Key vacuum technology issues to be solved in evacuated tube transportation

Evacuated tube transportation （ETT） will be one of the ultra-large-scale vacuum application areas. This paper lists some key vacuum technology issues in ETT： （1） how to construct ultra-large-scale vacuum chamber with lower cost and high reliability, （2） how to evacuate gas out of the ETT tube in short time, （3） how to release heat or reduce temperature in the vacuum tube, （4） how to avoid vacuum discharge, （5） how to make vehicles with airproof shells and life support system, and （6） how to detect leaks and find leak positions efficiently. At the same time, some solutions are proposed.

Modelling and analysis of parameters of vacuum tube solar collector with U-shaped tube for different climates

In this study,based on the energy balance for different components of a double-layered vacuum-tube solar collector with a U-tube,the thermal performance of the collector unit is investigated separately using an analytical and quasi-dynamic method.The model used in this study determines the temperature distribution in longitudinal and radial directions.In this research,the effects of physical parameters and heat transfer including the size of the collector,thermal-loss coefficient,absorption coefficient,mass flow and thermal resistance of the air layer under different climate conditions have been evaluated on the performance of the vacuum-tube collector.The results showed that by increasing the diameter of the tube with constant length,the annual thermal efficiency of the collector increased.Also,in a fixed-diameter tube,with increasing tube length,the annual efficiency increases,but this increase is meagre for lengths of>1.5 m.The optimal mass flow rate for maximum efficiency has been obtained for cities with different climates.According to the results,the optimal flow for different climates has different values that can be optimized as a relationship between the average solar radiation annually as a symbol of temperature and flow.

Some possible station layouts and characteristics of evacuated tube transportation

Since Maglev vehicles will run in a closed vacuum tube,the layout of the terminal stations of evacuated tube transportation（ETT） will differ from the traditional railway stations.This paper deals with some possible station layouts of ETT,e.g.,a station with an airlock,a station without an airlock,above ground and underground stations,and stations with either level arrayed or rotation platforms.Then different station layouts are compared,and characteristics of each are analyzed.Finally,a more secure mode for ETT station layouts is suggested,which can be the basis for future ETT station layout and designs.

Concrete-Filled Steel Tube Arch Bridges in China

In the past 20 years, great progress has been achieved in China in the construction of concrete-filled steel tube （CFST） arch bridges and concrete arch bridges with a CFST skeleton. The span of these bridges has been increasing rapidly, which is rare in the history of bridge development. The large-scale construction of expressways and high-speed railways demands the development of long-span arch bridges, and advances in design and construction techniques have made it possible to construct such bridges. In the present study, the current status, development, and major innovative technologies of CFST arch bridges and concrete arch bridges with a CFST skeleton in China are elaborated. This paper covers the key con- struction technologies of CFST arch bridges, such as the design, manufacture, and installation of steel tube arch trusses, the preparation and pouring of in-tube concrete, and the construction of the world＇s longest CFST arch bridge-the First Hejiang Yangtze River Bridge. The main construction technologies of rein- forced concrete arch bridges are also presented, which include cable-stayed fastening-hanging cantilever assembly, adjusting the load by means of stay cables, surrounding the concrete for arch rib pouring, and so forth. In addition, the construction of two CFST skeleton concrete arch bridges-the Guangxi Yongning Yong River Bridge and the Yunnan-Guangxi Railway Nanpan River Bridge--is discussed. CFST arch bridges in China have already gained a world-leading position; with the continuous innovation of key technologies, China will become the new leader in promoting the development of arch bridges.

Numerical Simulation of the Thermal Conductivity of Thermal Insulation Pipeby Vacuum and High Pr essur e Ar gon Pre- filled

By analyzing the insulation effect of argon-filled tubing and vacuum-insulated tubing before and after hydrogen permeation respectively,a conclusion can be drawn that the insulated tubing filled with high pressure argon is better than the vacuum insulated tubing considering the lifetime and heat insulation effect.

Stress Analysis of the Glass Bulb of 35-inch(V)120°Color Picture Tube

A simulation of the stress analysis for a vacuum glass bulb of 35 inch (V) 120° Color Picture Tube(CPT) has been developed. It is shown that extra large deflection angle Color Picture Tube is viable. Increase in the deflection angle will shorten the de

Air flow exploration of abrasive feed tube

An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then directed through a chamber and then fed into a secondary nozzle, or mixing tube. During this process, a vacuum is generated in the cham- ber, and garnet abrasives and air are pulled into the chamber, through an abrasive feed tube, and mixes with this high speed stream of water. Because of the restrictions introduced by the abrasive feed tube geometry, a vacuum gradient is generated along the tube. Although this phenomenon has been recog- nized and utilized as a way to monitor nozzle condition and abrasive flowing conditions, yet, until now, conditions inside the abrasive feed line have not been completely understood. A possible reason is that conditions inside the abrasive feed line are complicated. Not only compressible flow but also multi- phase, multi-component flow has been involved in inside of abrasive feed tube. This paper explored various aspects of the vacuum creation process in both the mixing chamber and the abrasive feed tube. Based on an experimental exploration, an analytical framework is presented to allow theoretical calculations of vacuum conditions in the abrasive feed tube.

絮凝-真空抽滤-土工管袋联合处理泥浆脱水模型试验

近年来,土工管袋因其良好的排水反滤性能广泛应用于河湖清淤泥浆的脱水处理中,但在脱水后期存在脱水速率缓慢的问题。为此,开展物理模型试验验证在添加絮凝剂的条件下,采用增压式抽真空来增加土工管袋内泥浆后期脱水固结速率的可行性,同时还比较了“空气动力振荡法”与“管袋顶部加荷法”2种方法的抽滤脱水效率。试验结果及分析表明:“空气动力振荡法”会使土工管袋内的原本相对密实泥浆出现裂隙,使得土工管袋内泥浆的气密性被破坏;“管袋顶部加荷法”增加了管袋内泥浆压力,提高了反滤层两侧的压力梯度,使得清淤泥浆的抽滤速度提高;真空抽滤可以显著降低土工管袋内部、抽滤管道周围的泥浆含水率,且抽滤管道越靠近土工管袋中心,抽滤效率越高,泥浆含水率也越低。

Experimental Study of a Solar Thermal Incubator Using a Phase-Change Material for Off-Grid Use

The aim of this study was to provide a simple, easy-to-use incubation system for small-scale rural poultry farmers far from the electricity grid. To this end, a naturally ventilated solar thermal incubator was built and experimentally tested. A U-shaped evacuated tube collector and a wooden crate holding 50 eggs were used to build the solar thermal incubator. Water was used as the heat transfer fluid, and an EPCM was integrated into the incubation chamber for operation at night or when the sun was hidden. The heat generated by the solar collector and stored in the heat transfer fluid is transported to the incubation chamber by thermosiphon to heat the chamber. Temperature and humidity probes powered by a solar panel were placed at various locations to monitor the thermo-hygrometric efficiency of the incubation system. The incubator, heated by natural convection, proved to function normally, and the incubation chamber was maintained throughout the incubation period within a temperature range of 35.53˚C to 39.53˚C and relative humidity averaging 49.4% to 68.5%. The experiment was carried out by introducing 30 eggs and the results of the experimental study showed that the incubator’s efficiency was 87%. The performance tests gave a fertility rate of 93% and a hatching rate of 93%, i.e. 28 fertile eggs and 26 hatched eggs, respectively.

低真空管道列车关键气动问题研究进展

低真空管道列车系统结合应用了管道运输和磁浮推进技术,是一种颇具潜力的未来地面高速交通方式。列车在极狭长的管道空间内长距离往返,通常诱发以管内壅塞现象为主导的大尺度跨声速流动和多车干扰,导致气动阻力急剧增加和气动热环境恶化,从而面临突出的空气动力学问题。本文从管道全场和列车近场两个视角出发,对管道列车流动特征进行了总结,并对近年来国内外该领域气动力/热/噪声研究的进展进行了梳理。在此基础上,围绕管道列车全线多车运行热点问题,对运行速度、管道阻塞比、发车间隔、运行模式的选取进行了讨论。最后,展望了低真空管道列车气动研究领域未来发展方向,指出高效研究方法、多车运行流动干扰、多车运行气动热、长大管道气动噪声、减阻/降热/降噪技术等是今后需要重点研究的领域。

有载分接开关真空管操动机构力学特性动态仿真

真空管操动机构是换流变有载分接开关的核心部件,其机械结构较为复杂,且因其频繁操作常导致机械机构发生塑性形变与损伤,从而发生换流变故障。研究有载分接开关真空管操动机构力学特性动态仿真能够弥补传统测试手段无法直观展示应力分布的不足,并为真空管操动机构的设计与改进提供理论基础。首先,在ANSYS中建立了基于隐式非线性动力学的真空管操动机构瞬态动力学仿真模型,采用Von Mises屈服准则与等向硬化模型计算模型等效应力;其次通过有限元分析了操动机构整体的应力分布情况;最后针对性地分析了凸转盘、凸杆、支撑机构和真空管的应力分布情况,从而便于深入分析分接开关在各种工况下的工作原理,并有助于根据应力分布情况有效改进操动机构机械结构,并在设计阶段预见并避免可能的故障模式。

基于真空管的无水冷微波消融针的设计

为减少组织碳化,提高微波消融治疗的有效性,本研究根据现有水冷法的原理,设计了一款基于双层不锈钢真空管的无水冷微波消融针。利用离体猪肝实验,验证了真空管隔热的有效性;根据有限元仿真方法建立了微波消融仿真模型,并通过实验验证,达到了更好的消融效果。仿真和实验结果表明,无水冷真空管微波消融针无消融尾迹;与传统带水冷的消融针相比,在相同剂量下,无水冷真空管可得到更大的消融区域和更小的碳化区域。本研究证明了真空管用于无水冷消融的可行性,可为后续设计微波消融针提供新的思路。

基于传播图理论的真空管飞行列车的无线信道建模与容量分析

无线信道建模是分析和评估无线通信系统特性的重要环节。为了满足下一代轨道列车的通信需求,本文基于传播图信道建模理论,对真空管环境下列车在管道内运行过程中的无线电传播信道进行研究。结合朗伯散射模型和几何绕射理论模型进行仿真,过程中主要考虑了视距传输、单散射径、单散射加绕射三种情况。仿真得到了多输入多输出(multiple-input multiple-output,MIMO)条件下的信道传输矩阵,提取并分析了功率时延谱、K因子、多普勒谱和信道容量在列车处于不同位置时的变化情况,结果表明,所提出的模型有助于分析在真空管场景下MIMO系统的信道衰落特性和信道容量。

基于重叠网格的真空管道高速列车运行条件对温度场影响分析

为研究真空管道列车在运行时管道内的温度场与管道截面积、真空度和运行速度之间的关系,利用仿真软件Fluent,并结合重叠网格技术对不同列车运行速度、管道截面积和真空度进行仿真,分析了其对管道内和列车表面温度场的影响情况。研究结果表明,管道截面积的增加以及运行速度的降低会导致列车表面以及管道内温度降低;管道内真空度的增加对管道内温度场影响不大,但会使列车表面温度呈上升趋势。

内聚焦真空管集热器热泵系统实验研究及分析

本文提出了一种集热蒸发器为内聚焦真空管的直膨式太阳能热泵来提升系统性能,并搭建实验台获取实验数据,深入研究不同工况下系统的热力学性能。结果表明,太阳辐照强度对系统性能影响显著,当太阳辐照强度由400 W/m^(2)上升到800 W/m^(2)时,系统COP由4.18升至5.34,集热效率由0.94降至0.67,此时系统损由1175.33 W升高到2290.27 W,系统效率由16.82%下降到11.99%,此外循环水入水温度和环境温度对系统的性能影响远小于太阳辐照强度。集热蒸发器是系统从太阳辐射获取能量的部件,对它的设计优化将有助于改善系统性能。

太阳能真空集热管热损分析与试验研究

基于热平衡法提出了一种动态热平衡热损计算方法,并进行了验证,同时分析了环境温度、进口温度、流量对真空集热管热损的影响。结果表明,热损随着环境温度的降低、进口熔盐温度的升高和熔盐质量流量的降低而增大;当辐照强度在700 W/m2以上时,真空集热管获得的热量大于热损并能稳定工作,说明槽式光热电站在东南沿海等太阳能资源相对不足的地区有一定的适用性。

真空管道内直线电机定子温度分布与散热特性研究

为研究真空管道内直线电机定子的温度分布和散热特性,建立了直线电机定子温度分布三维数值计算模型,利用Fluent软件模拟了定子在通电及散热阶段的温度场变化,研究了不同管道压力(0.005、0.01、0.02、0.05、0.1atm)对线圈表面自然对流换热性能的影响,分析了自然对流换热与辐射换热的相对强弱。研究结果表明,列车单次运行引起的定子温升很小,线圈最高温升为14.6℃,经两小时散热后温升仅为0.55℃;通电线圈产生的热量95%以上通过导热传递给铁芯和支架,而通过对流和辐射所传递的热量非常少,管道内压力对线圈表面的自然对流换热量有很大影响;线圈表面的辐射换热量大于自然对流换热量。研究结果为真空管道直线电机定子的温升特性及散热方法研究提供了理论依据。

新型槽式太阳能真空吸热管设计方法及其光学性能研究

针对传统槽式太阳能集热系统工质运行温度受限,以及真空吸热管表面能流密度分布不均而引起的热应力过大等问题,文章在不改变聚光器结构的条件下,提出了一种新型的槽式太阳能真空吸热管的设计方法,通过减小金属内管直径、下移金属内管位置以及在金属内管上方加装双曲线型二次聚光器来提高太阳能聚光比,改善了金属吸热管表面能流密度分布。利用仿真计算方法研究了新型槽式太阳能真空吸热管的光学性能,结果表明:和传统槽式太阳能真空吸热管相比,该新型结构在仅损失1.88%光学效率的情况下将聚光比从62 kW/m^(2)提升至71 kW/m^(2);能流密度分布均匀度改善了55.05%,提升了聚光-吸热系统的整体性能。

长沙至衡阳低真空管道磁浮线路方案动力性能评估

低温超高真空管磁悬浮是当前世界各国争相发展的超高速交通方式之一。目前,该研究正处于起步阶段,有必要对其动力性能进行评估。以长沙至衡阳低真空管道磁悬浮试验线为例,建立低温超导电动悬浮制式的车辆-线路耦合模型,分析磁浮车辆通过该段线路时的动力性能。首先,计算得到以1 000 km/h速度运行时的车体垂向和横向加速度、悬浮力及导向力情况。在此基础上,绘制各动力性能指标的频数直方图,分析其在不同区间的分布情况,研究各动力性能指标随曲线半径的变化规律。研究结果表明,磁浮车辆通过长沙至衡阳线路时,计算得到的车体垂向和横向加速度均低于舒适性限值,动力性能满足要求;从车辆动力性能角度来看,缓和曲线长度设置为1 400 m合理;曲线半径20 000 m、车速1 000 km/h与横坡为16°相匹配,各项动力性能指标较优。研究结果可为超高速磁悬浮线路设计提供参考建议。

低真空管道高速磁浮交通无线通信系统性能评估方法研究

由于受列车高速移动引入的多普勒频谱扩展影响较小,基于泄漏电缆架构的无线通信技术在管道或隧道场景内的高铁移动通信中得到广泛应用。考虑到多普勒频移和电波传播损耗随着载波频率的降低而减小,采用700 MHz标准频段的5G系统被认为是实现低真空管道高速磁浮交通中无线通信的关键途径。面向该通信场景,基于几何单跳多输入多输出泄漏电缆信道模型,分析和对比高速移动场景下视距、非视距的多普勒频谱特征。在此基础上,基于5G标准帧结构,采用一种低复杂度的最小均方误差时域信道估计方法,评估信道估计的归一化均方误差性能,并仿真对比相应系统的频谱效率和误块率性能。仿真结果表明,基于泄漏电缆的700 MHz频段5G系统能够支撑最高速度达1000 km/h的低真空管道高速磁浮交通无线通信应用。