Numerical investigation on mixed recirculation casing treatment in centrifugal compressor

The casing treatment is one of passive control techniques to extend the operating stability of centrifugal compressor and has been successfully adopted, commonly in the impeller. In the paper a mixed recirculation casing treatment simultaneously used in the impeller and diffuser is presented, and its effect on the extension of operating range as well as the mechanism is investigated numerically. The results shows that, an appropriate mixed recirculation strategy can increase the stall margin of compressor by 9.39% though at the costs of the efficiency sacrifice of 1.7% under the design condition.