Influences of athwart blade-angle slots casing treatment on the performance of subsonic axial-flow compressor were investigated with the experimental and unsteady numerical simulation methods. The experimental and unsteady numerical calculation results showed that the rotor gained about 30.1% stall margin improvement at the cost of decreasing about 12% peak isentropic efficiency of smooth wall casing with athwart blade-angle slots casing treatment. The detailed analysis of rotor blade tip flow-field indicated that the tip clearance leakage flow was improved with athwart blade-angle slots casing treatment and the blockage created by low energy clearance leakage flow in blade tip was removed in blade tip with smooth wall casing

so the stability of rotor was improved. It was found that the ability to improve rotor stability of slot was affected by the relative position of blade and slot

and moreover

back flow in slot and the interaction of injecting flow brought by slot and blade tip mainstream resulted in serious flow loss

leading to decline of the rotor isentropic efficiency. The numerical calculation results also showed that the stall margin improvement and the level of decreasing isentropic efficiency reduced about 10.4% and 64% respectively by making the athwart blade-angle slots casing treatment move forward about the 55% axial chord of blade tip.