Interaction mechanism between the tip leakage flow and inlet boundary layer in a highly loaded compressor cascade based on scale-adaptive simulation

Abstract

Based on the scale-adaptive simulation, the interaction mechanism between the tip leakage flow (TLF) and the inlet boundary layer (IBL) and its effects on the tip flow field and aerodynamic performance of the compressor cascade were investigated. The time-averaged results show that the IBL reduces the blade tip load near the leading edge region, decreases the axial momentum of the TLF, and inhibits the development of the TLF to a certain extent. On the other hand, the IBL promotes the coupling of the tip leakage vortex, secondary vortex, and separation vortex and induces breakdown, resulting in a large area of severe flow separation in the corner region, greatly reducing the diffusion capacity and significantly increasing the flow loss in the tip region. The analysis of the unsteady transient flow fields indicates that the unsteady fluctuation in the tip region is mainly caused by the tip leakage vortex and flow separation near the blade trailing edge. The former is suppressed under the influence of the IBL, while the latter is amplified. The high-intensity oscillation due to the breakdown and decomposition of the tip vortex structures plays a critical role in the fluctuation of the cascade performance. By means of proper orthogonal decomposition, it is found that the IBL enhances the fluctuation of small-scale vortex structures related to flow separation and leakage flow and makes the stability of the tip flow field worse.