Gas Field Modeling And Water Management Of Proton Exchange Membrane Fuel Cell

The gas field modeling of proton exchange membrane fuel cell (PEMFC) can provide scientific guidance for optimization design of gas field. Effective water management of fuel cell can improve the fuel cell performance as the proton exchange membrane humidified well and the electrode do not flood.At first, a mathematical model is described to model the working process of PEMFC in this dissertation, it accounts simultaneously for the fluid flow, gas diffusion in the porous media, phase change of water, water transfer in proton exchange membrane and electrochemical reaction. The studied domain consists of fluid channels, diffusion layers and catalyst layers of anode and cathode, and membrane. That transport phenomena occurred in the whole fuel cell is described by the generalized equation, and different physical parameters and source terms are employed for different layers.Then, gas field of fuel cell stack inlet air manifold and cathode flow field are modeled by computational fluid dynamics software Fluent. The simulation results of inlet air manifold show that the uniformity of the velocity at outlet of the manifold are improved by using the appropriate bell-mouthed inlet and clipper-built baffle, and inlet pressure needed of the manifold decrease. The simulation results of cathode flow field show that the oxygen concentration on interface between cathode catalyst layer and diffusion layer of serpentine flow field is larger than it of pin structure, and the water concentration is smaller, gas velocity in diffusion layer of serpentine flow field is much larger than it of pin structure.At last, the transport equations and electrochemical dynamics equations are solved simultaneously by PEMFC module of software Fluent, and the water distribution and current density distribution in proton exchange membrane, the saturation and oxygen concentration distribution on interface between cathode catalyst layer and diffusion layer, water concentration distribution across MEA and the V-I curve are all obtained. The effect of the current density and fuel cell temperature, humidified temperature of cathode and anode, porosity of porous diffusion layer on the results mentioned above are discussed. The results show thatwhen the cathode humidified temperature increase, the humidification of membrane and fuel cell performance improves at lower current density, while the saturation in diffusion layer increases and the performance decreases at higher current density. Humidification of membrane and fuel cell performance improves when the anode humidified temperature increases, the saturation in diffusion layer decreases and fuel cell performance improves when the fuel cell working temperature increases, the resistance of diffusion layer decreases and the performance improves when the porosity adds.