| With the increasingly serious problems of fossil energy shortage and climate warming in human society,it is increasingly urgent to promote the electrification of transportation based on renewable and clean energy.Proton exchange membrane fuel cells have the advantages of zero emission,high efficiency and strong environmental adaptability,and have become an important technology choice for the power source of transportation vehicles.At present,performance such as power density is one of the key factors limiting the further popularization of fuel cells.The structural size of the flow field and the thickness of the gas diffusion layer jointly determine the gas and water transfer process in both horizontal and vertical directions inside the fuel cell,which affects the improvement of performance.However,there is still a lack of research on the two-dimensional mass transfer characteristics in flow field structure and diffusion layer design based on the target operating conditions.Therefore,it is necessary to further study the multi-directional mass transfer mechanism and the related design method.This paper studies the fuel cell modeling method for the joint optimization of the parameters of flow channels and gas diffusion layers.A three-dimensional mechanism model of is established to reveal the influence mechanism of structural design on the spatial distribution of internal states.The diffusion layer is further divided into the chamber under flow channels and the chamber under ribs,and the horizontal diffusion process under the rib is simplified based on the lumped parameter discretization in chambers and the assumption of mass transfer paths related to the flow field structurediffusion layer thickness.A reduced-dimensional simplified model for the fast joint optimization of flow field width-diffusion layer thickness is established,which effectively describes the internal states such as mass transfer differences between the flow channel region and the rib region,and significantly reduces the calculation time.This paper developes the joint design method of the flow field width and diffusion layer thickness of fuel cells.Based on the quantitative decomposition of polarization overpotential and model simulation,the influence mechanism of rib width on the internal state and fuel cell performance is studied,and the sensitivity of flow field pressure drop to the variation of structure size is analyzed.The mechanism of the effect of flow field and diffusion layer joint design on the horizontal and longitudinal mass transfer process is studied.Based on the quantitative relationship between rib width,diffusion layer thickness and performance,a joint optimization process is proposed.Optimization design of fuel cell stacks for different scenarios and experimental verification are conducted.This paper studies the fabrication method of fine flow fields for high power density fuel cells.A flow field forming method based on ultrafast laser technology with short pulse width is proposed,and the influence of the fabrication process on the surface characteristics of graphite plates is analyzed.The laser parameters are optimized for high processing accuracy and efficiency.The experimental verification of the performance of laser processed channels is conducted based on the large-area commercial graphite plates.In this paper,a new exploration is conducted in the joint optimization of the flow field width-diffusion layer thickness and the fabrication of fuel cells flow fields,which has reference value for the related studies.The results of this paper have been applied to the development of unmanned drone and vehicular fuel cells.The related design theory also serves the development of domestic fuel cell stacks,which achieves 60%performance improvement under the target working conditions.The peak power density of the fuel cell with refined flow-field based on the ultrafine laser technology is increased by 31% compared to the conventional wide flow field. |
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