混氢天然气输气站场泄漏扩散数值模拟

将氢气混入天然气管网是目前世界上实现氢气大规模输送的最有效方式。氢气爆炸极限为4.0%～75.6%,上下限范围宽,且分子直径比甲烷小,极易泄漏,给输气站场带来很大隐患。针对多组分物系混氢天然气的泄漏,基于修正的二元扩散系数及热力学因子计算方法,计算了混氢天然气三物系Fick扩散系数矩阵,用来描述混氢天然气中各组分分子间相互运动的传质过程,以FLUENT为平台进行了CFD数值模拟分析,研究发现,混氢天然气泄漏后其扩散受到障碍物及风速等因素的影响;同体积混氢天然气与不含氢天然气泄漏,混氢天然气爆炸下限扩散半径更小;较低含氢量的混氢天然气泄漏后氢气组分爆炸区域仅限于泄漏点附近。研究结果可为站场内发生混氢天然气泄漏扩散提供预警和防护指导。

Numerical Simulation of Leakage and Diffusion in Hydrogen Mixed Natural Gas Transmission Station

Mixing hydrogen into the natural gas pipeline network is currently the most effective way to achieve large-scale hydrogen transportation in the world. The explosion limit of hydrogen is 4.0%~75.6%, the upper and lower limits are wide, and the molecular diameter is smaller than that of methane, which brings great hidden dangers to gas transmission stations. Hydrogen mixed natural gas is the leakage of multi-component system. Based on the modified binary diffusion coefficient and thermodynamic factor calculation method, the Fick diffusion coefficient matrix of three-component system of hydrogen mixed natural gas is calculated, it is used to describe the mass transfer process of molecular motion among components in natural gas mixed with hydrogen. CFD numerical simulation analysis is carried out on the platform of fluent. The results show that the accumulation mode of hydrogen mixed natural gas after leakage is similar to that of natural gas, and its diffusion is affected by obstacles and wind speed; when the same volume of hydrogen mixed natural gas and non hydrogen natural gas leak, the lower explosion limit diffusion radius of hydrogen mixed natural gas is smaller; after the leakage of natural gas with low hydrogen content, the explosion area of hydrogen component is only near the leakage point. The research results can provide early warning and protection guidance for the leakage and diffusion of hydrogen mixed natural gas in the station.