Study On Impact Resistance Ability Of Large Fuel Cell Stack

Clean and efficient proton exchange membrane fuel cell(PEMFC)becomes popular because of energy shortage and environmental pollution.PEMFC with metal bipolar plates has a bright future in transportation,aerospace equipment and other fields because of its lightweight,but the service environment of the stack is harsh.Except for clamping force,multiple loads,such as temperature change,random vibration and impact,will change the porosity of gas diffusion layer and the stress of key component like membrane electrode assembly and sealing joint strip,which affects the performance of stack then.Based on equivalent stiffness theory,the finite element model of bolt-clamped metal bipolar plate PEMFC stack is established in this paper to discuss the change of contact pressure between cells under extreme temperature,and to give the mechanical response of the stack under vibration and impact load.The bipolar plate is divided into four regions,and the equivalent stiffness model of the stack is obtained by calculating the equivalent stiffness of each region.Compared with the equivalent stiffness model of a single cell stack and the pressure-sensitive paper experiment,the contact pressure error between layers is within the acceptable range,which further proves the accuracy and rationality of the equivalent stiffness model.The vibration modes of the stack within 2000 Hz is calculated,the first-three-order modes are global modes with concentrated frequencies.The most dangerous area is in the sealant region close to the inlet endplate.The first-order modal frequency is 560.94 Hz.The last-third-order modes are the local mode in the rib region with scattered frequencies,and the rib region of middle cells is more dangerous.Additionally,the possibility of damage caused by the random vibration in the length and width direction in the cells is larger than that in the clamping direction,the components near the blind endplate suffer the severest damage.The impact analysis of the stack shows that the maximum displacement of cells close to endplates is relatively small under impact loads,but possible relative slippage occurs firstly in these cells.Regarding the critical impact acceleration as one of the criteria to evaluate the resistance ability of the stack under the impact in the cell plane,the relation between the critical impact acceleration and the static friction coefficient is given.With the same static friction coefficient,the resistance ability of the stack under vibration in width direction is better than that in length direction.The analysis results based on thermal-mechanical coupled model of the stack shows that temperature change makes the contact pressure uniformity in both the rib and sealant regions become worse.The contact pressure in the rib region increases as the temperature increases,but it decreases in the sealant region.In addition,the relation between the uniform stress from equivalent model and the local stress of the detail structure is established through the local structure,and the relation between the average stress in the rib region.The maximum local stress of carbon paper is given,so that the failure of carbon paper in this region can be quickly judged from the uniform stress of equivalent model.