EAST ICRH天线法拉第屏蔽冷却结构优化

现有的法拉第屏蔽(FS)冷却结构无法满足未来EAST 长脉冲稳态运行的要求,需要进行优化改进。通过理论和数值模拟方法,对FS原有冷却结构进行了优化设计,并获得了改进后FS冷却管道的流速和压力分布。通过比较不同进口条件下FS流体压降和结构温度分布情况,获得了适合优化后FS结构运行的流动参数,为未来ICRH天线FS的运行提供了理论指导。     

火电厂直接空冷凝汽器传热性能实验研究

直接空冷凝汽器的传热性能是火电厂空冷机组优化运行和设计的重要依据.针对实际运行的某典型600 MW直接空冷机组的冷端系统,利用红外热像仪测量了不同空冷凝汽器翅片管束表面的温度分布,并与热电偶测量的温度进行比较分析.发现,受管内蒸汽流向和凝汽器冷却三角内空气流场的综合影响,顺流和逆流凝汽器的壁面温度都表现出从上至下逐渐上升的趋势,为进一步预测凝汽器空气侧流场特性和进行空气侧的传热强化提供了参考;通过实验研究,获得了机组空冷凝汽器单元空气侧传热系数关联式.本文的结果对变工况条件下空冷机组的优化运行以及空冷凝汽器设计的改进具有指导意义.     

液态Au和Ag冷却过程的分子动力学模拟

采用反映原子多体相互作用的FS势模型,通过分子动力学方法研究了贵金属Au、Ag在温度2000~300 K之间的冷却过程,考察其结构变化特点,给出了冷却过程微观结构转变的重要信息.     

环形磁场金属等离子体源冷却流场的数值模拟与优化

环形磁场金属等离子体源作为一种全新的等离子体源结构,可用于产生高度离化、无大颗粒、高密度的离子束流,但传统流道结构不能保证其高效、均匀散热,大功率工作时可能引起密封胶圈的烧蚀失效,需对其冷却流场进行优化设计.利用Solidworks Flow Simulation软件对等离子体源冷却流道进行模拟,分析出入水孔分布角度、孔数、孔径以及入水孔高度对冷却效果的影响规律,并对流道结构参数进行优化.结果表明,增大水孔的周向分布范围,有利于提高散热的均匀性;入水孔设置在结构上层有利于减少冷却水的温度分层现象,使铜套和密封胶圈都处于较好的冷却状态;适当减小孔径有利于增大冷却水射流速度,增大湍流程度强化传热,提高换热效率.优化后的流场结构可以提高冷却水的利用率,在相同流量条件下获得更好的冷却效果,改善等离子体源的放电稳定性,为环形磁场金属等离子体源的冷却结构设计提供理论依据.     

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利用ANSYS/CFX对聚变堆氦冷多喷嘴冷却偏滤器模块在相同高热负荷条件但不同冷却条件下进行了有限元数值分析,得到了偏滤器冷却单元的温度和换热系数分布图,将该温度场作为结构力学分析的加载条件,利用ANSYS/Mechanical对冷却模块进行了稳态条件下的结构应力分析,得到了具有不同结构参数的偏滤器模块的应力分布.通过分析各结构参数对偏滤器模型的热应力的影响,对结构参数进行筛选,得到内应力相对较低的结构设计,从而优化多喷嘴氦冷偏滤器结构.     

金属银熔体快冷过程的计算机模拟

利用分子动力学模拟技术研究了由周期性边界条件控制的500个银(Ag)原子构成的金属Ag熔体快速冷凝过程.冷却速率为8×1013K/s.模拟在FS(Finnis-Sinclair)相互作用势的基础上,通过双体分布函数、键对分析技术、键取向序等多种方法,对液银快速冷凝过程的微观结构转变特性作了分析,给出了连续快速冷凝过程中液银原子间依靠相互作用力形成的独特的微观结构图像.并考察了冷却过程中体系能量和元胞体积随温度的变化.模拟结果表明在快速冷凝过程中液Ag没有形成bcc结构的倾向.     

开槽前扩孔及复合角对气膜冷却的影响

本文对开槽前扩孔及在此基础上加30°、45°和60°不同角度复合角的气膜冷却结构进行了数值模拟,计算了指定冷却壁面的温度场分布以及冷却效率.结果表明:引入复合角后,能够改善冷却气膜在壁面的横向分布,复合角越大,气膜分布越均匀.在高吹风比下,复合角结构能够产生较大的气膜覆盖范围和较好的冷却效果.     

HIRFL–CSRm Betatron振荡随机冷却

对拟在HIRFL CSRm上建造的横向自由振荡随机冷却进行了数值优化计算和设计,得到了最佳带宽、冷却时间、频谱上束流谱密度分布函数随时间的变化,以及在冷却过程中束流横向位移的分布等值,并且对功率限定情况作了讨论,从而为冷却系统的设计、优化、建造和运行提供了理论依据     

改善局部难冷区域的一种导叶层板端壁

受二次流的影响,气膜冷却端壁表面存在大量难冷区域。紧凑型层板结构可以实现端壁的双侧冷却,从而缩小难冷面积。本文通过改变气膜孔布局,设计了一种可以有效改善局部难冷区域的层板冷却端壁。在主冷流温比1.5下,测量了端壁表面的温降特性和综合冷却效率分布,通过与均匀气膜布局的层板端壁相比较,发现:采用改进后的层板结构,可以显著降低端壁表面温度,缩小难冷区域面积,获得更均匀的冷却效果。且压力侧根部区域与吸力面前缘区域冷却效果增幅尤甚。另外,此层板的改进优势随着质量流量比的增加变得更明显。     

液态银快速冷凝过程的微观结构演化研究

利用计算机模拟了在周期性边界条件下由500个银原子构成的液态Ag模型系统以8×1013K/s的速率快速凝固的全过程.模拟在FS相互作用势的基础上,通过双体分布函数、键对分析技术等多种方法,对液Ag快冷凝固过程的微观结构转变特性作了分析,给出了连续快速冷凝过程中液Ag原子间依靠相互作用力形成的独特的微观结构图像.模拟结果表明在快速冷却过程中液Ag没有形成bcc结构的倾向.     

实现玻色-费米混合气体量子简并的四极Ioffe组合磁阱设计

四极Ioffe组合磁阱(QUIC磁阱)是由一对四极线圈和一个Ioffe线圈组合构成的一种Ioffe-Pritchard磁阱,它已广泛应用在囚禁中性原子和实现蒸发冷却原子的实验中.设计了两种不同结构的四极线圈和Ioffe线圈,并对其进行了相应的数值模拟和测试.通过比较获得了一种参数优化的QUIC磁阱,这为QUIC磁阱线圈的优化设计提供了参考.最后在优化的QUIC磁阱中,采用射频蒸发冷却俘获⁸⁷Rb原子,实现了⁸⁷Rb原子气体的玻色-爱因斯坦凝聚,同时采用“共同冷却 关键词： 四极线圈 Ioffe线圈 四极Ioffe线圈组合磁阱 原子冷却     

Thermocyclic testing of heat-resistant coatings at megawatt three-phase plasmatron

Some new types of heat-resistant coatings developed at present were tested for thermal fluxes and temperatures implemented in flame channels of modern rocket engines. The megawatt three-phase alternatingcurrent plasmatron was used for testing. The thermal flux distributions were measured for uncooled targets using thermocouples and thermal imaging tools. Coated samples were installed to the model cooled by water under high pressure. The mechanical strength of coatings at thermocyclic testing was studied and heat conduction of heat-resistant layers was determined in operation conditions.     

中国固态增殖剂试验包层系统的氦气冷却系统仿真计算

根据中国固态增殖剂试验包层氦气冷却系统的系统设计和布置情况,利用大型一维流体仿真软件 Flowmaster 建立了氦气冷却系统的仿真模型。利用该仿真模型,模拟了氦冷系统在产氚包层系统不同工况下氦气流动情况以及各种参数的分布情况,得到了热等待工况、热备用工况、正常运行工况和除氚工况下系统的主要工艺点的温度、压力和流速分布等相关参数,为系统的设计和设备选型提供参考。同时,该仿真模型和结果对中国聚变工程实验堆氦冷系统的仿真模拟具有一定的参考意义。     

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According to the system design and arrangement of helium cooling system of China helium cooled ceramic breeder (CHCCB), helium cooling system simulation model is built using large one-dimension fluid simulation software Flowmaster. For different operation conditions of tritium breeding blanket system, helium flow conditions and parameter distribution are simulated for helium cooling system, using such simulation model. Temperature, pressure and velocity distributions and other related parameters have been obtained on different scenarios for hot waiting state, hot standby state, normal operation state and tritium out-gassing state, which provide reference for the design of system and equipment selection. Meanwhile, the model and simulation results have some reference significances for the simulation of helium cooling system for CFETR.     

100 mK bolometers for the submillimetre common-user bolometer array (scuba) I. Design and construction

We describe the design and construction of bolometric detectors for SCUBA - the Submillimetre Common-User Bolometer Array for the James Clerk Maxwell Telescope in Hawaii. The instrument contains 131 individual detectors, in two arrays, optimized for the submillimetre atmospheric transmission windows. The detectors are cooled by dilution refrigeration to a temperature of 100 mK, so that the receiver performance will be limited by photon noise from the sky and telescope background in all wavebands. A future paper will describe the performance of the detectors with reference to typical data obtained during the laboratory commissioning period.     

Focusing of longitudinal ultrasonic waves in air with an aperiodic flat lens

Modeling and experimental results of an ultrasonic aperiodic flat lens for use in air are presented. Predictive modeling of the lens is performed using a hybrid genetic-greedy algorithm constrained to a linear structure. The optimized design parameters are used to fabricate a lens. A method combining a fiber-disk arrangement and scanning laser vibrometer measurements is developed to characterize the acoustic field distribution generated by the lens. The focal spot size is determined to be 0.88 of the incident wavelength of 80-90 kHz at a distance of 2.5 mm from the lens. Theoretically computed field distributions, optimized frequency of operation, and spatial resolution focal length are compared with experimental measurements. The differences between experimental measurements and the theoretical computations are analyzed. The theoretical calculation of the focal spot diameter is 1.7 mm which is 48% of the experimental measurement at a frequency of 80-90 kHz. This work illustrates the capabilities of a hybrid algorithm approach to design of flat acoustic lenses to operate in air with a resolution of greater than the incident wavelength and the challenges of characterizing acoustic field distribution in air.     

Spin-dependent parton distributions from polarized structure function data

In the past year, polarized deep inelastic scattering experiments at CERN and SLAC have obtained structure function measurements off proton, neutron and deuteron targets at a level of precision never before achieved. The measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and also to obtain information on the parton distributions in polarized nucleons. We perform a global leading-order QCD fit to the proton deep inelastic data in order to extract the spin-dependent parton distributions. By using parametric forms which are consistent with theoretical expectations at large and smallx, we find that the quark distributions are now rather well constrained. We assume that there is no significant intrinsic polarization of the strange quark sea. The data are then consistent with a modest amount of the proton's spin carried by the gluon, although the shape of the gluon distribution is not well constrained, and several qualitatively different shapes are suggested. The spin-dependent distributions we obtain can be used as input to phenomenological studies for future polarized hadron-hadron and lepton-hadron colliders.     

Studies of the Fermi surface of V3Si by 2D ACAR measurements

We report two-dimensional angular correlation of annihilation radiation (2D ACAR) measurements using positrons in single crystals of V₃Si. Anisotropic structure commensurate with the reciprocal lattice is observed and attributed to the complex Fermi surface (FS). A simple geometrical model for the FS is developed and compared with folded ACAR distributions. The results of a 3D reconstruction are compared with recent band calculations.     

Optimization of a GaN-based irregular multiple quantum well structure for a dichromatic white LED

GaN-based irregular multiple quantum well(IMQW) structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes(LEDs) are optimized in order to obtain near white light emissions.The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain,well-coupling,valence band-mixing and polarization effect through employing a newly developed theoretical model from the k · p theory.Several structure parameters such as well material component,well width,layout of the wells and the thickness of barrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure.Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two,the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness.The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.