Stall propagation in axial compressors

Abstract

A theory of stall propagation in a cascade of airfoils of high solidity has been developed which includes the effects of finite blade chord and of the boundary layer response to changes in angle of attack. The theory is valid for small perturbations in velocity about a mean flow- condition with finite pressure rise across the cascade, provided that the pressure fluctuations behind the cascade are much smaller than those ahead of the cascade. The solution for the velocity of stall propagation indicates that the velocity increases with the wave length of the stall cell, tending towards a limiting value for very large stall cells. The wave length of the stall cells at the beginning of rotating stall is dependent on the magnitude of the boundary layer time delay. The theory predicts propagation velocities within 25% over a wide range of wave lengths for a stationary circular cascade and a rotating blade row which have been tested. The experiments have confirmed that an increase in wave length is accompanied by an increase in propagation velocity if other parameters are unchanged.