液氢箱蒸气冷却屏/仲-正转化复合结构绝热性能预测

为探析蒸气冷却屏中仲-正转化释冷对于液氢贮箱绝热性能的提升效果，建立了设置仲-正绝热转化室的VD-MLI/VCS二维模型。对复合绝热结构的传热规律和绝热性能开展了多角度分析。研究发现：仲-正转化室布置在VCS管长50%处时绝热效能最佳，贮箱漏热为0.101 W·m^-2，相比不设置仲-正转化室减少了7.17%；绝热设计中，调整VCS位置能最多减少54.17%漏热损失，相比调整仲-正转化室位置效果更显著；沿冷蒸气流动方向，漏热量先升高、再降低，随后再次升高；增加仲-正转化室可提升VCS出口侧的绝热效果，使贮箱各处绝热性能更加均匀。该研究为液氢贮箱的复合绝热结构设计提供更加准确的理论依据和技术支撑。     

电子倍增CCD相机制冷绝热设计

对电子倍增CCD(EMCCD)相机制冷的必要性以及热电制冷器(TEC)的特点进行了说明,阐述了真空绝热的优势,分析了真空绝热失效条件,提出了真空绝热的难点及真空保持方案,分析了相机芯片发挥其性能所需的制冷温度,对制冷相机漏热途径进行了分析,计算了克服漏热所需的制冷功率,并设计了制冷绝热方案,对相机进行了稳态热分析建模,将多级热电制冷器进行了参数化转化并将其带入模型边界中,经过迭代拟合得到了相机杜瓦及芯片温度分布,分析了绝热制冷方案的可行性。     

不同种类破空气体对高真空多层绝热低温容器真空丧失后传热的影响

通过实验,分别利用氮气、空气、氧气和氦气作为破空气体,对高真空多层绝热低温容器在真空完全丧失后的漏热进行了研究。结果表明,多层绝热结构对于绝热真空完全丧失后的低温容器能够起到一定的保护作用,初始和最终漏热和渗入到绝热真空夹层中气体的性质密切相关。     

用于低温存储系统的多层绝热性能分析

真空多层绝热的性能好坏直接影响到低温贮箱的安全性。根据修正的Lockheed模型,计算冷边界温度、热边界温度、层密度等对均匀层密度多层绝热性能影响,并对三区域变密度的多层绝热性能进行分析,最后针对在轨、地面状态时对低温贮箱漏热方面的要求提出采用复合多层绝热的概念,得出复合多层绝热具有优良的隔热性能。     

高真空多层绝热低温容器整体热分析及试验验证

对35 m'高真空多层绝热低温容器在满载液氧的状态下进行热分析,得到标准状态下该容器漏热量的分布范围及相应的静态蒸发率分布,分析了导热和辐射漏热在总漏热的比重.将计算结果和静态蒸发率试验进行对比,结果符合较好,说明计算的准确性和有效性.进而分析了冷态下玻璃钢支承件和罐体的接触情况.结果可为高真空多层绝热低温容器的设计、...     

超临界氦贮罐实验研究及漏热分析

采用高真空多层绝热结构,研制了一套超临界氦球形贮罐。对贮罐进行漏热估算和应力校核,漏热估算为1.44 W,应力符合设计要求。在液氦加注过程中,监测液氦温度波动特别大,且温度计引线管上有结霜现象出现,分析漏热原因是出现了剧烈热声振荡。将温度计引线管与增压管连通,连通后热声振荡消除。对该超临界氦贮罐进行液氦密封憋压绝热性能测试,液氦压力到达2 MPa的时间约7.5 h,压力平均上升速率为0.267 MPa/h,换算成漏热量为12 W,仍远远大于漏热估算值,分析是由于在连通管路中形成了环流,造成较大漏热。提出了该类超临界氦贮罐的设计改进原则。     

聚氨酯真空隔热板

介绍了环保、节能型聚氨酯真空隔热板研制的关键技术。分析讨论了真空板芯材的泡孔尺寸、开孔率及真空度等因素对真空隔热板性能的影响并给出了试验结果。     

有效导热系数对低温容器日蒸发率的影响

低温容器是气体液化分离加工工业中的重要设备，绝热设计是低温容器设计的重要组成部分，它直接影响低温容器的日蒸发率。在不同的绝热材料和一定漏热温差的条件下，给出了普通绝热和真空粉末绝热型低温容器的日蒸发率与热材料的有效导热系数以及绝热层厚度之间的关系曲线。为简化设计和比较低温容器的特性提供方法和依据。     

大口径低温管道变工况漏热特性分析与优化

建立了一个包含辐射漏热、固体导热和残余气体导热分析的复合热力学模型,对高真空绝热低温管道在热边界温度(环境温度)变化、冷边界温度变化(压力变化或者改变流体)和真空度变化等变工况的漏热特性开展了研究。结果表明,热边界温度(环境温度)对漏热量的影响显著高于冷边界温度改变(流体种类改变或者管道内压力变化)导致的影响;当真空度为10—10~(-2) Pa区间,随着真空的改善,漏热量明显变小,不过当真空度优于10~(-3) Pa时,真空的进一步改善对漏热量的影响不再显著。     

大口径液氢真空输送管的研制

根据大推力氢氧火箭发动机试车要求,设计加工了液氢主管道,介绍了液氢主管道原理及组成,着重介绍大口径液氢真空输送管的结构特点,在结构安全方面给予了充分考虑,特别是真空弯管的支撑及温度应力补偿等,并给出了较为详尽的传热计算方法.针对试验中出现的现象,对大口径真空法兰的密封和漏热进行了深入的研究探讨,在绝热形式的选择上阐明了二氧化碳冷凝真空多层绝热与高真空多层绝热相比的优点,并在使用中得到证实.     

Attempt of integration of a small commercial ammonia-water absorption refrigerator with a solar concentrator: Experience and results

The integration of a small commercial ammonia-water absorption refrigerator with a solar concentrator as heat source was analyzed theoretically and experimentally. Operation parameters of the fridge were determined by parametric fitting experimental data using a thermodynamic model of the cycle leading to a working pressure of 25 bar, weak and strong solution concentrations of 15% and 30% respectively and a COP of ∼0.18. As sold, the fridge can operate with a reduction in the electric power supply of up to 40%. Results showed that the Parabolic Concentrator (PC) used can deliver temperatures above 200 °C for almost 6 h with an average useful power delivery and efficiency of 530 W and 26% respectively. During laboratory test runs it was possible to hold the refrigeration cycle running in a very unstable regime despite the inappropriate heat distribution in the generator unit due to the lower temperature heat source used (220 °C). However, outdoor testing with the sun as energy source proved unsuccessful due to the higher heat losses that occur at the pipes connecting the PC with the fridge.     

Use of heat emitted by broken optic fibers: A new approach for damage detection in composites

Optic fibers, stripped of their jacket, weakened and embedded in a composite plate structure, cracked due to the occurrence of cracks and delaminations in the composite. At the location of a crack in a fiber, transmitted laser-light energy was converted into thermal energy, causing the temperature in the neighborhood of the crack to rise. The temperature change was detected with the aid of an infrared camera. Dynamic numerical simulations of the heat development in the vicinity of the fiber crack were performed. An analytical solution of the temperature distribution on the surface of the composite plate above a fiber crack was also developed. Both analytical and numerical results showed the feasibility of detecting and monitoring the hot spot on the composite plate caused by optic fiber cracking, by use of infrared emission from the fibers. This was successfully confirmed in experiment. The influence of parameters such as depth of the fiber below the surface of the plate, heat conductivity coefficient and light power, on the temperature distribution was also studied. Ultrasound scan of the damaged plate confirmed the accuracy of the hot-spot method in defining the damaged area.     

不饱和聚酯／聚氨酯互穿网络聚合物基玻璃纤维增强 …

研究了以不饱和聚酯／聚氨酯互穿网络聚合物为基的玻璃纤维复合材料的动态热机械性能及应用性能。结果表明,在不饱和聚酯树脂中加入５％－１０％的聚氨酯,使基质形成互秀利于提高由此得到的复合材料的性能。     

热处理对MIM薄膜二极管Ta2O5绝缘膜微结构及其I-U特性的影响

制备了一种用于有源矩阵液晶显示、具有对称结构的MIM薄膜二极管 ,其中Ta2 O5膜采用溅射 /阳极氧化两步法工艺制成。对绝缘膜进行真空热处理 (一步热处理 )和经真空热处理后再进行大气热处理 (真空 /大气两步热处理 )。用原子力显微镜和透射电子显微镜分析了Ta2 O5膜的微结构 ,测试了MIM薄膜二极管的I U特性曲线。讨论了热处理对Ta2 O5绝缘膜微结构和MIM薄膜二极管I U特性的影响 ,并指出了MIM薄膜二极管I U特性和绝缘膜微结构之间的关系     

纤维增强复合材料三明治板破片穿甲数值仿真

研究破片对（由钢板、纤维增强复合材料板及钢板叠合而成）纤维增强复合材料三明治板穿甲过程中能量转化规律。进行破片模拟弹丸(FSP)对不同结构三明治板高速穿甲数值仿真,获得FSP破片对16种三明治板的弹道极限,并与实验结果对比验证数值仿真的可信度。通过分析数值仿真结果,进一步研究破片临界贯穿条件下纤维增强复合材料三明治板各组成部分吸能比率与结构尺寸相关性。结果表明,不同厚度夹层板的吸能比率恒定(芳纶纤维10.41%,玻璃纤维2.68%),夹层板内能随厚度的增加呈二次函数增加。由此获得破片对纤维增强复合材料三明治板弹道极限速度计算方法。     

丁腈基聚氨酯／石墨复合材料的结构与性能研究

以端羟基聚丁二烯丙烯腈（HTBN）和甲苯二异氰酸酯为原料,采用本体聚合的方法,制备了石墨改性型聚氨酯弹性体（PUE）。研究了石墨的加入量对聚氨酯弹性体的物理机械性能的影响,并对复合材料进行热性能分析,结果表明：随着石墨含量的增加,PUE的拉伸强度和撕裂强度先增加后降低,当石墨加入量为6％时,复合材料的强度出现峰值;石墨／PUE复合材料的耐热性能明显提高。     

层间混杂复合材料装甲板防弹性能及其防弹机制

为研究层间混杂复合材料装甲板的防弹性能及其防弹机制,采用钢芯弹侵彻层间混杂复合材料装甲板。以超高分子量聚乙烯（Ultra high molecular weight polyethylene,UHMWPE）纤维、对位芳香族聚酰胺纤维作增强纤维,水性聚氨酯（Waterborne Polyurethane,WPU）树脂和环氧树脂（Epoxy resin,EP）作基体,采用热压工艺制备单向（Unidirectional,UD）结构的层间混杂复合材料装甲板。研究混杂比例、防弹面和树脂基体对混杂复合材料装甲板防弹性能的影响以及弹击后混杂复合材料装甲板的破坏形貌,分析混杂复合材料装甲板的防弹机制,并对复合材料装甲板的破坏机制进行了分析。结果表明:混杂复合材料装甲板的防弹性能优于其任一单一纤维复合材料装甲板;WPU的防弹性能要优于环氧树脂;以UHMWPE纤维复合材料充当防弹面时,混杂复合材料装甲板具有更好的防弹性能;纤维拉伸变形和装甲板分层是纤维复合材料装甲板主要的吸能方式。      

Internal stresses and voids in SiC particle reinforced aluminum composites for heat sink applications

Metal-matrix composites (MMC) are being developed for power electronic IGBT modules, where the heat generated by the high power densities has to be dissipated from the chips into a heat sink. As a means of increasing long term stability a base plate material is needed with a good thermal conductivity (TC) combined with a low coefficient of thermal expansion (CTE) matching the ceramic insulator. SiC particle reinforced aluminum (AlSiC) offers the high TC of a metal with the low CTE of a ceramic. Internal stresses are generated at the matrix-particle interfaces due to the CTE mismatch between the constituents of the MMC during changing temperatures. Neutron and synchrotron diffraction was performed to evaluate the micro stresses during thermal cycling. The changes in void volume fraction, caused by plastic matrix deformation, are visualized by synchrotron tomography. The silicon content in the matrix connecting the particles to a network of hybrid reinforcement contributes essentially to the long term stability by an interpenetrating composite architecture.     

内嵌倾斜压电柱复合材料板的压电振动特性分析

针对1-3型内嵌倾斜压电柱复合板结构,建立压电复合板结构的有限元模型,并推导出变形关系和形函数;应用拉格朗日方程,建立了单元结构的运动方程。针对不同倾斜角度压电柱复合板进行有限元仿真分析,研究了复合压电板的正压电特性,并对复合压电板的能量损耗因子进行分析。研究结果表明：在相同压力下,压电柱的倾斜角度对复合板的弯曲模态频率影响较大。随着压电柱体倾斜角度的增大,模态频率降低,弯曲变形增大;同时,倾斜柱体棱长变长,产生电压增大。悬臂板在压力作用下,沿宽度方向产生反对称电势。在压电陶瓷柱的倾角达到57时,损耗因子达到最大。采用内嵌式倾斜压电柱复合板结构,降低了压电板的脆性,保证大尺寸压电板的结构均匀性和应用。     

Frictional properties of metal-insulator interfaces

The energy by which a normal zone may be created in a cryostable composite superconductor derives almost exclusively from frictional heating, which originates from the movement of conductor against insulator. The magnitude of the frictional heat pulse depends on the mechanical properties of the winding, the frictional properties of the conductor-insulator interface, and the dynamics of the slip process. Quantification of the frictional heat pulse is presently under investigation; this paper presents preliminary results.