Leakage and diffusion simulation and explosion risk analysis of urban nature gas pipeline

In the crowded city zones, the serried high buildings will affect the discharging dispersion and flow field of nature gas pipelines greatly. A certain developed city was researched as a case in this paper. The cubic geometry model was constructed, the k-εturbulent diffusion model and SIMPLE arithmetic were adopted to simulate the turbulent diffusion field of urban nature gas pipeline leakage among buildings. The simulations were carried out with three pipeline inner pressures and ambient wind velocities. Based on the simulation results, the fire and explosion hazardous field of leakage gas were analyzed according to its explosion limits. Analysis results indicate that the turbulent diffusion of CH₄ gas is influenced by the pipeline inner pressure, wind velocity and the surrounding buildings. At the same time, the diffusion field is greatly affected by the wind velocity which causes the leakage flow an obvious offset from the vertical axis. This phenomenon will increase the hazardous gas density and the risk level in the inner side of buildings against the air flow. This is meaningful for the construction of urban flammable pipelines.