Mechanical Structure Design And Analysis Of Thin Shell Metallic Bipolar Plates Of Fuel Cell

Proton Exchange Membrane Fuel Cell(PEMFC)is considered as a powerful alternative to traditional energy sources because of its high efficiency conversion rate and pollution-free features,and has great development prospects in the fields of automobiles,aviation,portable batteries,etc.As one of the core components in the fuel cell,the bipolar plate directly affects the working efficiency and life of the stack.With the idea of lightweight bipolar plates,thinner,lighter and stronger metallic bipolar plates have become the primary choice.Due to the hollow design of the flow channel and the multilayer assembly requirements of the metallic bipolar plate,the strength and stability of the structure will be affected when the package load is applied.At the same time,the bipolar plate with processing errors will cause the distribution of the contact stress of the GDL,which will cause the performance of the stack to decrease.The present study focuses on three aspects: the mechanical properties of the flow channel structure,the influence of single-plate processing errors on the contact stress of the GDL,and the stability of the multi-layer bipolar plate structure.The analysis and optimized design of the metallic bipolar plate could provide a theoretical basis for the actual processing design.Firstly,in view of the requirements for the rigidity,strength and stability of the singlechannel structure of the stamped metallic bipolar plate,the influence of the design parameters such as the thickness of bipolar plate,ridge width,height and sidewall inclination angle of flow channel on the mechanical properties of the channel structure was studied.The rigidity,strength and anti-instability characteristics of the bipolar plate structure were studied under the loading conditions of the package load and the combined effect of the air pressure and the package load.It was found that reducing the thickness of the metallic bipolar plate,increasing the width of the ridge back of the flow channel and increasing the inclination angle of the flow channel will reduce the rigidity and strength of the structure,and increasing the height of the flow channel will cause greater structural deformation.Among the four design parameters,the thickness of the bipolar plate has the greatest influence on the mechanical properties of the flow channel.The existence of gas pressure in the flow channel has little effect on the mechanical properties of the structure.Then,the finite element model of the metallic bipolar plate and the GDL was established,and the influence of the height error and warping shape error of the bipolar plate on the contact stress of the GDL was investigated.It was revealed that the average value of contact stress decreased with the increasing error,and the standard deviation of contact stress increased with the increasing error.The evaluation criteria of the contact performance between the bipolar plate and the gas diffusion layer were defined,and the multi-objective problem of the average value and standard deviation of the contact stress under different error conditions was converted into a single-objective problem of total satisfaction through the satisfaction function.The maximum processing error under the premise of meeting contact performance requirements were determined.Finally,a stack model of the sealing area of the metallic bipolar plate frame was established.Taking the 15-layer stack structure as an example,the equivalent deformation theory was used to determine the main deformation area.The local seal structure was refined,and the critical load and modal shape of the structure were calculated.It was found that the seal area produced a "snake-like" unstable bending deformation.As the number of stack layers increases,the critical load of the structure decreases.In order to improve the ability of structure to resist instability,the effects of metallic bipolar plate materials,bipolar plate thickness and the width of bipolar plate sealant region on critical load were investigated.The results showed that increasing the elastic modulus of the material,the bipolar plate thickness and the frame width are beneficial to improve the stability of the structure.