Analysis of Stall Mechanism and Flow Control Strategies for Stability Enhancement on a Nine-Stage Axial Flow Compressor

Efficient and stable operation across an extended range of conditions remains a primary objective in multi-stage axial compressors. In this context, thoroughly investigating the stall mechanism in compressors equipped with variable stator vanes (VSVs) and developing effective flow control strategies is crucial for enhancing stability. This study presents a systematic numerical investigation aimed at improving the aerodynamic stability of a nine-stage axial compressor. A detailed examination of the stall mechanism revealed that, at 74.1% of the corrected design rotational speed, the root leakage flow from S1, S2, and S4 (where Si denotes the stator of the ith stage) obstructs the stator passages, ultimately driving the compressor into an unstable state. Based on this finding, the platforms of S1, S2, and S4 were advanced, leading to the design of the move platform forward (MPF) flow control strategy. The MPF strategy resulted in a normalized peak efficiency improvement (NPEI) of 0.9% and a stall margin improvement (SMI) of 1.62%. However, limitations in enhancing the internal flow field remained. Consequently, a combined flow control strategy was devised by integrating the forward movement of the S1, S2, and S4 platforms, optimized hub line configurations, and partial stator modifications. The results indicate that the combined strategy more significantly enhances compressor performance, achieving an NPEI increase of 1.46% and an SMI improvement of 9.62%, while exerting a less pronounced effect on the near stall (NS) mass flow (MF) compared to the MPF strategy.