Residual stress and plastic strain analysis in the brazed joint of bonded compliant seal design in planar solid oxide fuel cell

This paper uses finite element method (FEM) to predict the residual stress and plastic strain in the brazed joint of sealing foil-to-window frame in bonded compliant seal (BCS) design in a planar solid oxide fuel cell (PSOFC). The effects of window frame material type, sealing foil thickness, filler metal thickness and window frame thickness on residual stress and plastic strain are discussed. Large residual stress is generated in the joint, and the stress and strain are concentrated around the fillet. It is proved that the BCS design can mitigate and trap some residual stress by plastic deformation within the sealing foil. The residual stress and the ability of trapping stress of sealing foil are affected by window frame material and structure thickness. Based on the comprehensive considerations of the impact of residual stress and plastic strain, Alloy 625 as a window frame material is found to be better than Haynes 214, Hastelloy X and SUS 316L. The optimum thickness of sealing foil and filler metal BNi2 are found to be 150 μm and 75 μm, respectively. The residual stress and plastic strain are increased with the increase of window frame thickness.     

加氢换热器角焊缝密封接头焊接工艺参数优化

利用有限元软件ABAQUS,开发了一个顺次耦合的角焊缝焊接热应力计算程序,研究了加氢高压换热器板式焊接密封接头应力场的分布;以此数值模拟结果为基础,结合正交试验设计方法,分析了焊接电流、电弧电压、焊接速度及预热温度4个工艺参数对焊接残余应力场的影响,找到一组使焊接残余应力最小的最优焊接工艺参数.结果表明,焊接速度对焊接残余应力的影响最大,该角焊缝焊接残余应力的最高值集中在焊缝和热影响区附近.研究结果为优化加氢高压换热器板式焊接密封的焊接工艺,预防焊接密封接头的开裂失效提供了理论基础.

Abstract：

Using the finite element analysis software ABAQUS, a sequentially coupled fillet welding thermal-stress program was developed to calculate the stress distribution of plate sealing joint in the high pressure hydrogenation heat exchange. Based on the numerical solutions and the orthogonal method, the influence of four welding parameters including welding current, welding voltage, welding speed and preheating temperature on residual stress distribution was analyzed and a group of optimal welding parameters were obtained, which provided a reference for preventing the failure of fillet weld sealing joint in the high pressure hydrogenation heat exchange.     

采用修正θ投影法预测Cr25Ni35Nb炉管钢的蠕变性能

在不同温度和不同应力下对Cr25Ni35Nb炉管钢进行了蠕变试验;并采用修正后的θ投影法对该钢的蠕变曲线进行了拟合,得到了蠕变方程中参数iθ的数学表达式,建立了该钢在任意温度和应力条件下的蠕变曲线方程,并据此预测了950℃、18 MPa下该钢的蠕变曲线。结果表明:预测曲线和试验曲线吻合较好。     

压力容器筒体的非概率可靠性分析

传统的可靠性分析采用的是概率方法,它需要不确定参量的详细统计信息以确定其概率分布.而压力容器多处于较为严苛的工作环境中,难以准确获得不确定参量的准确概率分布.为此,基于区间模型的非概率可靠性理论,用区间方法来描述压力容器筒体参数,提出压力容器筒体强度的非概率可靠性指标的计算方法.该方法仅需要知道不确定参量的边界,克服了概率方法的局限,且很大程度的降低了计算工作量.通过实例分析,表明该方法是有效可行的.     

12Cr1MoV过热器管劣化行为研究

通过高温时效试验、微观组织分析、碳化物萃取、碳化物相X-Ray衍射分析以及力学性能试验,研究了不同球化级别12Cr1MoV过热器管钢的组织、碳化物含量、相组成以及力学性能。结果表明,碳化物含量与球化级别呈抛物线关系。球化是一个加速的过程,前期主要完成碳化物相种类转变,中后期主要表现为碳化物形态的变化。球化级别与碳化物相含量的比值(M23C6/M3C)近似呈抛物线关系。随着球化程度提高,材料高温强度下降,伸长率提高。     

Effect of brazing temperature on tensile strength and microstructure for a stainless steel plate-fin structure

This paper presented a vacuum brazing technology for 304 stainless steel plate-fin structures with BNi2 filler metal. The effect of brazing temperature on tensile strength and microstructure has been investigated. The tensile strength is increased along with the increasing of brazing temperature. The microstructure is very complex and some Boride compounds are generated in the brazed joint. Full solid solution can be generated in the middle zone of joint when the brazing temperature is increased to 1100 °C. The brittle phases always exist in the fillet no matter how the brazing temperature changes, but the microstructure in fillet becomes more uniform and the tensile strength is increased with the brazing temperature increasing. In total, the brittle Boride compounds are decreased with the brazing temperature increase. Brazing with a filler metal thickness 105 μm and 25 min holding time, 1100 °C is the best suitable brazing temperature and a tensile strength of 82.1 MPa has been achieved for 304 stainless steel plate-fin structure.     

CPC热管式真空管集热器的集热效率研究

介绍了CPC(compound parabolic concentrator)热管式真空管集热器的结构,对CPC热管式真空管太阳能集热器进行了传热分析,并对CPC热管式真空管集热器、热管式真空管集热器和CPC热管式集热器的集热效率进行了对比计算。CPC热管式真空管集热器的集热效率的理论计算和试验结果表明:CPC热管式真空管集热器的集热效率最佳。     

Analytical and experimental study of premixed methane–air flame propagation in narrow channels

This study investigates analytically and experimentally the influence of preheat temperature on flame propagation and extinction of premixed methane–air flame in single quartz tubes with inner tube diameters of 3.9, 3, 2 and 1 mm respectively. The effects of preheat temperature, tube diameter, equivalence ratio and mixture flow rate on the flame speed and extinction conditions are determined. The analytical results show that high preheat temperature of the mixture can effectively suppress flame quenching, and the occurrence of stable solution in the slow flame branch extends the flammability limit leading to possible flame propagation in mini channels. Experimental results confirm that the flame speed increases and the flammability limit shifts toward the fuel lean direction either through increasing the preheat temperature or decreasing the mixture flow rate, or both. Decrease of propagating flame speed is observed before the stoichiometric equivalence ratio at high preheat temperatures. The analytical model provides insights into how propagating flame in mini channels can be sustained; however, the model is only good at predicting flame speed near the fuel lean branch. Influence of Cu²⁺ ions exchanged zeolite 13X catalyst on flame speed is also addressed. It is noted that the zeolite based catalyst can lower the preheat temperature requirement in order to sustain the flame propagation in narrow channels.     

水下枪械膛口速度的统计试验及其结果分析

为研究水下枪械弹丸出枪口的运动速度变化规律,提出了一种膛口速度测试的新方法:在距枪口3 m内,采用一对标准线圈靶,在多个位置点对弹丸进行多次重复测量,并以各位置点的平均速度进行拟合,再反推到枪口,得到枪口速度及弹丸在距枪口3 m内的速度变化规律.该方法避免了常规多个线圈靶同时测量时由于各线圈靶的动态特性不一致而造成的测...     

Numerical modeling of a jetting fluidized bed gasifier and the comparison with the experimental data

A model for a jetting fluidized bed gasifier is developed, treating the grid, bubble and freeboard zones in series. Reactions including char combustion, steam gasification, CO₂ gasification and water–gas shift reaction are taken into account. The effects on model predictions of assumptions regarding the primary products of char combustion and char reactivity factor are analyzed by comparing the predictions with experimental data from a bench-scale jetting fluidized bed gasifier using different kinds of chars. Contributions of various reactions and different zones and phases to carbon conversion are analyzed.