An experimental study on annular clearance flow control strategy using hole-type suction in a variable stator vane cascade

Variable stator vane (VSV) is widely adopted to extend the stable operating range in advanced compressors, but it also introduces annular clearance leakage which causes tremendous loss production. Therefore, the controlling strategy using hole-type suction is investigated to suppress the annular clearance leakage and aerodynamic loss. Flow visualization and detailed flow-field measurements identified three critical secondary vortex structures: the suction-side annular clearance leakage vortex (ALVSS), pressure-side annular clearance leakage vortex (ALVPS), and radial clearance leakage vortex (RLV). Subsequently, six endwall suction hole positions were strategically designed to target these vortices. Among these, suction at the low-speed region between the ALVSS and ALVSL demonstrated the most substantial reduction (12.84%) in total pressure loss, effectively suppressing both formation of ALVSS and its coupling with the RLV, whereas suction targeting the ALVPS had minimal effect. Further analysis revealed that the suction hole positioned at the RLV region could consistently outperform other suction holes under lower suction flow rates and maintain superior effectiveness. These findings highlight the importance of strategically aligning suction locations with dominant vortex generation zones, demonstrating that hole-type suction at critical locations could effectively enhance compressor aerodynamic performance.