Research On The Application Of Water Hammer Protection Of Air Valves In Long Water Supply Systems

With the development of the economy of different countries and the increasing demand of water resources, which people require day by day, more and more cities are in order to solve the sharp contradiction between supply and demand of water resources, long distance and large-scale water delivery cascade pumping stations must be built. In order to prevent the water-supply systems from causing water hammer accidents because many kinds of reasons when transient phenomenon taken place in pipe, When we design, it is necessary to make water hammer analysis, predict and simulate the occurrence of water hammer accidents and diffuse law at power failure to the pumps. Besides considering the routine pressing water hammer, it must be considered that some position in pipeline may take place the circumstances of gas-liquid two-phase hydraulic transient such as gas release, producing hole in flow and liquid column separation. It is of the key that predicting and control studying of gas-liquid two-phase hydraulic transient in pipeline systems for optimizing engineering design, reducing the fabrication cost of the projects, guaranteeing the project safe operation, they have important theory meaning and practical value.The dissertation consists of the following five chapters:Chapter one presents the purpose and significance of the dissertation, introduces the calculation analytical method of two-phase hydraulic transient in pressurized water conveyance pipe systems, and summarizes the historical and current situation of two -phase hydraulic transient.Chapter two describes the basic equations of water hammer, pump boundary condition of pump stoppage caused by power failure, the boundary condition of upstream and downstream pond and commonly used water hammer measures in long distance water -supply systems.Chapter three expounds primary calculate models and characteristics method, implicit finite-difference method, specified time intervals method with interpolations of two- phase hydraulic transient and Lax-Wendroff two step method.Chapter four Sets up the mathematics models calculated in two-phase hydraulic transient and the boundary condition of air valve protection, by taking Guangdong Dayawan Water Supply Project as an example, according to the numerical simulation andanalyses in water hammer characteristic of pump system on not adding the air valves and operating mode with air valves, and calculates the influence on hydraulic transient process of the change in numbers > setting positions > quotieties of gas ingress and release of air valve, research detailedly on function of water hammer protection with air valve in water-supply system of long distances, it has elicited valuable conclusions and suggestions on engineering design and movement.Chapter five summaries the whole research works on the basis of above research, and puts forward the thinking and imagination that will be studied further in the future.