Investigation of transitional flow in a transonic compressor rotor with hub leakage using large eddy simulation

Abstract

The hub leakage flow has been acknowledged as an important factor for performance deficiency of axial-flow compressors. Meanwhile, the laminar-turbulent transition in compressors is highly sensitive to the upstream flow state and significantly affects the flow loss. In the present work, quasi-wall-resolved large eddy simulation of a transonic axial-flow compressor rotor at the near-peak-efficiency point is carried out to investigate the effects of hub leakage as well as its absolute tangential velocity on the compressor performance and the laminar-turbulent transition in the blade passage. It is confirmed that the hub leakage with an absolute tangential velocity of 0.5 wheel speed can result in the near-hub total pressure deficit. With the hub leakage taken into account, the predicted total pressure ratio and adiabatic efficiency agree well with the experimental data. The simulation results indicate that increasing the absolute tangential velocity of hub leakage would intensify the near-hub vortices, elevate the endwall turbulence level, increase the near-hub flow loss, and cause a remarkable total pressure ratio drop. This work promotes the understanding of complex flow mechanisms in axial-flow compressors in the presence of hub leakage.