EXPERIMENTAL INVESTIGATION OF ROTATING STALL IN A HIGH SPEED MULTI-STAGE AXIAL COMPRESSOR

Pressure measurements using high frequency response sensors have been carried out in the 31/2-stage high speed compressor CREATE (rotation speed: 11543 RPM, Rotor 1 tip speed: 313 m/s). The pressure signals obtained at several axial positions during the onset of instabilities are first presented. Before the surge, 12 rotating stall cells are characterized and are localized in the region of the interactions between the tip clearance flow and the stator wakes. Their rotation velocity (85% of the rotation speed of the compressor shaft) has been measured using 6 sensors equally spaced over the circumference. This paper shows how the rotating stall cells influence the flow field in the whole compressor and finally collapse into one large and unique cell, leading to the surge.