Numerical study of the coherent characteristics of the blade tip of a micro centrifugal compressor and its application in a new unsteady casing-treatment experiment

The tip-leakage vortex, as the dominant coherent structure of the blade tip of a compressor, is an important source of losses in centrifugal compressor rotors; it limits the stall margin and can even cause compressor surge. The miniaturization of mechanical components has attracted significant attention; however, the miniaturization of compressors—particularly centrifugal compressors—further increases the adverse effects of the tip-leakage vortex. This study sought to establish a new passive unsteady flow-control method for a micro centrifugal compressor using equal-circumferential-spacing through-holes on its casing. This approach fully exploits the unsteady characteristics of the flow field. A numerical study of the coherent characteristics of the blade tip was carried out using dynamic mode decomposition. The numerical conclusions were then applied to a physical system. The results of experimental tests of this system indicate that the improved flow-control method can increase the maximum efficiency and stall margin of the compressor by 2.5% and 9.0%, respectively, and it can also increase the maximum pressure ratio.