Research On Safe Operation Mode Of Long-distance High-lift Water Transmission Project

China’s total water resources are abundant,but the per capita occupancy is relatively small.The main feature is the uneven distribution of water resources in time and space,and the contradiction between supply and demand is outstanding.Therefore,the establishment of a long-distance water delivery project across regions and across basins is one of the first-choice technical means to realize the rational dispatch of water resources.The long-distance high-lift water conveyance project is generally composed of a water supply system of a pressurized pump station and a gravity flow water conveyance system,and has the advantages of less water loss and convenient operation and maintenance.In order to ensure the safety and economic operation of water delivery projects,the economic operation mode of water supply systems and the protective measures under sudden power failure have become an important technical topic that experts and scholars in the industry generally pay attention to.This paper takes the direct supply of Yangqu raw water in the connecting section of the Wanjiazhai Yellow River Diversion Project in Shanxi Province as the research object,and establishes the mathematical model and boundary condition equations for the steady-state and transient operation of the pressurized pumping station and gravity flow system;The working principles and characteristics of non-engineering water hammer protection measures such as hydraulic control check valves,air valves,air tanks,flow regulating valves,overpressure relief valves,etc.are analyzed,and the corresponding mathematical models and boundary condition equations are established;According to the influence of the parameters such as the height of the air chamber of the air tank,the cross-sectional diameter,the initial liquid level,the intake and exhaust coefficients of the air valve on the effect of the protective water hammer,a sensitivity analysis is carried out.Reasonable selection of the type;calculation of the hydraulic transition process of the pressure pumping station system and gravity flow water delivery system of the project,based on the calculation results,the closing rules of the two-stage hydraulic control check valve,the installation position,elevation and caliber of the air valve,Theparameters such as the closing time of the pressure regulating valve are reasonably optimized to determine the best protection plan.The main conclusions are as follows:(1)Through the steady-state analysis of the booster pumping station system,it is concluded that the pump efficiency and pumping station efficiency of the single pump,two pumps,and three pumps of the booster pumping station are parallel,which meets the requirements of "Pump Station The Design Code requires that the pump selection of the pumping station is reasonable.(2)Reasonably extend the closing time of the flow regulating valve at the end of the gravity flow system,which can effectively improve the valve closing water hammer caused by the valve closing,and is conducive to the safe operation of the system.(3)When the water hammer of the air valve protection system is used,a larger intake coefficient and a smaller exhaust coefficient can effectively improve the negative pressure problem of the pipeline system;increasing the diameter of the air valve within a reasonable range is conducive to improving the system water hammer.(4)When the water hammer of the air tank protection system is used,increasing the height,cross-sectional diameter,and initial liquid level of the air tank within a reasonable range is beneficial to the water hammer of the protection system.(5)When the two-stage hydraulic control check valve + air valve + air tank joint protection is adopted in the booster pump station system,the maximum pressure,minimum pressure,and maximum reversing speed of the pump all meet the design standards and requirements;the gravity flow system is regulating Under the condition that the pressure regulating valve closes for 600 seconds,the terminal installation of an air tank + the installation of an air valve along the line for joint protection can make the maximum pressure and minimum pressure of the pipeline meet the design requirements.(6)Through the analysis and research of this paper,it provides technical support for the safe operation of the Yangqu raw water direct supply project in the connection section of the Wanjiazhai Yellow River Diversion Project in Shanxi Province,and also optimizes the design and operation management of the same type of long-distance water delivery projects.Provide technical basis.