低比速混流式水轮机小开度叶道涡流动分析

Flow Analysis of Inter-Blade Vortices in a Low-Specific-Speed Francis Turbine under Small Opening Conditions

混流式水轮机在偏离最优工况下运行时,转轮叶道内会出现旋转涡流,影响水轮机的高效稳定运行。为研究低比速混流式水轮机在小开度工况下叶道涡的流动特性,基于Navier-Stokes方程及Sparlart-Almaras一方程湍流模型,对运行在小开度不同转速工况下的某低比速混流式水轮机,进行三维全流道定常流动数值模拟。计算结果表明:在小开度工况下,两种转速条件存在着分布位置不同、形状大小不一的叶道涡;随着转速的增加,旋涡结构趋于不稳定,内部流场的流态变得非常紊乱,水轮机能量转化效率降低,叶道涡的流动特性与转轮转速密切相关。

When the Francis turbine is operated under deviating from the optimal working condition,there will be a rotating vortex in the runner blade,which affects the efficient and stable operation of the turbine.In order to investigate the flow characteristics of the inter-blade vortices at Low-Specific-Speed Francis turbines under small opening conditions.The Navier-Stokes equation and the Sparlart-Almaras equation turbulence model are used to simulate the three-dimensional full-flow steady flow of a Low-Specific-Speed Francis turbines at small opening conditions at different rotational speeds.The results show that under the condition of small opening degree,there are inter-blade vortices with different distribution positions and different shapes and sizes in the two rotation conditions,with the increase in the rotational speed,the vortex structure tends to be unstable,and the flow state of the internal flow field becomes disordered,and the hydraulic efficiency of the turbines decreases.The flow characteristics of the inter-blade vortices are closely related to the rotational speed of the runner.