Experimental Comparison of Jet Modes Using Self-Excited Sweeping Jet Actuator in Compressor Cascades

Self-excited sweeping jet actuators (SSJAs) are effective for controlling flow separation in compressors. To improve their adaptability and effectiveness, this study introduces a novel jet-mode switching strategy via the opening and closing of feedback channels. Wind tunnel tests and oil-flow visualizations were performed on a controlled diffusion airfoil (CDA) compressor cascade under various incidence angles to assess four jet modes: steady-straight jet (SSJ), steady-upward jet (SUJ), steady-downward jet (SDJ), and unsteady sweeping jet (SWJ). Among them, the SWJ mode showed the best overall performance by effectively delaying profile separation. It induces streamwise vortices that enhance momentum exchange near the wall, reducing total pressure loss by up to 28.2%. Steady modes provided limited control, with SDJ even increasing corner losses. In contrast, SUJ significantly reduced corner separation under near-stall conditions, demonstrating its specific advantage among steady modes. By elucidating the distinct mechanisms of each jet mode, this study proposes a flexible and energy-efficient flow control method. The findings offer new insights for enhancing aerodynamic performance and extending the stable operating range of axial compressors without added complexity.