Stall transients of axial compression systems with inlet distortion

A previously derived system of differential equations, based on fluid mechanics, is extended to provide a theory to predict how rotating stall or surge will develop in an axial compression system under combined influences of inlet distortion and throttle ramping. Results are relevant to the problem of stagnation stall of gas turbines. It is found that stall margin is improved by large aerodynamic lag in the compressor. Both stall and recovery transients are considered. A distinction between axisymmetric and in-rotating-stall compressor performance characteristics leads to a concept of rotating-stall stability that explains the appearance of classic stall at low stage loading and the hysteresis associated with rotating stall. The influences of various system parameters are systematically explored, and the large B parameter, tall compressor characteristic diagram, and rapid throttle closure are all found to favor surge, while large distortion and small shut-off head relative to peak pressure rise both favor rotating stall. When surge occurs, rotating stall is usually also present.