Study On Leakage And Diffusion Of Pipeline Gas In Soil Under Hardened Pavement

The leakage of natural gas in soil is hidden,and once the concentration of methane in soil reaches the limit of explosion,there is a risk of explosion.Therefore,it is of great significance to determine the leakage point quickly after the leakage,and to clear the law of leakage and diffusion.In this paper,the process of leakage and diffusion of small holes in medium pressure natural gas pipeline under hardened pavement is analyzed theoretically and numerically.Based on the basic theory of turbulent jet,the basic theory of porous media and the basic theory of fluid mechanics,this paper analyzes the diffusion process of natural gas in soil,which is a small hole leakage model of buried pipeline,calculates the leakage quantity,and finally using CFD numerical simulation software performs three-dimensional numerical simulation.the distribution of methane concentration in different time of soil at different leakage port position,leakage port aperture and leakage pressure is obtained.In the analysis of natural gas explosion limit area,the upper and lower limit radius of natural gas explosion at hardened pavement and the upper and lower limit distance of explosion are defined first,and then the variation of the upper and lower limit radius of explosion is changed with time when different leakage port position,leakage port aperture and leakage pressure are compared.The results show that when the leakage port position is not the same,in the early stage of the leak,the leakage port is located directly above the danger range is the largest,in the late stage of leakage,the leak port is located directly below the hazard range.The increase of leakage aperture and the increase of pipeline pressure will make the mass flow rate of leakage,the greater the danger range at the same time.Finally,the influence of leakage on cable ditch is analyzed,knowing that no matter where the leak is located in the natural gas pipeline,the cable laid at a horizontal or vertical clearance of 0.5 m will instantly reach the explosion limit range.