Casing treatment effects on a multistage axial compressor over a wide range of Reynolds number

This study investigates the effects of casing treatment (CT) on a multistage axial compressor over a wide range of Reynolds numbers (Re) through experimental and numerical methods. A compressor test rig with continuously variable Re was employed to evaluate the CT's impact on compressor performance. The CT improves the compressor stall margin by 3.73%, 12.27%, and 18.16% at Re = 8.7 × 105, Re = 1.2 × 105, and Re = 4.5 × 104, respectively. Numerical simulations further reveal the stall mechanisms at varying Re and the operational principles of the CT. At Re = 8.7 × 105, stall initiates in the first stator due to flow separation near the hub, exacerbated by a low-momentum region. The CT mitigates hub-side blockage and redistributes the spanwise flow field, improving stator inlet conditions. At Re = 1.2 × 105, stall is linked to trailing-edge separation at the first stator blade tip, caused by upstream rotor suction surface separation that worsens the stator inlet flow. The CT alleviates rotor blade tip separation, improving stator inlet incidence and delaying stall onset. At Re = 4.5 × 104, stall originates at the first rotor blade tip, driven by the interaction of tip leakage flow and suction surface separation. The CT suppresses leakage flow and reduces radial transport, significantly improving tip flow characteristics. These findings demonstrate the CT's ability to improve compressor stability over a broad Re range, offering insights for optimizing the CT designs in advanced axial compressors.