带分流叶片水泵水轮机转子强度及模态分析

Analysis on rotor strength and mode of pump-turbine with splitter blades

以带分流叶片的水泵水轮机为研究对象,基于CFD与FSI方法分析其泵工况下转子的振动特性,对3种开度即小开度9.8°、最优开度17.5°和大开度24.8°下的流场进行数值模拟,将额定工况下的流场结果导入转子结构实现单向流固耦合,对带预应力的转子模型进行形变与等效应力分析.此外,还计算了转轮的干湿模态,对比分析了不同条件下转轮的振动特性.结果表明:不同开度对应的预应力下转轮形变与等效应力分布规律相似,转轮形变主要发生在上冠低压侧.按节径数ND在转轮圆周方向划分振动扇区描述振型规律时发现,各扇区内转轮上冠、下环低压侧的振幅较大.湿模态下水介质对转轮振型影响不大,但会明显降低转轮的振幅.预应力对转轮固有频率影响较小,可忽略不计,但在湿模态下,转轮固有频率会显著下降,这表明分析结构振动特性时应充分考虑水介质作用.

This study considered a model of a pump-turbine with splitter blades operating in pump mode.Vibration characteristics of the rotor of the pump was analyzed based on CFD and FSI methods.Steady simulations of flow conditions under three opening degrees,namely small opening degree of 9.8°,optimal opening degree of 17.5°and the large opening degree of 24.8°,were conducted.The results under rated working conditions were imported into the rotor structure to realize unidirectional fluid-structure coupling.Further,deformation and equivalent stress of the rotor with pre-stress were analyzed and the wet and dry modes of the runner were also calculated to analyze vibration characteristics of the runner under different conditions.The analysis reveals that deformation of the runner under the pre-stress corresponding to different openings is basically the same as the equivalent stress distribution and the deformation of the runner mainly occurs on the low-pressure side of the upper crown.In addition,vibration sectors were divided in the circumferential direction to describe the characteristics of the vibration shape according to the number of pitch diameters.It is found that the relative amplitude of the low-pressure side of the upper crown and lower ring of the runner in each sector is relatively large.Furthermore,the additional mass of water in the wet mode has little effect on the modal characteristics of the runner,but it has a significant impact on the amplitude.Lastly,the influence of pre-stress on the natural frequency of the structure is small and can be ignored,while the natural frequency of the structure decreases significantly in the wet mode,indicating that the additional mass effect of water should be fully considered when the vibration characteristics of the structure is analyzed.