Analysis Of Thermal-mechanical Coupling Effect On Assembly Pressure In Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is an electrochemical device that directly converts the chemical energy of reaction gases into electrical energy, without generating pollutions. PEMFC offers the potential advantages of low operation temperature, quick start, high power density, high efficiency, no pollution and so on. It is expected to become a prominent energy generation technology and can be used as main power sources in automotive. The key component is Membrane Electrode Assembly (MEA) on which contact pressure is very important. The change of contact pressure on MEA has a great impact on the fuel cell performance. Lower contact pressure may increase the interfacial contact resistance between the gas diffusion layer (GDL) and bipolar plate and thus the system efficiency is reduced, even can cause the leakage and internal shorts, on the other hand, higher pressure may decrease the porosity of GDL increasing the difficulty for mass transferring, even can damage the GDL.This paper focuses on contact pressure between MEA and bipolar plate during the process of fuel cell operation. The change discipline of contact pressure under thermal-mechanical coupling effect was investigated using simulation modeling method and experimental method.Firstly, theoretical basis of the thermal-mechanical coupling finite element modeling for PEMFC stack was introduced including basic equation, basic solution (especially non-linear problem solution), temperature stress, etc. Proper analysis method was chosen to solve PEMFC stack assembly.Secondly, ABAQUS software was used to establish a three-dimensional model of PEMFC thermal-mechanical coupling effect. The model included end plates, gaskets, bolts, nuts, bipolar plates and MEA, using temperature field to simulate the temperature changes, and applying preload to simulate the bolt - nut connecting which provides assembly pressure. The result showed that thermal-mechanical coupling effect has a great impact on contact pressure.Thirdly, experiments were carried out to analyze thermal-mechanical coupling effect in various stacks with different end plates. Due to significant impact of thermal-mechanical coupling effect, contact pressure on MEA was increase greatly. Thermal-mechanical coupling effect could affect contact pressure to various degrees for different materials and different geometry of the stack components.Finally, the compensation of thermal-mechanical coupling effect was investigated. Gasket thickness has a great influence on the assembly pressure which could be used to compensate thermal-mechanical coupling effect. This is helpful for the PEMFC assembly.