Effect of Front and Rear Rotor Stages on Aeroelasticity in Multi-Stage Environment

An energy method based on the mixing-plane model and phase lagged boundary condition has been developed to estimate the flutter characteristics of rotor blades in multi-stage environment. The effects of front and rear rotor stages on the aerodynamic damping of the rotor blades have been investigated using this method. The results show that the mixing-plane model enables to consider the averaging effect of the other stages on the aeroelasticity of the checked rotor blades without having to perform the unsteady full annual multi-stage (FAMS) flow computations. Comparing with the isolated rotor blade, the upstream and downstream rotor stages have a significant influence on the aeroelasticity of the rotor blade with altering the intensity and location of the shock wave and separation flow region on suction surface. It is worth to point out that the neighbor rotor stages reduce the effect of the inter-blade phase angle (IBPA) on the aerodynamic damping. Moreover, the impact of the rear rotor stage on aerodynamic damping of the rotor blade is more remarkable than that of the front one. Compared to the measured data, the capability of this method used in the aeroelasticity assessment of a multi-stage turbomachine has been validated. Furthermore, the relationship between the aerodynamic damping and the motion of the shock wave has been revealed, which can assist the compressor design.