The stall inceptions in an axial compressor with single circumferential groove casing treatment at different axial locations

Circumferential groove (CG) casing treatment is known to be a good method to improve the stall margin of axial compressor. Recent studies on single groove indicate the stall margin improvement (SMI) is significantly affected by groove's axial location, which means the effects of the groove on the passage flow should be further studied as the groove's axial location is changed. In this paper the features of stall inception with and without the groove treatment are experimentally researched in a low-speed axial compressor. The contour of static pressure on casing is obtained by fast-response pressure transducers concentrative mounted as a line in chordwise direction, and the data acquired by transducers in circumferential direction is processed with the method of wavelet analysis to demonstrate the development of stall inception. It is found the stall inception is the typically spike-type for smooth casing (without treatment), which is manifested as short-scaled disturbance of only 2-4 blade passages when it appears. Two single grooves at different axial locations, which can be ineffective and effective in SMI, are further tested. The results indicate the stall inception is still spike-type for both of them. However, for the ineffective groove, the stall inception is found to be relatively longer-scaled disturbance. For the effective groove, it is still the typical short-scaled disturbance similar to the smooth casing. In the further study on double grooves treatment in which the ineffective groove is included, the stall inception is also found to be relatively longer-scaled type. According to these experimental results and previous CFD simulation, the groove with almost no SMI is believed to take different effects on the compressor which modifies the stall inception into the relatively longer-scaled type, and the corresponding tip-region flow structure deserves more future study in this regard.