Understanding the Aerodynamic Damping Behavior of an Industrial Axial Compressor Rotor With Multi-Row Effects

The evaluation of aerodynamic damping in compressor rotor airfoils is key to predict forced response amplitudes, since the fluid flow effects generate the most important contribution to the overall damping. The experimental and numerical assessment of aerodynamic damping has been studied from a long time and different methodologies have been proposed and validated in the Literature: the first objectives of such studies were the evaluations of the flutter occurrence to design flutter resistant or tolerant configurations. Yet, the study of damping can be extended to stable configuration in order to distinguish between mechanical and aerodynamic contributions. The experimental campaigns are usually intended to measure the mechanical damping through in vacuum test campaign, or the overall damping with in-situ measurements (with strain-gauges or tip timing techniques). On the other hand, classical flutter method can be also applied to predict the positive damping from a numerical point of view. In this context, the paper presents an in-depth numerical investigation of aerodynamic damping of an industrial axial compressor transonic stage. The effect of multi row interaction is assessed in and out of resonance conditions. For a specific mode, the numerical predictions are compared with overall damping measured by processing the related frequency response.