泵站前置竖井进水流道三维湍流数值模拟与模型试验

Three-dimensional turbulent numerical simulation and model test of front-shaft tubular inlet conduit of pumping station

为探求大型泵站竖井流道的标准化水力设计方法,对基于规则化设计的竖井进水流道进行了三维湍流数值模拟,研究9个不同工况下的流道内部流动特性,揭示不同水平截面和纵向截面的流速分布,分析水泵入口断面的速度分布均匀度、加权平均入流角以及流道水力损失随流量变化规律。结果表明:竖井进水流道流线平顺,水流均匀渐缩,无漩涡或脱流,流态良好;水泵入口断面的速度均匀度和入流角度随流量变化很小,其平均均匀度Vu=95.46%,入流角度?=87.94°;流道水力损失随流量增大而增大,但局部阻力系数随流量增大而减小。设计制作了透明模型进水流道,测得9个不同流量下的流道水力损失,比较了数模与试验结果,并观测流态。由模型进水流道的试验结果可得出,流道水力损失较小,局部阻力系数2?6.249 10???,未见不良漩涡,数值结果与试验结果基本吻合。开展了竖井流道模型泵装置的能量特性试验,测得5个叶片角度下模型泵装置Q-H、Q-P和Q-η曲线。试验结果表明,模型泵装置在特低扬程较大的范围内均具有较高效率,其中在叶片角-2°、装置扬程1.83 m时的最高效率可达80.52%。该研究可为大型泵站竖井流道的水力优化设计提供参考。

The tubular shaft inlet conduit is one of the most important structural styles which is suitable for a low-water-head pumping station, and it is gradually widely used in irrigation and drainage of water conservancy projects, such as in the South-to-North Water Diversion Project and Tai-Hu lake treatment project in China. Eighteen large-tubular shaft pumping stations have already been built or are under construction in China since 2004. To meet with engineering demands, research on improving the efficiency of a tubular shaft pump system has been undertaken since the first tubular shaft pumping station Mei-Lianghu was constructed and put into operation. Some results, aimed at every specific engineering project, have been acquired by means of model tests, three-dimensional turbulent numerical simulations, and empirical practice, but a standard design method for the optimized tubular shaft inlet conduit could not be derived from those references until now. In order to derive a feasible design method, three-dimensional turbulent numerical simulation was applied to investigate the internal flow pattern of a certain front-tubular shaft inlet duct which was due to the idea of regular outline design. On the basis of systematic research on the internal flow characteristics about nine variable operating conditions, the streamlines and velocity contours on the horizontal plane and different cross sections were revealed, the uniformity of axial velocity distribution and velocity deflection angle at the pump suction were obtained, and the hydraulic loss of the inlet conduit was also quantitatively calculated. It turned out that the streamlines are good with no vortices, the uniformity of axial velocity distribution is as high as 95.46%, and the axial velocity angle approaches 87.94%. The results also show that the hydraulic loss increases with increasing flow rate, while the loss coefficient decreases. In order to validate simulation results, a small-scale, transparent, Plexiglas model of the inlet conduit was made. Its hydraulic loss was measured and compared with numerical calculation data for nine different volumetric fluxes, and the flow patterns in the inlet duct were observed as well. Test results proved that the hydraulic loss is small, the loss coefficient is 6.249x10-2, and no vortices were found. It also revealed that simulation results are consistent with experimental data. Furthermore, the energy characteristic curves of the model pump set were acquired for five blade angles through the pump set model tests. According to experimental results, we conclude that the model pump set has a higher efficiency across a large range of low-water head, and its peak efficiency is 80.52% with water head 1.83 m and a blade angle of-2.