埋地燃气管道泄漏扩散特性分析

Investigation on natural gas leakage and diffusion characteristics

研究埋地燃气管道发生泄漏事故后天然气在土壤中的泄漏扩散规律有助于及时发现泄漏源,预测泄漏气体的扩散范围,减少事故损失。采用DesignModeler软件建立了埋地燃气管道泄漏扩散三维数值模型,采用Fluent软件对不同工况下甲烷气体在土壤中的泄漏扩散过程进行了数值模拟,对比分析了管道压力、泄漏孔径、土壤类型、土壤温度以及土壤含水率对甲烷体积分数和气体横向扩散距离的影响。压力、泄漏孔径和土壤温度与甲烷浓度呈正相关关系。压力、泄漏孔径和土壤温度越大,相同泄漏时间内土壤中的甲烷浓度越高,达到爆炸下限所需时间越短,危险性越高;土壤含水率越高,相同泄漏时间内的甲烷浓度越低。在低压状态下,气体分子间的相互作用较小,导致含水率越高,气体的横向扩散距离越大;土壤类型对甲烷扩散有较大影响,气体在砂土中的扩散距离最大,爆炸危险性最高,其次是壤土。黏土的黏性阻力系数和惯性阻力系数远小于砂土和壤土,因此,气体在黏土中的浓度最低,危险性最低。研究结果为埋地燃气管道的泄漏风险评估与管道监控管理提供了参考。

Studying the diffusion patterns of natural gas in soil after leakage accidents of buried low-pressure gas pipelines helps in promptly identifying leakage sources,predicting the spread range of leaked gas,and reducing accident losses.This study utilized Design Modeler software to establish a three-dimensional numerical model of the diffusion of methane gas from small holes in buried gas pipelines.Fluent software was employed to numerically simulate the leakage diffusion process of methane gas in soil under different conditions.The effects of pipeline pressure,leakage hole diameter,soil type,soil temperature,and soil moisture content on methane volume fraction and lateral gas diffusion distance were comparatively analyzed.The study revealed a positive correlation between pressure,leakage hole diameter,and soil temperature with methane concentration.Higher pressure,larger leakage hole diameter,and higher soil temperature led to higher methane concentration in the soil within the same leakage duration,resulting in shorter time to reach the explosive lower limit and greater danger.Conversely,higher soil moisture content resulted in lower methane concentration within the same leakage duration.However,under low-pressure conditions,minimal molecular interactions among gas molecules led to higher soil moisture content,resulting in greater lateral gas diffusion distance.Soil type significantly influenced methane diffusion,with gas spreading furthest in sandy soil,posing the highest explosion risk,followed by loamy soil.The viscosity resistance coefficient and inertial resistance coefficient of clayey soil were much smaller than those of sandy and loamy soil,hence,gas concentration was lowest and danger was minimal in clayey soil.The aforementioned research findings provide valuable references for leakage risk assessment and pipeline monitoring and management of buried gas pipelines.