Impact of acoustic wave propagation characteristics on aerodynamic damping of rotor blades in a transonic axial compressor

The aeroelastic stability associated with the acoustic wave propagation characteristics of transonic rotor blades was numerically investigated in this study. The influence of the vibration frequency on the aerodynamic damping of the first bending mode was primarily considered at different speeds, including both work and stall points. We found that the state of acoustic wave propagation associated with aeroelastic instability is closely related to rotational speed. At low speeds near stall points, the risk of aeroelastic instability is confined to the upstream cut-off state. However, at high speeds near stall points, aeroelastic instability may occur in both the downstream cut-off state and the acoustic wave propagation state of the upstream cut-off frequency, further expanding the range of the acoustic wave propagation state in which aeroelastic instability can arise. The research findings show that for suction surfaces, aerodynamic work is affected not only by acoustic wave propagation characteristics, but also by shock waves, radial flow, and reflux in the flow field. However, for pressure surfaces, the acoustic wave propagation characteristics play a significant role. When aeroelastic instability occurs, negative damping predominantly arises from the pressure surface. To investigate why lower-order modes are more prone to aeroelastic instability, specific simulations were conducted for the first bending and twisting modes under different operating conditions in the downstream cut-on state. When the vibration frequency significantly exceeds the downstream cut-off frequency, the blade phase is minimally influenced by acoustic wave propagation characteristics, and the rotor is aeroelastically stable in these phases. Simultaneously, there is an approximately linear increase in the unsteady pressure amplitude with increasing vibration frequency, and the aerodynamic work is predominantly influenced by the unsteady pressure amplitude.