Stall propagation in a cascade of airfoils

Abstract

An experimental investigation of stall propagation in a stationary circular cascade by means of high speed schlieren and interferometer photography is described. This investigation suggests an analytical approach to the problem which is valid only for an isolated blade row in an infinite flow field but which is not restricted to small unsteady perturbations or an assumed simplified cascade geometry. Conditions necessary for the existence of the assumed type of stall cells are described and equations are derived for the velocity of stall cell propagation. The propagation velocities predicted for the theoretical potential flow-model correlate with all the experimental values measured in an isolated rotor within 15%. Analysis of the flow model predicts a tendency for the assumed type of stall cell to split with increasing incidence of the mean flow through the blade row which appears to correlate with the experimental observation of a trend for increasing numbers of cells in the rotor.