功能梯度阳极固体氧化物燃料电池热应力数值模拟研究

Numerical Simulation of Thermal Stress in Solid Oxide Fuel Cells with Functional Gradient Anode

固体氧化物燃料电池(SOFC)各部件间的材料属性差异导致电池在制造和运行过程中应力过高,使用功能梯度材料电极可以减小SOFC的残余应力和热应力。本研究基于COMSOL Multiphysics 6.0软件建立完整结构的SOFC多物理场耦合模型,采用四种不同的分布曲线表征阳极材料的组分分布,对功能梯度阳极SOFC的残余应力和运行热应力进行数值计算。结果表明,电池在制备过程中,使用功能梯度材料能显著减小阳极所受的拉应力,该现象在常温下更加明显。二次曲线分布相比于无梯度分布,还原前阳极的室温最大拉应力减小47.69%,还原后室温最大拉应力减小35.74%。电池在运行过程中,电化学反应产热和气体对流换热导致入口和出口形成温差,金属框在出入口以及肋与电极接触的位置存在较大的应力集中现象。功能梯度材料可以显著减小阳极、金属框及电解质所受的最大应力,其中材料组分为二次曲线分布时效果最明显。本研究对设计制造SOFC具有潜在的理论意义和工程价值。

Material property differences among components of solid oxide fuel cell(SOFC)lead to excessive stresses during cell fabrication and operation,among which functional gradient material electrodes have attracted attention for their ability to reduce residual and thermal stresses in SOFC.But so far,there is rare study on SOFC with functional gradient anode using numerical simulation of thermal stress.In this study,a multi-physics field coupling model of SOFC with complete structure was established by COMSOL Multiphysics 6.0.Based on multi-physics field coupling model and numerical simulation of the residual stresses and thermal stresses in SOFC,four different distribution curves were employed to characterize the component distribution of anode materials.The results show that the tensile stress of anode can be significantly reduced by using functional gradient material during fabrication at different temperatures,especially at room temperature.Compared with non-gradient distribution,the maximum tensile stress of the anode is reduced by 47.69%before reduction and 35.74%after reduction by using quadratic curve distribution.During the operation process,the heat generated by the electrochemical reaction and the convective heat transfer of gas leads to the temperature difference between inlet and outlet,resulting in significant stress concentration at inlet and outlet of the metal frame as well as at contact surface between rib and electrode.Functional gradient materials can significantly reduce the maximum stress on the anode,metal frame and electrolyte,which is particularly obvious when using quadratic curve distribution.Therefore,this research has potential theoretical significance and engineering value for designing and fabricating SOFCs.