The Analysis And Research On The Residual Stress And The Electrodes And Electrolyte Thickness Of Micro Tubular Solid Oxide Fuel Cell

The Micro Tubular Solid Oxide Fuel Cell(MT-SOFC)has been paid more attention by researchers due to its advantages of rapid start-up/shut-down,easy sealing and portable.The residual stress,induced by the difference in the thermal expansion coefficient of each component in the sintering process,has a significant influence on the lifespan and stability of MT-SOFC.Compared with the experimental method,the numerical simulation method is lower cost,higher efficient and easier to implement to study the residual stress of MT-SOFC.Therefore,the numerical simulation method is used to explore the influence mechanism of electrodes and electrolyte thickness on residual stress of MT-SOFC in this paper,in addition,the Weibull analysis method is adopted to predict its failure probability.Thus the MT-SOFC structure could be optimized to improve the stability of MT-SOFC.The specific research contents are as follows:1.First of all,the influence of the thicknesses of anode,electrolyte and cathode on residual are investigated.The results show that anode mainly undergoes tension stress while electrolyte and cathode mostly suffer compressive stress.For a chosen component(which means the dimensions of other components are fixed),the stress decreases with increasing its thickness.Then the failure probability of anode is calculated by Weibull analysis method,founding that anode is prone to failure with a thinner anode or thicker cathode and electrolyte,and the influence of cathode thickness on the failure probability is weaker than electrolyte thickness.Finally,the minimum anode thickness formula is given.2.The thermal expansion coefficient of the anode depends heavily on its Ni volume fraction.Therefore,the effect of Ni volume fraction on the residual stress and stability of anode,electrolyte and cathode.It is found that the maximum anode Ni volume fraction should be 50% to insure the safety of whole MT-SOFC.In addition,the minimum anode thickness formulas with various Ni volume fraction are obtained by analyzing the calculated data.These formulas provide a theoretical basis for MT-SOFC design.3.It is found that the traditional asymmetrical MT-SOFC has 1-2 orders of magnitude higher residual stress than the symmetric MT-SOFC by comparing the traditional asymmetric Ni-GDC/GDC/GDC-LSCF MT-SOFC with the symmetric electrode LSCF/YSZ/LSCF MT-SOFC.That is,the material has a great influence on the residual stress.Then the effects of Young’s modulus,Poisson’s ratio,and thermal expansioncoefficient on the residual stress are discussed in detail.The results show that the thermal expansion coefficient of the material has significant influence than the Young’s modulus and Poisson’s ratio,and the dependence relationship between the matching state and the stress state of the thermal expansion coefficient of each component is obtained.4.The stress state is closely related to the temperature of MT-SOFC.Therefore,the effect of temperature on the MT-SOFC stability is systematically discussed.The results show that as long as the anode failure probability is lower than the failure criterion at ambient temperature,the anode is always safe.Moreover,for the electrolyte and the cathode at the working temperature is more easily damaged than room temperature.Finally,the maximum cathode thickness calculation expression is obtained through data fitting combined with the minimum anode thickness formula.