frequency of around 2 kHz.
Short-circuiting of a batch of inverters proves to induce a rapidly amplifying pressure wave, accompanied by a significant depression of gas velocity. The pressure wave and velocity depression fronts propagate upstream through the flowing gas at sonic velocity relative to the gas.