汽轮机光轴迷宫式隔板汽封内部流场的数值模拟

Numerical Simulation of Flow Fields within Straight-Through Labyrinth Glands of Steam Turbine Diaphragms

采用数值方法研究了汽轮机低压整体加工尖齿和斜齿两种不同结构光轴迷宫式隔板汽封的三维内部流场。采用有限体积方法离散Navier Stokes方程,标准k ε两方程紊流模型封闭方程组。数值求解方法采用SIMPLE算法,迎风2阶格式求解对流项,迎风1阶格式求解扩散项。数值模拟结果证明了:在一定的隔板汽封轴向距离和相同的压力差条件下,齿数的减少导致泄漏量增加,同时揭示了光轴迷宫式隔板汽封内复杂的三维流场特性,为工程优化设计光轴迷宫式隔板汽封提供了理论依据和技术支撑。

3-dimensional flow fields in integrally machined low pressure straight-through diaphragm glands of steam turbines with both sharpened and with inclined fins are being studied with the help of numerical simulation. The finite volume method is used to discretize the Navier-Stokes equation together with a standard k-ε double equation turbulence model for closing the set of equations. SIMPLE algorithm was used for obtaining the numerical solution with second order upwind pattern for obtaining the convection terms and first order upwind pattern for the diffusion terms. Numerical simulation results show that, for fixed axial gland length and pressure difference, leakage increases with reducing number of fins. Simultaneously the complexity of the 3-dimensional flow field in the straight-through labyrinth gland cavities is revealed. All this provides some theoretical footing and technical support for optimizing the design of straight-through labyrinth diaphragm glands.