Experimental and numerical study of recirculation hybrid casing treatments in a high-speed axial flow compressor

This study experimentally and numerically investigates the impacts of two recirculation-based hybrid casing treatments, namely recirculation-groove casing treatment (CT) and recirculation-slot CT, on the stability and performance of a high-speed axial compressor rotor. The results show that both hybrid CTs enhance compressor stability at the cost of efficiency loss. The recirculation-groove CT achieves a stall margin improvement (SMI) of 19.19% with only 0.57% peak efficiency loss (PEL), outperforming the recirculation-slot CT, which provides 16.29% SMI with 1.22% PEL. Numerical analysis reveals confirms that the degree of tip blockage mitigation is the primary physical driver for stability enhancement. The recirculation-groove CT’s superior performance is directly correlated with its ability to achieve the lowest overall tip blockage factor across the passage by robust tip leakage flow ingestion and effective downstream flow management. Furthermore, unsteady analysis reveals that the recirculation-groove CT imposes a quasi-steady control over the tip flow field through strong, multi-dimensional momentum transport, whereas the recirculation-slot CT relies on localized, fluctuating exchanges. The recirculation-groove CT is confirmed as the optimal configuration, fundamentally driven by superior blockage reduction and coherent momentum transfer.