Multiphysics Coupling And Thermal Stress Analysis Of Solid Oxide Fuel Cells

Today,with the increasingly prominent energy problem,solid oxide fuel cell is regarded as a new and efficient clean energy conversion device,which has gradually become the focus of the improvement and development of new energy structure in the 21 st century.The research object of this paper is the flat plate SOFC,which has a wide range of applications.Based on the COMSOL finite element software,several SOFC multi-physical field coupling models are established to study the multi-structure from the aspects of electrochemistry,steady-state thermal stress,long-term thermodynamic performance and so on.The specific contents are as follows:In the study of cell performance,a multi-physical field model including electrochemistry,multi-material transfer and gas flow and diffusion was established,and the effects of co-flow,counter-flow and staggered flow on cell performance and internal material distribution were discussed.After determining the inflow form and the range of working voltage,the electrochemical analysis of the three configurations of SOFC was carried out,and the effects of the change of connector form on the performance of fuel cell were compared.Finally,it is found that the output performance of the SOFC designed with circular and bow channel is much better than that of the traditional SOFC.On the basis of single-pass channel optimization,a multi-pass channel optimization model is proposed.Finally,by comparing the traditional structure,it is found that the rearrangement of runner and connector rib plate can reduce contact resistance and ohmic loss to a certain extent and optimize current density distribution,and then improve the output power of the battery.In the study of the steady-state thermal stress of the battery,on the basis of the established electrochemical model,the elastic constitutive model is added to analyze the steady-state thermal stress of the battery by coupling with the temperature field,and the bow channel configuration is improved to obtain better thermodynamic performance.Finally,it is found that the optimized SOFC configuration not only has no decrease in battery output performance,but also has higher output power in part of the working voltage region,and effectively reduces the stress dangerous area in the connector,and the overall stress distribution of the battery is more uniform,which effectively improves the anti-failure ability of the structure and prolongs the service life of the battery.In the study of long-term thermal stress performance of fuel cell,based on the study of steady-state thermal stress,the creep theoretical model is further coupled with the original steady-state thermal stress to study the high-temperature creep phenomenon of fuel cell in a long time scale.Finally,it is found that the stress level caused by creep is smaller than the steady-state thermal stress level,but the equivalent creep strain is much larger than the steady-state thermal strain,which indicates that during the long-term operation of SOFC,the failure mode changes from stress failure to strain failure,so it is necessary to study the long-term mechanical properties of SOFC or analyze the creep life prediction.