半解析法求解水柱分离与断流弥合水锤问题及机理分析  

Solving water column separation and cavity collapse for pipelines by semi-analytical method

作　　者：韩凯 丁法龙 茅泽育[1] Han Kai;Ding Falong;Mao Zeyu(Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学水利水电工程系

出　　处：《农业工程学报》2019年第15期33-39,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点研发计划(2016YFC0402504)

摘　　要：为了应对长距离输水工程的水锤防护问题,分析了空气阀作用于波状管线有压输水系统发生水力过渡时的瞬态响应过程,提出了空穴增长和溃灭时间、管线最大含气率、最大压力峰值等参数的半解析公式,并由此探讨和研究影响空气阀水锤防护效果的关键因素。半解析解表明,位于空气阀下游的管段相对长度和管线高点的相对高程对系统的断流弥合水锤起了主导作用。将半解析解与特征线法数值解进行了对比,发现两者随主变量的变化趋势一致;分析了半解析解与数值解产生偏差的原因与半解析公式推导过程中几个假设的关系。结果证明,该文提出的半解析公式能够反映空气阀作为水锤防护装置时,主导断流弥合水锤压力峰值的关键因素。该研究可为水锤防护的相关研究提供参考。For pressurized water supply systems,excessive installation of air valves will inevitably increase the risk of secondary water hammer especially when the air valve fails.Therefore,reducing redundant air valves is of positive significance whether from the maintenance cost on apparatus or from the possible adverse impact caused by the malfunction.Compared to traditional analytical and numerical methods,the semi-analytical method adopted in this paper could not only ensure the clear and intuitive physical meaning of the research results but also expand the application scope of the analytical method,which was also conducive to the further study of key parameters.In this research,it aimed to find out the primary relationship between the function of air valves and the geometry characteristic of the system.Taking a simplified reservoir-pipe-reservoir system with one air valve installed at the elevated point for example,the research initially employed the basic theory of fluid transients to analyze the water hammer wave propagation process.Since the gas inhaled through the air valve separated the water column as the depressurized pressure arrived at the elevated point,the system was divided into 2 subsystems at the point according to their different wave propagation processes.The semi-analytical formulas of the target parameters such as the duration time of cavity growth and collapse,maximum air pocket volume and extreme pressure spike,were firstly proposed in a frictionless condition.Based on the formulas,it studied the key factors affecting the protective effect of the air valve against the water hammer.The semi-analytical solution indicated that the relative length of the downstream pipe section and the relative elevation of the high point played a leading role in the process of cavity growth and collapse.The effect of friction was later taken into the consideration of the semi-analytical expressions serving to reveal its influences on the system.Numerical simulations established on the method of characteristics,which

关 键 词：压力 模型 空气阀 半解析方法 液柱分离 断流弥合 特征线方法 

分 类 号：TV131.2[水利工程—水力学及河流动力学]