Stall Propagation in a Cascade of Airfoils

A small perturbation analysis of rotating stall is presented which includes the effects of finite pressure rise across the cascade, finite blade chord, and boundary-layer time delay. The theory yields a stability criterion for the initiation of rotating stall, upper and lower boundaries for the velocity of propagation, and a possible explanation for the mechanism governing the number of stall cells. Tests on rotating stall in a cascade and two rotors suggested a vortex-shedding model for fully developed rotating stall which is not limited to small perturbations and which appears to agree closely with the observed stalling mechanism.