多场耦合作用下固体氧化物燃料电池高温蠕变强度设计理论

Solid oxide fuel cell (SOFC) is a type of alternative energy technology for electrochemical conversion of chemical energy of hydrogen into electricity, and has attracted a lot of attention in recent years because it is simple to fabricate. But up to now, SOFC has not become commercial because of the structure integrity problem at high temperature. SOFC operates at high temperature (600-1000°C), and the time dependent creep deformation has a great effect on fracture and failure. In addition, large thermal stresses are generated induced by the mismatching of material properties and have a great effect on creep. Also, they must survive thermal fatigue due to the start-up and shut down. There pre-requisites should be fulfilled to ensure the mechanical strength, because the mechanical issues will affect the thermal-electrochemical behavior. The creep strength of SOFC is a function of temperature, mechanics and chemical. Therefore, this proposal studies the design theory of creep strength by multi-physics modeling coupled by temperature, mechanical and chemical. A coupling CFD-FEM is developed to calculate the creep stress. Firstly, a coupling mathematical model of thermal fluid-electrochemical reaction will be developed to predict the temperature field. The thermal-fluids analysis will be performed by CFD software Fluent. Thermodynamic equations for electrochemical reactions and equations governing the conservation of mass, momentum and energy are built and solved by a User Defined Function (UDF). Then the temperature field is incorporated into finite element software ABAQUS, and the thermal stress is calculated by a thermal-visco-elasto-plastic FEM. And the measurements of temperature and thermal stress will be carried out to verify the developed CFD-FEM program. The effect of redox reaction on mechanical properties will be studied by experiment, and some equations will be fitted and solved by a user subroutine to ABAQUS. The effect of redox on creep and stress evolution will be fully investigated. A damage constitute model by the interactions of creep, fatigue and oxidation will be developed, and a subroutine will be compiled by C-language code and incorporated into ABAQUS. A time dependent failure probability calculation method based on Weibull method affected by multiaxial stress will be developed to characterize the creep failure. The emphasis will be paid on the effects of redox reaction and creep on failure probability. We will also study the effect of geometrical dimensions and the fluid parameters on temperature field, creep strength and failure probability. And a design theory of creep strength for SOFC will be built by the multi-physics modeling and experimental study.

固体氧化物燃料电池（SOFC）是一种具有较好应用前景的新能源设备，目前尚未实现商业化，主要原因之一在于高温蠕变强度问题没有解决。项目拟建立温度、力学、化学耦合作用的蠕变强度设计理论。发展CFD-FEM流固耦合的蠕变应力计算方法：首先建立流动-电化学反应耦合数学模型，开发用户自定义函数，计算温度场分布；然后建立有限元模型，读取温度场计算结果，进行热粘弹塑性应力计算，并用试验验证。研究氧化还原反应对力学性能影响的理论方程，发现氧化还原反应对蠕变的影响规律。建立SOFC系统蠕变-疲劳-氧化还原反应耦合的损伤本构模型，编写子程序，进行全尺寸SOFC蠕变损伤有限元分析，开发多轴应力作用下时间相关Weibull失效概率计算方法，通过蠕变试验与断口分析，验证损伤模型。重点研究氧化还原反应、蠕变对失效影响规律。讨论几何参数和流动参数对蠕变强度和失效概率的影响规律，建立SOFC多场耦合作用蠕变强度设计方法。

固体氧化物燃料电池（SOFC）是一种具有较好应用前景的新能源设备，目前尚未实现商业化，主要原因之一在于高温蠕变强度问题没有解决。项目建立温度、力学、化学耦合作用的蠕变强度设计理论。发展CFD-FEM流固耦合的蠕变应力计算方法：首先建立流动-电化学反应耦合数学模型，开发用户自定义函数，计算温度场分布；然后建立有限元模型，读取温度场计算结果，进行热粘弹塑性应力计算，并用试验验证。研究氧化还原反应对力学性能影响的理论方程，发现氧化还原反应对蠕变的影响规律。建立SOFC系统蠕变-疲劳-氧化还原反应耦合的损伤本构模型，编写子程序，进行全尺寸SOFC蠕变损伤有限元分析，开发多轴应力作用的时间相关Weibull失效概率计算方法，通过蠕变试验与断口分析，验证损伤模型。重点研究氧化还原反应、蠕变对失效影响规律。讨论几何参数和流动参数对蠕变强度和失效概率的影响规律，建立SOFC多场耦合作用蠕变强度设计方法。