基于双向流固耦合水轮机转轮应力特性分析

为了开展基于双向流固耦合的水轮机转轮叶片应力特性分析,通过坐标变换将直角坐标系下的连续方程和动量方程变换到任意拉格朗日坐标系下,建立流场控制方程,采用FCBI-C方法得到离散方程.在旋转坐标系下建立结构静力学方程,采用有限元法进行离散,得到转轮的有限元方程.使用迭代法双向流固耦合,对流体方程和结构方程进行迭代,直到流固耦合系统收敛.通过基于双向流固耦合的混流式水轮转轮应力场计算可得:单、双向耦合条件下转轮应力和位移分布趋势基本一致,最大点位置相同;转轮的有效应力相对差值随着变形的增大而增大,均在位移变形值最大点最大;变形量大小是单、双向耦合计算结果差别的重要因素,在小变形情况下,精度要求不高时可用单向耦合代替双向耦合进行计算.

Stress analysis of Francis hydraulic turbine runner based on FSI

To carry out stress characteristics analysis based on two-way FSI,the Navier- Stokes equations and Continuity equation used were transferred to arbitrary Lagrangian- Eulerian( ALE) coordinate system firstly,then were discretized with the special finite volume method adopting flow-conditionbased interpolation( FBIC- C). The structure static mechanics equations used were established in rotation coordinate system,and were modeled with the finite element method. The two-way coupling iteration method between the fluid equations and the solid finite element equations was used to calculate until the coupling system is convergence. The structure calculation results based on two-way FSI showed that: the equivalent stress and deformation distribution of the runner in one-way and two-way FSI conditions are similar. The locations of maximum stress and deformation are the same. With the increasing of deformation,the relative difference of equivalent stresses gets higher. The highest relative difference values of equivalent stresses and deformations are both occurring at the maximum deformation point. Deformation mainly determines the difference between one-way and two-way FSI results.The one-way FSI is available if accuracy requirement is low at the condition of small deformation.