Mechanical And Long-term Performance Modeling Of Solid Oxide Fuel Cell Stacks

Solid oxide fuel cell(SOFC)is an new and attractive energy conversion instrument.As it converts the chemical energy into electricity directly with heat generating,the energy utilization is higher than the other traditional power generation facility.In addition,little pollutant emission,fuel flexibility and low noise emmition and other advantages make ia a promising candidate to be used as family power station,power plant,mobile power station,marine and military.As the experimental method is time-consuming and influenced by many complicated factors,the theoretical calculation becomes a new research method which can analyze the performance of SOFC directly and effectively and guide the design of experiments with high-efficiency and low cost.According to the working principle and characteristics,with a multi-physics coupled model,we can simulate and analyze effects of the geometry structure design,operating condition,optimizing the material properties,to obtain the quantitative information to optimize the SOFC to operate long-term mechanical stable.The theoretical calculation will be more and more important to provide ideas and guidance for SOFC design,which is of great significance to the development of SOFC.This dissertation focuses on the theoretical calculation of mechanical and long-term performance of solid oxide fuel cell.This dissertation includes the following contents:The first chapter mainly is a brief introduction of the background,the history and development,the basic structure and classification,principle of operation and the theoretical model to simulate the SOFC.Next,the application prospect and technical difficulties of the plate solid oxide fuel cell are mainly introduced,which illustrates that the imulation of mechanical properties and long-term performance is very important.In the second chapter,we firstly described the background and development of the mechanical model of solid oxide fuel cell,and the experimental and calculation is explained respectively.A detailed introduction of the theoretical mechanical model with structure mechanical model,geometry model and the effective properties of the porous composite electrodes is presented.A comparison of the theoretical and experimental data of the material properties is analyzed.Next,the mechanical properties of SOFC are comprehensively evaluated from the following aspects:(1)optimization of material components,(2)the working condition and working process have great influence on the mechanical properties of SOFC,(3)optimization of the geometry of the solid oxide fuel cell.We have made a comprehensive comparison of the parameters that affect mechanical properties and making the results more realisticIn the third chapter,we analyzed the inelastic deformation(i.e.creep strain).Under the condition of high temperature and long-term work,material deformation will lead to mechanical degradation such as such as fracture and delamination,so the material of the inelastic deformation is of very important significance for long-term performance.The secondary step of creep strain is a steady-state strain which keeps constant strain rate at a long-term,and the strain of this step occupy a large part of the total creep strain.So we analyze the secondary creep strain of solid oxide fuel cell in this chapter.The creep strain rate is affected by the material properties,temperature and the applied stress.And the porosity of the electrode is another important factor.In this chapter,the influence of these factors is presented.As the brittle ceramic crack with big strain,the life-time of the ceramic can be predicted.The forth chapter is the analysis of the mechanical and long-term performance of the solid oxide fuel cell stacks.Based on the temperature distribution derivedd from a fully coupled multi-physics model,we can analyze the stress-strain distribution,and the critical position in the stack.The relationship of creep strain rate and temperature distribution is also been discussed.In the fifth chapter,a brief summary of the dissertation is presented.