50 kA超导变压器杜瓦及高温超导电流引线的设计与优化

CICC超导导体性能测试用50 kA超导变压器由初级线圈和次级线圈组成,初级线圈浸泡在4.2 K液氦低温杜瓦中,次级线圈为CICC导体采用4.2 K/354 637 Pa超临界氦迫流冷却,液氦和超临界氦均由500 W/4.5 K制冷机提供,变压器低温杜瓦的理论液氦蒸发率为1.52 L/h。为减少电流引线漏热,超导变压器采用B i-2223/AgAu高温超导(HTS)二元电流引线,并且在颈管中部设计了一个新型的直接用液氮冷却的热截流装置来截断电流引线高温端的热流;最后对铜电流引线部分进行了尺寸优化计算,得到最佳截面积和直径分别为28 mm2和6 mm。     

6kA高温超导电流引线研制

6 k A电流引线的运行电流为6 k A,最大电流为8 k A,其换热器段采用液氮冷却设计,运行温区为77 K—室温,高温超导段为传导冷却,运行温区为5—77 K。介绍6 k A电流引线的结构设计、性能分析,以及相关低温实验。实验结果表明,6 k A电流引线的零电流下液氮需求低于0.46 g/s,5 K冷端漏热小于2.5 W,过流能力8 k A。     

合肥光源超导波荡器用二元电流引线的设计研究

电流引线作为连接室温电源与低温超导磁体的部件,温度跨越范围大,是低温恒温器的最主要热负荷之一。超导波荡器(SCU)用高温超导电流引线主要采取小型制冷机直接传导冷却的形式,通过对合肥光源超导波荡器(HLS-2 SCU)用400 A高温超导二元电流引线铜段的长度、截面等几何参数进行理论优化,以减小小型低温制冷机的热负荷。考虑室温端热阻以及铜段低温端的温度对最小漏热的影响,得出铜段最佳值参数。通过有限元仿真计算结果进行验证,得出的结果吻合的较好。最终确定了400 A高温超导电流引线的设计参数。     

低温真空电流引线热分析

对在两级制冷机传导冷却下由高温超导和铜组成的二元电流引线进行热分析.给出了不同运行电流下,在室温温度(300 K)和制冷机一级冷头温度(77 K)间铜电流引线的温度、热流分布.认为大电流运行下,传导热等于焦耳热的一半时,在二元电流连接点的热流最小.给出了在最小热流下电流引线的尺寸优化方法.     

稳态混合磁体15kA高温超导电流引线的设计

为了降低运行费用,正在建设中的中国科学院强磁场科学中心稳态混合磁体的电流引线采用高温超导电流引线.依据一种较为精确计算电流引线的方法,从传热学中的特征关联式出发,初步计算出了稳态混合磁体15 kA高温超导电流引线的基本尺寸与漏热.高温超导电流引线的常温段采用板式换热器的结构形式,增大了对流换热面积;超导段的保护体采用不锈钢,降低了对液氦热沉的热负荷.     

35 kJ高温超导磁储能(SMES)的热输运实验研究

研制了中国首台高温超导磁储能直接冷却系统,该系统不使用低温液体(液氦、液氮).在10-3Pa的真空度下,高温超导磁体线圈由1台单级GM制冷机从室温293 K冷却到19 K,Bi2223电流引线由另一台制冷机冷却到77 K以下.整个系统在通140 A直流电流的时候产生了4.5 T的磁场.系统连续运行480 h(20 d),磁体和低温系统各参数动态特性良好.实验研究表明,控制系统的漏热,优化磁体内部导冷结构,有效减少热传导部件的接触界面热阻是制冷机直接冷却高温超导磁体的关键技术.     

ITER 68kA高温超导特大电流引线的冷端漏热

ITER高温超导电流引线载流能力最大要达到68 kA,其试验件于2008年底加工完成并进行了低温试验,在载流能力、接头电阻、漏热和安全性等关键参数上取得了重要进展.讨论了ITER高温超导电流引线超导段冷端(5 K)漏热的理论值计算,并用热导率积分法进行了低温漏热测试,结果表明理论值与试验值基本吻合,试验件冷端漏热满足ITER国际组要求.     

高熵合金凝固用高精度低温超导磁体的研制

根据高熵合金凝固用高精度低温超导磁体的技术要求,研制1套磁场可达10 T,室温直径为100 mm的高精度传导冷却超导磁体。该超导磁体由1组Nb3Sn和4组Nb Ti线圈组成,同时设计并制造了直径650 mm、高612 mm的杜瓦。为降低磁体运行过程中漏热,采用1对150 A高温超导电流引线为磁体供电。磁体总质量388 kg,通过1台1.5 W@4.2 K的G-M制冷机作为冷源,经过62 h,将超导磁体冷却至2.92 K,磁体正常运行电流119.95 A,工作磁场10.001 T,励磁过程中未发生失超,运行稳定。同时,对强磁场下高熵合金的凝固进行实验研究,详细介绍了该超导磁体装置的设计、制造和测试过程。     

传导冷却电流引线热分析

为研究减小电流引线漏热的优化途径,从基本传热模型出发,对传导冷却电流引线进行了热分析,获得了最小漏热关系式,得到了综合优化参数关系式.通过实例分析提出降低电流引线温度较高端的温度,可以有效减小电流引线漏热.提出当综合优化参数偏离最佳值时,为减小漏热应当尽可能增大而不是减小该值.     

ITER高温超导电流引线测试杜瓦设计与分析

为了满足国际热核聚变反应堆计划(ITER)高温超导电流引线测试需要的低温及真空工作环境,根据杜瓦设计的各项技术指标要求,设计了ITER高温超导电流引线的测试杜瓦结构。通过对外筒体进行了结构强度校核分析,确定了外筒体的结构设计方案。对冷屏及其冷却管进行了设计、选型及压差计算,确定了冷屏设计方案。通过对冷屏绝热支撑结构设计及热负荷计算,确定了冷屏的各项热负荷情况。各项计算结果均满足要求,同时并对该ITER高温超导电流引线测试杜瓦成功进行了制造和测试。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...