Effects of stator blade stagger angle variations on flow characteristic and stability in a subsonic compressor

Variable stator vane (VSV) technology, which modulates the rotor incidence angle to adapt to off-design conditions, is an effective means of regulating compressor performance. However, the detailed flow mechanisms underlying this performance improvement require clearer elucidation. To elucidate the flow mechanisms responsible for stall margin enhancement and efficiency improvement, and to thereby establish a theoretical basis for optimizing VSV scheduling strategies, this work employed a combined experimental and numerical approach. The stagger angle was adjusted over a range of ±10° by rotating the blade profile about its radial stacking axis. While the variation had a negligible effect on the stall inception mass flow rate, it significantly influenced the pressure rise and efficiency. A positive adjustment of +10° increased the stage static pressure rise by approximately 8.9 % and improved the efficiency by roughly 7 % under near-stall conditions. Conversely, a −10° adjustment resulted in a substantial reduction in the near-stall pressure rise of approximately 21.4 % and degraded the efficiency across the entire operating range. Flow field analysis revealed that stagger angle variation primarily influences flow separation in the stator by modifying the incidence angle and diffusion factor, with limited impact on the rotor loading. Furthermore, unsteady simulations confirm that stall inception in this compressor is predominantly driven by the accumulation and blockage of tip flow, which originates from radial flow at the rotor trailing edge, coupled with the influence of rotor tip-leakage flow, and is independent of variations in the stator stagger angle. These results elucidate the aerodynamic mechanism by which VSV modulation affects stage matching, thereby providing a theoretical foundation for optimizing VSV scheduling strategies to extend the efficient operating range of single-stage compressors.