Stability analysis of large-scale coal-fired subsonic diagonal type MHD generators considering inlet and exit conditions

Abstract

The local linear perturbation analysis and the linear stability analysis of channel-length scale are carried out for coal-fired subsonic MHD generators of commercial scale. A disturbance in subsonic flow propagates with downstream and upstream traveling waves, and those waves reflect at inlet and exit boundaries. The local linear perturbation analysis examines the local growth rate of traveling waves which is determined by a dispersion equation. The linear stability analysis of channel-length scale, which is based on the characteristic equation derived from the inlet and exit boundary conditions, judges whether the waves grow or decay during their propagation and reflection. The local linear perturbation analysis shows that a conventionally designed channel which has near sonic velocity has a large growth rate of waves and tends to be unstable. A newly designed channel which has relatively low velocity has small growth rates. The linear stability analysis shows that disturbances in the conventionally designed channel grow during their propagation and reflection. The analysis of channel-length scale also shows that the newly designed channel can be stably operated. The results of linear stability analyses are confirmed by time-dependent calculations. (Author)