Resilience Study Of Pumping Station Pressurised Aqueducts To Cope With Water Hammer

As an important part of the infrastructure,the safety and reliability of urban water distribution systems are of wide concern.Water hammer occurring during system operation can cause dramatic pressure fluctuations in the pipeline,causing damage to the water transmission pipeline and its ancillary components,and is a major factor jeopardising the safe operation of the system.Traditional qualitative analysis and risk analysis of an individual node in the system are not sufficient to reflect the ability of the whole water transmission system to cope with water hammer,and the development of the concept of resilience has provided new ideas for the assessment of the ability of the water transmission system to cope with water hammer.The article proposes the concept of resilience of pumping station pressurised water distribution systems to cope with water hammer,and establishes corresponding quantitative indicators to evaluate the system’s ability to cope with water hammer and optimise water hammer protection schemes.The specific research work is as follows.(1)Resilience of water distribution systems to cope with water hammer and its evaluation.Based on the definition of resilience and its application in other fields,the concept of resilience of pumping station pressurised water distribution pipes in response to water hammer is proposed,a formula for calculating the resilience index based on the probability of pipe failure is given,and a Monte Carlo algorithm is used to solve for the probability of pipe failure,so that the system resilience index value can be calculated.This allows a quantitative assessment of the ability of an actual raw water distribution system to cope with water hammer.(2)Evaluation of the water hammer protection effect of check valves and parameter optimisation.Check valves are often required on pump discharge pipes,but different types of check valves and shut-off schemes have very different effects on water hammer protection.For the commonly used common check valves,liquidcontrolled butterfly valves and multifunctional pump control valves,the transient hydraulic simulation of water hammer at the pump stop is used as an evaluation criterion for the evaluation of the protection effect of the three and the optimisation of the shut-off scheme using resilience indicators.In the case of this study,if an ordinary check valve is set on the discharge pipe,its resilience value for water hammer is 0.524;when a liquid-controlled butterfly valve is used,its resilience value for water hammer can be increased to 0.730 through the optimisation of the shut-off scheme,and if a multi-functional pump control valve is used,its resilience value for water hammer can be increased to 0.830 after optimisation.(3)Evaluation of the water hammer protection effect of the two-stage closed air valve and parameter optimisation.The impact of each parameter of the air valve on the resilience of the water delivery system to cope with water hammer is interactive.In this study,orthogonal test methods were used to design five-factor,four-level simulation experiments on five characteristic parameters of the two-stage closed air valve,including the bore,intake coefficient,exhaust coefficient,size and exhaust port area ratio,and critical pressure ratio of the switching outlet orifice,etc.The impact of each parameter on the water hammer protection effect was compared and analysed through transient hydraulic simulation and calculation of resilience index,and the optimal air valve parameters were obtained.In this study,the air valve parameters of the water distribution system are: 100 mm bore,0.6 inlet coefficient,0.1 exhaust coefficient,0.2 orifice area ratio and 1.10 critical pressure ratio.0.921.(4)Resilience improvement strategy for pumping station pressurised water pipelines against water hammer.A single water hammer protection scheme often does not achieve good water hammer protection.In this regard,on the basis of "slow-closing check valve-air valve",further comprehensive protection measures are proposed:"check valve-one-way pressure regulator-air valve" combined solution,"check valve-air tank-air valve The "check valve-air tank-air valve" scheme.Through the transient hydraulic simulation and resilience index calculation,the resilience index value of water hammer of stopping the pump was increased to 0.982 and 0.983 respectively,and the resilience level of the two comprehensive protection schemes against water hammer reached "better".