An entropic lattice boltzmann scheme for the modeling of wetting in proton-exchange membrane fuel cells

Decarbonizing the transport sector requires the deployment of propulsion systems with low emissions of both CO2 and atmospheric pollutants. As a complement to established batteryelectric architectures, Proton-Exchange Membrane Fuel Cells (PEMFCs) represent a promising technology for integration in electric powertrains. Their large-scale deployment, however, remains primarily constrained by system- and material-related costs. In this thesis, these challenges are addressed along two complementary directions: (i) the design, fabrication, and experimental characterization of a modular PEMFC power system for mobility applications, and (ii) the development of a high-fidelity lattice Boltzmann framework for modeling and simulation of multiphase flow and wetting, aimed at resolving water transport in PEMFC Gas Diffusion Layers (GDLs). Within the HYMOBITALY project, a twin 2×16-cell PEMFC stack with symmetric distribution of reactants, distributed liquid cooling, and tailored flow fields was built and tested under both air/H2 and O2/H2 feeds. The prototype demonstrated stable operation over the investigated current-density range, with the efficiency of the twin configuration closely matching that of the single stacks, thereby validating the modular concept for scalable powertrains. However, the experiments confirmed that water management in the GDL is a critical design and operating constraint. To tackle this issue at the pore scale, a three-dimensional entropic cascaded lattice Boltzmann scheme, coupled with a Shan-Chen pseudopotential model, was developed, featuring a piecewise equation of state, a unified cohesive-adhesive interaction force, and a Coupled Boundary-Wettability scheme for off-grid curved surfaces. The method achieves thermodynamically consistent phase segregation and accurate contact-angle control over a wide range of density and viscosity ratios while strongly suppressing spurious currents, as verified through dedicated benchmark tests. The combined experimental and numerical results provide a consistent pathway toward a more accurate design of PEMFC porous components and modular fuel-cell power systems for sustainable mobility