Enhancing the stability of a high pressure ratio centrifugal compressor by using vaned diffuser recirculation

Pressure ratio, efficiency, and the stability operating range are the major criteria used to assess a centrifugal compressor. In this paper, a high pressure ratio single-stage centrifugal compressor is considered as a research object. A parametric investigation of recirculating flow control technology is used to treat the casing of the vaned diffuser in order to improve the compressor stall margin. The maximum achievable improvement in the comprehensive stall margin is 3.90%. The paper discusses how different injection configurations (circumferential and radial distributions) of the recirculation structure in the diffuser impact the flow field. The mechanism of influence of the injection opening position on the stall margin is explored. By implementing this technology, a reduction in the inlet Mach number at a high spanwise position of the diffuser, results in an increased critical incidence angle. Additionally, the technology effectively reduces flow separation at the throat of the diffuser and increased the flow area within this region. A comprehensive analysis is conducted to investigate the mechanisms underlying the influence of injection opening position on different energy loss categories in diffuser. A detailed discussion on the impact of casing treatment on high pressure ratio centrifugal compressors is provided, focusing on two aspects: expanding stall margin and efficiency loss.