考虑流固耦合的混流式水轮机转轮模态分析

迄今为止 ,国内的许多进口和国产的大型水轮机组转轮叶片都出现了不同程度的裂纹破坏 ,严重影响了电站的安全生产和机组的稳定运行1 ,2 ] 。大量的研究表明 ,导致裂纹产生的一个重要原因是水力激力引发的结构共振所产生的动载荷作用。特别是出现低频共振时 ,极易引起结构的严重破坏2 ] 。随着机组单机容量的不断地增加 ,转轮的固有频率降低 ,发生共振的危险性也更大。因此 ,针对转轮在水介质中的模态特性的研究具有十分重要的现实意义。本文运用全流固耦合的三维有限元方法对某一混流式转轮在水介质中的模态特性进行了研究 ,得到了转轮在水中的自振频率和振型等振动特性。结果表明 ,转轮在水中的第 1阶固有频率与叶片旋转频率相近 ,额定工况下的卡门涡频率又接近于转轮的高阶固有频率 ,这极有可能引发结构的共振 ,导致裂纹的产生。

Modal analysis of Francis turbine with considering FSI

Up to now,Cracks occur in many exported and home-made large hydraulic turbine to different degrees,which seriously affect the safety and stability of the hydraulic power station operation.Plenty of researches showed that one main cause of crack is the fluctuant load resulting from the structural resonance caused by hydraulic drive.Especially when the low-frequency resonance occurs,it would give rise to serious damage on the structure.The natural frequency of the turbine decreases as the capacity of unit increases,so the resonance is more likely to create great damage.Therefore,it is of practical significance to have a study on the mode characteristic of the turbine in water.The mode characteristic of a Francis turbine in water is studied by the method of three-dimensional FEA considering FSI in this paper,and the natural frequency and modes of the turbine are carried out.The result indicates that the first natural frequency of the turbine is close to the rotating frequency of the blades and the frequency of Karman vortex flow under rated work condition is near to the high natural frequency of the turbine,so it is very likely to stimulate the structural resonance with resulting in the cracks.