Experiment investigation on secondary flow loss and flow control mechanisms in a variable compressor cascade with penny cavities

Variable Stator Vanes (VSVs) with penny cavities are an important method to improve the efficiency of compressors. However, the annular and radial gaps in VSVs introduce complex flow structures, posing challenges in enhancing compressor efficiency. This article employs low-speed wind tunnel experiments to study the impact mechanisms of VSVs' adjustment angle and radial gap size on secondary flow losses and implements single-hole suction as a means of flow control to reduce total pressure loss. The results indicate that radial gap leakage has a certain inhibitory effect on annular gap leakage at general adjustment angles. Total pressure loss decreases initially as the radial gap increases but once the radial gap further enlarges and dominates the loss components, the total pressure loss increases proportionally with the radial gap. At extreme adjustment angles, where the lateral pressure gradient is significant, radial gap leakage intensity is high and comprises the major part of the loss, leading to an increase in total pressure loss in proportion to radial gap enlargement. Additionally, single-hole suction is effective under various conditions, with the potential to reduce total pressure loss by up to 19.4 %. These findings provide guidance for the application of VSVs in further improving compressor efficiency.