| The water from South-to-North Water Diversion Project is transferred to regulation and storage engineering of Miyun reservoir and the water is drawn by Tuancheng Lake and delivered backward by Jingmi diversion canal.Nine grades of pump stations are constructed to transfer the water from main canal of South-to-North Water Diversion Project to Miyun reservoir.The overall length of water diversion route is about 103 km.The overall water diversion scale from Tuancheng Lake to Huairou reservoir is 20 m3 /s;the overall water diversion scale from Huairou reservoir to Miyun reservoir is 10 m3 /s.by this project,the utilization efficiency of water from South-to-North Water Diversion Project can be guaranteed and the water efficiency can be sustained.In addition,the reliability and stability of urban water supply can be improved.The distance of water delivery pipe of this project is relatively long and the yield of water is great.The equipment and structures along the project are diversified.The way along the pipe is undulate.The start of booster pump station,emergency shutdown,assembling unit switching,the open and close of ear pump valve would all lead to fluid transient of the system and the change of pipeline pressure in particular.In order to ensure the safe and stable operation of the project,it is necessary to calculate the hydraulic transition process of the whole system so as to define the key engineering operating parameters.With the combination of the example of the design of Yanqi pump station,the eighth grade pump station of the engineering which transfers water from South-to-North Water Diversion Project to regulation and storage engineering of Miyun reservoir,by building the model of the overall water conveyance system and using mature theoretical approaches and calculating software,the influence of all kinds of parameters in the long-distance pressure water supply on hydraulic transition process is calculated and analyzed.The joint control of water pump,regulating valve,air valve,hydraulic control slow closing butterfly valve and other devices in the course of startup and stop process of pump station is studied.In long-distance pressure water delivery engineering,the extreme pressure value and the maximum inversion parameter of water pumping unit are defined.The start-stop law for rear hydraulic control slow closing butterfly valve of the water pump is determined.The arrangement of air inlet and discharge devices along the pipe is reviewed.Significant technical parameters and security assurance are provided for the design,adjustment and stable operation of long-distance pressure water conveyance system.This thesis introduces the modeling of hydraulic transition process of the water conveyance system of Yanqi pump station,the calculation model of fluid transient of the pipe,the calculation model of the boundary of water pump,the calculation model of valve boundary,the calculation model of the boundary of air valve,the mathematical model of pipeline connection and the building and algorithm of other key boundary conditions.In addition,the simulating calculations of all kinds of operation conditions are conducted.According to the computation,the start and stop procedure of water pump and the open-close law for rear hydraulic control slow closing butterfly valve are defined by analysis and research.The main conclusions are as follows:1.The set position of air valve of the pipeline in this project is reasonable.The negative pressure of pipeline system can be effectively controlled under all kinds of normal and fault conditions.2.The open-close law for rear hydraulic control slow closing butterfly valve which is defined by analysis and research can effectively control the extreme pressure value of the system,the inversion speed of water pump and the reverse-cascaded flow.3.In the course of pump set switch,proper extension of open-close interval of the water pump can reduce the highest pressure of the system and guarantee the security of the pipeline. |
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