||In this study, 3D FEM (finite element method) models of both single cell and dual-cell of PEMFC (proton exchange membrane fuel cell) had been established, separately. The commercial software ANSYS15.0 was adopted in order to observe the effect of bolt pre-loading variation on the contact resistance and porosity of GDL (gas diffusion layer) in PEMFC. Then, the obtained values of contact resistance and porosity of GDL were substituted into the electro-chemistry simulation software Fluent 15.0 and the effect of bolt pre-loading variation on the efficiency of PEMFC was discussed.|
In stress-strain analysis, a 3D PEMFC model with the reactive area of 25cm2 had been established through 3D drawing software SolidWroks 2013. The model includes membrane, catalyst layer, gas diffusion layer, flow channel plate, current collector and body plate which all elements were fixed by 12 pairs of bolt and nut. In order to apply bolt pre-loading on each pair of bolt and nut, the nuts were assumed to be fixed and the ANSYS built-in function, bolt pretension, was adopted. According to the simulative results, both contact resistance and porosity of GDL are decreasing while the bolt pre-loading increasing. The decreasing of contact resistance can reduce the ohmic loss effectively, and increase the efficiency of PEMFC. However, the decreasing of porosity of GDL will cause the increasing of resistance of permeability and resulted in the decreasing of the efficiency of PEMFC. The results of electro-chemistry simulation show that by increasing bolt pre-loading from 5MPa to 16MPa will result in 75.7% improvement of maxima power density of PEMFC. In a dual-cell PEMFC, the average equivalent stress of the GDL is increased due to the increase in the total thickness of the flow channel plates, thus greatly reduce the contact resistance of GDL. The simulative results indicate that due to the contribution of the reduction of contact resistance of GDL, the maximum power density of the dual-cell module is increased by 37.8%.
Keywords: Proton Exchange Membrane Fuel Cell, Contact Resistance, Porosity, Bolt Pre-loading, Power Density