600MW机组排汽缸流场特点及其结构优化

Flow Field Characteristic and Structure Optimization of Exhaust Hood in 600 MW Units

排汽缸结构复杂,导致流场混乱,容易形成不同程度的漩涡,造成能量损失。为此,运用流体计算软件Fluent对排汽缸进行数值模拟,研究了其内部流场特点,分析了扩压管出口宽度和内壁倾角对扩压管出口处流场的影响。流体从扩压管流出后,向上翻转进入上半缸,在上半缸形成了另一个漩涡。针对排汽缸内不同形式的漩涡,对扩压管出口结构进行优化改造和在拱顶处加装导流挡板,存在一个最优的扩压管出口宽度和内壁倾斜角度,使得扩压管出口附近漩涡最小;导流板的数量和安装位置对漩涡有不同程度的影响,通过模拟得出了最佳的挡板组合,能最大程度削弱排汽缸内的漩涡,改善其性能。

The complex structure of exhaust hood may cause the chaos of flow field, and produce different kinds of vortexes and energy loss. The model of exhaust hood was simulated with computational fluid dynamics software Fluent to study the characteristics of flow field, as well as the influence of diffuser outlet width and inner wall angle on the flow field at diffuser outlet. After flowing out of the diffuser, the field turns over into the upper half of exhaust hood and then produces another vortex thereby. According to the different types of vortexes in exhaust hood, the structure of diffuser outlet was optimized and deflectors were equipped in the upper half of exhaust hood. There are optimal diffuser outlet width and inner wall angle making the vortex minimum nearby diffuser outlet, and the number and installation site of the deflectors have different influence on the vortex. Finally, the best combination scheme of deflectors was obtained by simulation, which could furthest weaken the vortex in exhaust hood and improve its performance.