复合土壤下埋地掺氢天然气管道泄漏扩散规律影响研究

Study on the Influence of Leakage and Diffusion of Underground Hydrogen-Blended Natural Gas Pipelines in Composite Soils

摘要: 为研究掺氢天然气管道在砂土壤土复合条件下的泄漏扩散规律，基于流体力学及多孔介质理论，采用Fluent计算流体动力学软件建立复合土壤下掺氢天然气管道泄漏扩散的三维数值仿真模型，分析掺氢天然气在不同影响因素下的泄漏扩散规律。结果表明：土壤分层结构对气体扩散行为具有显著影响(砂土 > 上层壤土–下层砂土 > 上层砂土–下层壤土 > 壤土)，单一壤土中甲烷扩散到模型边界的时间是上层壤土–下层砂土结构的1.56倍，是上层砂土–下层壤土结构的1.4倍，更是单一砂土结构的2.8倍。并且土壤的分层结构会对气体扩散的路径造成影响，气体泄漏量随孔径增大而增加，其浓度分布则因砂土与壤土的孔隙结构差异而不同，复合土壤“葫芦状”分布的气体扩散云图与单一土壤层中椭圆形扩散云图形成鲜明对比。管道压力升高会增强气体横向扩散能力；掺氢比增加虽对甲烷扩散影响有限，但会显著缩短氢气扩散到模型边界的时间。该研究为掺氢天然气管道安全设计和泄漏防控提供了重要的理论参考。

Abstract: To investigate the leakage and diffusion behavior of hydrogen-blended natural gas pipelines in sandy soil composite conditions, a three-dimensional numerical simulation model of the leakage and diffusion of hydrogen-blended natural gas pipelines in composite soils was established using Fluent computational fluid dynamics software based on fluid mechanics and porous media theory. The leakage and diffusion behavior of hydrogen-blended natural gas under different influencing factors was analyzed. The results showed that soil stratification significantly influenced gas diffusion behavior (sand > upper loam-lower sand > upper sand-lower loam > loam). The time it took for methane to diffuse to the model boundary in loam alone was 1.56 times that in an upper loam-lower sand structure, 1.4 times that in an upper sand-lower loam structure, and 2.8 times that in a sand alone structure. Furthermore, the layered structure of soil affects the path of gas diffusion. Gas leakage increases with increasing pore diameter, while its concentration distribution varies due to the differences in pore structure between sand and loam. The “gourd-shaped” gas diffusion pattern of composite soils contrasts sharply with the elliptical diffusion pattern of single soil layers. Increased pipeline pressure enhances the lateral diffusion capacity of gas. While increasing the hydrogen blending ratio has a limited effect on methane diffusion, it significantly shortens the time it takes for hydrogen to diffuse to the model boundary. This study provides important theoretical reference for the safe design and leakage prevention of hydrogen-blended natural gas pipelines.