Flow mechanisms and loss analysis of cavity leakage flow in a 1.5-stage axial compressor

Due to the coupled effects of various cavity leakage flows, the loss mechanisms induced by leakage flow in multi-stage compressors remain insufficiently understood. Investigating leakage flow within a stage environment is crucial for revealing these mechanisms. In this paper, a 1.5-stage compressor without and with a labyrinth seal is modeled to elucidate the flow propagation mechanisms of leakage flow on the upstream and downstream rotors. Performance testing of a multi-stage compressor with labyrinth seals is conducted to validate the accuracy of numerical method. Furthermore, by introducing local entropy generation rates, a sub-regional method for quantifying losses originating from different sources is proposed. The results reveal a surprising finding: leakage flow reduces the downstream rotor losses by 1.14 %. This reduction is attributed to the improved flow field in the midspan region and the accumulation of low-energy fluid, which leads to a 0.08 % reduction in boundary layer loss. The mixing of leakage flow with the mainstream occurs at the stator leading edge, significantly altering the stator flow field. The newly generated cavity leakage vortex and the enlarged corner vortex increase secondary flow loss by 0.53 %, while the accumulation of low-energy fluid in the hub region raises mainstream loss by 2 %. This study offers valuable insights into mitigating losses caused by leakage flow and provides a theoretical foundation for controlling the impact of leakage flow in compressors.