Abstract: With the development of variable cycle aero-engines towards wider operating conditions, higher efficiency, and greater reliability, the loads on turbine rotor blades are continuously increasing, and their aeroelastic stability problems are becoming increasingly prominent. This study takes a wide-speed-range low-pressure turbine rotor blade as the research object, and systematically carries out aeroelastic stability assessment and flutter suppression design. First, based on the finite element method, the vibration characteristics of the rotor blade under different operating conditions are analyzed, and the influence of the cooling cavity and shroud structure on the blade's natural frequency and mode shape is investigated. On this basis, a comparative analysis of the aerodynamic damping of the first two modes under maximum subsonic cruise and design conditions is performed. The results show that under the maximum subsonic cruise condition, the blade row exhibits a stable state. However, under the design conditions with greater aerodynamic loads, the first two modes of the rotor blade have negative aerodynamic damping at specific nodal diameters (ND). Among them, the first mode has the smallest aerodynamic damping ratio at the -7 ND, which is -0.108%, and the second mode has the smallest damping ratio at the 18 ND, which is -0.046%, indicating a risk of aeroelastic instability. Further analysis of the cooling cavity and shroud structure reveals that the shroud can significantly change the blade's mode shape and frequency distribution, thereby effectively improving the aerodynamic damping level and achieving flutter suppression design. Finally, for low ND modes with large mode shape differences, the energy method based on phase shift conditions is used for calculation and verification. The research results of this study can provide an important reference for the aeroelastic safety analysis and structural optimization design of low-pressure turbines in the next generation of wide-speed-range, variable cycle engines.

Key words: Turbine rotor blade, Aeroelastic stability, Multi-condition, Shroud structure, Flutter suppression