Simulation Analysis Of Water Management Of Proton Exchange Membrane Fuel Cell

The shortage of fossil energy and the pollution of the ecological environment have become urgent problems in the world.Hydrogen has received increasing attention as a clean energy source.The hydrogen-oxygen proton exchange membrane fuel cell is a device that directly converts hydrogen energy into electrical energy.The water management capability directly affects the performance,cold start and service life of the fuel cell.This paper built models,simulated,and analyzed the water management capabilities of PEMFC from three aspects:plate flow field,operating condition parameters,and liquid water transfer characteristics in the flow channel.This paper analyzed the working principle of PEMFC,discussed the mathematical model of PEMFC reaction and heat and mass transfer process,and built a three-dimensional two-phase steady state model of PEMFC working process with different flow field structure and operating parameters.Based on the VOF model and a continuous surface tension model,a three-dimensional visual transient two-phase flow model for simulating the transmission process of liquid water in the flow channel is established,and simulation analysis is performed.Through the simulation analysis of PEMFC performance and mass transfer distribution of parallel,serpentine and grid-shaped polar plate flow fields.The results showed that the performance of the serpentine fuel cell is higher than that of the parallel and grid flow fields in the three polarization stages,the concentration of the reaction gas in the catalytic layer is higher,and the water content on the proton exchange membrane is relatively uniform,which is more suitable for PEMFC.And analyzed the performance and mass transfer phenomenon of PEMFC in the serpentine flow field under different operating parameters.The results showed that within a certain range of parameters,the higher the humidification rate of the cathode and anode intake air,the higher the water content in the membrane,the lower the membrane electrode impedance,the stronger the H~+hydration,and the higher the battery performance.As the operating pressure increases,the The catalytic layer reactant gas is more fully replenished,and the water content of the proton exchange membrane rises slightly,thereby optimizing the battery performance;as the operating temperature increases,the electrochemical reaction kinetic index rises,the electrochemical reaction intensifies,the proton exchange membrane water content rises,and the battery performance Also improved.Based on the VOF model,the transmission characteristics of the liquid water discharged into the flow channel at different positions on the GDL surface are simulated under different flow channel wall contact angles and different air flow rates.The results show that within a certain range of parameters,liquid water tends to remain spherical at high hydrophobic angles and passes through the corner of the flow channel in the form of droplets.The residual liquid water in the flow channel is reduced,and liquid water is more easily discharged from the flow channel,but the wall surface The liquid water discharged from the upper water outlet will be transmitted downstream along the junction of the wall surface of the flow channel and the surface of the GDL,which will hinder the transmission of the reactant gas into the GDL;high gas velocity will shorten the time for the droplets to detach from the water outlet and enhance the liquid Water bursts,splashes and rebounds in the flow channel.With the increase of the air flow rate,the speed of the liquid water exiting the flow channel is accelerated,but due to the strong air flow shear force,there will be a liquid flow at the junction of the GDL surface and the wall surface of the flow channel,which makes it difficult for the reaction gas to be transferred into the porous medium.