Quantitative investigation of oxygen transport in proton exchange membrane fuel cell: Considering cross-flow

Oxygen transport is a key factor limiting fuel cell performance. To quantitatively analyze the dominant mechanism of oxygen transport. In particular, the cross-flow under the rib (x-direction), as well as the effect of cathode flow field and spatially variable properties of gas diffusion layer (GDL). A threedimensional (3D), multiphase and non-isothermal model which considers Forchheimer's effect is described. And the oxygen flux under different mechanisms and directions is numerically researched. The results demonstrate that in membrane electrode assembly (MEA), under high current density, the main direction of oxygen transport is y-direction (through-plane). However, x-direction also accounts for a large proportion, especially in GDL and under low current density. Diffusion is the dominant mechanism in MEA, at 0.6 V output voltage, it accounts for more than 50% in GDL and 80% in microporous layer (MPL) and catalyst layer (CL). The 3D and serpentine flow field could enhance the oxygen convection in y-direction and x-direction, respectively, and then improve the performance. The spatially variable properties of GDL also change the oxygen flux distribution. Oxygen diffusive mass flux gradually decreases from gas channel side to MPL side rather than gradually increase. In addition, the age of reactant gas is introduced to quantitatively study the oxygen and hydrogen response speed. The results show that, in general, the age of oxygen decreases as current density increases and the situation is just opposite for hydrogen. The change rate for these two is almost a constant about 3 ms/(A cm(-2)) and 10 ms/(A cm(-2)), respectively. The "age-flux " diagram is also proposed to evaluate the reactant gas transport quality. This research provides a new approach and evaluation method for optimizing fuel cell design from the perspectives of oxygen transport quantification and the age of reaction gas. (C)& nbsp;2022 Elsevier Ltd. All rights reserved.