Reliability Analysis And Design Of Large Fuel Cell Stack

The proton electrolyte membrane fuel cell(PEMFC)is a new green power system with a broad development prospect.It has received much attention due to its high energy efficiency and environmental friendly.In practical application,reliability of products has attracted more and more attention.Thus how to improve reliability by designing structure is becoming one of the research hot spots.Selecting the PEMFC as analysis object and using the reliability analysis method,the influence factors of components reliability under clamping force load are analyzed.The aim of this paper is to increase the PEMFC stack by designing the clamping force and the thickness difference between the membrane electrode assembly(MEA)and the gasket.The components reliability is directly determined by the material strength and contact stress,according to the stress-strength interference theory.The strength standard of component is confirmed through integrating predecessors’ research results and the performance requirements.Moreover,the contact stresses of components are set up by MEAs of the equivalent stiffness model,which are directly determined by clamping force,components dimensions and elastic modulus.The contact stresses of components are random variables because they are usually affected by many uncertain factors in the production and clamping process.The first-order second moment method is adopted to analysis the probability distribution of contact stresses.The controlling variable method is adopted to investigate the sensitivity of contact stress,the result remonstrates that the component dimensions coefficient of variation have the biggest influence on the contact coefficient of variation.Based on the stress-strength interference theory and the strength standard of components,effects of contact stress on the reliability of components with different coefficients of variation are obtained.It is found that either too large or too small a contact stress is harmful to the component reliability,there exits an optimal contact stress interval to make components stay in a high reliability level and each component has its own optimal interval.Besides,the interval range decreases with the increase of variation coefficients.After the optimal contact stress of components is determined,the thickness difference and clamping force are designed in order to ensure the reliability of the stack.The results indicate that there exits optimal thickness difference between components and the optimal clamping force,which makes the stack reliability stay in a high level and improve the reliability significantly.This work can provide a valuable guidance in the design of stack structure for a high reliability of fuel cell stack.