中心复合设计法（二阶响应曲面设计）优化大面积燃料电池气动端板设计：接触应力分布仿真值和实测值的差异［设计因素其十四］

Investigation of contact pressuredistribution on gas diffusion layer of fuel cell with pneumatic endplate

M．M．Barzegari

M．Ghadimi

M．Momenifar

Abstract

Polymer electrolyte membrane fuel cell is apromising energy conversion device because of its high energy density， highefficiency and low emissions． Contact pressure on gas diffusion layers plays animportant role in the performance improvement of polymer electrolyte membranefuel cells by optimizing the ohmic and concentration losses． In this paper， geometric parameters of a pneumaticclamping system are optimized using a central composite design method andfinite element simulations to obtain the most uniform contact pressuredistribution on gas diffusion layers． The experimental data obtained by thepressure mapping system have been employed to validate the results of theoptimized clamping system． The embedded pressure measurement films are placedin the designed polymer electrolyte membrane fuel cell with an active area of400 cm2． The results reveal that themaximum difference between numerical and experimental results is less than 8％．Moreover， the contact pressuredistributions over the gas diffusion layer for the clamping systems ofpneumatic and conventional endplates are compared． The results demonstratethat the weight and efficiency ofthe clamping system with optimized pneumatic endplate is significantly betterthan the clamping system with conventional endplates．

Pneumatic：气动的

Fig． 1． Schematic diagram of the PEM fuel  cell with pneumatic clamping system．

Fig． 2． Finite element model of the PEMFC  stack with pneumatic clamping system．

Table 1 Mechanical and geometric  parameters of the PEM fuel cell components．

Table 2 Values of different levels of each  factor used in circumscribed CCD．

中心复合设计

The optimization  process is accomplished using central composite design （CCD） method． CCD is  an ideal solution for fitting a second－order response surface method （RSM）  which is a statistical technique that can be used for studying the effect of  several factors at different levels．

属于二阶响应曲面设计

Table 3 Design layout and FE simulation  results of CCD．

Table 4 Analysis of variance of Eq． （1）．

Table 5 Conditions for additional FE  simulations．

Fig． 3． 9－cells stack and pressure  mapping system for contact pressure measurement of gas diffusion layer．

Fig． 4． （a） Comparison of predicted  response variable by Eq． （1） and FE Simulation for five conditions， （b）  Relative errors of respective trials．

Table 5 The coded and uncoded optimized  values of the factors．

Fig． 5． Contact pressure distribution on  GDL of PEMFC stack with different geometric parameters of pneumatic clamping systems  along （a） X－axis， （b） Y－axis， （c） D－axis．

Fig． 6． Comparison of contact pressure  distribution on GDL for conventional and pneumatic clamping systems．

Fig． 7． Results of contact pressure  distribution over the active area for optimized clamping system， （a） CPRESS  distribution using pressure measurement film， （b） comparison of simulation and  experimental results along Y－axis， （c） difference between FE simulation and  experimental results．

Conclusion

In this work， geometric parameters of the  pneumatic clamping system are optimized to obtain the most uniform contact  pressure dis－tribution over gas diffusion layers． The optimization of a  pneumatic clamping system is carried out using a three－dimensional finite  element method． The design of simulation for optimization of the clamping system  is conducted using the statistical technique based on central composite  design method． The thickness of the  pneumatic endplate， the thickness of conventional endplate and the side  length of pneumatic endplate are the three factors used for the design of  simulation． The standard deviation  of contact pressure values for all nodes on the gas diffusion layer surface is considered as a response variable．  Five more randomly levels of  factors are selected to verify the model obtained by the response surface method． The results are compared with finite element simulation and the relative  errors are less than 4．5％． The considered  experimental setup is composed of 9－cells polymer electro－lyte membrane fuel cell stack with an  active area of 400 cm 2 ． The re－sults  showed that the use of optimized pneumatic endplate leads to a significant improvement in the  uniformity of contact pressure dis－tribution on the gas diffusion layer． The finite element simulation is validated through experimental data  obtained by the pressure mapping system  and the maximum difference is less than 8％． In addition， the contact pressure distributions over  the gas diffusion layer for the clamping  systems of pneumatic and conventional endplates are com－pared． The results reveal that the weight  and efficiency of the clamping system  with optimized pneumatic endplate is significantly better than the clamping system with  conventional endplates．

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