Water Hammer Analysis And Prevention In Long Distance Pumping Water Transmission System

With the development of industry, improvement of living standard and further development of towns and cities, water demand of cities is increasing rapidly. It is hardly to satisfy the water demand of living and industrial manufacture by only using water resources nearby these cities. In addition, the water resource distribution is quite uneven both in time and space over China, the conflict of water supply and demand is further worse, and the development of the economy and living standard are restricted. In order to meet the water demands ensure the normal water services, more and more long distance water transmission projects are founded, in which Water Diversion Project from South to North is the prominent milestone. Many factors affect the pipeline arrangement of long distance water transmission work, which make the elevation change of the pipeline vary greatly. When water hammer takes place, pressure will decrease in some parts of the pipeline, inspiration, gas release, liquid vaporization and water column separation may happen, while when pressure is increasing in turn, water interception collision may appear and the pressure can be extremely high. These will make the whole water supply system totally unsafe. So correct analysis water hammer of pumping water supply system, exact prediction its transient processes and rational selection the protection plan are very important to the engineering design optimizing and project safe operation guarantee, and have significant meaning and practical value to the water supply and economic development.The dissertation consists of the following contents:(1) The paper presents the purpose and significance of the research, tells the mechanism, classification, theory and analysis and computing methods of water hammer in water transmission system, and summarizes the current situation of water hammer.(2) The paper summarizes and presents the mainly used computing methods of water hammer wave velocity, gives the basic differential equations of water hammer and method of characteristics, details common boundary condition of method of characteristics in simple andcomplex pipeline system, including upriver and downriver reservoir, normal operating pumps, valves in pipeline and at the end of pipeline, pipe in series and branch piping.(3) Some conventional methods of sectioning of preesure pipeline system are introduced, and wave velocity method is studied and improved.(4) The boundary conditions of pump units closed-down in accident is established, including single pump, pump in series, pump in parallel, pumping set with by-pass pipe, and the numerical calculation is carried out.(5) The paper discussed the cause of formation and characteristics of gas cavity in hydraulic transient, and establishes primary calculate models of two-phase hydraulic transient of gas-liquid.(6)The paper expounds the constitutes of the equipment, protection mechanism, design point and characteristics of the common water hammer prevention measures in long distance pumping water supply system. Moreover, the corresponding boundary conditions of water hammer prevention measures, including simple surge tank, one-way surge tank, air valve, and two-phase butterfly valve control, are founded. Meanwhile, the design of air input and air exhaust of pipeline and the existing problems of air valve are simply discussed.(7) Analysis and calculation of water hammer in water supply project of an electricity plant at Yulin in Shaanxi Province are carried out, and properly water hammer prevention measures are given out.