Observations of Propagating Stall in Axial-Flow Compressors

This report gives the results of experimental investigations of an axial-flow compressor in stall. Hot-wire anemometer measurements of the velocity fluctuations in stalled operation of an axial-flow compressor have demonstrated that stalling occurs for the most part in well-defined regions over the compressor annulus. These regions rotate without changing shape in the direction of the blade rotation with a speed proportional to, but of smaller magnitude than, the rotor speed. Two principle types of propagating stall were observed, one with the stalled region or regions extending over part of the blade height, the other with a single stalled region over the full blade height.