高温氦气环境中石墨的水蒸气氧化特性模拟研究

在正常运行工况下高温气冷堆内石墨材料的氧化对石墨结构材料的服役时间有重要影响.主要介绍高温气冷堆燃料元件氦气孔道内石墨材料与水蒸气发生氧化反应的模拟.该模型使用COMSOL软件进行建模,采用k-ε模型模拟冷却剂的流动,使用Langmuir-Hinshelwood方程描述石墨与水蒸气的化学反应.使用该模型计算了冷却剂管道温度分布为线性、水蒸气压力低于1 Pa的氧化情况.计算结果表明,在堆芯底部氧化主要发生在表面,石墨材料转化率高于8%的厚度约1 mm.     

球床沸水堆燃料组件稳态换热数值模拟研究

以球床沸水堆（PBWR）燃料组件为研究对象,运用CFD商用软件FLUENT,采用多孔介质模型和欧拉两相流模型,燃料组件流动沸腾换热进行计算分析。分析额定工况下的燃料组件内稳态热工水力特性及孔隙率对计算结果的影响。计算结果表明：球床沸水堆燃料组件横截面的热工参数分布与传统压水堆的壁面加热管道相比具有新的特点,采取适当的燃料组件结构孔隙率,可获得较大堆芯换热效率及较小的堆芯压降。     

基于不同流变模型的面板堆石坝堆石流变特性研究

为了研究堆石料的流变特性,更好地预测坝体位移的发展趋势,以猴子岩面板堆石坝工程为例,基于全量流变模型与增量流变模型,采用免疫遗传算法对堆石料流变参数进行反演,并对比分析了两种流变模型的计算结果。结果表明,两种流变模型计算差异较大,其中全量流变模型计算的流变量从坝基到坝顶逐渐增加,流变极值位于坝顶,而增量流变模型计算的流变量比全量流变模型大,极值位于坝体中部,更符合实际观测情况;同一高程上的不同位置,全量流变模型计算的流变量相差不大,增量流变模型计算的流变量为中间大、两侧逐渐减小,更符合坝体沉降分布规律。     

低温半导体热电堆内部温度分布的动态特性分析

本文建立了低温半导体热电堆的一维非稳态导热方程，并采用Binder—Schmidt显式方法，对低温热电堆内部温度分布进行了数值计算。分析表明，低温半导体热电堆内部温度场在发电循环建立后6—lOs内能够达到平衡状态，具有较好的动态响应特性。     

基于分布参数轴系模型的汽轮发电机扭振仿真模型：第一部分：理论分析

给出了分布参数模态降价模型力输入的处理方法，解决了模态降阶模型在建模过程中的困难，使这种模型可以实用化。首先分析了汽轮机蒸汽力矩和电磁力矩在轴系上的分布特性，然后给出了两种计算力矩作用系数的算法。与低阶集中质量模型仿真比较表是，分布参 模型降阶模型仿真精度高，仿真速度快。     

368Q型发动机曲轴疲劳强度有限元分析

对一个轿车发动机的曲轴进行了符合实际情况的三维建模,校核了曲轴在交变截荷下的疲劳强度,并通过曲轴的疲劳试验对分析和计算结果进行了验证,对忽略惯性力,忽略相邻曲拐影响,忽略扭矩的简化模型分别进行了计算,得出了不同建模方法对计算结果精度的影响,对曲轴圆角形状优化,圆角应力分布和强化工艺等相关问题进行了探讨。     

锅炉单相区段的嵌套建模方法

提出了一种基于集中参数的嵌套结构建模方法，从机理分析、传递函数近似分析及仿真所得到的结果均表明：应用该建模方法所获得的数学模型能较好地逼近分布参数模型，且计算量较小。这既有利于数值计算的稳定性，也易于满足实时仿真的要求。图５参９     

LC300重型载货汽车冲焊驱动桥壳ANSYS分析

本文采用有限元软件ANSYS对LC300桥进行了建模、计算和分析。通过采用误差估计等技术处理手段,得到了计算精度较高的有限元模型,为进一步降低桥壳故障率,提供了理论参考。     

LC300重型载货汽车冲焊驱动桥壳ANSYS分析

本文采用有限元软件ANSYS对LC300桥进行了建模、计算和分析。通过采用误差估计等技术处理手段,得到了计算精度较高的有限元模型,为进一步降低桥壳故障率,提供了理论参考。     

内燃机进气流动数值计算中三维几何建模问题的探讨

本文主要对内燃机进气流动数值计算中的三维几何建模的方法进行了探讨，并针对进气道稳流试验台的仿真计算提出了几种几何模型，计算结果与试验数据进行了比较，分析了各模型的计算误差，表明三维简化几何模型的结构对计算精度有较大影响。     

Thermal stress analysis of a planar SOFC stack

The aim of this study is, by using finite element analysis (FEA), to characterize the thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack during various stages. The temperature profiles generated by an integrated thermo-electrochemical model were applied to calculate the thermal stress distributions in a multiple-cell SOFC stack by using a three-dimensional (3D) FEA model. The constructed 3D FEA model consists of the complete components used in a practical SOFC stack, including positive electrode–electrolyte–negative electrode (PEN) assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seals. Incorporation of the glass-ceramic sealant, which was never considered in previous studies, into the 3D FEA model would produce more realistic results in thermal stress analysis and enhance the reliability of predicting potential failure locations in an SOFC stack. The effects of stack support condition, viscous behavior of the glass-ceramic sealant, temperature gradient, and thermal expansion mismatch between components were characterized. Modeling results indicated that a change in the support condition at the bottom frame of the SOFC stack would not cause significant changes in thermal stress distribution. Thermal stress distribution did not differ significantly in each unit cell of the multiple-cell stack due to a comparable in-plane temperature profile. By considering the viscous characteristics of the glass-ceramic sealant at temperatures above the glass-transition temperature, relaxation of thermal stresses in the PEN was predicted. The thermal expansion behavior of the metallic interconnect/frame had a greater influence on the thermal stress distribution in the PEN than did that of the glass-ceramic sealant due to the domination of interconnect/frame in the volume of a planar SOFC assembly.     

Two-dimensional temperature distribution estimation for a cross-flow planar solid oxide fuel cell stack

The uniform temperature distribution of a cross-flow planar solid oxide fuel cell (SOFC) stack plays an essential role in stack thermal safety and electrical property. However, because of the strict requirements in stack sealing struture, it is hard to acquire the temperature inside the stack using thermal detection devices within an acceptable cost. Therefore, accurately estimating the two-dimensional (2-D) temperature distribution of the cross-flow stack is crucial for its thermal management. In this paper, Firstly, a 2-D mechanism model of a cross-flow planar SOFC stack is established. The stack is divided into 5*5 nodes along the gas flow directions, which can reflect the stack states with moderate computational burden. Then, experimental test data is utilized to modify and validate the stack model, guaranteeing the model accuracy as well as the reliability of model-based state estimator design. Finally, easily-measured stack inputs and outputs are selected, and a temperature distribution estimator combined with unscented kalman filter (UFK) approach is developed to achieve accurate and fast temperature distribution estimation of a cross-flow SOFC stack. Simulation results demonstrate that the UKF-based temperature distribution estimator can precisely and quickly achieve the temperature distribution estimation of the cross-flow stack under both static state and dynamic state changes and is applicable to cross-flow stacks with different size or cell number as well, the maximum estimated absolute error is less than 0.15 K with an absolute error rate of 0.015%, which indicates the developed estimator has good estimation performances.     

Three-dimensional multi-physics modelling and structural optimization of SOFC large-scale stack and stack tower

Multi-physics modelling of the Solid Oxide Fuel Cell (SOFC) stack requires significant computational resources. Design optimization of large-scale stacks and stack towers has always been a challenge in recent years. This study establishes a three-dimensional multi-physics model based on a two-step coupling using the BP neural network. The comparison between the novel model and the traditional fully coupled model in both accuracy and computing resource requirements are explored. The novel method has high effectiveness for modelling the large-scale stacks. Based on this, planar SOFC 50-cell stacks and 150-cell stack towers are simulated. The results show that, the flow uniformity of fuel distribution of the stack towers can decrease more than 30% comparing with the 50-cell stack, which leads to significant deterioration of the voltage and temperature distribution. The parameters of manifold and buffer area and channel height of the stack tower is optimized to achieve better uniformity of flow and voltage distribution and lower temperature gradient simultaneously.     

Computer simulation of a biomass gasification-solid oxide fuel cell power system using Aspen Plus

The operation and performance of a SOFC (solid oxide fuel cell) stack on biomass syn-gas from a biomass gasification CHP (combined heat and power) plant is investigated. The objective of this work is to develop a model of a biomass-SOFC system capable of predicting performance under diverse operating conditions. The tubular SOFC technology is selected. The SOFC stack model, equilibrium type based on Gibbs free energy minimisation, is developed using Aspen Plus. The model performs heat and mass balances and considers ohmic, activation and concentration losses for the voltage calculation. The model is validated against data available in the literature for operation on natural gas. Operating parameters are varied; parameters such as fuel utilisation factor (U_f), current density (j) and STCR (steam to carbon ratio) have significant influence. The results indicate that there must be a trade-off between voltage, efficiency and power with respect to j and the stack should be operated at low STCR and high U_f. Operation on biomass syn-gas is compared to natural gas operation and as expected performance degrades. The realistic design operating conditions with regard to performance are identified. High efficiencies are predicted making these systems very attractive.     

4×4阵列管式固体氧化物燃料电池（SOFC）堆温度场和流场初步分析

通过对实验中管式SOFC堆的数学建模仿真方法,研究实验中的百瓦级4×4管式电池堆内部的流体流动、传热和组分浓度等特性,分析电池参数对电池内部气体流速、温度和浓度分压分布。计算结果和实验测试发现：流场和压力场基本均匀,温度场变化在±34．7K,而阵列电池管开路电压测试值在1．0～1．15vg间,基本满足电堆工作要求。     

Mini CHP based on the electrochemical generator and impeded fluidized bed reactor for methane steam reforming

The paper presents a configuration of mini CHP with the methane reformer and planar solid oxide fuel cell (SOFC) stacks. This mini CHP may produce electricity and superheated steam as well as preheat air and methane for the reformer along with cathode air used in the SOFC stack as an oxidant. Moreover, the mathematical model for this power plant has been created. The thermochemical reactor with impeded fluidized bed for autothermal steam reforming of methane (reformer) considered as the basis for the synthesis gas (syngas) production to fuel SOFC stacks has been studied experimentally as well. A fraction of conversion products has been oxidized by the air fed to the upper region of the impeded fluidized bed in order to carry out the endothermic methane steam reforming in a 1:3 ratio as well as to preheat products of these reactions. Studies have shown that syngas containing 55% of hydrogen could be produced by this reactor. Basic dimensions of the reactor as well as flow rates of air, water and methane for the conversion of methane have been adjusted through mathematical modelling.The paper provides heat balances for the reformer, SOFC stack and waste heat boiler (WHB) intended for generating superheated water steam along with preheating air and methane for the reformer as well as the preheated cathode air. The balances have formed the basis for calculating the following values: the useful product fraction in the reformer; fraction of hydrogen oxidized at SOFC anode; gross electric efficiency; anode temperature; exothermic effect of syngas hydrogen oxidation by air oxygen; excess entropy along with the Gibbs free energy change at standard conditions; electromotive force (EMF) of the fuel cell; specific flow rate of the equivalent fuel for producing electric and heat energy. Calculations have shown that the temperature of hydrogen oxidation products at SOFC anode is 850 °C; gross electric efficiency is 61.0%; EMF of one fuel cell is 0.985 V; fraction of hydrogen oxidized at SOFC anode is 64.6%; specific flow rate of the equivalent fuel for producing electric energy is 0.16 kg of eq.f./(kW·h) while that for heat generation amounts to 44.7 kg of eq.f./(GJ). All specific parameters are in agreement with the results of other studies.     

Effect of air flow rate distribution and flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration

This study investigates the effect of non-uniform distribution of the air inlet flow rate and change of air flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration. This study considers three patterns of air inlet flow rate in the transverse direction of each stack, and five patterns of air inlet flow rate in the stacking direction. The software package for simulation is reliable through an accuracy comparison, and it analyzes the current density, temperature, and thermal stress distribution of a SOFC stack with 20 layers. The results show that the progressively increasing profile of the air inlet flow rate along the x direction drops the cell thermal stress of a SOFC unit. Moreover, the non-uniform profile of air inlet flow rate in the stacking direction affects the position of the region with high thermal stress of the SOFC stack, and changing flow direction of the air obviously drops down the thermal stress without affecting the power generation of the SOFC stack.     

Performance comparison of cocurrent and countercurrent flow solid oxide fuel cells

Solid oxide fuel cell (SOFC) is a complicated system with heat and mass transfer as well as electrochemical reactions. The flowing configuration of fuel and oxidants in the fuel cell will greatly affect the performance of the fuel cell stack. Based on the developed mathematical model of direct internal reforming SOFC, this paper established a distributed parameters simulation model for cocurrent and countercurrent types of SOFC based on the volume-resistance characteristic modeling method. The steady-state distribution characteristics and dynamic performances were compared and were analyzed for cocurrent and countercurrent types of SOFCs. The results indicate that the cocurrent configuration of SOFC is more suitable with regard to performance and safety.     

Time dependent failure probability estimation of the solid oxide fuel cell by a creep-damage related Weibull distribution model

In present paper, a new model is proposed and embedded into the finite element software ABAQUS to estimate the time dependent failure probability of the solid oxide fuel cell stack. The results show that sealant is the potential failure region of the solid oxide fuel cell stack, while the failure probability of the anode, electrolyte and cathode are very small within the operation time of 50,000 h. The creep and damage distribution of the components reflect that the proposed model can reasonably predict the time dependent failure probability of the solid oxide fuel cell stack. Increasing either the characteristic strain, Weibull modulus or decreasing the operating temperature can decrease the failure probability of the SOFC stack. For the sealant, to ensure the high temperature integrity of the SOFC stack, the characteristic strain should be larger than 0.01 or Weibull modulus should be higher than 8.0 under the operating temperature of 600 °C.     

A computational fluid dynamics and finite element analysis design of a microtubular solid oxide fuel cell stack for fixed wing mini unmanned aerial vehicles

Computational fluid dynamics (CFD) and finite element analysis (FEA) are important modelling and simulation techniques to design and develop fuel cell stacks and their balance of plant (BoP) systems.The aim of this work is to design a microtubular solid oxide fuel cell (SOFC) stack by coupling CFD and FEA models to capture the multiphysics nature of the system. The focus is to study the distribution of fluids inside the fuel cell stack, the dissipation of heat from the fuel cell bundle, and any deformation of the fuel cells and the stack canister due to thermal stresses, which is important to address during the design process. The stack is part of an innovative all-in-one SOFC generator with an integrated BoP system to power a fixed wing mini unmanned aerial vehicle. Including the computational optimisation at an early stage of the development process is hence a prerequisite in developing a reliable and robust all-in-one SOFC generator system. The presented computational model considers the bundle of fuel cells as the heat source. This could be improved in the future by replacing the heat source with electrochemical reactions to accurately predict the influence of heat on the stack design.