Numerical investigation on discrete circumferential grooves casing treatment of axial flow compressor

Abstract

To ensure that aeroengines could adapt to complex operating conditions, stability margin is one of the mandatory indicators in the design process of axial-flow compressors. Expanding the stable operating range of compressors using flow control technologies such as casing treatment has long been a research hotspot in this field. Although conventional full-annulus casing treatment achieves a significant stability enhancement effect, it suffers from problems including large efficiency loss and structural limitations, resulting in limited engineering applications. To address the above issues, this paper proposes an improved scheme of discrete circumferential grooves casing treatment. Taking a high-speed subsonic axial-flow compressor rotor as the research object, numerical investigations are conducted to investigate the influence of different coverage ratios on the compressor performance. The results show that conventional full-annulus circumferential grooves increase the stability margin by 11.27% but reduce the peak efficiency by 0.61%. When the coverage ratio of discrete circumferential grooves is greater than 1/3, the stability margin is improved by no less than 6.42%, which meets the stability enhancement requirement while significantly reducing efficiency loss. Flow field analysis reveals that discrete circumferential grooves exert a discontinuous effect on the tip flow. They can act on two or three cascade passages simultaneously within one blade pitch, achieving multi-directional suction and injection of low-speed fluid near the blade tip and thus improving the internal flow. Meanwhile, discrete grooves draw part of the tip leakage flow crossing adjacent passages into the grooves, suppress the circumferential propagation of leakage flow, alleviate downstream passage blockage.