Influence of the S-shaped transition duct on stability and performance of an adjustable compressor with an annular clearance

The impact of inlet distortion induced by the S-shaped transition duct on an adjustable compressor was investigated, which has an annular clearance inside the stator flow passage. Steady and unsteady RANS numerical method was adopted and the results show that both the inlet distortion and clearance leakage flow could increase the stall margin and decrease the total pressure ratio and efficiency in an original compressor. However, in an adjustable compressor the stall margin is decreased by 5.5% relatively due to the inlet distortion. The tip leakage vortex (TLV) is decelerated due to inlet distortion, which makes it more prone to breakdown. In the stator flow passage, the clearance leakage flow has a more pronounced effect than the inlet distortion and causes the corner separation to expand. The inlet distortion exacerbates the annular clearance leakage flow (ALF) by 29.5% at hub region, which makes the flow condition more disordered and enlarges the corner separation. The unsteady characteristics proved that the ALF at the hub region has a more unsteady behavior. This study uncovers the coupling mechanism of the inlet distortion and stator clearance leakage flow in an adjustable compressor, providing a theoretical foundation for the aerodynamic and stability design.