|
Polymer Electrolyte Membrane Fuel Cell (PEMFC) is widely considered as one of the most promising clean energy power sources to compete with internal combustion engines in the future, especially for portable power, mobile electronic products, small fixed station and automobiles, because of its high energy efficiency, low operating temperature, high power density, capability of quick start-up, and advantages of clean and quiet. However, the operation process of a PEMFC is usually in relation to multi-component gas transport, and multiphase flow. These complex physical and chemical phenomena are usually tightly coupled. As a result, the detailed experimental data within a PEMFC is hard to obtain due to the complexity of fuel cell structure and the limitation of the scale of fuel cell. Therefore, the numerical simulation of PEMFC technology as a necessary complement to the experiment has an important engineering and academic significance.First of all, the test system to investigate the performance of self-assembled PEMFC under the different operating conditions was established. Significant impacts on the fuel cell performance were found by increasing gas pressure, temperature, inlet gas relative humidity and clamping force. The accuracy of the result of the numerical simulation was also qualitatively verified.Secondly, according to the finite element theory, we used ANSYS software to build a mechanical model of PEMFC. In order to make some elastic deformation occurred in the gas diffusion layer (GDL) of a PEMFC, four different clamping forces were inposed to the bipolar plate of PEMFC. In this study, the deformation profiles of the GDL under different clamping force were different from each other. With an increase in clamping force, the thickness of GDL under the rib gradually became thinner. On the other hand, no matter how much clamping force imposed, the thickness of GDL under the channel almost remained unchanged.Finally, a two-dimensional two phase flow model was built by multi-physics software of COMSOL Multiphysics based on the model which has been analyzed by ANSYS software. The changes of porosity as a result of variation in thickness of GDL were analyzed, with relation to permeability, diffusivity, electrical conductivity, and the resulting changes in water content and distribution in the cathode diffusion layer. We found that with increasing the clamping force, the porosity tends to decrease gradually, and the water contents of the catalyst layer and gas diffusion layer tend to increase. In addition, an increase in current density will result in an increase of water content of catalyst layer and gas diffusion layer, leading to much more difficulties in water management.
|