PEM燃料电池中质子交换膜内水和质子的迁移特性

Transport characteristics of water and proton in membrane of PEM fuel cells

质子交换膜的水含量及水和质子的迁移对PEM燃料电池的性能具有重要影响.提出了一个稳态两相流数学模型,用以研究质子交换膜中的水迁移和水含量及其与质子传递阻力的关系.模型耦合了连续方程、动量守恒方程、物料守恒方程和水在质子交换膜中的传递方程.通过与实验数据对比,验证了模型的有效性.分析模拟结果发现,当电流密度相同时,沿气体流动方向,质子交换膜中水的电渗拉力系数、反扩散系数和水力渗透系数逐步增大,而水的净迁移系数逐步减小;同时,质子交换膜的含水量增加,质子传递阻力逐步下降;增大电池的操作压力,电渗拉力系数、反扩散系数、水力渗透系数、水净迁移系数和质子膜的含水量增加,而质子传递阻力下降,使燃料电池的性能得到了提高.

Water and proton transport together with water content in proton exchange membrane showed significant effects on the performance of PEM fuel cells. A steady state two-phase flow model is presented to study water transport and water content in the membrane as well as the relation between water content and proton transport resistance. This model couples the conservation of mass, momentum and species equations with transport equation in the membrane. Simulation results indicated that the polarization curves agreed well with experimental data. For the same current density, coefficients of electro-osmotic drag, back diffusion and hydraulic permeation with water content in the membrane increased gradually along the gas flow direction, while net water transport coefficient arid proton transport resistance decreased as operating pressure increased; at the same time electro-osmotic drag, back diffusion, hydraulic permeation and net water transport coefficients and water content in the membrane increased rapidly, while proton transport resistance decreased, which improved the performance of PEM fuel cells.