Study Of Proton Exchange Membrane Fuel Cell Diffusion Layer Based On The Lattice Boltzmann Method

The Proton Exchange Membrane Fuel Cell(PEMFC), It is an electrochemical device which will continue to supply a fuel and oxidizer in the chemical energy into electrical energy continuously. The Proton Exchange Membrane Fuel Cell(PEMFC) is provide with advantages, such as efficient and safe, environment-friendly, low operating temperature, quick start-up,etc. And it is considered as one of the best energy and a method of hydrogen use. It has broad market prospects and great commercial value in civil power, small power station power supply.The diffusion layer of membrane electrode(MEA) as an important part of its physical structure and the physical parameters of the different directly affects the operation performance of fuel cell. At present, system performance analysis of proton exchange membrane fuel cell, multiple uses mechanism model, solving the complex, can not reflect the effect of the internal structure of the battery on the performance of the system. This paper uses the lattice Boltzmann method and the advantage of parallel characteristic is good, easy calculation, using D2Q9 model to simulate the study of porous gas diffusion layer(GDL), porosity, diffusion layer thickness, stoichiometric, humidification temperature and other factors influence on the PEMFC output performance through the analysis of diffusion. At the same time, make the analysis of the effect on the performance of PEM fuel cell output also for the partial pressure of hydrogen, oxygen partial pressure, temperature, cell membrane area, film thickness under different operating conditions, and this paper uses MATLAB software analysis on PEMFC performance simulation, the conclusions are as follows:Conclusion through the lattice Boltzmann method:The effective diffusion porosity is too small is not conducive to the fuel gas in diffusion layer, the electrochemical reaction is not sufficient that the battery performance decline; porosity is too large although the diffusion of gas to improve, but the electrochemical reaction will make more sufficient diffusion of liquid water formation layer, cause local water flooding, reduce the cell performance;Membrane fuel cell diffusion layer thickness decreases in favor of gas transfer proton exchange, but the thickness of diffusion layer is too thin, gas diffusion efficiency, reduce the cell performance. The thickness of diffusion layer is too thick, the decreasing rate of the catalytic layer surface chemical reaction, reduce the cell performance;Layer water content increasing will restrict oxygen diffusion transfer of proton exchange membrane fuel cell, reduce the effective porosity, reduce the cell performance; Excess air coefficient of diffusion layer in proton exchange membrane fuel cell(<5) is beneficial to improve the performance of the battery is increased, but when the excess air coefficient increases from 3 to 4, the cell performance for gas velocity becomes large to carry out more water, leading to a reduction in anti diffusion into the proton exchange membrane water, reduce the water content of the membranes, ohmic polarization grow larger and the battery performance variation. So commonly used air stoichiometric number 3; Humidification temperature is lower than 50℃, the higher the temperature of the battery performance and better battery. The increase of current density of humidity and temperature at 60℃-80℃ when performance change obviously, fuel cell. So the general battery temperature at around 80 degrees is appropriate, humidification temperature is lower than the battery temperature is 5-10℃.Increasing the gas pressure can be improved battery performance. The cell performance improves with the increase of hydrogen pressure, but the increase of oxygen partial pressure significantly better than; To increase the battery temperature can improve the performance of the battery. When the PEM fuel cell at 80℃, the battery performance optimization. When the temperature is below 80℃, as temperatures rise, the battery performance is improved; on the contrary, when the temperature is higher than 80℃, as temperatures rise, the battery performance decreases;Effect of film thickness on the cell output performance mainly reflected resistance of film on the output performance of the fuel cell performance decreases with the increase of film thickness; At low current density, the effective area is smaller than the performance of the battery cell large effective area; at high current density, the effective area of the battery cell performance is larger than the effective area is small.This study contributes to a better understanding of the proton exchange membrane fuel cell two-phase internal transfer, and provides guidance for the design and operation of the battery condition of PEMFC diffusion layer selection.