Diffusion Analysis Of Natural Gas Pipeline Leakage Under Thermal Load

With the development of energy and economy,energy which has the advantages of its cleanness,high efficiency and high calorific value,more and more gets the favor of people.Natural gas is a kind of energy,and has abundant reserves.So it is widely used in people's production and life.As the same time,natural gas pipeline industry has also got the rapid development.At present,the factors that natural gas pipeline crossing areas widely,the influence of the external environment and pipeline defects and so on,could lead to pipeline leakage and then cause fires and other accidents.The thermal load produced by the fire has some influence on the diffusion of natural gas and the normal use of the pipeline.Therefore,the leakage and diffusion of natural gas under the thermal load need the necessary research,and strain and harmful consequences caused by pipeline leakage and the law of pipeline stress.The research has provided important application value for taking the effective rescue measures and targeted fire safety countermeasures.In this paper,a leakage and diffusion model of natural gas pipeline under the thermal load is established firstly.The diffusion cloud of natural gas in leaking pipeline is simulated to get the diffusion characteristics of natural gas under the thermal load.Then based on ANSYS finite element software,the thermal-structure coupling analysis model of pipeline is established to analyze the change rule of thermal stress in the leaking pipeline.At last,the harmful consequences of pipeline leakage are analyzed.The studied details are follows:1.Based on the basic theory of fluid mechanics,the flow characteristics of natural gas pipeline leakage and diffusion are analyzed and the formula for calculating the leakage of natural gas pipeline is given.Then the basic governing equations of gas flow are established,and the combustion mechanism of natural gas and the calculation method of jet flame shape are discussed.2.When natural gas pipeline is leaking,considering two conditions that combustion caused by natural gas leakage and environmental fire,the leakage and diffusion model of natural gas pipeline under thermal load is established.Then the validity and validity of the model are verified by using the existing literature data.Then the influence of leakage conditions,environmental conditions and adjacent distance on the diffusion process of natural gas is further simulated.3.Based on the fundamental research of natural gas pipeline leakage consequence and damage criterion,the jet fire damage model and its analytical solution are obtained,and its harm consequence is quantitatively evaluated.That is considering the limit failure in this paper,jet fire radiation radius to surrounding buildings is close to 93 m,and the damage radius to people reaches 147 m.4.The factors including fire radiation and convection heat transfer will lead to changes of the thermal stress of pipeline.So the thermal-structure coupling analysis model of natural gas pipeline considering temperature effect is established based on the basic theory of thermal stress and ANSYS finite element analysis software.More important,compared with the results with considering the combined effects of temperature and pipeline operating pressure,it is found that the effect of the leakage aperture on the maximum stress at high temperature is very small only considering the temperature effect.Considering the combined effects of temperature and pipeline operating pressure,pipeline operating pressure will cause the local stress redistribution of the pipeline leakage hole.With increasing pipeline operating pressure,strain increases,and its growth trend is similar to that of exponential.When the leakage hole may crack,the limit of the internal pressure is obtained.Through the study of this paper,the natural gas pipeline leakage and diffusion model and the thermal-structure coupling analysis model are both established.Then the diffusion characteristics of natural gas and the harm consequences of pipeline leakage are studied.The research results can provide theoretical support for the inspection,the maintenance of natural gas pipeline accidents,and provide basic data for fire safety work.