深邃泵站多相流临界水深及其内部复杂流态特性机理研究

This study focuses on the critical water level characteristics of multiphase flow and the evolution mechanism of complicated flow pattern in underground pump station using theoretic, parallel and testing techniques. Based on sub-grid scale models for large eddy simulation (LES) and VOF (volume of fluid) interface-reconstructed models, so that LES models combined with VOF for vapor-liquid two-phase flows simulating of underground pump station are proposed. Then, the two-phase LES-VOF combined model of cavitation air mass is developed by introducing Mixture cavitation model. High-speed photography and PIV technology are used to observe the evolution process of various complicated flow patterns in underground pump station, then the critical water level evaluation system of complicated flow patterns and multiphase flow in underground pump station is proposed through the relevant image post-processing recognition program, furtherly, which mainly in order to provide a new technology to predict the critical water level of multiphase flow in underground pump station, improve its internal flow patterns, increase the efficiency of pumping units and operating stability. Meanwhile, the experimental data are used to validate the rationality and the reliability of the above-mentioned models and numerical schemes. In short, this investigation aims at putting forth a new technique for study of the complicated flows in underground pump station.

拟采用数值计算、试验研究和理论分析为基本手段，深入研究深邃泵站内部多相流临界水深特性及其内部复杂流态演化机理。基于大涡模拟（LES）亚格子模型和流体体积方法（VOF）液面重构模型，发展深邃泵站自由液面气-液两相流LES-VOF计算模型。然后通过引入Mixture空化模型，发展空化气团两相流LES-VOF计算模型。利用高速摄影及PIV技术试验观测深邃泵站内部各类复杂流态演化过程，然后编制相关图像后处理识别程序，构建深邃泵站内部复杂流态及多相流临界淹没水深评判体系，为预测深邃泵站内部多相流临界淹没水深、改善其内部流动形态、提高泵组运行效率、增强泵组运行稳定性提供技术参考。同时，通过一系列试验数据验证建立的计算模型的合理性及可靠性。本研究将为深邃泵站内部复杂流态研究提供一种新方法。

深邃泵站在海绵城市建设、重大公共卫生事业、污水处理、区域调水等重大领域具有广泛建设需求，其内部各类涡旋流态对整个泵站系统安全稳定高效运行具有重要意义。目前国际上关于其建设处于起步阶段，可参考成功案例较少，此外因其结构等与传统式泵站多处不同，传统式泵站相关设计方法与理论不再适用。针对深邃泵站内部多相流临界淹没水深及其复杂流态特性机理问题，采用理论分析、数值模拟及模型试验相结合手段，研究了深邃泵站内部各类涡旋流态及其演化机理。利用高速摄影及PIV技术观测深邃泵站内部各类涡旋流态演化过程，编制相关图像后处理程序，定量化提取数据进行分析；揭示了深邃泵站典型工况下空化/截流气团的演化过程及其机理；建立了基于LES-VOF方法及针对空化/截流气团的Mixture空化模型的深邃泵站数值计算模型；构建了一套深邃泵站内复杂流态数理模型，为深邃泵站多相流临界淹没水深数理预测模型提供基础；建立了更全面的泵站内部漩涡流态阶别分类；构建了深邃泵站运行涡型图谱，深入揭示其内部各类漩涡运行演化过程。研究结果表明：深邃泵站内泵组抽吸作用力最大，水位较高时，深邃泵站进水池内部会频繁出现液下漩涡，水位降低，各类漩涡发生频率明显升高，同时主池体内自由液面漩涡被撕扯为断裂涡带吸入泵组，同时管路内壁出现各类复杂液下涡，上述现象均与泵组强烈吸力相关；另一方面，进水池内部水位降低过程中，泵组性能失稳并伴随噪音，随后泵组性能剧烈下降，噪音明显，最终无量纲水位（水位/管径）降低至<5.15时，泵组失效，效率为零；第三，针对减小或消除深邃泵站主管路进口处的空化/截流气团的策略为：主管路进口倒圆或采用不剧烈的几何梯度变化，倒圆半径为0.10 D 左右最好；最后，推荐深邃泵站内部流态主要无量纲数包括雷诺数、弗劳德数、角度弗劳德数、韦伯数、罗斯比数及艾克曼数。本项目研究成果为深邃泵站水力优化设计及其内部各类有害涡旋流态的抑制及消除提供有力参考。