417 / 2018-12-23 20:30:36

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 Moving Blades Based on Harmonic Balance Method

谐波平衡法；末级动叶；气动阻尼；颤振；叶间相位角/Harmonic Balance Method; last stage moving blade; aerodynamic damping; flutter; inter-blade phase angle

全体主题 > 涡轮机

汽轮机低压缸的性能优化对汽轮机的总体效率和稳定性的提高至关重要。而日益增大的发电需求使得低压末级排气面积不断扩大，末级动叶也随之愈发细长。这种叶片往往有着较低的刚度和大的展弦比；同时叶片顶部经历的流速较高，以上原因均使得低压末级动叶对于颤振（气动弹性不稳定）十分敏感。虽然现代汽轮机长叶片往往通过拉筋、围带等阻尼装置进行减振，但叶片气弹稳定性研究作为叶片前期设计的一部分，仍然是不可忽略的。本文基于谐波平衡法分析汽轮机低压缸末级动叶一阶振动模态下的颤振特性，对同一种叶型的自由叶片和围带叶片两种形式进行了研究，获得了设计工况不同叶间相位角下的气动阻尼。对于自由叶片形式，叶间相位角在-30°至-120°时动叶的气动阻尼为负，叶片处于易发生颤振状态；而对于围带叶片形式，叶片在所有情况下均处于气弹稳定状态。针对以上结果给出了±90°叶间相位角时叶片不同时刻的做功功率密度和流场特征，并对比分析了振型对于气动阻尼大小的影响。
The performance optimization of low pressure (LP) steam turbine is significant to improve the overall efficiency and stability. However, the increasing demand for power generation makes the exhaust area of LP cylinders continuously expand, which forces the last stage moving blades (LSMBs) become longer and thinner. This king of long blade often has low stiffness and high aspect ratio, and its tip part usually works in high-speed flow region. Both of which make LSMB very sensitive to flutter (aeroelastic instability). Although the long blades of modern steam turbine are often damped by dampers such as part-span connector and blade shroud, researches on the aeroelastic stability of the blades, as part of the early design of the blades, are unavoidable. In present work, one-way FSI simulation of LP steam turbine LSMBs under designed condition is studied using Harmonic Balance Method. Flutter characteristics in first mode family of one blade both in freestanding and shrouded forms are calculated in different inter-blade phase angles (IBPAs). The results show that for freestanding blade, there is a period range (-30° to -120°) in flutter situation but the shrouded blade is always in stable situation. Wall power density and flow characteristics in different moments are also presented in IBPA ±90°. The influence of vibration mode on aerodynamic damping is also analyzed.