基于CFD的城市埋地天然气管道泄漏扩散数值分析

Numerical Simulation of Leak and Diffusion of Buried Natural Gas Pipeline Based on CFD Approach

针对城市埋地天然气管道泄漏天然气扩散问题,基于计算流体动力学CFD方法建立城市埋地天然气管道泄漏扩散数值模型,对天然气的主要成分--甲烷在土壤中的扩散行为进行模拟与分析,根据甲烷的爆炸极限观察天然气泄漏扩散危险区域变化,并分析不同孔隙率土壤对天然气扩散的影响。研究结果表明:埋地天然气管道泄漏气体扩散至土壤过程中,气体浓度等值线出现不规则变化,高浓度区等值线近似为椭圆,浓度梯度随时间的增加而减小,爆炸下限位置在天然气泄漏初期迅速变化,10 s后以均匀速度向地表移动;土壤孔隙率对天然气对流扩散影响显著,孔隙率越大,管道泄漏口处高浓度区域越大,中浓度区域越小,低浓度区域越容易扩展到地表,浓度梯度变化趋势相似。

Aiming at gas diffusion from the leakage of urban buried natural gas pipelines,a numerical model of leakage and diffusion of urban buried natural gas pipelines is established by using the computational fluid dynamics(CFD)method,in which the diffusion behavior of the main component in soil of natural gas,methane,is simulated and analyzed,the variation of the gas leakage diffusion risk area is observed according to the explosion limit of methane,and the impact of soil with different porosity on natural gas diffusion is analyzed.The results show that the gas concentration contour changes irregularly when the gas diffuses into the soil from the buried natural gas pipeline.The contour of the high concentration area is approximately elliptical,and the concentration gradient decreases with time.The position of the lower explosion limit changes rapidly in the initial stage of natural gas leakage and moves to the surface at an even speed after 10 seconds.The soil porosity has a significant influence on the convection diffusion of natural gas.The larger the porosity,the larger the high concentration area at the leakage point of the pipeline,the smaller the medium concentration region,the easier the low concentration region extends to the surface,and the concentration gradient changes similarly.