Study On Hydraulic Transition Characteristics Of Pipe Arrangement In Water Supply System Of High-rise Building

Water hammer is a kind of hydraulic transition phenomenon in pressure pipeline,which is an important factor that affecting the safe operation of water supply system in high-risen building.However,at present,the research focus of water hammer in building water supply pipeline is mainly introduced on the causes,harm and protection of building water hammer and so on,but lack of in-depth exploration of hydraulic transition characteristics under different layout forms of water supply system pipeline network.Therefore,this paper takes the layout form of the up-to-down form and down-to-up form in high-risen building water supply system as the research object,and analyzes the influence of the two pipeline layout forms on the water hammer in the process of accident pump shutdown and rapid valve closing.Firstly,the reasons and effects of water hammer are analyzed.This paper introduces the derivation of water hammer wave velocity and basic differential equation,and on the basis of the characteristic line numerical calculation method,the compatibility equation which is convenient for computer programming is given,which provides the theoretical basis for the water hammer simulation in the following paper.Secondly,two kinds of pipeline arrangement,which are common in water supply system,are taken as research objects.The maximum pressure envelope and minimum pressure envelope are taken as the criterion to distinguish the damage of water hammer,and the hydraulic transition characteristics of two types of pipeline arrangement are analyzed.The results show that the two arrangements can withstand the maximum pressure of water hammer because of the large safety margin of the pipeline,but for the minimum pressure,the upward feeding mode is more likely to produce negative pressure vacuum and water column separation.Combined with relevant hydraulic knowledge,the forming conditions of water column separation cavity are explained,and the reason why water column is more likely to occur under the upward flow is analyzed.Thirdly,the calculation program of water hammer in building water supply system is established,and the calculation function which can be realized by the program is introduced,to provide technical guidance for water hammer protection of high-risen building water supply pipeline.Through building the experimental platform and carrying on the water hammer simulation experiment,the experiment data and the simulation data are compared to verify the reliability of water hammer calculation program.Fourthly,taking a high-risen building as an example,two kinds of pipeline layout water supply models are constructed,and hydraulic transient simulation analysis is carried out.The results show that in the case of pump shutdown,the maximum pressure of water hammer from the down-to-up form and up-to-down form pressure is 120.2m and 181.6m,respectively.In the case of rapid closing valve,the maximum water hammer pressure on the down-to-up form and up-to-down form pressure is 118.2m and 136.9m,respectively.Under the two hydraulic transition conditions,the maximum pressure of water hammer is controlled within the range of the pressure value of the pipeline,do not leading risk of pipe burst.However,according to the analysis of the minimum water hammer pressure,under the two hydraulic transition conditions conditions,the phenomenon of negative pressure vacuum is more likely to occur in the up-to-down form of the horizontal main pipe,resulting in water column separation.Therefore,the down-to-up form is better than the up-to-down form in the pipeline layout.In view of the influence of water hammer on building water supply system,designed the water hammer protection measures of air pressure water tank and multi-function water pump control valve.The results show that both of them can reduce the maximum positive pressure and achieve the purpose of protecting the safety of the sanitary appliances and pipeline system.Meanwhile,air pressure water tank can effectively control the formation of negative pressure and ensure the safe operation of pipelines.