This paper performs time-accurate 3Dunsteady numerical simulations on Rotor37 with cases of screwed slots

slots with cell

and semicircle slots respectively in order to improve casing treatment and acquire lower mass flow at near stall condition.The presented results show that the stall margin increment of slots is closely related to their effects on the leakage flow and their ability to suck the leakage vortex under the help of differential pressure at blade tip.If enough transfer ability is available

the higher the pressure head is

the more powerful the suction will be

and more significant increase will be gained in nearsurge flow stability.The cell on the top of slots can improve the condition of translation with an effect to expand stall margin.And screwed slots angular to the blade can make use of more pressure head between its inlet and outlet to enhance suction;however

non-negligible decreases in efficiency are also observed in this situation.