The Study On Hydraulic Transition At The Long-Distance Water Transfer Pipeline System

Due to the expansion of urban sprawl, urban water demand continues to increase, and the distribution of water resources in China is extremely uneven. The groundwater in the northern region is severely over mining, and some of the local water sources can not meet the needs of urban sustainable development, and cause serious environmental security risks. Therefore, a large number of water diversion projects have emerged in the past few years. This kind of long distance water conveyance project uses the pipeline, the pipeline along with the terrain fluctuation, through the river, the road leading up and down fluctuation; the pump station head and the flow is big. In the event of an accident, stop the pump or valve quick closing case, because of the flow inertia and compressibility, will produce more intense pressure fluctuates in the pipeline and spread quickly along the pipeline. The local high point in the pipeline appears negative pressure, the air intake valve, water vapor and dissolved gas release;the bubble will gradually increase or even cut off the water, resulting in the water column separation. When the water reflux,Two of water crashing, water vapor liquefied or dissolved, resulting Cavities Collapsing and Column Separation hammer may cause the pipe to burst or dented destruction, it will seriously affect the normal safe operation of the water pipeline. So it is necessary to analyze and simulate the hydraulic transition process comprehensively and thoroughly on such projects, through the simulation of water hammer process, analysis of the pressure change process and distribution, thus seeking to weaken the transition process, to avoid the harm of water hammer, and provide scientific basis for the engineering design and operation.This article describes the establishment of hydraulic transition process modeling, pumps,valves,air valves and other common key boundary conditions and characteristics line algorithm.This paper combines YuQuanSan Pumping water line model, introduce pumps,valves,air valves and other basic data processing methods, and simulation pumping accidents; according to head and flow curves of the transition process,optimize the air flow valve arrangement and Valve switching process. According to the simulation, the following conclusions:(1) Rational arrangement of the air valve can effectively reduce the negative pressure in the pipeline;(2) two-stage valve off mode can effectively improve the flow of the pump down, reducing the negative pressure in the pipeline;(3) limit water hammer pressure both from the perspective of effectiveness or reliability, are required to take various measures to jointly deal with;(4) Pump station of the water hammer protection difficultly, it suggested inverter-driven pumps, and gradually shut down the pump when the power supply is normal, weakening the water hammer pressure.