The Study On Optimization And Protection Of Water Hammer In Large-height Water Supply Pipeline

The water hammer phenomenon in the pipeline often damages the pumps,valves and other equipment,which would influence the normal water supply of the city.Because the previous water supply network does not require the calculation of water hammer,there are less research on water hammer in China.However,more and more water hammer accident made people pay more attention to the danger of water hammer.Water supply in hill is restricted by terrain conditions,so the water transmission pipeline could change a lot and water supply could cause height difference.In addition,the flow conditions in pipeline are unstable and easy to change.When an unexpected condition occurs,such as pump stopping caused by a sudden power outages,the water hammer of cavities could collapse prone to pipeline.If the condition more serious,it will cause pipeline broke,pump house flooded and son on that will result in large economic losses.Therefore,it is of great significance to optimize engineering design and ensure safety of water supply through numerical simulation of the water hammer and adopting the appropriate water hammer protection measures.In this paper,the mechanism of water hammer generation,the calculation theory and the protection method are deeply understood,focusing on the method of characteristic line method for water hammer calculated.The calculation steps of the characteristic line method are solved by solving the valve-closing hammer of the simple pipeline.Self-made computer program that combined with understand to the calculation method of the characteristics line method achieved to solve value-closing hammer simulation by itself.It can be calculated directly value-closing hammer in the project,according to the result analyze the impact by the change of value-closing action and value-closing time.The first calculation by programming,with a high head pressure water supply pipe line of water hammer protection as an example,analyzed and shut off valve effect of time on the valve-closing hammer;then using Hammer software,taking large height difference of water supply pipeline of a scenic area of Shandong Province for example,research on water hammer protection method,analysis of the Characteristics of water hammer protection equipment such as two-stage butterfly valve slow closing,air valve,one-way surge tank air vessel and so on.Different protection measures are optimized to simulated the water hammer protection effect,and the optimal water hammer protection scheme is obtained.The main conclusions are as follows:?1?Through the study of the mechanism of water hammer,it is recognized that water hammer will occur at any time in the water supply pipeline.Depth study of the use of characteristic lines to solve the water hammer method,mastered its calculation steps,in order to further study the water hammer and engineering design laid a solid foundation.Once the valve closed or suddenly stop the pump,water hammer caused great harm,and the water hammer when the pipeline pressure suddenly rose enough to destroy the pipeline connection,the pipeline leakage is mainly caused by the water hammer conclusions;?2?Different off the valve action different effects,to combine the actual water delivery situation,through a reasonable design to get the best off valve program.The use of check valve two-stage slow closing of the water hammer protection measures,the positive pressure water hammer to reduce the effect is better,but not to reduce the negative pressure on the pipeline.Slow closing check valve closed action to be targeted to design,once the design is not correct,will cause more adverse effects.Engineering simulation found that the maximum step-up valve when the pump step-up value of 263.6m H₂O,the use of slow-closing check valve to reduce the pressure,closing time less than 60 s,the pressure is greater than the pump boost,and 30 s When the valve is closed,the maximum boost value reaches a maximum of 318.2 m H₂O;?3?On the basis of developing the numerical simulation program of valve water hammer,we will continue to develop water hammer program under different constraints to apply to water hammer calculation and simulation in different conditions;?4?The water supply pipe for water hammer protection,the air valve with fast forward and slow out of the way into the exhaust,is conducive to reducing the maximum boost value of the pipeline,set the air valve check valve after the maximum boost value of 241.3 m H₂O,Which is about 20 m H₂O lower than the boost when the pump is stopped.However,for the larger water supply project,the use of slow closing check valve,composite air valve to reduce the negative pressure effect is not ideal,need to be combined with the one-way regulator tower can effectively reduce the negative pressure within the pipeline;?5?Air tank volume is not large,but the buck and steady pressure results are remarkable,suitable for use in the scenic area,especially in the small flow,large difference between the water supply protection effect is better,can make water hammer in the pipeline The pressure becomes very smooth,and by comparing the position of the optimization study,the air tank should be located near the pump outlet.Engineering simulation,the use of composite air valve and slow closing check valve in combination,check valve water hammer maximum boost of 157.6 m H₂O.After adding an air tank with a capacity of 2000 L,the maximum boosting value of the water hammer at the check valve drops to 107.7 m H₂O,the booster decreases by about 50 m H₂O,and the negative pressure of the pipe is well eliminated;?6?Pipeline design,the topographic map after the layout of the pipeline need to manually calculate the extraction of elevation,through the study can use Hongye municipal pipeline software directly extract the topographic map on the layout of the pipeline elevation,reduce the workload;water hammer calculation,the establishment of CAD and Hammer software file conversion,can greatly improve the efficiency and accuracy of water hammer modeling.