埋地管道泄漏天然气在分层填筑土壤扩散数值模拟研究

城市埋地天然气管道发生泄漏不易被发现，并易产生爆炸、火灾、中毒等次生事故，针对低压埋地天然气管道施工分层填筑与不分层填筑的两种情况建立模型，依据多孔介质模型修正后的基本控制方程，采用FLUENT组分运输模型、RNG k-ε湍流模型，对管道沟渠分层填筑与不分层填筑气体泄漏扩散情况进行数值模拟。根据仿真土壤含气摩尔量划分三个浓度区域进行分析，分层填筑土壤分界处砂土含气量达到低浓度的时间较快约为60 s，12 min可以达到高浓度区域。两种材质交界面处，高浓度气体扩散存在延迟，中浓度和低浓度气体扩散在交界面处扩散曲线有明显拐点，进入到上层土壤材料后扩散速率加快，不分层填筑模型扩散速率没有明显改变。

Numerical simulation research on diffusion of natural gas leaking from buried pipeline in layered filling soil

The leakage of urban buried natural gas pipeline is hard to discover, and some secondary accidents such as explosion, fire and poisoning are easy to occur. A model was established aiming at two situations including layered filling and unlayered filling in construction of low pressure buried natural gas pipeline. The basic control equations were revised according to the porous media model, and the numerical simulation on gas leakage and diffusion under the conditions of layered filling and unlayered filling in pipeline trench was conducted by applying FLUENT component transport model and RNG k-ε turbulence model, then three concentration regions were divided according to the molar quantity of gas in the simulated soil. The results showed that the time for the gas quantity in the sandy soil on the soil interface with layered filling to reach low concentration was quicker, which was about 60 s, and the time to reach high concentration was 12 min. on the interface of two materials, the diffusion of high concentration gas had a delay time, and the diffusion curves of medium and low concentration gas on the interface had obvious inflection point. The diffusion rate accelerated after entering the upper soil, while the diffusion rate in the unlayered filling model had no obvious change.