Unsteady flow simulation of a transonic compressor coupled with casing treatment

A self-recirculating casing treatment is designed for a transonic compressor stage and its performance at 100% rotational speed is numerically investigated. The casing treatment consists of 9 segments within every rotor blade pitch and each segment is built by one bleed port, one injection port and one bridge channel connecting the bleed and the injection ports. The coupled unsteady flow through the compressor blade passages and the casing treatment is simulated with a state-of-the-art CFD solver TRACE. At the stator-rotor and the treatment-rotor interfaces a conservative zonal approach and a conservative mixed-cell approach are applied, respectively, both of which are in second-order accuracy. The calculated results show that the self-recirculating casing treatment herein is able to effectively extend the stall margin by improving the flow conditions near the casing and by weakening the tip leakage flow. The casing treatment is also found to be able to reduce the incidence to the downstream stator blade near the casing thereby delaying the separation over the stator blade suction surface. (author)