Rotating stall in a single-stage axial flow compressor

This paper describes the results on an experimental investigation of rotating stall flow inside a single-stage axial flow compressor: Tests were carried out in two steps. First, measurements were taken to investigate the transition process into rotating stall. The compressor starts into rotating stall via the ''modal route'' with a single rotating stall cell. Further throttling yields to a two-cell shape followed by a significant outlet pressure drop. Both transition processes are discussed in detail. Results from the Moore-Greitzer theory are compared with measured data. In a second step, measurements were taken to determine the three-dimensional unsteady structure of a fully developed rotating-stall cell. Based on unsteady total pressure and three-dimensional her-wire data, the structure of a rotating stall cell could be resolved in detail upstream and downstream of the rotor. A typical part-span stall was Sound. By inserting the measured data into the Euler equations, convective and unsteady effects on the pressure fluctuations can be isolated A dependence between the radial flow inside the stall cell and the unsteady pow accelerations was found.