基于动网格技术的混流式水轮机转轮内部瞬态流动数值模拟

水电站过渡过程常常引起水力机组压力脉动、振动和水锤等现象,严重影响电站的安全稳定运行。为了准确捕捉水轮机在过渡过程中的动态特性,本文区别于常规的稳态分析方法,采用CFD计算软件Fluent14.0,利用基于有限体积法的动网格技术对某混流式水轮机的活动导叶和转轮组成的单流道进行了三维瞬态流动数值模拟。真实模拟了在大波动过渡过程中转轮内部流态的变化,分析了导叶关闭过程中转轮内部压力场和速度场的变化过程。计算结果表明:动网格技术能够较好地模拟水轮机转轮内部流场的动态变化,其计算结果为三维过渡过程的研究提供了理论依据。

Numerical simulation of transient flows in Francis turbine runner based on dynamic mesh method

For a hydropower plant, strong pressure fluctuations, vibrations and water hammer could occur during a transient process, resulting in negative effects on the safety and stability of its operation. To capture the dynamic properties of a turbine at the transient stage, we have adopted the CFD Fluent 14.0 and a dynamic mesh method on the basis of finite volume method, and simulated the three-dimensional transient flows in the guide vane and runner passages of a Francis turbine. This method focuses on simulation of the internal flow changes in the runner caused by large-fluctuation transients and analysis of the corresponding changes in velocity and pressure fields. Thus it is distinguished from the conventional steady-state analysis methods. The calculation results indicate that the dynamic mesh method is effective and successful and it provides a new tool for the study of three-dimensional flow transients.