The effect of different clearance geometry configurations on aerodynamic performance in a high-load compressor cascade

The clearance flow of compressor variable stator vanes has a significant impact on compressor performance. Most clearance flow experimental research work has been carried out in compressor cascades with lower turning angle (lower load). The clearance flow in a higher load compressor cascade is relatively more complicated due to three-dimensional (3D) flow separation. In the present work, the effects of different heights and locations of clearances in a compressor cascade on aerodynamic performance and separation flow were investigated experimentally in a low-speed plane cascade wind tunnel. The objective of this investigation is to study the characteristics of different clearance configurations depending on the clearance height and the clearance axial position, and make an attempt to verify the possibility of a local clearance flow that improves the performance. The cascade outlet section aerodynamic parameters were measured by "L" five-hole probe. The ink-trace flow visualizations on the cascade surface and lower end wall were performed. The results show that with the increase in clearance size, the core area of high loss is moving to the end wall and the morphology of limiting streamlines on the suction surface changes gradually from separation lines to reattachment lines. The separation lines on end wall gradually moved to the middle of the cascade and the separation area increased gradually. The above reasons caused high loss zone gradually extended to the end wall. Thus, the loss at mid-span declined slightly while the loss on the end wall was increasing. Otherwise, cascade load reduced significantly when the clearance height became 3 mm, and the change magnitude of limiting streamline morphology in the flow field which was influenced by clearance flow at the rear of the blade reached to a minimum. So the loss and load came to a minimum, respectively. The impact of the clearance in the rear of a blade on loss and flow is weaker than the other schemes, with a slightly larger loss and separation with respect to the original scheme without a clearance. It may be expected to improve the cascade performance further by an appropriate design of clearance near the trailing.