Experimental and Numerical Investigation of Blade Loading Influence on Aerodynamic Damping in an Axial Compressor

In recent years, both numerical and experimental research has been conducted to investigate the relationship between aeroelasticity and aerodynamic instabilities. Computational Fluid Dynamics (CFD) methods serve as a powerful tool for understanding unsteady flow phenomena, but their reliability depends on validation against experimental data. However, validation data for aerodynamic damping remains limited. Additionally, accurately measuring the aerodynamic damping of rotating test objects remains a significant challenge. This paper presents reliable damping measurements conducted in closed-loop axial compressor facility, focusing on the influence of blade loading on aerodynamic damping. Aerodynamic damping measurements were performed at four operating points, all at the same rotational speed, including conditions near stall. The aerodynamic damping was measured by sweeping the excitation frequency and measuring the frequency response. Measurements were taken at three inlet total pressure levels to extrapolate damping at vacuum conditions. The measurement data showed minimal influence of mistuning, as all blades exhibited the same peak frequency and nearly identical damping values. No sudden changes in aerodynamic damping were observed across different blade loading conditions, however, damping tended to increase as blade loading increased. CFD simulations predicted the aerodynamic damping well with an average relative error of 15 % and a maximum relative error of 34 %. The simulation indicated that most of the aerodynamic work acted on the suction surface in a stabilizing manner. As the blade loading increased, the location of maximum aerodynamic work shifted upstream. However, this shift had no significant impact on the aerodynamic damping in this test object. The validated CFD code can be used to further investigate the aeroelastic behavior of similar test objects.