Performance Analysis Of PEMFC With Prestress

PEMFC is a new energy generation device with high energy efficiency and is pollution-free,which has a good application prospect.This paper mainly used the method of macro simulation to study the performance of PEMFC under different conditions and it has guiding significance for improving the performance of PEMFC.Based on a large number of related literature on PEMFC,the development history,working principle,structural composition,application characteristics and research status of PEMFC were expounded.Based on mass transfer theory,electrochemistry,fluid mechanics and solid mechanics theory,a three-dimensional,two-phase,constant temperature,steady state model of PEMFC with a serpentine flow field was constructed,and the model was analyzed by finite element method.The solid mechanics model,the mass transfer model and the electrochemical model were coupled in this modle.A verification test was performed,which parameters was similar to the model.The validity of the model was verified by experimental data.The solid mechanics module was used to simulate the stress,displacement and effective porosity distribution of GDL under the preload of PEMFC.The effective porosity data was substituted into the porous media material transfer module and the secondary current distribution module for the next mass transfer and electrochemical analysis.The molar concentration distributions of oxygen,total water,and liquid water were obtained,as well as the protons electron current distribution in GDL and ion current distribution in PEM.The results show that the prestress reduced the effective porosity of the GDL under the rib and hindered the diffusion behavior of the reactants and products.In the GDL under the rib at the corner of the flow channel,due to the change in the direction of material flow,water concentration increased and oxygen concentration decreased,resulting in lower current density.The flow field structure promoted the increase of the current density in the GDL under the rib,the current density on the GDL surface at the junction of the flow ridges was significantly concentrated,and lateral currents appeared in the GDL.The different parameters were changed to explore the effects of different prestress,different GDL thickness,and different rib width on the performance of PEMFC.The results show that the effective porosity of GDL under the rib decreased with the increase of the prestress.The water concentration and liquid water concentration of the GDL under the rib at the corner of the flow channel increased significantly,resulting in a lower current density in the corresponding PEM.The best prestress is 2MPa.As the thickness of GDL decreased,the oxygen concentration in the GDL under the rib decreased,and the water concentration andliquid water concentration increased.The current density concentration on the GDL surface at the junction of the flow channel and the rib became significant.The best GDL thickness is0.3mm;as the width of rib increased,the oxygen concentration in the GDL under the rib decreased,and the water concentration and liquid water concentration increased.The current density on the GDL surface at the junction of the flow channel and the rib gradually decreased.The best rib width is 0.85 mm.