基于谐波平衡法的汽轮机末级叶片气动阻尼计算

Aerodynamic Damping Calculation of Steam Turbine Last Stage Rotors based on Harmonic Balance Method

采用谐波平衡法分析了汽轮机低压缸末级动叶自由形式和围带形式的颤振特性,获得了不同叶间相位角下的气动阻尼。研究发现:在设计工况下自由叶片叶间相位角在-30°^-150°时气动阻尼为负,叶片处于易发生颤振状态;当考虑围带时,叶片气弹稳定性发生了显著变化,在全行波域均处于稳定状态;由于振型、振幅的分布变化,围带叶片压力侧振动引起的压力扰动相位不再随叶间相位角发生明显改变,使得原本自由叶片上的气弹稳定性规律被破坏。

A one-way FSI simulations of low-pressure steam turbine last stage rotors in both unshrouded and shrouded forms are carried out by using harmonic balance method.Aerodynamic damping results of unshrouded blade for different inter-blade phase angles(IBPA)show that IBPA is a significant impact on aerodynamic damping and there is a period range(-30°to-150°)in flutter situation.With shroud,the feature of aeroelastic stability changes significantly and it is stable in the whole travelling wave domain.Due to the change of mode and amplitude,the phase of pressure disturbance induced by the vibration on the pressure side no longer significantly changes with IBPAs,thus the aeroelastic stability rule on the original unshrouded form is destroyed.