高速水流冲磨与空蚀耦合作用下过流壁面蚀损机理研究

Abrasion and cavitation damage of discharge structures is always one critical technical problem need to be well solved in the hydropower projects. Several large hydropower stations with high dam are built in recent years, whose discharge flow velocity increases obviously, then the erosion of abrasion and cavitation are becoming more serious. Faced to the present shortcomings of correlation research, the mechanism study of coupling effect between abrasion and cavitation will be conducted here. Bernulli principle of hydraulic engineering is employed to make the water and sand mixed automatically, and the cavitation defense technology of sudden expansion body type is adopted to develop the test equipment that can simulate the coupling effect between abrasion and cavitation of high speed flow. The advanced high speed camera system is taken to capture the impulse impact shape of the cavitation flow with sand. Synthesize hydrodynamic characteristics, erosion feature, vibration and sound, the coupling effect mechanism between abrasion and cavitation is revealed. The environmental scanning electron microscope and digital image technology are applied to study the erosion mechanism of different materials, and the erosion model considering the flow cavitation number, sand ratio, sand diameter and the mechanics parameters of the material is proposed. The suitable boundary condition and failure criteria are selected, in the FEM frame, nonlinear transit dynamic contact method is set to simulate the interaction between the high speed flow with sand and the discharge structure to predict the erosion process of the overcurrent wall. The results will present science and technology support for the development of new erosion resistance material and the erosion resistant design of the projects.

泄水建筑物的冲磨和空蚀破坏一直是水利水电工程中有待妥善解决的关键技术难题，尤其近年来高坝巨型水电站的建设使泄流速度大幅提高，冲磨和空蚀问题愈加突出。本文针对目前相关研究存在的不足，开展高速水流冲磨与空蚀耦合作用机理研究。利用水力学Bernulli原理实现水沙自动混掺、引入突扩体型抗空蚀措施，发明冲磨与空蚀耦合作用试验装置；借助先进的高速摄像系统捕捉含沙水流空化气泡溃灭瞬间冲击形态，综合水动力特性、振动与噪声、蚀损特征，揭示冲磨与空蚀耦合作用机理；采用环境扫描电镜和数字图像技术研究不同性质材料的蚀损机制，提出冲磨与空蚀耦合作用下融合水流空化数、含沙量、粒径、材料力学特性等参数的蚀损模型；选择合适的边界条件和破坏准则，在有限元框架内建立高速挟沙水流与泄水结构非线性瞬态动力接触分析方法，预测过流壁面的蚀损进程。研究成果将为抗蚀新材料研发和泄水建筑物抗蚀设计提供科技支撑。

针对水利水电工程中一直存在、尚未得到妥善解决的泄水建筑物的冲磨和空蚀破坏技术难题，以及在冲磨与空蚀耦合作用机理及过流壁面蚀损机制方面研究的不足，本项目以揭示高速挟沙水流冲磨与空化耦合作用过流壁面蚀损机理为目标，历时四年研究，先后完成了空化空蚀水动力荷载特性试验、空蚀冲磨单独作用机制与影响因素试验、冲磨与空蚀耦合作用试验装置研发、冲磨与空蚀耦合作用机理试验研究、冲磨与空蚀耦合作用下过流壁面蚀损预测模型研究、窄缝空化特性与掺气减蚀机理研究及工程应用等研究工作。通过项目研究，阐明了高速水流空化水流作用区水动力荷载特性、混凝土材料空蚀破坏机制及蚀损进程、材料冲磨破坏机理与影响因素；基于Venturi空化空蚀试验装置和水力学Bernulli原理，成功研发了高速高压水流自动挟沙装置、高速水流冲磨与空蚀混合作用试验系统，创建了高速水流冲磨与空蚀耦合作用试验新技术，揭示了混凝土材料在冲磨与空蚀耦合作用下的蚀损机理及二者的相互促进机制；提出了新的水下棱石法科学模拟推移质对各种材料的冲磨作用；明晰了混凝土材料空蚀、冲磨与水流空化数、流速、含沙量、微粒含量、硬度、粒径以及壁面材料力学参数等各种影响因素之间的内在关系，建立了冲磨与空蚀耦合作用下融合多参数的材料蚀损模型，用于泄水建筑物过流壁面蚀损进程数值预测，研究成果为抗蚀新材料研发和泄水建筑物抗蚀设计提供科技支撑；揭示了窄缝强空化自然通气及高水头工业阀门强迫通气抑制空化机理，提出了可应用于实际工程的高水头阀门防空化技术，并在大藤峡水利枢纽船闸、景洪水力式升船机等国家重大工程建设中得到应用，充分体现了科技服务工程的支撑作用，发挥了一定的经济社会效益。项目研究取得的多项创新成果在学科发展、行业科技进步、工程建设等方面发挥一定的促进作用，相关技术具有很好的推广应用价值和前景。