Study On The Characteristics Of The Leakage Diffusion And Explosion Of Natural Gas Pipeline In Confined Space

With the rapid development of gas industry, gas pipeline is going to be the mainmedium of transportation of natural gas, and building a complex gas pipelinenetwork become a prerequisite for natural gas transport. Uncontrolled gas network islikely to bring great safety troubles, this kind of disasters and accidents are mostlycaused by leakage of the pipe inner gas such as fire, explosion and poisoning. So it isthe first consideration to measure pipeline network system security analysis. As it’sknown the probability of gas leaking converting into explosion is95%, theprobability of converting into fire is80%. Making sure of the gas pipeline networksecurity is related to people’s lives and property, social stability and the industrialproduction.Firstly, based on Fluent Numerical platform, the gas leakage diffusion processin30m×5m×5m long narrow confined space was simulated by studying on urbanmedium pressure gas pipe network system. The concentration distributioncharacteristics of gas pipeline leakage diffusion were achieved in the condition of0.118MPa leakage pressure, through the establishment of a two-dimensionalnumerical model. And on the basis of the leakage pressure, leakage aperture andobstacle factors of limited space gas diffusion concentration distribution wereanalyzed. Finally based on small size pipe experiment platform for burningexplosion test, the pipeline flow field of the flame structure development wascaptured by using high speed schlieren system and high frequency pressure sensortechnology. Combined with the means of CFD numerical simulation, it’s discussedthat the influence of different methane concentration of gas burning explosion andthe development law of velocity and pressure. the conclusions were following:(1) High-speed gas jet into the limited space, with the surrounding relativerange between the stillness of the air speed of discontinuity, and existed momentum,mass and heat exchange under the effect of fluid viscosity, which is caused thediscontinuity surface constantly disturbed and steady vortex. Gas concentrationdistribution presented a layered phenomenon and gradually achieved stablestructures over time. (2) Leakage pressure and outlet flow velocity was positively than relationship,the increase of flow velocity of gas in the constraint space diffusion and convectioncaused by gas diffusion area also increases, the danger zone also enlarged;Simulation of space within the danger zone increases with the increase of leakageaperture; Obstacle is higher, the leakage distance nearer the orifice, the more obviouseffects on the gas diffusion, beyond a certain distance, to airflow diffusion does notproduce obvious effect.(3) The velocity and the pressure had all demonstrated the similar rule in theprocess of flame-propagation. The curve had all experienced three stages whichinclude slowly rising stage, peak stage and the attenuation stage. While theconcentration is9.5%, velocity and pressure value are the largest, and the timeneeded the shortest. The experimental data can be concluded that numericalsimulation curve with the experimental curve is almost the same change trend,through the numerical simulation data and similarity comparing and analyzing.Numerical simulation method can be described evolution law of gas explosion inconfined space from the macro-perspective.