Abstract: Aiming at the process on leakage of buried gas pipeline in urban area, and considering gas of different constituents and concentration leakage based under multi building condition, using computational fluid dynamics (CFD) software to establish the three-dimensional physical model of buried pipeline in the leakage process, the environmental wind field and leakage rate into the boundary conditions in the form of user-defined functions were introduced, and the simulation process was divided into steady-state simulation in environmental wind field and transient simulation in leakage. And the leakage process was divided into continuous leakage and leakage after pipe valve closing, and the gas leakage rules were analyzed. The results showed that: It was necessary to simulate the steady state in environmental wind field. There existed three low velocity zones near the flow field and a large velocity gradient on the edge of the building. It showed the following characteristics that the confined leakage of oil layer diffusion, low velocity zone upstream gathering, gas cloud rising, hydrogen sulfide deposition and diffusion and so on in the gas continuous leakage stage. It showed the characteristics of the gas diffusion continuity and dissipation from top to bottom in the valve closed stage. Based on the conditions above, comparing methane, hydrogen sulfide had larger diffusion range, later dissipation time, and greater risk.

Key words: Natural gas, Buried pipeline, Leakage, Building, Numerical simulation

摘要： 针对城镇埋地天然气管道泄漏扩散过程, 考虑多建筑物条件下不同组分、 不同浓度的气体扩散规律, 利用计算流体力学( CFD) 软件建立埋地管道泄漏扩散过程的三维物理模型, 将环境风场和泄漏速率以用户自定义函数形式引入边界条件中, 将模拟过程分为环境风场的稳态模拟和泄漏扩散的瞬态模拟两步, 又将泄漏扩散过程分为持续泄漏扩散和管道阀门关闭后的泄漏扩散两个阶段, 分析天然气的泄漏扩散规律。结果表明, 环境风场的稳态模拟是十分必要的, 建筑物附近流场存在三个低速区, 建筑物边缘存在较大的速度梯度; 天然气的持续泄漏扩散阶段呈现土壤层局限扩散、 上游低速区积聚、 气云浮升、H₂S的沉积扩散等特征, 在阀门关闭后的阶段呈现气体扩散延续性、 气云由上而下消散等特点; 在本文工况条件下, H₂S比CH₄的扩散范围大, 消散时间晚, 危险性更大。

关键词: 天然气, 埋地管道, 泄漏, 建筑物, 数值模拟