多组分气体在多孔介质中扩散过程的数值模拟

Numerical Simulation of Multicomponent Gas Transport in Porous Media

通过对已有的多组分气体在多孔介质中的扩散模型与实验结果对比,发现尘气模型(DGM)与实验结果吻合较好,并利用该模型对CH_4/O_2/N_2三元混合气体在不同孔径的多孔介质内扩散过程进行了数值模拟,分析了扩散与对流两种机理在有/无压差下对扩散通量的影响,对比分析了干燥和含水非饱和多孔介质中的扩散过程.结果表明在无压差的扩散过程中也存在对流;气体的扩散速度随孔径的减小先增大后减小;含水非饱和多孔介质中扩散速度减弱。

In this paper, the equations governing the transport of multicomponent gas through porous media are examined with experimental data for CH4/O2/N2 in 1D geometry, and the Dust Gas Model （DGM） is the most appropriate model to simulate gas transport phenomena inside porous media. Numerical technique for DGM model is used to calculate the diffusion and advection fluxes and determine which mechanism is dominant in gas transport. The effect of pressure difference, pore diameter and water saturation are analyzed. The results show that advection process also exists on condition that there is no pressure difference between inlet and outlet. The gas velocity first increases with media pore diameter decreasing and then decreases. Water in porous media slows the gas transport process because of the relative pore diameter and permeability.