燃料电池电堆活性区接触应力分布的影响因素：端板厚度、端板材料、密封模型、密封件硬度、电池节数、电池位置（设计因素其二）Investigation of contact pressure distribution over the active area of PEM fuel cell stack

E． Alizadeh

M． M． Barzegari

M． Momenifar

M． Ghadimi

S． H． M． Saadat

Abstract

Contact pressure distribution over the active area of proton exchange membrane fuel cell （PEMFC） has significant effects on the performance of PEMFCs． Even clamping pressure over the membrane electrode assembly （MEA） affects contact resistance， characteristics of porous media and sealing task． This paper develops a PEM fuel cell model to study the contact pressure distribution over the membrane electrode assembly using finite element model． At first， the three－dimensional model of a single cell was reduced to a two－dimensional model to decrease the calculation time． After validation of the obtained results via the pressure sensitive films， the effect of some parameters such as thickness and material of the end plates， sealant hardness， number of the stack＇s cells and position of the cell on the contact pressure distribution over the MEA were investigated． The results reveal that optimizing mentioned parameters leads to design PEM fuel cells with proper contact pressure distribution over the MEA．

Fig． 1 e （a） Exploded PEM fuel cell view， （b） Two－dimensional PEM fuel cell model．

Table 1 e Mechanical properties of the PEM fuel cell components．

Fig． 2 e Symmetric two－dimensional model of the PEM fuel cell．

Fig． 3 e （a） Three－dimensionalmodel of the PEM single cell， （b） Symmetric conditions and load configurations of PEM fuel cell
model．

Fig． 4 e The uniaxial compression specimen （a） Experiment， （b） Simulation．

Fig． 5 e Response zone for typical viscoelastic solid

Fig． 6 e Multi－step relaxation test with five minutes delay for each stage．

Fig． 7 e Uniaxial， biaxial and planar fittings with Neo－Hookean model using experimental data．

Hyperelastic material models such as Mooney－Rivlin， Arruda－Boyce，
Yeoh， Neo－Hookean and Ogden are used to fit the test data and extract hyperelastic constants． The Neo－Hookean model is stable in whole strain domain．

很大篇幅都在讲密封件的本构模型与实验的对应关系。

Fig． 8 e Comparison between test data and simulation with and without friction．

The calculated friction coefficient is assumed to be 0．3 （contact model） in the test．

Fig． 9 e Contact pressure distribution over the MEA of twodimensional
and three－dimensional PEM single cell model with different thicknesses of end plates．

端板厚度对接触压强分布的影响

Fig． 10 e Position of pressure sensitive film in PEM fuel cell．

Fig． 11 e Contact pressure distribution over the MEA of PEM Single cell， （a） Stainless steel end plate with 30mmthickness （b）Stainless steel end plate with 50 mm thickness．

Fig． 12 e Contact pressure distribution over the MEA of PEM Single cell with flat bipolar plate and bipolar plate with flow field．

时刻需要考虑应力分布对接触电阻的影响

According to Fig． 12， the results of the case using flat bipolar plate has the same trend as bipolar plate with flow field．contact pressure over the MEA in flat bipolar plate decreases with increase of the contact area．

Fig． 13 e Stress distribution over the MEA of PEM single cell．

Fig． 14 e Contact pressure distribution over the MEA of PEM Single cell for different end plates materials and thicknesses．

端板材料的影响

Fig． 15 e Contact pressure ratio for Steel and Aluminum with different thicknesses of end plates．

The compression ratio parameter is defined as minimum contact pressure divided by maximum contact pressure．

Fig． 16 e Contact pressure distribution over the MEA of PEM Single cell for three different hardness of the sealant．

密封件硬度

Fig． 17 e Contact pressure distribution over the MEA of single cell， three cells and fifteen cells stacks．

电堆节数的影响

Fig． 18 e Contact pressure distribution over the MEA of fifteen cells stack．

Fig． 19 e Contact pressure distribution over the MEA of first cell and middle cell of fifteen cells stack．

短堆中边缘节和中心节应力分布的差异

Conclusion

In this paper， a finite element simulation method is used to
investigate the effect of thickness and material of end plates，
sealant hardness， number and position of cells on the contact
pressure distribution over the surface of the MEA． Two dimensional
model is used instead of three－dimensional model and the results are compared with experimental results which were obtained by pressure sensitive films． It is concluded that increasing the flexural rigidity of the end plates leads to decrease in deflection of them． Increasing the flexural rigidity of end plates can be obtained by selecting suitable
thickness and proper material． In addition， the other way to
decrease deflection of the end plates is to reduce the applied
torque on the bolts which can be accomplished using softer
sealant． Furthermore， increasing the number of cell causes to
have better contact pressure distribution over the MEA．