Investigation of Spike Stall Inception and its Propagation in a Low Speed Axial Compressor Rotor

Investigation of spike stall formation and its propagation in a low-speed axial-flow compressor is the main aim of this study. Experimental measurements are performed in a low speed axial compressor test rig. Measurement parameters include instantaneous velocity and static pressure at the stall inception process. For this purpose several hot wire probes and a high response pressure transducer is used in data acquisition procedure. Instantaneous fluctuations of velocity at upstream of the blade row show that spike stall inception is accompanied by flow separation from the leading edge of the rotor blade and formation of a vortex subsequently. This vortical structure extends over the blade span. Stall cell propagates with a circumferential speed lower than rotor wheel speed which is equal to 66% of rotational speed in this compressor. Furthermore, wavelet frequency analysis is employed for detail investigation of spike disturbances and capability of this method in distinguishing the spike stall is presented. Wavelet analysis, by representing the temporal variation of frequency spectrum, shows dominant phenomena in the transient process from stable operation to the stall inception condition.