The influence of a coupled casing on the performance of a multistage compressor under inlet distortion conditions

Abstract

In order to increase the stalling margin of a compressor under different inlet conditions, especially under inlet distortion conditions, a new coupled casing processing structure is proposed in this paper. The new structure combines the characteristics of traditional circumferential slot and axial slot casing treatments. First, based on numerical simulation results of the simplified calculation model, a control variable method is used to design the coupled casing treatment and an effective casing treatment scheme (CCTF) is obtained. Then, experiments and multistage full-channel numerical simulations are used to study the effect of CCTF on the compressor performance under uniform and distorted inlet conditions. The stability expansion effect and the mechanism of the structure under inlet distortion conditions are analyzed in detail. The results show that the jet in CCTF obstructs the main flow and causes additional mixing loss, but inhibits the expansion and crushing of the leakage vortex, thus increasing the stall margin of the compressor. Under near-stall conditions, the tail-circumferential groove provides about 64.8% of the flow rate, which improves the stability expansion capability of the casing treatment. When there is distortion at the inlet, CCTF can still effectively improve the stability.