固体氧化物燃料电池关键构件多物理场耦合作用下的热机械行为研究

Solid oxide fuel cell (SOFC) has been considering as a highly efficient device to convert chemical fuels directly into electrical power. Compared with traditional energy conversion technologies, SOFC has many significant advantages, including high efficiency, high volumetric and gravimetric, low pollutant emission and noise, easy-fabrication, as well as no re-charge duration. However, SOFCs have not yet become fully commercialized because there are still several technological challengers need to be resolved. The one of the most important challengers is the integrity and reliability of its structure during a long time high-temperature operating. Generally, SOFCs operate at a high temperature (600-1100 °C), which is the range that the electrolyte becomes conductive to oxygen ions but nonconductive to electrons. The high operating temperatures are both advantage and disadvantage for the SOFCs. The advantages lie in minimization of polarization losses and fuel impurity tolerance, while the disadvantage is that very limited materials can be used as components in such a high temperature. In addition, large thermal stresses are generated during the SOFC operation process due to the mismatching of thermal expansion coefficient of different components in SOFCs. The stresses and thermal cycling will cause the failure of the cells. Considering the SOFC is a complex system and composed of components with different materials, it is essential to understand the interaction of these components, as well as the thermomechanical behaviors of whole SOFC structure and the mechanism of the degradation of performance of SOFC. In this proposal, thermomechanical behaviors of SOFC will be studied and a coupled multi-physics single planar SOFC model will be tried to build to predict its fatigue life. Firstly, the thermal and mechanical properties of membrane electrode assembly (MEA), which consists of several layers as a composite, and other components will be tested at different elevated temperatures and the relationship between these physical properties and operating temperatures will be studied. Secondly, the microstructure evolutions of the main components and electrochemical effects in the cell will be studied. The relationship between the microstructure evolution of these components and degradation of performance of SOFC will be investigated and mechanism of degradation of SOFC will be clarified. In addition, the residual stress distributions in MEA and main components will be measured by electron backscattered diffraction and X-ray diffraction, and their effects on thermomechanical fatigue behaviors of SOFC will be evaluated. At the end, based on the results of studies above, a coupled multi-physics single SOFC model will be built through finite element method and verified to predict the fatigue life of planar SOFC.

固体氧化物燃料电池（SOFC）作为一种高效、清洁、无污染的新能源技术具有广泛的应用前景，目前仍未实现全面商业化，主要原因在于高温及重复启动热循环工况下电池材料和结构强度问题没有解决。本课题拟研究多物理场耦合作用下平板式SOFC关键构件热机械行为和材料微观组织演变对电池性能劣化的影响。通过开发微试样试验方法获得不同温度下电池构件材料力学性能和热学性能随温度变化的本构关系；通过背散射衍射（EBSD）和X射线衍射方法研究SOFC内部残余应力与循环热应力对材料微观组织演变的影响；阐明电池构件热机械疲劳损伤的微观机理；建立SOFC多场耦合热机械疲劳损伤模型，开发与ABAQUS软件连接的子程序，导入本构关系并建立有限元模型，通过理论分析与实验验证有限元模型的正确性。讨论电池密封结构、构件几何尺寸、形状等因素对电池结构应力、疲劳损伤和失效概率的影响，建立SOFC在复杂环境下的热机械疲劳寿命评价准则。

固体氧化物燃料电池（SOFC）作为一种高效、清洁、低噪音、无污染的新能源技术具有广泛的应用前景，目前仍未实现全面商业化，主要原因在于高温及重复启动热循环工况下电池材料和结构强度问题没有解决。本课题旨在研究多物理场耦合作用下平板式SOFC关键构件热机械行为和材料力学性能本构演化对电池性能的影响。通过开发小冲杆微试样试验方法获得不同温度下电池主要构件材料力学性能和热学性能随温度变化的本构关系；通过背散射衍射（EBSD）和X射线衍射方法研究SOFC内部残余应力与循环热应力对材料微观组织演变的影响；阐明电池构件热机械蠕变疲劳损伤的微观机理；建立SOFC多物理场耦合理论模型，开发与ABAQUS软件连接的子程序，导入高温材料本构关系并建立有限元模型，实现对SOFC工作和启动的多物理场有限元模拟。通过理论分析与试验结果验证模型的有效性与正确性。研究电池密封结构、构件几何尺寸、形状、流道布置、阳极镍体积分数等因素对电池结构应力、蠕变疲劳损伤和失效概率的影响，提出了梯度孔隙阳极优化的SOFC PEN结构以及高温极端环境下单电池的寿命评价准则。研究结果为平板式固体氧化物燃料电池钎焊自适应密封结构强度以及PEN结构强度研究提供了可行的试验方法和数据，也为平板式SOFC实现长期高效稳定运行的优化设计提供了重要理论基础。