Theory of compressor stability enhancement using novel casing treatment, part II: Experiment

A stall precursor-suppressed casing treatment is designed to enhance stall margin for both subsonic and transonic compressors. It is noted that the open area ratio of the stall precursor-suppressed casing treatment is only 4-10%, far smaller than conventional casing treatments, with over 50% open area ratio. The effect ofthe novel casing treatment on the stall margin and efficiency of compressors has been investigated experimentally. The results show that the stall precursor-suppressed casing treatment can improve the stall margin by about 8-18% without significantly decreasing the efficiency of the related fan/compressors. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with such casing treatment. It is found that the stall precursor-suppressed casing treatment will delay the nonlinear development of the stall process by suppressing the propagation of the stall precursor waves, as compared with the evolution of the precursors without casing treatment. This is consistent with the design strategy of the stall precursor-suppressed casing treatment.