Mechanism of influences of axial positions of axial skewed slot casing treatment on a compressor performance

Two investigations were performed for an axial-flow compressor rotor to explore the effects of axial positions of axial skewed slot casing treatment on the rotor performance. The steady operating range of compressor rotor was extended and the compressor efficiency was reduced with all casing treatments in the experimental and numerical investigations. The ability to improve the rotor steady operating range was the best when the axial position of casing treatment was unchanged. The ability was depressed obviously by moving the axial position of casing treatment backwards. The degree of damage on compressor isentropic efficiency was decreased when the axial position of casing treatment was moved forwards or backwards. The detailed analyses of the flow-filed in compressor with casing treatment indicate that, the development of tip leakage vortex could not been restrained by moving the axial position of casing treatment backwards, and the pumping ability of slot was reduced likewise, thus weakening the effect of extending the steady operating range of compressor; the work of blade forcing on air in the blade tip was not only increased, but also the flow loss caused by tip leakage flow and secondary flow were reduced when the axial position of casing treatment was moved forwards or backwards, making the rotor isentropic efficiency increase if compared the slot with axial position unchanged.