The improved effect of casing treatment in axial compressors was studied by using an unsteady simulation method.Numerical calculation was performed for the cavity casing treatment with oblique slots under one-rotor and one-stage environment as well as for axial slots casing treatment of Rotor 37.The influence of downstream stator upon casing treatment simulation was also analyzed.The results show that

this computation method could simulate unsteady casing treatment

but the casing treatment cannot extend the stall margin of a compressor until the dangerous section is near the tip of rotor blade.It's found that the real role of casing treatment cannot be manifested accurately under one-rotor environment

and the presence of downstream stator would change the dangerous section of upstream rotor.