新型低温高压液氢容器的夹套预冷计算

提出了一种新型的低温高压液氢容器结构,并对其中的夹套结构进行了工程设计、预冷分析及预冷计算,从而说明采用夹套结构可以节省昂贵的液氢,此液氢容器结构也适用于贮存液氧。     

关于夹套容器设计的探讨

夹套容器是将作为一个完整压力室的夹套连接在容器筒体、封头外部形成的多腔压力容器。使用夹套的目的一般是加热或冷却容器及其内部介质,也可作为容器的密封绝热室。它在石油、天然气、化工装置上得到广泛应用。本文对夹套容器的设计进行了深入探讨。     

新型扁平绕带式低温高压容器设计研究

介绍用作液氢贮罐等场合的扁平绕带式低温高压容器的设计理论与方法,提出了一只10m^3液氢贮罐计算实例我。该种低温高压容器结构合理,安全可靠、制造简便,是一种优化的低曙高压容器。     

高压低温容器的航天应用

介绍了高压低温容器航天应用的主要领域和国内外航天研究机构地面试验设施所用高压低温容器的现状,比较和总结了其主要的结构形式.针对中国航天发展的研制和试验需求,结合国内设计制造能力,介绍了国内新研制的高压液氢、液氧容器的结构形式和加工使用情况,并指出下一步高压低温容器发展方向和需研究的问题.     

低温容器的蒸汽爆炸现象初探

拟讨论的蒸汽爆炸现象定义为液体因处于较大的过热度而急剧汽化，介质所处空间因大量气体得不到及时释放而使压力骤然升高引发的一种物理爆炸，在低温容器中，液氮，液等介质可能处于数兆帕的压力下，如果容器的某一位置因某种外在原因出现裂口，则其内部的压力会迅速降低，导致液体过热，如果过热度较大，则不能排除低温容器发生蒸汽爆炸的可能性，本文从介绍蒸汽爆炸的机理入手，建立了过热液体中产生均匀核化时汽泡的形成，生长模型，并利用该模型对低温容器的介质发生蒸汽爆炸的可能性进行了探讨。     

低温高压锻造容器研制

从设计方案的确定、总体结构的设计压容器的设计和加工过程.该2 m3容器在20 K的低温和18 MPa的高压下工作,根据其工作性质、加工制造周期等因素,采用堆积绝热形式.在容器外采用LN2夹套,内容器采用锻焊结构.该容器为国内首次设计压力最高,温度最低,采用锻造技术加工的低温高压容器.加工完成后经使用单位检验、调试与试验表明,该容器满足设计和使用要求.     

低温容器在国民经济中的应用

随着低温技术的发展和应用,各行各业对沸点温度低于120K的低温液体的需要日益增长,促进了低温容器的发展。低温液化气体包括液氦(4.2K)、液氢(20.4K)、液氖(27.3K)、液氮(77.3K)、液氩(87.3K)、液氧(90.17K)、液化天然气(112K)。这里综述了低温容器在我国农业、林业、卫生、商业、文化、地质矿产、建设、能源、机械、电子、航空航天、冶金、化工等各部门的应用现状以及未来的发展前景。     

低温容器支承结构的装配状态对支承功能的影响

对满载液氧的35立方米高真空多层绝热低温容器的支承结构在不同接触状态下进行热-结构耦合分析,得到该容器漏热量的分布范围和支承件上的温度分布,以及温度载荷和冲击载荷共同作用下支承件各方向应力、位移分布,分析了不同装配状态下玻璃钢支承件和外罐接触界面之间间隙的变化情况和各方向应力分布情况。     

新系列低温容器

Planer产品公司开发了一套完整的新系列低温容器，有铝质杜瓦瓶和电冰箱，以及贮存N2和He用的不锈钢容器等。新系列低温容器包括从最小的实验室用铝质杜瓦瓶到最大的不锈钢用户站和大容量贮存系统。这新系列产品具有竞争价值，并且有很高的技术要求。     

液氦输送技术

正确掌握液氦输送方法，对减少液氦预冷量，充分利用氦气冷量和提高液氦输送效率有着十分重要的经济意义，对液氦输送管的结构特点和使用要求及液氦预冷，液氦的输送方法和几种特殊容器的输送方法做了介绍。     

特种低温内压筒体抗中击设计

用有限元方法计算了低温液氧储槽内筒在3.92 MPa、10g冲击条件下的应力分布情况,通过分析获得了一种合理的内筒结构并对冲击加强板进行了优化设计.     

Determining solid-fluid interface temperature distribution during phase change of cryogenic propellants using transient thermal modeling

Control of boil-off of cryogenic propellants is a continuing technical challenge for long duration space missions. Predicting phase change rates of cryogenic liquids requires an accurate estimation of solid-fluid interface temperature distributions in regions where a contact line or a thin liquid film exists. This paper described a methodology to predict inner wall temperature gradients with and without evaporation using discrete temperature measurements on the outer wall of a container. Phase change experiments with liquid hydrogen and methane in cylindrical test cells of various materials and sizes were conducted at the Neutron Imaging Facility at the National Institute of Standards and Technology. Two types of tests were conducted. The first type of testing involved thermal cycling of an evacuated cell (dry) and the second involved controlled phase change with cryogenic liquids (wet). During both types of tests, temperatures were measured using Si-diode sensors mounted on the exterior surface of the test cells. Heat is transferred to the test cell by conduction through a helium exchange gas and through the cryostat sample holder. Thermal conduction through the sample holder is shown to be the dominant mode with the rate of heat transfer limited by six independent contact resistances. An iterative methodology is employed to determine contact resistances between the various components of the cryostat stick insert, test cell and lid using the dry test data. After the contact resistances are established, inner wall temperature distributions during wet tests are calculated.     

低温液体火箭发动机循环预冷模拟试验

进行了低温液体火箭发动机自然循环预冷过程的模拟实验,试验证明了回流管进入储箱液面之上和进入液面之下的两种方案均可实现自然循环预冷,但是要维持自然循环继续进行,前者必须增加引射,而后者不需引射。模拟试验结果可供进一步试验研究参考。     

低温系统的预冷过程和计算

对低温系统的预冷过程做了分析，研讨了各种因素对预冷过程的影响，介绍了预冷耗液量计算公式的推导，给出了LHe,LH2,LN2和LO2预冷耗液量计算图。利用计算图可以方便地计算预冷耗液量。     

低温绝热气瓶真空寿命模拟试验研究

提出了对绝热气瓶真空夹层逐次充入模拟气体进行绝热气瓶漏气和材料放气的真空寿命模拟试验评价方法。试验实例表明:低温绝热气瓶静态蒸发率在低温下夹层压力>5×10^-2Pa后迅速上升,即5×10^-2Pa可视为夹层真空寿命终结的拐点(或阈值)。5A分子筛在液氮温度下对氮具有巨大的吸附潜力,对氢表现出弱的吸附能力。真空绝热夹层的材料放气对真空寿命的影响远远大于漏气的影响,提高绝热气瓶真空寿命的技术途径是减小夹层材料的放气率和改善内置吸附剂对氢的吸附能力。模拟试验能直观、实际、准确地研究漏气和放气对真空寿命诸因素的影响,为确定切合实际的设计参数和工艺提供参考数据,进而推广用于各类真空绝热型低温容器的真空寿命评价和应用。     

Thermal acoustic oscillations in triple point liquid hydrogen systems

Thermal acoustic oscillations are often observed in tubes which penetrate a cryogenic system and are closed at the warm end and open at the cold end. Such tubes are genrally used for filling or vetning the tank, providing relief pressure or inserting instruments taps. Large amounts of heat (of the order of ten to a thousand times more than by normal heat conduction) can be transferred into a cryogenic system when such thermaloscillations occur. A number of studies examining thermal acoustic oscillations in liquid helium systems have been performed by Rott et al. However, only minimal consideration has been given to such oscillationsin liquid and sluch hydrogen systems. This study extends Rott's theory to the stability aspects of thermal acoustic oscillations for a straight tube closed at the warm end and inserted into a Dewar flask filled with triple point liquid hydrogen when the cold open end is located above the liquid surface. These results can also be applied to a slush hydrogen when the pressure in the Dewar flask is reduced to the triple point pressure of hydrogen. Numerical results have been obtained in this study for developing stability curves, establishing oscillation frequency characteristics and identifying critical configurations for initiating such oscillation. The mechanisms associated with the two branches of the stability curves for thermal acoustic oscillations have also been investigated.     

Linear sloshing frequencies in the annular region of a circular cylindrical container in the presence of a rigid baffle

Sloshing in any type of container may invite instability to it. If some part of the free liquid surface in the annular region of a specially designed circular cylindrical container is covered with an annular baffle, the natural frequencies and the response of the liquid in the container undergo a drastic change. A partly covered free surface shifts the natural frequency above and away from the control frequency of the vehicle, in which the liquid-filled container is placed, which results in the reduction of sloshing mass participating in the dynamic motion of the system. The fundamental natural frequency of an inviscid and incompressible liquid is determined for increasing width of the baffle that is attached to the outer tank wall on the free surface. It is observed that by increasing the width of the baffle, natural frequencies can be significantly increased. Investigations are also carried out for different values of Bond number, which depicts different states of surface tension, and for varying values of the part of the radius in the fluid region. It is also observed that by increasing the fluid height inside the container, the natural frequencies can be increased, which results in reduction of sloshing.     

低温容器在水蒸气膜态凝结前后的绝热效果分析

绝热失效严重影响了低温容器的经济和安全运行。膜态凝结的出现是绝热失效最直接的表现。提出了用低温容器表面温度与空气露点温度的比较来判别低温容器的绝热是否失效的方法。理论上,分析了低温容器表面水蒸气膜态凝结出现前后的换热机理。在一个高真空多层绝热低温容器上进行了实验,测量并分析了水蒸气膜态凝结前后低温容器表面温度和液氮蒸发速度的变化。理论分析和实验均验证该方法对于判别绝热效果的有效性和可行性。     

Curvature effects on pressure-induced buckling of empty or filled double-walled carbon nanotubes

Summary The curvature effects of interlayer van der Waals (vdW) forces on pressure-induced buckling of empty or filled double-walled carbon nanotubes (DWNTs) are studied for various radii, length-to-radius ratios, end conditions and internal-to-external pressure ratios. The analysis is based on a double-elastic shell model and assumes that the interlayer vdW pressure at a point between the inner and outer tubes depends not only on the change of the interlayer spacing, but also on the change of the curvatures of the inner and outer tubes at that point. Here the role of filling substances inside DWNTs is modeled by a uniformly distributed internal pressure. The present work aims to study the curvature effects on critical radial pressure. An explicit formula is obtained for the external buckling pressure of empty or filled DWNTs. The critical value of external pressure is estimated with various internal-to-external pressure ratios. It is shown that the curvature effects play a more significant role in buckling problems under radial pressure for small radii DWNTs than under pure axial stress. Our results show that loading transfer through vdW forces prior to buckling is important for the pressure-induced buckling of DWNTs rather than axially compressed buckling.