水泵水轮机启动过程转轮动应力分析

启动过程中转轮的动应力特性是评价水泵水轮机组稳定性的一个重要指标。为分析某原型混流式水泵水轮机组在水轮机模式启动过程中转轮的振动响应，重点分析水力激励力的瞬变特性对动应力的影响，首先针对水轮机启动过程选取不同转速工况点分别进行了稳态和局部瞬态动应力计算，然后结合转轮固有模态和动静干涉理论分析了异常振动产生的原因。其中，水力激励力通过计算流体动力学分析得到，动应力的求解采用基于声固耦合构建的单向流固耦合方法。对比稳态和瞬态计算的结果可知，在共振工况附近，激励力的瞬变特性对转轮的振动有显著影响。一方面使得启动过程中的高水平振动滞后于理论共振工况，另外动应力幅值远低于稳态分析的结果。然而在非共振区域，稳态和瞬态计算得到的动应力水平相近。

Dynamic Stress Analysis of Pump-turbine Runner during Start-up

For hydraulic turbine, especially pump-turbine, the dynamic stress characteristics of runner during start-up is an important index to evaluate the stability of unit. Aiming to analyze the vibration response of a prototype Francis pump-turbine runner during start-up in turbine mode, focusing on the influence of the transient of the hydraulic excitation force on the dynamic stress. Firstly, the steady-state and local transient dynamic stresses were calculated for different rotating speeds during the start-up process. Then, the causes of abnormal vibration were discussed based on the modal analysis and the rotor-stator interaction analysis. Among them, the hydraulic excitation force was obtained by computational fluid dynamics analysis, and the dynamic stress was solved by acoustic-structure based one-way fluid-structure interaction method. Comparing the results of steady-state and transient analysis, it can be seen that the transient of the excitation force had a significant effect on the vibration response near the resonance working condition. The high-level vibration in the transition process laged behind the theoretical resonance condition, and the dynamic stress amplitude was far lower than that estimated by the steady-state method. But outside the resonance region, the dynamic stress levels obtained by steady-state calculation and transient calculation were very close. Besides, resonance was easy to occur only when a hydraulic excitation force corresponded to both the frequency and mode shape of a natural mode of the runner. The above results can provide a reference for the assessment of dynamic stress in the transition process.