Study On Leakage And Diffusion Of Capillary Holes In Natural Gas Pipelines In Underground Pipeline Corridors

With the development of urbanization,the underground pipeline and corridor system is also developing rapidly,which integrates many kinds of urban pipelines,such as communication,water conservancy,electricity and natural gas pipelines,and is the lifeline of a city.There are many kinds of pipelines in underground pipelines,most of which are dangerous to some extent.The gas transported by natural gas pipelines is inflammable and explosive,and there is the risk of leakage and diffusion.Once leakage occurs,it may cause fire and explosion accidents,it brings a certain security threat to the underground city pipelines and the normal production and life of the above-ground residents.Therefore,it is necessary to study the theory and technology of natural gas leakage and diffusion.The research on the leakage of natural gas pipeline in the underground pipeline corridor has a relatively mature theoretical system and research achievements both in theory and technology at home and abroad,but the research process is generally pipeline leakage and large hole leakage.In practical engineering,pipeline leakage is generally due to the third party damage in the pipeline rupture leakage,the accident has the characteristics of sudden,serious,usually the daily safety management is difficult to prevent in advance through technical means.Because of the slow diffusion speed and small leakage amount,it is difficult to give an alarm in time,which causes the leaking gas to stay in the pipe cabin for a long time,and with the increase of the diffusion time,the concentration of gas per unit volume is not high,but the total amount of gas in the whole tube cabin will continue to increase,resulting in great security risks.The research on the theory and technology of capillary leakage is helpful to form long-term prevention mechanism of leakage accident.In order to solve the problem,the paper first studies the gas transport process in the pipeline,including the basic movement of gas molecules in the pipeline,the energy exchange theory in the process.Secondly,the theoretical model and Law of capillary leak diffusion are studied by combining the knowledge of fluid mechanics and kinematics.Thirdly,according to the related physical and geometric models of engineering construction,numerical simulation is carried out with the help of scientific software,and the early-warning mechanism and detection technology of gas pipeline capillary leakage accident are studied.Finally,the General Law of leakage and diffusion of capillary holes in underground pipeline is obtained,and the influenceof different factors on the process of leakage and diffusion is obtained through comparative study.When a single leak hole is leaking,the diffusion process is symmetrically distributed in the case of no wind.The bigger the source strength is,the faster the diffusion is.When the ventilation speed is lower than the leakage rate,there will be some gas diffusing upward.When the ventilation speed is higher than the leakage rate,the gas will not be diffusing upward.When the leakage holes are distributed on both sides of the pipeline,the leakage diffusion is initially symmetrical about the leakage center.Over time,the diffusion gas will converge between the two leakage sources,because of the existence of the wall,the diffusion at both ends will cause a large amount of local gas accumulation.The presence of an obstacle changes its trajectory.