PEMFC带沟槽气体扩散层内传输特性孔隙网络模拟

doi:10.11949/0438-1157.20191438

摘要/Abstract

摘要：

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。

关键词: 燃料电池, 气体扩散层, 孔隙网络模型, 沟槽, 扩散, 渗透率

Abstract:

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.

Key words: fuel cells, gas diffusion layer, pore network model, groove, diffusion, permeability

中图分类号:

TQ 021.4

黎方菊, 吴伟, 汪双凤. PEMFC带沟槽气体扩散层内传输特性孔隙网络模拟[J]. 化工学报, 2020, 71(5): 1976-1985.

Fangju LI, Wei WU, Shuangfeng WANG. Pore network simulation of transport properties in grooved gas diffusion layer of PEMFC[J]. CIESC Journal, 2020, 71(5): 1976-1985.

图/表 15

图1 带沟槽气体扩散层的规则孔隙网络模型

Fig.1 Regular pore network model of GDL with groove

表1 孔隙和喉道尺寸分布

Table 1 Pore and throat size distribution

参数		μ/μm	σ/μm	a/μm	b/μm
孔隙分布		10	1	8	12
喉道分布	展向x×y	5	1	3	7
喉道分布	纵向z	6	1	4	8

图2 孔隙网络模型验证

Fig.2 Validation of pore network model

表2 不同沟槽位置的GDL参数

Table 2 Parameters of GDL with different groove positions

案例	GDL厚度/μm	沟槽个数	沟槽深度/μm	沟槽宽度/μm	孔隙率/%
案例1	250	0	—	—	63.7
案例2	250	1	100	150	65.0
案例3	250	1	100	150	65.0
案例4	150	0	—	—	63.7
案例5	250	2	100	150	66.4
案例6	250	2	100	150	66.4

图3 液相饱和度为0.2时不同沟槽位置的GDL气液相界面

Fig.3 Gas-liquid interface in GDL with different groove positions when water saturation is 0.2

图4 突破和干燥状态下不同沟槽位置的GDL性能参数

Fig.4 Performance parameters of GDL with different groove positions under breakthrough and dry conditions

图5 不同沟槽位置的GDL突破时水饱和度沿厚度的分布

Fig.5 Water distribution in through-plane direction of GDL with different groove positions at breakthrough

图6 不同沟槽位置的GDL氧气有效扩散率随水饱和度变化曲线

Fig.6 Oxgen effective diffusivity as function of water saturation in GDL with different groove positions

图7 不同沟槽位置的GDL液相相对渗透率随水饱和度变化曲线

Fig.7 Liquid relative permeability as function of water saturation in GDL with different groove positions

图8 不同沟槽深度和宽度的GDL突破参数

Fig.8 Performance parameters of GDL with different groove depths and widths under breakthrough conditions

图9 不同沟槽深度的GDL水侵毛细压力曲线

Fig.9 Water invasion capillary pressure curve in GDL with different groove depths

图10 不同沟槽深度的GDL氧气有效扩散率和液相相对渗透率随液相饱和度变化曲线

Fig.10 Oxygen effective diffusivity and liquid relative permeability as function of water saturation in GDL with different groove depths

图11 不同沟槽宽度的GDL水侵毛细压力曲线

Fig.11 Water invasion capillary pressure curve of GDL with different groove widths

图12 不同沟槽宽度的GDL氧气有效扩散率随饱和度变化曲线

Fig.12 Oxygen effective diffusivity as function of water saturation in GDL with different groove widths

图13 不同沟槽宽度的GDL液态水相对渗透率随液相饱和度变化曲线

Fig.13 Relative liquid permeability as function of water saturation in GDL with different groove widths

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