窄缝射流空化诱发止水强烈自激振动机理及防治技术研究

In view of the practical condition of valve top seal hydraulic damage of high head ship lock and no measures proposed, it is very necessary to carry out the study on self-excited vibration mechanics and control technology of valve seal induced by narrow slit jet cavitation with the super high head and large scale development of ship lock. In this program, the new 1:1 slice test technology of top seal without scale effect will be proposed to study the interact mechanics between the severe self-excited vibration of the top seal and unstable jet cavitation in the small opening of the valve. Systematical tests of the influence factors to the self-excited vibration will be conducted to reveal the critical instability condition and unstable region and construct the inner relationship between the self-excited vibration and dynamic characteristics, narrow slit width, flow velocity, downstream pressure and so on. Based on the deformation of the top seal under different water head, material nonlinear constitutive model will be formulated considering the volume deformation. The flow-structure interaction numerical analysis method will be built involving the nonlinear and large deformation characteristics of the top seal to predict the self-excited vibration stress and the seal life. The new technology of natural aeration of the top seal will be proposed to control the cavitation and self-excited vibration. It will achieve the demand of project application after demonstration and optimization. The research results will be benefit for the optimization of the seal structure, prediction of the seal life and the control of the cavitation and self-excited vibration. Also the development about the coupling self-excited problem study between flow and the hyper-elastic material like rubber will be promoted.

针对高水头船闸阀门顶止水频繁水力破坏而无计可施的现状以及船闸超高水头、大型化的发展趋势，开展窄缝射流空化诱发止水强烈自激振动机理及防治技术研究十分迫切。本项目拟通过研发无缩尺影响的顶止水1:1切片试验技术，研究揭示阀门小开度顶止水强烈自激振动与非稳定射流空化相互作用机理；通过止水自激振动各种影响因素系统性的试验研究，揭示止水的临界失稳条件和不稳定区间，构建自激振动与顶止水动力特性、窄缝宽度、流速、下游压力间的内在关系；基于不同水压条件下止水的变形特性，提出融入止水体积变形的材料非线性本构模型，建立考虑止水非线性大变形特性的流固耦合振动分析方法，预测止水自激振动应力与寿命周期；提出抑制顶止水不稳定空化与自激振动的自然通气新技术，通过论证并优化后达到工程应用的条件。研究成果将为顶止水结构优化、寿命周期预测、空化与自激振动防治提供科技支撑，也将促进其他超弹性结构与流体耦合自激振动问题的研究发展。

在船闸日益高水头、大型化背景下，阀门顶止水空化、自激振动及水力破坏问题愈加突出，针对相关研究的不足，采用1:1切片试验技术及数值模拟相结合的方法，先后完成了窄缝射流空化诱发阀门顶止水自激振动机理试验研究、阀门顶止水自激振动影响因素试验研究、考虑止水非线性大变形特性的流固耦合振动数值分析方法研究、抑制顶止水空化与自激振动新技术研究等工作，揭示了窄缝射流空化诱发止水自激振动机理，提出了行之有效的防治措施。.设计三试件同步试验装置，实现了三种配方止水试件在相同的试验条件下开展抗冲磨试验，揭示了止水材料冲磨破坏微观特征及主要影响因素；研制了高水头阀门顶止水空化振动1:1切片试验装置，实现了现场阀门顶止水的工作条件真实模拟和反演，为高水头阀门顶止水安装变形特性、挡水变形特性、自激振动特性研究提供了很好的试验平台；水动力学试验揭示了射流空化是引起阀门开启初期冲击性振动的原因，窄缝射流空化在止水下表面产生20~80Hz的宽频压力脉动，易引起柔性止水大变形失稳，诱发自激振动；止水自激振动表现为稳定、持续、窄带、高频振动，在止水周围产生周期性的脉动压力，强度是正常缝隙射流脉动的10~30倍，止水自激振动是引起阀门结构强振动和止水水力破坏的主要原因；缝隙宽度、材料硬度、止水结构形式是自激振动的主要影响因素，缝隙宽度越大较大、止水较硬、止水厚度越大，自激振动越不容易发生，随着止水缝隙宽度的增加，自激振动频率减小、振幅增大，随着止水硬度的增大，自激振动频率增大、振幅减弱。.基于本项研究，提出了阀门顶止水工作条件三项改善措施，以延长顶止水的使用寿命，尤其增加挡水板可以减小止水变形、抑制自激振动，达到很好的改善效果。形成的高水头阀门顶止水结构型式、安装控制、抑振措施等关键技术，先后在大藤峡水船闸、葛洲坝船闸中得到应用，发挥了很好的科研服务作用，并将在更多高水头船闸运行管理中应用。