Wake Vortex Shedding and Circulation-Based Correlations for Time-Averaged Performance in a Subsonic Compressor

Enhancing compressor loading through unsteady mechanisms has long been of interest. Based on unsteady numerical simulations of the TA36 low-speed axial compressor stage, this study investigates wake vortex shedding to clarify the mechanism of unsteady aerodynamic effects under different rotor-stator spacing conditions. The results show that, at small rotor-stator spacings, wake vortex shedding occurs in both the spanwise and streamwise directions. Spanwise shedding is caused by the misalignment between the rotor trailing edge and stator leading edge, and it periodically influences the stator suction-side flow and suppresses corner separation. Streamwise shedding is induced by the stator leading-edge pressure potential, forming periodic vortices within the stator passage at the blade-passing frequency. To quantify their aerodynamic effects, two circulation-based correlations are established. One relates the relative circulation of the spanwise shedding vortex to the corner-loss coefficient, and the other links the circulation of the streamwise shedding vortex to the total pressure rise increment. These correlations provide a quantitative connection between instantaneous shed-vortex circulation and time-averaged compressor performance. Under the present conditions, the unsteady effects lead to a total pressure rise coefficient gain of up to 0.03 and an efficiency increase of up to 2.90 percentage points. The present study provides a circulation-based quantitative framework for interpreting unsteady aerodynamic effects in axial compressor stages.