PEMFC带沟槽气体扩散层内传输特性孔隙网络模拟

采用三维孔隙网络模型计算了不同沟槽参数下气体扩散层(GDL)的液态水突破压力、毛细压力分布、气体扩散率和液相相对渗透率随饱和度变化,并从孔隙尺度角度探究了沟槽的作用机制。研究结果表明:沟槽改变了GDL的毛细压力分布,提供了液态水直接传输路径并优化了GDL内氧气和液态水的分布,从而提高了氧气有效扩散率。沟槽位置对氧气传输有明显影响,对液相传输的影响取决于是否形成贯穿GDL的传输路径;沟槽加深,氧气和液态水传输性能增强,沟槽穿透GDL时传输性能达到最佳;沟槽变宽,液相传输性能增强,氧气传输性能在低饱和度范围内先增强后减弱。综合各因素,给出了氧气和液态水传输性能最优时的沟槽参数。

Pore network simulation of transport properties in grooved gas diffusion layer of PEMFC

Three-dimensional pore network model was performed to investigate water and oxygen transport in gas diffusion layer (GDL) with groove. The capillary pressure at breakthrough, the capillary pressure curve, the oxygen effective diffusivity and the relative permeability as a function of liquid saturation were calculated. Moreover, the mechanism of groove was explored from the perspective of pore level. The results indicate that groove changes the capillary pressure distribution of the gas diffusion layer, provides a direct transport path for liquid water and optimizes the gas-liquid distribution in GDL, thereby improving the oxygen effective diffusivity. The position of groove has a significant influence on oxygen diffusion, the influence on liquid transport depends on whether a liquid transport path through GDL is formed. Additionally, the oxygen and water transport enhances with the groove deepen, especially the optimal transmission performance is obtained when the groove penetrates the gas diffusion layer. With increase of the width of groove, while liquid relative permeability improves, oxygen effective diffusivity increases first and then decreases at low water saturation. Based on various factors, the groove parameters are given when the oxygen and liquid water transmission performance is optimal.