混合气体在典型多孔介质内扩散过程的数值模拟

为研究孔径大小对扩散过程的影响及组分之间在扩散过程中的相互作用,采用Maxwell-Stefan模型对混合气体在典型多孔介质内的扩散过程进行了数值模拟.首先引用前人的实验结果验证了该模型及数值方法的可靠性.在此基础上,采用该模型研究了孔径大小对CH4/Ar二元混合气体在多孔介质内扩散过程的影响,以及CH4/Ar/H2三元混合气体在多孔介质内扩散过程中各组分之间的相互作用.研究表明:当孔半径小于0.5μm时,CH4/Ar的扩散过程随孔半径的增大而加快,当孔半径大于0.5μm时,CH4/Ar的扩散过程不受孔半径的影响;当不同组分之间的相互拖带作用大于自身的浓度梯度作用时,可能产生逆向扩散、局部压力回升现象;小分子较大分子扩散得快;Maxwell-Stefan模型能够有效地模拟多元混合气体的扩散过程.

Simulation on Diffusion Processes of Multicomponent Gas Mixture in Typical Porous Media

The diffusion processes of gas mixture in typical porous media were simulated by the Maxwell-Stefan model to study the effect of pore radius on the diffusion process and the interaction between each species of multicomponent during diffusion in porous media.The model and the numerical method adopted here were verified by the experimental data in literature.Then the effect of pore radius was examined on the diffusion process of CH4/Ar mixture and the interaction between CH4/Ar/H2 during diffusion in porous media.The results show that the diffusion of CH4/Ar will rise with an increase in the pore radius when it is smaller than 0.5 μm while the diffusion process is independent on the pore radius when it is larger than 0.5 μm.Moreover,the adverse diffusion may occur when the dragging effect is stronger than the concentration gradient effect.In addition,species with small molecules diffuse faster than those with big molecules.These results imply that the Maxwell-Stefan model can describe the diffusion process of multicomponent gas mixture efficiently.