Numerical Simulation Of Leakage Diffusion In Buried Gas Pipeline

Buried gas pipelines have certain concealment because they are laid in the soil.If the pipeline has leakage accident,it is difficult to be found in time.When the concentration of the gas reaches a certain threshold,it will cause harm to the human body.Once the gas encounters an open flame,serious accidents such as fire and explosion may occur.Therefore,it is of great significance for enterprises to study and summarize the causes of leakage accidents in natural gas pipelines,and to simulate and analyze the laws of natural gas diffusion after pipeline leakage,so as to effectively prevent the risk of leakage or to take professional remedial measures when pipeline leakage accidents occur.This paper uses analytic hierarchy process(AHP)to summarize and analyze the possible causes of pipeline leakage accidents.It systematically combines the concepts of basic gas flow theory,basic leakage rate model and porous media theory to study the diffusion of leaking gas in pipelines.Then,Pipeline Studio software was applied to study the pressure change of the pipeline leakage points during the gas leakage process.ICEM was used to establish a three-dimensional geometric structure model,and FLUENT software was used to perform numerical analysis and simulation of gas flow in soil over time.In the simulation calculations of this paper,the main component of natural gas,methane,is used as the research object to analyze the effects of different leakage pipeline pressures and different leakage pore diameters on the diffusion of natural gas leakage.The distribution cloud maps of methane mass fraction at different time nodes was studied,and the distribution of methane at point 5 mm above the leak hole O point,point N at 1 cm,point P at 5 cm and point Q at 10 cm was monitored.The results show that in the early stage of leakage,the methane molecules diffuse into the soil in a spray pattern.During the diffusion process,the gas is affected by the inertial resistance and viscous resistance of the soil,and the rate of leakage and diffusion decreases accordingly.Over time,methane began to spread around the soil,and the diffusion area continued to increase.For the same time node,under the condition of the same pipeline pressure,the pore diameter of pipelineleakage becomes larger,the more gas flow rate of leakage is,the more diffusion area is increased,which is a positively correlated influence.When the size of the leak hole is fixed,the diffusion conditions of different pipeline pressures are simulated.The initial diffusion area is small,the methane concentration is low,and then the diffusion area continues to increase.The concentration gradient gradually decreases from inside to outside,and the methane mass fraction near the leakage hole reaches 90%.At the same time node,the higher the pipeline pressure,the higher the methane concentration in the soil in the same area.Under the same operating conditions,the closer the M point,N point,P point and Q point to the leak hole,the higher the concentration of methane.As the gas continuous to escape,the concentration of these four points continues to increase,and the low concentration area gradually replaced by high concentration.By simulating the change of methane leakage under different pipeline pressures and different leakage apertures,and analyzing the law of natural gas diffusion in the soil,it can effectively determine the occurrence of leakage,prevent accidents,and reduce the harm caused by accidents.