混合刷式密封泄漏特性的数值研究

为分析某型号汽轮机改进的刷式密封结构的密封性能，采用non?Darcian多孔介质模型的Reynolds?averaged Navier?Stokes方程数值求解方法，对泄漏流动特性及转子表面、刷束自由高度和保护高度的压力、速度、湍流动能分布规律进行数值研究，并与迷宫密封进行相应的比较。结果表明：相同的间隙和压比下，混合刷式密封流场分布要比迷宫密封复杂，泄漏量明显小于迷宫密封；相同的结构和参数下，泄漏量随着压比的上升而增加；转子表面的轴向压力和湍流动能从进口到出口呈现阶梯状递减趋势，保护高度的径向压力基本趋于常数值；刷束径向速度和湍流动能随着压比的上升而增加，刷束下半部分和后挡板保护高度对泄漏特性影响比较大。研究结果为汽轮机刷式密封的结构设计，改善性能，提供了理论依据。

Numerical study of leakage flow characteristics in hybrid brush seal

To know the sealing performance of an improved brush seal on turbine, the leakage flow characteristics and distribution on rotor surface, bristle pack free height and fence height were numerically analyzed by adopting a non-Darcian porous medium model. And a corresponding comparison between labyrinth seal and brush seal was performed. The analysis shows that at the same clearance and pressure ratio the flow fields in hybrid brush seal are more complex than that in labyrinth seal and the leakage rate of brush seal is significantly less than that of labyrinth seal, at the same structure and parameters the leakage rate increase with the rise in pressure ratio. More over, the axial static pressure and turbulent kinetic energy of rotor surface gradually decline with a ladder-like distribution from inlet to outlet, the racial static pressure of fence height tends to be constant values. The radial velocity and turbulent kinetic energy increase with the rise in pressure ratio. The lower parts of the bristle and the fence height have obvious effect on the leakage characteristics. The results provide theoretical basis for the design of brush seal structure and the improvement of performance.