Topology optimization and performance simulation of the transition zone of the proton exchange membrane fuel cell flow field

Flow field design is key to boosting proton exchange membrane fuel cell (PEMFC) performance. The often-overlooked transition zone between the bipolar plate (BPP) flow field’s distribution and mainstream zones causes uneven reactant distribution, harming cell performance. This study proposes a hybrid methodology for optimizing the PEMFC transition zone. A 2D topology optimization (TO) framework is established to generate a novel flow structure with low flow resistance and high distribution uniformity, where the objective function balances pressure drop reduction and flow uniformity improvement. The optimized 2D structure is then extruded to form a 3D flow field, and its performance is evaluated using a developed 3D two-phase half-cell multiphysics model. Results show that the TO-derived transition zone structure introduces tailored baffle configurations, reducing the flow velocity standard deviation by 41.6% at 2.0 A·cm⁻² and enhancing cell output performance by 26.7% under the same conditions. Results from the operational condition sensitivity analysis demonstrate that the TO flow field achieves a higher performance improvement rate under high temperature/humidity, low stoichiometric ratio/pressure. The improvement rate is higher under a higher rib width ratio and more flow channel branches—conditions where flow maldistribution or reactant scarcity is more pronounced. This work fills the research lacuna in PEMFC transition zone design, offering valuable insights for future large-area bipolar plate development.