Analysis of Transport Phenomena in Cracked GDL Microstructures on PEMFC Performance Using Coupled LBM-FVM Method

다국어 초록 (Multilingual Abstract)

The gas diffusion layer (GDL) plays a critical role in determining the overall performance of proton exchange membrane fuel cells (PEMFCs) gas transport, water management, and electronic conductivity. This study presents a comprehensive multiscale modeling approach to investigate the influence of GDL microstructure and cracked GDL on transport behavior. At the microscale, the lattice Boltzmann method (LBM) is employed to analyze four GDL configurations, including fixed-diameter fiber, fixed-diameter spherical, random-diameter spherical, and a combined fiber/spherical structure. The effects of structural parameters such as thickness and porosity on tortuosity, permeability, and effective gas diffusion coefficient are systematically examined. Results show that porosity has a more significant impact on mass transport than thickness, and spherical structures provide higher diffusion efficiency due to their less tortuous pathways. The study further explores the influence of GDL cracks on gas transport using LBM simulations. It is found that crack depth has a greater effect on mass transport than crack width, as deeper cracks. Uncertainty quantification (UQ) is applied to evaluate the sensitivity of GDL performance to variations in structural parameters such as porosity, thickness, crack geometry, and operating conditions, offering a statistical perspective on performance variability and design. A coupled three-dimensional LBM-FVM PEMFC method is developed to bridge pore-scale transport with full-cell performance. Pristine and cracked GDL parameters obtained from LBM simulations are integrated into a PEMFC model via OpenFOAM. Simulations of cathode-cracked, anode-cracked, and both-sides-cracked GDLs are examined. Cathode-cracked GDL is the most severe performance degradation, highlighting that the cathode plays a more crucial role in fuel cell operation than the anode. Additionally, higher operating pressure and optimized cathode inlet velocity enhance voltage and power density. While the anode inlet velocity and GDL porosity have an insignificant impact on PEMFC performance.

목차 (Table of Contents)

• ACKNOWLEDGEMENTS i
• ABSTRACT ii
• CONTENTS iv
• LIST OF FIGURES vii
• LIST OF TABLES xi
• LIST OF ABBREVIATIONS xii
• LIST OF NOMENCLATURE xiii
• CHAPTER 1. INTRODUCTION 1
• 1.1 Overview 1
• 1.2 Research Object 6
• 1.3 Thesis Outline 8
• CHAPTER 2. MATERIAL AND NUMERICAL METHOD 10
• 2.1 Particle Scheme - Lattice Boltzmann Method 10
• 2.2 Fluid Scheme - Finite Volume Method 33
• 2.3 Mass Transport Properties 44
• 2.4 LBM-FVM Coupling 47
• 2.5 Grid Convergence Index 49
• 2.6 Uncertainty Quantification 51
• 2.6.1 Point - Collocation Non - Intrusive Polynomial Chaos Method 52
• 2.6.2 Statistical and Sensitivity Analysis 54
• 2.6.3 Leave-One-Out Cross-Validation Error 56
• CHAPTER 3. MASS TRANSPORT PROPERTIES IN VARIOUS GDL STRUCTURES 57
• 3.1 Introduction 57
• 3.2 Computational Domain and Boundary Conditions 58
• 3.3 Validation 63
• 3.3.1 Grid Convergence Index 63
• 3.3.2 Validation 64
• 3.4 Results and Discussion 66
• 3.3.3 Effect of GDL Microstructure on Mass Transport Properties 66
• 3.3.4 Pressure and Velocity Distribution 70
• 3.5 Conclusion 74
• CHAPTER 4. MASS TRANSPORT PROPERTIES IN CRACKED CARBON - PAPER GDL 76
• 4.1 Introduction 76
• 4.2 Computational Domain and Boundary Conditions 78
• 4.3 Validation 80
• 4.3.1 Grid Convergence Index 80
• 4.3.2 Validation 81
• 4.4 Results and Discussion 83
• 4.3.3 Effect of Crack on Mass Transport Properties 83
• 4.3.4 Uncertainty Quantification Results 90
• 4.5 Conclusion 97
• CHAPTER 5. EFFECT OF CRACKED GDL ON PEMFC PERFORMANCE 99
• 5.1 Introduction 99
• 5.2 Computation Domain and Boundary Conditions 100
• 5.3 Validation 104
• 5.3.1 Grid Convergence Index 104
• 5.3.2 Validation 105
• 5.4 Results and Discussion 106
• 5.4.1 Species Mass Fraction, Temperature Distribution 106
• 5.4.2 Effect of Cracked GDL 107
• 5.4.3 Effect of Operating Pressures 109
• 5.4.4 Effect of Cathode Inlet Velocities 112
• 5.4.5 Effect of Anode Inlet Velocities 115
• 5.4.6 Effect of GDL Porosities 117
• 5.5 Conclusion 120
• CHAPTER 6. CONCLUSION 122
• REFERENCE 125