| As an alternative power source for stationary,mobile and portable applications,proton exchange membrane fuel cell（PEMFC）has attracted more and more attention due to its outstanding advantages,and is considered to be the third energy revolution in humankind.core driving force.Among them,mass transfer and water removal in porous electrodes of PEM fuel cells have become an important issue,which is closely related to the overall performance of the cell.Optimizing the flow field design to study the problem of cathode water management can not only effectively avoid electrode "water flooding" The occurrence of this phenomenon is of great significance for promoting the mass transfer of reactant gases and improving the performance of PEMFC.In order to optimize PEMFC water management and improve the uniformity of mass transfer inside the cell,this study proposes a conical flow field structure（FFC）to improve the internal reactant transport and water removal of PEM fuel cells,and analyzes whether the contact resistance is considered or not（ECR）Effect of this conical FFC.By building a 3D multiphase fuel cell model,this study numerically investigates the effect of conical FFC on the internal physicochemical processes and overall performance of the cell.Conical FFCs without and considering the ECR between the bipolar plate and the gas diffusion layer were comparatively evaluated.Compared to conventional FFCs,the increase in the edge-to-exit ratio（LI/O）of the inlet to outlet enhances oxygen transport,water removal,and cell performance for tapered FFCs that do not consider ECR.However,for the tapered FFC considering ECR,the increase of LI/O ratio showed a trend of first increase and then decrease on reactant transport,water removal and cell performance.However,the reduction of the LI/O ratio reduces the overall performance of the cell with or without the tapered FFC of the ECR.Compared with all tapered FFC designs,the optimal tapered FFC design with LI/O of1.2 exhibited more uniform reactant and current density distribution,which reduced the coefficient of variation of current density and oxygen molar concentration by about 21.4%and 8.5%,thereby improving the overall battery performance.The above study found that the appropriate conical parallel FFC design is beneficial to solve the problems of reaction uniformity and flooding in the cell,and at the same time,it is necessary to consider ECR in the numerical simulation of PEMFC.The new conical flow field structure provides a good idea for improving the problem of uneven internal mass transfer in the parallel flow field of PEMFCs.The quality and flooding problems have not been improved very well.In this study,in order to solve the problem of more liquid water under the flow channel ribs,a novel flow field was designed.By arranging auxiliary channels in the hollow ribs of the single cell of PEM fuel cells and drilling a series of auxiliary channels on the auxiliary channels Array of holes.This novel design rationally utilizes the ribs of the bipolar plates to increase the volumetric efficiency of the parallel channels,thereby improving cell performance and uniformity of current distribution.A threedimensional multiphase flow FLUENT model was developed to analyze the effects of various parameters on oxygen and water saturation distribution,cell performance,and current uniformity.The combination of auxiliary channels and pore arrays was found to provide additional pathways for reactant transport and water removal.Rational optimization of flow field geometry,such as pore size,area ratio of array pores and auxiliary channels,and uneven distribution of array pores,can further improve cell performance and current uniformity at extremely low voltage drops.Therefore,this new flow field structure provides the possibility to study the auxiliary channel of PEMFC,further improve the mass transfer problem under the fin and effectively manage the water.The two new flow fields proposed in this paper have guiding significance for the flow field design of PEMFC. |
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