Observations of Stall Cells in a Single Stage Compressor

Abstract

A specially developed pressure-measuring instrument has been used to observe instantaneous values of the pressure, velocity and direction of the flow in a single stage, low hub-tip ratio, axial compressor. During stall propagation, the flow appeared to change from a point on the unstalled characteristic towards a point on the fully stalled characteristic and back again. The stall cells occurred only at the tips of the rotor blades. Despite these large fluctuations in the instantaneous flow, the time-average overall pressure rise characteristic was of the "progressive stall" type. The experiment demonstrated, therefore, a realistic model for the theoretical analysis of fully-developed stall cells.