含泄水孔混流式水轮机间隙流动数值模拟

建立了包括混流式水轮机转轮上冠和顶盖间的空腔、泄水孔以及转轮前密封间隙流道中的水体模型在内的全流道几何模型,通过三维数值模拟,研究了主流道内速度和压力分布以及空腔、泄水孔和密封间隙内的流动特征,揭示了混流式水轮机上部空腔压力与泄漏水量随不同密封间隙尺寸、不同泄水孔直径和数目的变化规律。根据数值模拟结果,最终确定水轮机泄水孔数目为6个,直径为40 mm,间隙宽度为1 mm,该模型额定工况下流量为5 109 m3/h,间隙泄漏水量占机组流量的0.3%,水轮机效率为86.75%,与试验测试结果基本一致,表明所研究的间隙流计算方法可为水轮机泄水孔直径、数目以及密封间隙等细部结构尺寸的权衡确定提供参考依据。

Numerical Simulation of Clearance Flow in Francis Turbine with Weep Holes

The whole flow passage of Francis turbine including clearance structure such as cavity between crown and top cover, weep hole and seal passage of runner was built to study pressure distributions and velocity distributions in main passage as well as clearance flow characteristics by CFD method. Variation rules of leakage flux and static pressure in chamber head of the turbine was revealed due to different micro channel clearance widths, weep hole diameters and numbers. ICEM structured grid was used to divide the key components to analyze the seal clearance flow. The sizes of grid nodes were set up as one smaller regional area and another larger one according to the large space between the main passage and seal passage. The numerical results showed that seal widths, weep hole diameter and number had an impact on flux leakage and pressure in chamber head. According to numerical simulation results, the weep hole number was determined as 6, weep hole diameter was 40mm and seal width was 1mm. Under the rated condition, turbine installation efficiency was 86.75% with flow rate of 5109m3/h, and the clearance leakage reach 0.3% of the whole unit flow. The calculation results agreed well with the test, which showed that clearance flow calculation method could provide scientific basis for the design of Francis hydraulic turbine weep hole diameter and number, and details of seal gap structure. The results would benefit to avoiding the hydraulic vibration and ensure the secure and efficient operation of units.