Design and experimental investigations of a new type of casing treatment for an axial flow compressor

A new type of bend skewed groove casing treatment was designed on the basis of the test results of the axial skewed groove casing treatment. The influences of utilizing it on an isolated axial-flow rotor, as well as comparisons between it and the axial skewed groove, have been investigated experimentally. The effects on overall performance of the axial chord of the rotor exposed to the treated area have been examined, and the ideal axial position of the casing treatment relative to the rotor leading edge was found. For the tested rotor with the new casing treatment, experimental results showed that significant improvements in stall margin were observed without efficiency penalty (in some axial locations) at two different speeds. Compared with the axial skewed groove casing treatment, the new treated casing at the axial exposure does not increase the secondary circulation in the radial- circumferential plane based on x-wire, hot-wire measurements under the operating conditions near peak efficiency. This can be considered to be one of many factors that keep the rotor efficiency identical.