在我国能源结构转型的过程中，抽水蓄能电站发挥着重要的储能作用。作为电站的核心装备之一，水泵水轮机工况转换频繁，机组的转轮、螺柱等关键部件往往面临严重的振动，甚至疲劳破坏、断裂失效等问题，因此开展水泵水轮机关键部件在暂态过程中的动态响应机理研究具有重要的现实意义。本文建立了水击波影响下的考虑水体附加质量的水泵水轮机关键部件暂态过程动态响应数值计算方法。将管路系统一维水击波与机组内三维非定常流动耦合，求解暂态过程中关键部件所受的瞬时水力激励；基于声学流固耦合理论，考虑周围水体附加质量对动态响应特性的影响，通过与实测数据的对比，验证了计算方法的准确性。基于以上方法，对水泵水轮机发电工况开机过程及甩负荷过程中转轮的动态响应进行了数值模拟。发现在开机过程中，转轮应力受多重因素影响：叶片进水边与下环“T”形连接部位主要受叶片正背面压差的作用，随水力矩变化，而其他位置主要受离心力影响，随转速变化；此外，随着转速上升，动静干涉造成的压力脉动频率不断增大，依次经过转轮前三阶固有频率，激发了前三阶模态。在甩负荷过程中，管路系统内的水击波引起了转轮动应力的低频脉动；在转速最大时刻附近以及反水泵工况区内，转轮的前三阶模态同样被激发，但与开机过程不同的是，激发模态共振的是流场中涡旋运动引起的频率范围较宽的高幅值压力脉动。暂态过程中，转轮的瞬时共振会引起动应力幅值的瞬时增大，造成机组振动加剧的同时降低了转轮的疲劳寿命。提出了暂态过程间隙流影响的顶盖座环连接螺柱应力非线性变化预测方法，研究了瞬变水力激励力、非轴对称顶盖结构、预紧力及预紧顺序对螺柱动力特性的影响。甩负荷过程中，顶盖与转轮间隙内的流动引发瞬时水力激励，导致螺柱的应力、拉力与相对刚度等均呈现非线性变化；同时，相比其他螺柱，顶盖支撑肋板附近的螺柱应力集中更大，更容易发生疲劳破坏；最后阐明了预紧顺序造成的螺柱预紧力损失现象，并对不同预紧顺序进行了对比。本研究揭示了暂态过程中转轮及螺柱等关键部件的动态响应特性，为蓄能机组安全稳定运行提供了机理分析和科学依据。
In the process of energy structure transformation in China, pumped storage power station plays an important role in energy storage. The pump-turbine is one of the core equipment of the power station, and its working conditions are changed frequently. The runner, bolt and other key components often suffer serious vibration, fatigue damage and other problems. Therefore, it is of great significance to study the dynamic response of key components of pump turbine in the transient process.A numerical method is established to predicted the dynamic response of the key components in transient process by considering the water hammer and the added mass of water. The one-dimensional flow of the pipeline system is coupled with the three-dimensional unsteady flow in the unit to slove the hydraulic excitation in transient process. Based on the acoustic-structure interaction theory, the influence of added mass is taken into consideration. The accuracy of the method is verified by comparing with the experiment data from on-site measurements.The dynamic responses of runner during the start-up process and load rejection process in turbine mode were simulated. It was found that the stress was affected by multiple factors during start-up. The "T"-shaped connection between the blade leading edge and the band was mainly affected by the pressure difference between the pressure side and the suction side of blade, and changed with the hydraulic torque, while other positions were mainly affected by centrifugal force and changed with the rotating speed. In addition, as the rotating speed increased, the frequencies of pressure fluctuation caused by rotor-stator interaction increased, passing through the first three natural frequencies of runner, exciting the first three modes. During the load rejection process, the water hammer in the pipeline system caused the low-frequency fluctuation of the dynamic stress. The first three modes of runner were also excited near the maximum-rotating-speed condition and the maximum-reversed-flow condition. However, the excited mode resonance was caused by the high frequency and high amplitude pressure fluctuation, which is induced by vortex motion. In the transient processes, the instantaneous excitation of mode will contribute to a sharp increase of the dynamic stress of runner, which will aggravate the vibration of the unit and reduce the fatigue life of the runner.A numerical method was proposed to predict the nonlinear stress of multibody-structure, which consists of head cover, stay ring and bolts by considering the influence of the clearance flow during transient processes. The influence factors on the dynamic characteristics of blots were studied, such as transient hydraulic excitation, non-axisymmetric structure of head cover, pre-load and pre-loading sequence. During the load rejection process, the flow in the clearance between the head cover and crown caused transient hydraulic excitation, which leads to nonlinear changes of stress, tension, and relative stiffness of bolts. In addition, compared with other bolts, the bolts near the ribbed plates suffered more significant stress concentration and has shorter fatigue life. Finally, the phenomenon of pre-load loss caused by pre-loading sequence was explained, and the pre-loading sequence was optimized.The dynamic response characteristics of the runner, bolts and other key components in the transient processes were studied in this paper, and the results provide a scientific basis for the safe and stable operation of pumped storage units.
