| As an important method of water resource scheduling and supply,water pipelines are widely utilized in modern society.However,due to the uniqueness of different projects,pipelines and pump unit equipment may experience serious pressure pulsation issues after the pump accidently stops.Therefore,selecting safe,reliable,economical,and practical water hammer protection measures,and optimizing the parameters of water hammer protection equipment,has important theoretical and practical significance for ensuring the safe and stable operation of the pipeline system.This paper focuses on a water lifting project in Yunnan Province,analyzing the water hammer protection and joint protection effects of the multi-functional water pump control valve and air valve single equipment.Additionally,based on the response surface method,the protection effect of air tank parameters on water hammer was studied and the parameters were optimized and analyzed.The main research work and conclusions are as follows:(l)The water hammer theory is used to establish a mathematical model of the hydraulic transition process of the pressurized pipeline,and the characteristic line method is combined to analyze the steady-state and accident shutdown of the three operating water levels.The research results show that water supply requirements can be met under the three operating water levels in steady-state operation.However,water hammer protection measures need to be taken to ensure safe operation of the water delivery pipeline when the pump stops due to an accident.(2)The research studies the different protection characteristics of the multi-function water pump control valve under the linear closing,two-stage closing,and three-stage closing modes.The research results show that reasonable selection of fast closing time,fast closing amount,and total valve closing time can effectively reduce water hammer pr€ssure,and the speed of the water pump can meet the specification requirements.When the three-stage closing method is adopted, it will play a further control effect on the water hammer problem.(3)The research analyzes the water hammer pressure before and after the installation of the air valve and simulates the arrangement position,quantity,intake aperture,and exhaust aperture of the air valve in the pipeline.The research results show that a compound air valve with a suitable aperture can achieve the purpose of reducing negative pressure and positive pressure at the same time.Using the two-stage closing method of the multifunctional water pump control valve and the combined protection scheme of the compound air valve can effectively improve water hammer pressure problems and excessive reversal of the water pump.(4)Using the response surface method,the parameters of the air tank were optimized to obtain the optimal combination that takes into account the maximum and minimum pressure heads as response values,and the diameter of the connecting pipe,cross-sectional area,air-water ratio,and tank height as influencing factors.By analyzing the influence order of each parameter on the maximum and minimum pressure heads and their interaction,and combining the economic benefits of the project,the optimal parameter combination was obtained.The research results indicate that the diameter and cross-sectional area of the connecting pipe of the air tank are the most sensitive parameters affecting the maximum and minimum pressure heads during the hydraulic transition process of the water pipeline.The optimal combination includes a connecting pipe with a diameter of 100mm and a cross-sectional area of 7.5m~2,an air-water ratio of 1,and a tank height of 10m,resulting in an air tank volume of 75m~3.Compared to not having an air tank installed,this optimal combination reduces the maximum positive pressure by 42.26%and increases the maximum negative pressure by 88.72%. |
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