Abstract: At present,for the numerical simulation of the PEMFC (Proton Exchange Membrane Fuel Cell) perfor- mance,it is assumed that the porous media in the GDL (Gas Diffusion Layer) has a constant porosity.But in fact,the GDL deformation caused by the compression of bipolar plate ribs can lead to the non-uniform porosity of the GDL.In this paper,aiming at the GDL deformation and the non-uniform porosity,which are caused by the assembly pres- sure,based on the finite element theory and the computational fluid dynamics software,a non-uniform porosity func- tion (UDF,User Defined Function) is deduced by introducing the structural mechanics analysis into a FLUENT simu- lation model.Simulation results show that,for the GDL below the rib,the changes of the porosity cause the gas flow rate in the longitudinal section in the Y direction to increase from the middle to the bipolar plates,and that,due to the nonuniformity of the porosity,the gas concentration below the rib is lower than that below the flow chan- nel,and the water content increases leads to a water accumulation phenomenon,which are negative to maintaining the performance of fuel cells.Moreover,the accuracy of the deduced function is verified,meanwhile the change rules of the operating temperature and humidity with the fuel cell voltage are discussed,and the temperature distribution inside the fuel cell is also investigated.It is found that the temperature of the electrochemical region at the cathode side below the flow channel is higher than that at the anode side,which reflects that,for the actual fuel cell,the water accumulation phenomenon at the cathode side causes its heat transfer speed to be slower than that at the anode side.

Key words: PEMFC performance simulation, GDL deformation, non-uniform porosity, user-defined function, current density