Numerical Simulation Of Leakage And Diffusion Flow Field Of Urban Buried Gas Pipeline

At present,China’s natural gas is mainly transported through pipelines.If gas leakage occurs due to pipeline damage,it will cause major accidents such as personnel poisoning,fire or explosion.The accident leakage models are small hole leakage under the ground and large hole leakage caused by construction.Based on the characteristics of two kinds of leakage accidents,this paper studies the law of gas leakage and diffusion in soil under different scenarios through three-dimensional numerical simulation,as well as the changes in hazardous areas after gas leakage in atmospheric space,so as to provide a theoretical basis for emergency treatment and gas pipeline laying.In this paper,the leakage characteristics of urban buried pipelines are studied by numerical simulation.The mathematical models of different accidents are established,the relevant theories are expounded,the fluid control equations are solved,and the theoretical derivation formula of gas leakage is obtained,which is the basis for fitting the quantitative formula.The reliability of the mathematical model is proved by comparing the change of methane concentration in the experimental model.The law of gas leakage and diffusion in soil pores was studied.The analysis shows that the methane concentration cloud map shows a left-right axisymmetric distribution,the concentration gradient is distributed from the middle high to the surrounding low,and the leakage amount reaches a stable and unchanged in a short time after the fluctuation.The dangerous radius of 45 ° elbow is the largest,followed by 90 ° elbow,and the straight pipe is the smallest;The distribution area of methane concentration in soil is positively correlated with pipeline pressure;The buried depth of pipeline has a profound influence on the distribution pattern of gas diffusion flow.The leakage aperture is positively correlated with methane concentration;The circular leakage hole has the largest leakage risk area,followed by rectangle and triangle.The dangerous range of diffusion in silty sand is the largest,followed by loam and clay;The soil moisture content is negatively correlated with the lower limit of methane explosion.The law of large pore leakage and diffusion of gas in atmosphere is studied.The conclusions are as follows: for determinant,confining and oblique forms,the wind speed is positively correlated with the dangerous area of methane diffusion within 0m/s-9 m/s;When the temperature is-10 ℃-30 ℃,it has a temporary effect on the initial stage of gas diffusion;The height of buildings is within 15 m-50 m.The higher the buildings,the greater the vortex intensity,and the greater the dangerous range of gas diffusion in residential areas.Enclosed building layout has the worst gas circulation,followed by the oblique layout,and the determinant layout has the best gas circulation.At the same time,there is a negative correlation between the dangerous area and the gas circulation.Therefore,the enclosed layout has the largest dangerous area and the worst safety.Therefore,the intensity of safety inspection should be strengthened.The law of gas leakage and diffusion in soil atmosphere was studied.When there are two buildings symmetrical about the leakage hole on the surface,the gas diffusion is only limited near the surface,the horizontal diffusion degree is greater than the vertical diffusion degree,and the dangerous range is also concentrated near the surface between the two buildings.