MEA Water Transport Experimental Analysis And Numerical Simulation Of Proton Exchange Membrane Fuel Cell

Proton Exchange Membrane Fuel Cell（PEMFC）is one of the most popular green power systems with broad application prospects.The presence of water affects the conductivity of Proton Exchange Membrane（PEM）and the transfer and distribution of reaction gas,which are related to the PEMFC performance.Therefore,water management is one of the key factors affecting the commercialization of PEMFC.To achieve correct water management requires an in-depth understanding of the PEMFC water transfer processes.As the core of PEMFC,Membrane Electrode Assembly（MEA）is the place of material transfer and electrochemical reactions,which determines the performance of the cell.This thesis firstly introduces the cell’s warking principles,development and application,and the important components.Focuses on the water transfer process in the MEA,studies the effect of operating conditions on the water transfer in PEM and the PEMFC performance.Then,based on the high-precision mathematical model of PEMFC,the test data of the water teansfer experiment and the polarization curve experiment are used to validate the relevant parameters in the model.Subsequently,under different operating conditions（relative humidity,current density,cell temperature,working pressure and gas flow mode）,the mathematical model was used to simulate and analyze the water transfer phenomenon and water distribution in MEA,and optimize the cell performance.The results show that in a certain range,when the increase of relative humidity,cell temperature and working pressure,the PEMFC performance increases gradually,but the influence of concentration polarization will be aggravated by the high relative humidity,resulting the cell performance decline.Therefore,keeping the high relative humidity of anode side and appropriately reducing the relative humidity of cathode side can improve the performance of PEMFC.In addition,increasing the cell temperature and working pressure results in a more uniform distribution of water on both sides of the membrane.However,high temperature will make the PEM water loss serious,proton conductivity and cell performance decline.High gas pressure will also aggravate the accumulation of liquid water under high current density,hinder the diffusion and mass transfer of reaction gas,and affect the PEMFC performance.When the increase of current density,the electroosmotic drag water flux and electrochemical reaction water increased,and the relative humidity of cathode side is gradually greater than that of anode.When the current density continues to increase to 1.5 A·cm^-2,liquid water begins to form in the pores of the catalytic layer on the cathode side.Controlling the countercurrent gas flow of anode and cathode and reducing the thickness of proton exchange membrane will increase the PEM water transmission flux,which is beneficial to the uniform distribution of water in the PEM,can improve the wetting of the membrane,reduce the influence of concentration polarization and improve the performance of PEMFC.