Simulation Study On The Structure Of Gas Diffusion Layer And Flow Field Plate In Proton Exchange Membrane Fuel Cell

At the goal of "30·60 carbon neutralization and carbon peaking",hydrogen energy is considered as one of the ideal alternative fuels under the dual carbon goal because it contains no carbon elements and can be made from a variety of substances.Hydrogen fuel cell technology is expected to be one of the main utilization methods of hydrogen energy.As the key components of the fuel cell,the flow field plate and the gas diffusion layer together constitute the flow field structure of the cell,which is responsible for the distribution and redistribution of the reaction gas,the assembly pressure between single cells directly affects the contact structure between the two,resulting in the diffusion layer structure and transport properties vary unevenly,affecting the performance of fuel cells.In this paper,the gas diffusion layer and the flow field plate flow channel structure of the proton exchange membrane are taken as the research objects.With the help of mutiphysical field coupling software COMSOL,the combination of numerical simulation and theoretical analysis is used to study the effect of the gas diffusion layer structure and transport characteristic parameters on fuel cell performance;the structural of gas diffusion layer and fuel cell performance changes under different assembly pressures;three optimized flow channel structures were proposed,and the working process of fuel cells were simulated.The main work and achievements of the paper are as follows:Firstly,the performance of fuel cells under different diffusion layer porosity,thickness and porosity gradient was simulated by the electrochemical model of the fuel cell.The results show that when the diffusion layer porosity is 0.6,the comprehensive performance of the cells is the highest;Under the condition of ensuring the mechanical strength of the diffusion layer,the thinner the diffusion layer,the better the performance of the fuel cell;The four porosity gradient methods designed in this paper all improve the performance of the fuel cell to varying degrees in different aspects.Among them,the gradient method in which the porosity increases linearly along the gas inlet direction has the most significant improvement in fuel cell performance.Secondly,based on the solid mechanics and electrochemical coupling model of the fuel cell,the changes of the diffusion layer structure and transport characteristics under different assembly pressures and the influence of the cell performance were studied.The simulation results show that with the increase of the assembly pressure,the diffusion layer structure and the inhomogeneity of the material distribution in the fuel cell intensify,and the fuel cell performance decreases.When the assembly pressure is 2MPa,the membrane water content is the highest,the proton conductivity is the highest,and the current and power density there is a sudden drop in the rate of reduction.Finally,three optimal designs of flow channel structures are proposed for the phenomenon that the assembly pressure aggravates the uneven change of the gas diffusion layer structure and reduces fuel cell performance.The simulation results show that the contact structure between the field plate and the diffusion layer under the assembly pressure is improved by introducing the bevel angle of the flow channel rib,and the fuel cell performance is improved;when the channel-to-rib width ratio is 1.25-1.75,the overall performance of the fuel cell is the best;the inclined structure of the channel sidewall increases the diffusion rate of the reaction gas to the reaction interface,and when the slope is 70°-75°,the comprehensive performance of the fuel cell is the best.