Study On Water Hammer Protection For Water Conveyance System Of High Lift Pumping Station

China is a country with extreme shortage of water resources and uneven distribution.In order to solve the problem of supply and demand of water resources,a large number of water conveyance projects have been built,and most of the water hammer problems caused by accident stop pump have been destroyed in the process of water conveyance,so equipment is needed to protect them.Through the study of different water hammer protection equipment,it can play a greater protective effect and provide reference for similar projects.Based on the water conveyance project of Jingdian Phase I pumping Station,this paper focuses on analysis of the protection effect of a single device and parameter optimization by using water hammer software,as well as the calculation and analysis of the combined protection of various equipment.The main research results are as follows:(1)A single protective measure is taken for water hammer protection in the water conveyance system of high lift pumping station.Although this measure can not meet the protection requirements,it can obtain better protection effect by optimizing the size specification of the equipment and adjusting the operation procedure parameters under the most unfavorable conditions.(2)Through the analysis of the simulation results of the actual project,the reasons of the pipe burst accidents occur when the pump stops under the original protective measures are found.In the simulation and analysis of the non-traditional protection measures to change the slope of the upstream and downstream pipelines on both sides of the 3~#anchor block,it is found that reducing the elevation of the pipeline nodes here can effectively alleviate the positive pressure of the water hammer and the volume of the broken flow cavity.However,when the node elevation of 3~#anchor block pipeline is reduced to the same elevation as that of 2~#anchor block,the location of the maximum cavity will also be transferred to 4~#anchor block,and the negative pressure in the whole process remains unchanged.This protection method can effectively improve the water hammer hazard caused by accident pump shutdown.(3)Through the analysis of the simulation results of various protection schemes in actual engineering,it is found that on the basis of effectively controlling the backflow and reverse speed of the pump,adopting the combined protection method of two-stage slow-closing valve and compound air valve can reduce the whole negative pressure of the pipeline,but there are high positive pressure and vapor cavity;By adopting the combined protection mode of two-stage slow closing valve and one-way surge tank,the positive pressure of pipeline and cavitation cavity are well controlled,but there is still a large negative pressure in the whole process.The combined protection measures of two-stage slow-closing valve,compound air valve and one-way pressure regulating tower are adopted,and the positive and negative pressure of the pipeline and the vapor cavity are effectively controlled,and the protection effect is the best.Combined with the simulation results,it is found that setting the one-way surge tank at the place where the inflection point of the pipeline is most obvious and generating cavitation can only effectively improve the positive pressure of the entire pipeline and the phenomenon of water column breaking;The installation of compound air valve in proper position can obviously reduce the positive and negative pressure along the pipeline and the negative pressure is effectively controlled,so as to avoid the problem of pipeline collapse.When the pump stops in case of accident,the change of pipeline pressure can be better controlled.