Influence of cathode channel blockages on the cold start performance of proton exchange membrane fuel cell: A numerical study

Abstract

Proton exchange membrane fuel cell (PEMFC) performance is mainly limited by the oxygen transport to the cathode catalyst layer. Using gas flow channel blockages can effectively enhance oxygen transport. Previous research efforts demonstrated the beneficial effect of blockages on the performance of PEMFC. However, to date, the impact of flow channel blockages on the cold start performance of PEMFC has not been studied. In this work, a three-dimensional, transient, non-isothermal cold start model is developed to investigate the influence of adding staggered blocks in the cathode gas channels of a parallel flow field. The model is validated by previous experimental data. It is revealed by simulations that the addition of blockages helps to mitigate the oxygen transport limitation over the cold start duration, thus a better cold start performance is achieved. The simulated results show that the cathode full-blockage placement enhances the cold start performance much better than the partial blockage one. The local current density distribution in the full-blockage configuration case has greatly advanced, especially under the land region, due to the induced strong forced convection. More importantly, the existence of full blockages drives more oxygen into the CL for the reaction; therefore, more water correspondingly is generated, resulting in more amount of ice formation in the cathode CL, which is not favorable to the cold start process. However, despite the relatively higher ice fraction of the full-blockage case, the enhanced oxygen transport plays more dominant role at the late stages of the cold process by improving the uniformity of ice distribution in the flow direction and significantly boosting the local current density under the land region. The present article provides helpful insight in the possible utilization of the cathode channel blockage approach for assisting the design optimization of cold start process of PEMFCs.