Stall Inception in a Compressor with Subsonic, Transonic, and Supersonic Inlet Conditions

A combined experimental and computational approach has been used to investigate the stall inception mechanisms and subsequent poststall behavior of a single-stage axial compressor running at different operating conditions, determined by its rotational speed. This paper emphasizes differences in the origin of stall inception depending on the associated inlet flow regimes: 60% speed (subsonic), 80% speed (transonic), and 100% speed (supersonic). At all speeds, stall is initiated with spike-type disturbances that develop into full-span rotating stall. This paper demonstrates for the first time that for a single compressor geometry, a variety of mechanisms can be responsible for the sources of the blockage leading to stall inception depending on the rotational speed. At 60% speed, the inlet flow is subsonic and the primary driver is a corner separation forming between the casing and blade suction surface. At 80% speed, the spillage of tip leakage jet ahead of the leading-edge plane combines with a small shock-induced corner separation to cause sufficient total blockage and subsequent stall inception. Finally, at 100% speed, the mechanisms are the same as at 80% speed but with a greater blockage contribution from the corner separation due to a stronger shock creating a larger separation.