Numerical Study On Diffusion Of The Natural Gas Leakage From Buried Gas Pipeline

With the rapid development of the natural gas industry, the natural gas pipeline are widely distributed and some potential problems such as life safety and production losses resulted from the pipelines gas leakage are becoming more and more serious. Due to the corrosion of bacteria and current, external damage or other factors, the gas leakage accident often occurs. Once the gas leakage occurs and not be handled timely, it is likely to cause combustion and explosion and even the second explosion. With the above background, study of the gas diffusion in soil has the great engineering significance for immediate handling the gas leakage, preventing the damage and deducing losses.Soil is a typical porous media and the gas diffusion in soil is accompanied by heat and mass transfer in the porous media. In this paper, based on the theory of porous media and some governing equations including continuity, momentum, energy and component equations, the diffusion process of the gas leakage from the buried pipeline is studied by numerical simulation. The simulated results predict the mole concentration field of methane in soil and its variation with times. Comparing the simulation with the reported experimental results, the volume-averaged method of porous medium has proved to be relatively effective.Effects on the gas diffusion in soil by some factors, such as the gas pressure, the inlet size, the soil diameter, the porosity and blocks, have been studied. The simulated results shows that the more the gas pressure, the faster the gas diffusion in soil and the easier the component concentration in soil reaches to saturated value; the larger the inlet-size, the bigger the concentration of the gas at a same monitoring site and at the same time; the early concentration of methane is distributed in soil differently at the two conditions with the one leakage at the top of the gas pipe and the other at the pipe bottom. With time increasing, the concentration contours of the gas tends to be same; if there is a block in soil, the gas will avoid the block and diffuse, and cause the concentration difference near the block.