Stall inception and control in a transonic fan, part B: Stall control by discrete endwall injection

This paper reports on a half-annulus numerical investigation of discrete tip injection in a transonic compressor rotor. The effect of injection on controlling stalling disturbances is investigated by activating endwall injection at an in-stall condition, caused by an enlarged-tip blade. Furthermore, choke to stall time-accurate computations have been carried out in order to study the effect of discrete injection on extending the stable operating range. Investigating the near-stall condition with injection reveals that the occurrence of the time-averaged leading-edge vortex spillage is the key path to stall inception, similar to the smooth casing. Nonetheless, when tip injection is discrete, limited instantaneous vortex spillage can occur over the leading edge of the blades approaching the injector.