基于格子玻尔兹曼方法的PEMFC微孔层气体传质分析

doi:10.16085/j.issn.1000-6613.2024-1136

摘要/Abstract

摘要：

基于格子玻尔兹曼方法（LBM）建立微孔传质数值模型，采用不同结构参数对质子交换膜燃料电池（PEMFC）中的微孔层（MPL）物理模型进行重构，并对其气体传质性质进行模拟计算。结果表明：MPL的氧气有效扩散系数随孔隙率下降而降低，当孔隙率由80%下降至40%时，受克努森扩散影响带来的阻力由51%上升至83%；若假设MPL孔隙率一致，有效扩散系数随PTFE含量上升而提升，若假设碳格点总量一致，则受孔隙率下降影响，有效扩散系数随PTFE含量上升而下降；MPL的有效扩散系数随碳球半径提升而提升，随碳球种子占比提升而下降。基于以上研究，将具有不同孔隙率的MPL与阴极催化层（CL）组合后进行传质、反应耦合模拟计算。结果表明，当MPL的孔隙率下降时，对应CL中离聚物的氧气浓度下降1.7%，含水量上升2.7%，MPL气体传质阻力的增加具有阻碍反应气传质和增加微孔内相对湿度的作用。研究结果对PEMFC中MPL的设计与利用具有理论指导意义。

关键词: 质子交换膜燃料电池, 微孔层, 传质, 数值模拟, 格子玻尔兹曼方法

Abstract:

A numerical model for mass transfer in micropores was established based on the lattice Boltzmann method (LBM). The physical models of the microporous layer (MPL) in the proton exchange membrane fuel cell (PEMFC) were reconstructed using different structural parameters, and the gas transfer property was simulated. The results show that the effective oxygen diffusion coefficient in the MPL decreases as porosity decreases from 80% to 40%, with resistance due to Knudsen diffusion increasing from 51% to 83%. Assuming a constant MPL porosity, the effective diffusion coefficient increases with PTFE mass fraction; however, assuming a constant total number of carbon lattices, the effective diffusion coefficient decreases with increasing PTFE mass fraction due to the reduced porosity. The effective diffusion coefficient of the MPL increases with the radius of the carbon spheres and decreases with an increasing carbon seed fraction. Moreover, a mass transfer and reaction coupling simulation was conducted by combining MPLs of different porosities with the cathode catalyst layer (CL). The results indicate that as MPL porosity decreases, the oxygen concentration in the ionomer of the CL decreases by 1.7%, and the water content increases by 2.7%. Increased gas transfer resistance in the MPL has the effect of hindering reactant gas transfer and increasing relative humidity within the micropores. These findings provide theoretical guidance for the design and utilization of MPLs in PEMFCs.

Key words: proton exchange membrane fuel cells, microporous layer, mass transfer, numerical simulation, lattice Boltzmann method

中图分类号:

TK91

周敬皓, 张朝阳, 胡昊星, 王思茗, 刘静远, 魏光华. 基于格子玻尔兹曼方法的PEMFC微孔层气体传质分析[J]. 化工进展, 2025, 44(9): 4898-4907.

ZHOU Jinghao, ZHANG Chaoyang, HU Haoxing, WANG Siming, LIU Jingyuan, WEI Guanghua. Numerical analysis of gas transfer in microporous layer of PEMFC based on lattice Boltzmann method[J]. Chemical Industry and Engineering Progress, 2025, 44(9): 4898-4907.

图/表 14

表1 MPL和CL模型的基本物理参数

物理量	数值
碳的密度 $ρ C$ /g·cm^-3	1.8
PTFE的密度 $ρ P T F E$ /g·cm^-3	2.2
铂的密度 $ρ P t$ /g·cm^-3	21.45
离聚物的密度 $ρ I$ /g·cm^-3	2.0
铂载量 $γ P t$ /mg·cm^-2	0.1
CL厚度 $l C L$ /nm	1390
MPL厚度 $l M P L$ /nm	2080

表1 MPL和CL模型的基本物理参数

物理量	数值
碳的密度 $ρ C$ /g·cm^-3	1.8
PTFE的密度 $ρ P T F E$ /g·cm^-3	2.2
铂的密度 $ρ P t$ /g·cm^-3	21.45
离聚物的密度 $ρ I$ /g·cm^-3	2.0
铂载量 $γ P t$ /mg·cm^-2	0.1
CL厚度 $l C L$ /nm	1390
MPL厚度 $l M P L$ /nm	2080

表2 MPL模型的基准结构参数

孔隙率 $ε$	PTFE质量分数 $ω P T F E$	碳球半径 $r C$	碳球种子占比 $ω S$
60%	30%	15~25nm	30%

表2 MPL模型的基准结构参数

孔隙率 $ε$	PTFE质量分数 $ω P T F E$	碳球半径 $r C$	碳球种子占比 $ω S$
60%	30%	15~25nm	30%

表3 CL模型的结构参数

孔隙率 $ε$	铂与碳的质量比 $θ P t$	离聚物与碳的质量比 $θ I$	碳球半径 $r C$
35%	1.0	0.6	15~25nm

表3 CL模型的结构参数

孔隙率 $ε$	铂与碳的质量比 $θ P t$	离聚物与碳的质量比 $θ I$	碳球半径 $r C$
35%	1.0	0.6	15~25nm

图1 重构MPL与CL物理模型截面示意图

表4 计算模型的模拟参数

物理量	数值
温度 $T$ $/ K$	353
压力 $P$ / $P a$	$1.01325 × 105$
交换电流密度 $i 0$ / $A · m - 2$	0.015
参考氧气浓度 $C O 2, r e f$ / $m o l · m - 3$	40.96
阴极传递系数 $α c$	0.6
过电位 $η$ / $V$	-0.6
入口氧气浓度 $C O 2, i n$ / $m o l · m - 3$	10
入口相对湿度 $R H i n$	80%

表4 计算模型的模拟参数

物理量	数值
温度 $T$ $/ K$	353
压力 $P$ / $P a$	$1.01325 × 105$
交换电流密度 $i 0$ / $A · m - 2$	0.015
参考氧气浓度 $C O 2, r e f$ / $m o l · m - 3$	40.96
阴极传递系数 $α c$	0.6
过电位 $η$ / $V$	-0.6
入口氧气浓度 $C O 2, i n$ / $m o l · m - 3$	10
入口相对湿度 $R H i n$	80%

图2 D3Q19网格模型示意图

表5 模拟结果与文献的对比

测试方法	数据来源	测试参数	测试结果
Bruggeman测试	本文	$D O 2 e f f / D O 2, b$	0.3323
Bruggeman测试	Bruggeman等^[30]	$D O 2 e f f / D O 2, b$	0.3288
Bruggeman测试	Hou等^[16]	$D O 2 e f f / D O 2, b$	0.3312
MPL有效扩散率测试	本文	$D O 2 e f f$	$1.693 × 10 - 6 m 2 / s$
MPL有效扩散率测试	Chan等^[11]	$D O 2 e f f$	$(1.5 ± 0.2) × 10 - 6 m 2 / s$

表5 模拟结果与文献的对比

测试方法	数据来源	测试参数	测试结果
Bruggeman测试	本文	$D O 2 e f f / D O 2, b$	0.3323
Bruggeman测试	Bruggeman等^[30]	$D O 2 e f f / D O 2, b$	0.3288
Bruggeman测试	Hou等^[16]	$D O 2 e f f / D O 2, b$	0.3312
MPL有效扩散率测试	本文	$D O 2 e f f$	$1.693 × 10 - 6 m 2 / s$
MPL有效扩散率测试	Chan等^[11]	$D O 2 e f f$	$(1.5 ± 0.2) × 10 - 6 m 2 / s$

图3 不同孔隙率重构MPL模型的结构与传质性质

图4 不同PTFE质量分数重构MPL模型的结构与传质性质（孔隙率一致）

图5 不同PTFE质量分数重构MPL模型的结构与传质性质（碳格点数量一致）

图6 不同碳球半径重构MPL模型的结构与传质性质

图7 不同碳球种子占比重构MPL模型的结构与传质性质

图8 不同MPL孔隙率时MPL/CL区域孔隙中XY截面的氧气浓度分布、传质方向的氧气浓度与相对湿度

图9 不同MPL孔隙率时CL离聚物中的氧气浓度和含水量

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