Experimental Research And Numerical Simulation On Transient Characteristics Of Air-bearing Water Flow In Water Pipeline

In the process of water delivery,due to pump shutdown,sudden valve closure,blockage,poor air valve exhaust,etc.The pipeline is often in a gas-water two-phase flow state,and the interaction between the two phases can easily cause abnormal transient pressures.Pressure fluctuations cause severe vibrations in the water pipeline,causing accidents such as leaks and pipe bursts,which is very detrimental to the safe operation of the water pipeline.Therefore,this paper uses a combination of experimental research and numerical simulation to study the transient characteristics of air-bearing water flow during water transportation.The main research contents and conclusions are as follows:(1)The transient flow test platform for gas-containing water pipelines was built,the working fluid water flow was 20-30m3/h,and the gas flow was 0-10L/min.The transient flow was introduced by quickly closing the valve,and the different influence of factors on the pressure and flow of each node of the pipeline.The results show that the smaller the leak hole and the closer the leak location is to the upstream reservoir,the larger the transient water hammer pressure peak at each node of the pipeline,and the longer the pressure decays to stability;the inlet flow rate decays linearly under the influence of different factors.(2)A test platform for adding air tanks was built to explore the influence of air tanks on the transient characteristics of gas-containing water pipelines.The results show that the air tank can not only effectively reduce the transient water hammer pressure,but also has a buffering effect on the sudden rise of pressure in the pipe,so that the transient water hammer pressure peak is more gentle at the sharp point;The air tank has no obvious influence on the attenuation of the inlet flow.(3)The mathematical model of gas-bearing flow transient flow based on unsteady friction is constructed,and the characteristic method is used to calculate and solve it.The model is verified by experiments,and the influence of different factors on the pressure at the end of the valve is analyzed.The result shows the lower the gas content and the greater the initial flow rate,the greater the transient water hammer pressure at the end of the valve;different initial flow rates and smaller leakage will not cause significant changes in the cycle;The closer the leak location is to the upstream reservoir,the smaller the difference in the pressure curve of each node of the pipeline.Therefore,the amount of leak and the location of the leak can be roughly judged based on the pressure and cycle changes.