基于流固耦合的混流式转轮受力与振动特性分析

Force and Vibration Analysis of Francis Turbine Based on Fluid Solid Coupling

围绕转轮结构稳定与机组安全运行问题,基于流固耦合理论,对混流式水轮机进行流场仿真与转轮结构响应求解。首先,将流道水压作为荷载进行静力学计算,校核转轮强度,并获取不同工况下应力与变形分布;然后,开展瞬态计算,探究转轮动应力随时间的变化规律;最后,通过预应力模态计算获得多阶振频与振型,分析水力共振的可能性。结果表明,受力符合材料强度要求,应力集中在转轮叶片出口边,随着功率增大应力峰值位置从轮毂交接处向下环交接处发展,交变应力的波动周期与运转周期一致。流道内压力脉动中2倍叶频引发的共振对转轮体现为摆动、挤压、扭转型,3倍叶频激发转轮产生6阶及以上共振,对叶片破坏作用最大,导叶与转轮动静干涉诱发转轮共振可能性低。

Focusing on the structural stability of the runner and the safe operation of the unit,this paper implemented CFD in Francis turbine and solve runner structure response based on fluid-solid coupling theory.Firstly,it implemented static calculations to check the strength of the runner,and obtained the distribution of stress and deformation under different working conditions.Secondly,it carried out transient calculations to explore the development of the dynamic stress of the runner.Finally,it obtained multi-order vibration frequency and mode through pre-stress modal calculation,and analyzed the possibility of hydraulic resonance.The results show that the stress is concentrated on the outlet edge of the runner blade,and the peak position of the stress develops from the junction of the hub to the junction of the shroud as the power increases,and the fluctuation cycle of the alternating stress is consistent with the operation cycle.The resonance caused by the 2 times the blade frequency in the pressure pulsation in the flow channel embodies the oscillating,squeezing,and torsion type on the runner.The 3 times the blade frequency excites the runner to generate 6 th order and above resonance,which has the greatest damage to the blades.The guide vane runner is static and dynamic.The possibility of interference induced hydraulic resonance is low.