质子交换膜燃料电池微扩散层孔隙结构与渗透率的孔隙尺度模拟

Pore Structure and Pore Scale Simulation of Permeability of Micro-Porous Layer in PEM Fuel Cell

运用基于球体的模拟退火方法和动态颗粒堆积模型数值重建了微扩散层(MPL),其中前者更能准确地反映多孔介质的孔隙特性.利用具有多反射固体边界的多弛豫时间格子玻尔兹曼方法模拟了重建的微扩散层内的单相流动.系统地分析了碳相体积分数、聚四氟乙烯(PTFE)载量、孔隙率和PTFE分布方式对微扩散层孔隙结构和渗透率的影响.结果表明:微扩散层渗透率随碳相体积分数和PTFE载量的增加而减小,且PTFE的分布方式影响微扩散层的孔隙结构和渗透率.KC关联式低估了MPL的渗透率,通过拟合计算数据提出了预测MPL渗透系数的关联式,预测结果与孔隙尺度模拟结果的相对误差小于12%.

Numerical reconstructions of the micro-porous layer(MPL)have been performed by using the sphere-based simulated annealing method and the dynamic particle-packing model,of which,the former is more accurate to reflect the pore structures of the porous media.The single-phase flow inside the MPL reconstructed is simulated by using the lattice Boltzmann method(LBM)with multi-relaxation time(MRT)and multi-reflection(MR)solid boundary.The effects of carbon volume fraction,polytetrafluoroethylene(PTFE)loading,porosity,and PTFE distribution on the pore structure and permeability of the MPL are studied.The results show that the MPL permeability decreases with the increase in carbon volume fraction and PTFE loading,and the pore structure and permeability of MPL are also influenced by the distribution of PTFE.The Kozeny-Carman(KC)equation underestimates the permeability of MPL and a modified correlation to predict the permeability coefficient of MPL is proposed.The relative error between the results predicted by this correlation and the pore scale simulations is less than 12%.