Effects of blade loading distribution on hub leakage flow of cantilevered stator

The hub leakage flow of the cantilevered stator has a significant impact on the axial compressor loss and aerodynamic stability. The formation and development of the hub leakage flow are affected by the blade loading level and distribution, but the internal mechanism of this effect is not fully understood in previous studies. This paper uses a novel experiment facility with a high-speed moving endwall and numerical simulation methods to focus on the influence of a fore-loading and highly-loaded cantilevered cascade on the hub leakage flow and its mechanism, and compared with a typical middleloading controlled diffusion airfoil cascade. The results demonstrate that although the two cascades have different blade loading levels, the radial distribution of the entropy loss coefficient at the condition of moving endwall is almost identical, which is related to the development location and radial extent of the leakage flow in the two cascades. The position of maximum hub leakage flow rate is delayed relative to the position of maximum blade loading, due to the increase of circumferential momentum by the leakage vortex in the passage. The main cause for the entropy loss is the coupling effect between the product of the leakage flow velocity and injected angle and the mainstream velocity. Based on the findings of this paper, for the hub airfoil of the cantilevered stator, the fore-loading airfoil design can achieve higher loading capacity when the outlet entropy loss distribution is similar. This provides a useful idea for the design of cantilevered stator.