Stability of open-cycle supersonic disk MHD generator

Abstract

The present paper analyzes the stability of open-cycle supersonic disk MHD generators, and discusses the effects of their load conditions on stabilizing the generators. A sensitivity analysis evaluates the spatial growth rate of inlet disturbances during propagation along the MHD channel. The analysis shows that the growth rate (the sensitivity) is greatly affected by the load conditions and that constant load current operations result in very high sensitivity. The paper then proposes a method of linear stability analysis for supersonic disk MHD generators considering their load conditions in order to analyse an instability induced by load current disturbances. Whether the disturbances grow or decay is judged in a way similar to Nyquist's method. The sensitivity analysis, the linear stability analysis and time-dependent calculations show that the constant load voltage operation with multiple-loading schemes is effective in suppressing instability and high sensitivity and that series inductors do not always stabilize the generator.