封闭式进水池顶板附壁涡流动机理及控制研究

The closed sump is one of typical inlet passages of pumping station.There are two kinds of vortexes in the sump , free-surface vortex and wall-attached vortex, which threaten the security of pumping system. The wall-attached vortex which happen from wall below free surface is difficult to be discovered and prevent. The flow mechanism and influence factor of the wall-attached vortex are complex. The scale and flow rate of closed sumps becomes larger and larger. It is necessary to broaden the stable operating region of closed sump and to prevent and eliminate vortexes..Two sets of test system of closed sump will be built to test the hydraulic performance and 3-D flow field. The effect of flow and geometric parameter that affect the wall-attached vortex will be studied by hydraulic performance test. The dynamic pressure of key sections will be test by high dynamic pressure test technology. The frequency spectrums and chaos theory will be applied to analyze the characteristic frequency of premonition and nonlinearity performance of wall-attached vortex. The control strategy will be studied by unsteady CFD calculation. The occurrence of vortex system will be caught by 3D-PIV and high-speed photography. Based on test,CFD and theory analysis, the relationship between the hydraulic performance with beginning and evolvement of wall-attached vortex will be analyzed. A theory will be set up to give the estimation rule and control method of wall-attached vortex. The hydraulic stability theory of closed sump will be expanded and perfected. The future research results will have large academic and engineering values to ensure the safety and efficient operation of closed sump.

开敞式进水池封闭式改造后，有效消除水面涡，但其顶板处易诱发新的附壁涡，隐蔽性强，流动机理和影响因素复杂，较难防治。随着泵站开敞式进水池封闭式改造持续开展，拓宽其稳定运行范围，提高顶板附壁涡防治能力十分必要。本项目拟建立封闭式进水池实验装置进行附壁涡水力特性和三维流动测试。基于水力特性实验装置研究附壁涡发生对水泵系统影响，建立附壁涡与流动和几何两大影响因素关系；采用高频动态压力测量技术测试顶板附壁涡演化过程中池内关键位置的压力脉动，基于频谱分析和混沌理论研究顶板附壁涡的特征频率和非线性特性。通过非定常CFD计算优选顶板附壁涡防治策略，运用高速摄影和3D-PIV技术捕捉顶板附壁涡形态及涡系结构。采用实验与模拟相结合开展顶板附壁涡流动机理及控制研究，力求从机理上把流动特性与附壁涡发生、演化关联起来，建立顶板附壁涡判断准则和提出防治策略，进一步拓展和完善泵站进水池水力稳定性理论。

随着我国灌区改造和中小型泵站更新改造的实施，拓宽泵站稳定运行范围，防治顶板附壁涡显得十分迫切和必要。本项目以模型实验为手段，采用高速摄影、图像处理、高频压力脉动测试和时频分析的方法，结合数值模拟，对封闭式进水池顶板附壁涡的发生机理和防治措施等核心关键问题展开研究。本项目主要研究成果包括：.（1）设计建立了具有透明观测实验段的封闭式进水池循环实验装置，实验装置可进行顶板附壁涡流动机理、压力脉动、水力性能和消涡措施实验。.（2）探明了封闭式进水池顶板附壁涡演化过程及其形态特征；揭示了顶板附壁涡的形成机理，顶板上水流冲汇是顶板附壁涡成因，水流冲汇形成的水流交汇界线的位置和形态决定了顶板附壁涡的发生位置及发生形态；发现了顶板附壁涡发生时的两个压力脉动频谱特征，一是由压力下降引起低频脉动幅值显著增大，顶板附壁涡的特征低频频率为1.11 Hz；二是涡附着区域的叶频压力脉动幅值随涡的发展溃灭而先增大后减小。.（3）揭示了流量、水深和顶板高度对封闭式进水池顶板附壁涡形成的影响，发现了顶板附壁涡发生频次随流量、水深和顶板高度变化的统计特征；发现了顶板附壁涡发生的两个前兆特征，一是存在于水泵后方顶板上的具有压力陡降特征的低压脉动，二是顶板上叶频压力脉动幅值的分布特征。.（4）研究了不同消涡措施对顶板附壁涡的抑制效果，发现了后壁中隔墩结构的消涡措施能有效地抑制顶板附壁涡的发生，发明了两种可有效消除顶板附壁涡的消涡措施——梯形中隔墩结构和壁面栅条结构，并进行了实验验证。