Study On Pump Failure Water Hammer With Water Column Separation In Long-distance Flat Pipeline

In recent years,with the continuous development of China's economy and society and the rapid growth of population,people's demand for water has increased dramatically.However,the distribution of water resources in China is affected by precipitation,and the spatial distribution is uneven,it is fewer and fewer from south to north and from east to west.In order to solve the problem of uneven distribution of water resources in space,long distance water transfer project came into being,and get more and more attention.Long distance water transfer project construction has invested a lot of manpower and financial resources,once accident occurs,not only caused huge economic losses,it will also cause bad social impact,therefore,to ensure the safe operation of pipelines is very important.In the actual project,we need to make detail calculation and analysis on water hammer in water pipelines,and select the economic and reasonable water hammer protection measures according to the result of the analysis to ensure the safe operation of long distance water transfer project.The paper briefly expounds the flow characteristics of gas-liquid two phase flow in long distance pressure pipeline and airbags boosting mechanism and the common exhaust method.The paper makes a detailed description of the characteristic method used in the calculation of water hammer,establishes the mathematical model of the special boundary point such as pump and tank based on characteristic method,analyzes the generation principle of the two kinds of cavity(steam-cavity and air-cavity)and boundary control equations.The paper discusses the function and applicable conditions of water hammer protection equipment in various long distance water transfer project,and deduces the control equations as special boundary points,introduces the process of using computer language to calculate the source program.In the long distance flat pipeline water project,for the pump head is low,the pump unit inertia is small,the pipeline is longer,the pipeline is easy to produce serious water column separation hazards.Also,the pipeline slope is small and the lack of exhaust power,the pipeline is easy to save gas and produce pressure shock.Therefore,it is of great significance to simulate the water hammer.Finally,takes Hubei Yingcheng city Han River drinking water project as the example,establishes the water hammer calculation mathematics model in longdistance flat pipeline with water column separation,simulates the pressure when pump failure in long distance flat pipelines.Through the comparison and analysis of various water hammer protective equipments such as common exhaust valve,constant speed buffer exhaust valve,overpressure relief valve,air tank,box type two-way surge tank,finally chose using the constant speed buffer exhaust valve as the best exhaust equipment and using the box type two-way surge tank as the economic and effective pressure stabilizing equipment,and concluded that the combination of the two protective equipments was the best protection scheme.This paper provides a reference for water hammer protection of similar water transfer project.