大型水电机组顶盖垂直振动异常原因分析及对策

针对某大型电站混流式水电机组自投产来一直存在顶盖垂直振动异常问题,采用真机振动试验方式,获取了该水电机组于不同运行工况下的顶盖垂直振动峰值及对应的频谱曲线。基于有限元法构建了机组顶盖的高精度动力学仿真模型,获取了该机组顶盖的固有频率及其对应振型,并同步采用真机模态实测方法对顶盖的固有频率进行验证。在此基础上,通迆顶盖振动频谱曲线与其固有频率的对比分析,捕获了机组顶盖垂直振动异常的根本原因,设计并实施了顶盖补强方案,改变了顶盖的刚强度与固有频谱。经真机试验验证,顶盖补强有效地降低了顶盖垂直振动幅值,降低了机组的运行风险。

Cause Analysis and Countermeasure of Abnormal Vertical Vibration of Top Cover of Large Hydropower Unit

In view of the abnormal vertical vibration of the top cover of a large-scale Francis hydropower unit since its commissioning, the peak vertical vibration of the top cover and the corresponding frequency spectrum curves of the unit under different operating conditions are obtained by using the real-machine vibration test method. Based on the finite element method, a high-precision dynamic simulation of the top cover of the unit is constructed. The natural frequencies of the roof cover of the unit are obtained from the true actual turbine model, and the natural frequencies of the roof cover are verified synchronously by the actual modal measurement method. On this basis, the fundamental causes of the abnormal vertical vibration of the top cover of the unit are captured through the comparative analysis of the vibration spectrum curve of the top cover and its natural frequencies, and the top cover is designed and implemented. The reinforcing scheme changes the rigidity and natural frequency spectrum of the roof. The real machine test shows that the reinforcing of the top cover effectively reduces the vertical vibration amplitude and reduces the operation risk of the unit.