Modeling And Simulation For Proton Exchange Membrane Fuel Cell

The proton exchange membrane fuel cell (PEMFC) is considered as one of the most promising alternative automotive power sources to compete with internal combustion engines due to its higher efficiency, lower overall emission and eco-friendliness. There are many factors that influence the performance of PEMFC, such as working pressure, working temperature, relative humidity etc. Based on the mathematical simulation for the single PEMFC, this thesis studies the effect of these factors on the performance of PEMFC.First of all, based on the Matlab/Simulink, the steady-state mathematical model of PEMFC is developed with the characteristics of mass transfer and electrochemical. The model parameters are obtained according to the experiment. Results of simulation are compared with the experimental results. The thesis discusses the effect of some parameters which contain work pressure, work temperature, relative humidity, thickness of gas diffusion layer (GDL) on the steady-state performance of fuel cell, and discusses the effect of working current density, working pressure and working temperature on the efficiency of fuel cell. The results are as following: (1) The cell performance is improved with increasing the pressure of cathode and anode, especially working on the high current density. While working on the high current density, increasing the pressure of cathode can significantly improve the efficiency of fuel cell. (2) Partial pressures of oxygen and hydrogen decrease as the fuel cell temperature increases, but the hydrogen pressure decreases more rapidly. In the range of operating temperature, the thermodynamic voltage, the ohmic overvoltage and activation overvoltage all decrease as the fuel cell temperature increases, but the cell voltage increases. (3) Relative humidity affects the effective partial pressures of the reactants. With the increase of relative humidity, the effective partial pressures decrease. (4) The oxygen and hydrogen partial pressure presents approximately linear decreasing tendency along the diffuse direction, but decreasing of the oxygen effective partial pressure is more obvious while the fuel cell working on the high current density.Based on the single cell experimental verification of the simulation model, the distribution of thermal dissipation, output voltage of fuel cell and temperature changes with time are investigated. Through establishing simulation model of water transfer in the proton exchange membrane, the effects of humidity of reactant and the working current density on water content of membrane are studied. The results are as following: (1) Thermal dissipation from the cathode is much more than anode. (2) The cell structure affects thermodynamic characteristics of fuel cell and its response time is different. Temperature and voltage of fuel cell change slowly, reach a stable value while current step change. (3) Water content is easy to be saturated for cathode side of the membrane under high current density and high cathode humidity.