Experimental and Numerical Investigation of the Temperature Field of a Fixed-Point Cavity

The temperature field non-uniformity of a blackbody cavity is one of the components of uncertainty of fixed-point realization. Here a study of the design and opportunities of the temperature furnace used in VNIIM is described. The dependence of the uniformity of a temperature field on various factors is shown by results of numerical calculations of a temperature field of VNIIM??s copper and gold fixed-point cells, realized with the software packages Elcut 5.3 and Ansys 11.0. A thermophysical model of the phase transition considered as steady state with convection and radiation heat exchange to an environment is applied. The basic focus is made on calculation of the radiation heat exchange between crucible elements and the environment and a furnace cavity, as a dominating component of the heat transfer. Results using analytically and numerically calculated angular factors of radiation of heat exchange are discussed. The data obtained in measurements of a temperature field of a cavity fixed point during phase transitions of copper and gold by a spectrocomparator with high sensitivity, are also shown here. Both theoretical calculation and experiment were realized at various distributions of temperature along an external surface of a crucible. Good agreement of results between steady-state calculation of a temperature field and the measured data with the best entry conditions is observed. The average value of non-uniformity of a temperature field along a cavity for points of phase transition of copper and gold for an 88?mm long graphite crucible with a 54?mm deep, 8?mm diameter cavity was 40?mK, and the temperature drop across the graphite wall was 20 mK. In this paper the reasons for occurrence of large gradients inside a fixed-point cavity during the phase transition, received during some experimental research, are also discussed.     

Power Transformers Internal Insulation Design Improvements Using Electric Field Analysis Through Finite-Element Methods

Understanding the potential and electric field distribution in the insulation system of a transformer during transients is vital to its construction. Therefore, we have developed a method for electric field analysis inside a power transformer. The method consists of the following steps. (1) A lumped parameter equivalent model is constructed by dividing transformer windings into several blocks. (2) The electric circuit parameters of this model are calculated. (3) Employing the results of the transformer transient model analysis as boundary conditions, a 2-D asymmetrical electric field finite-element analysis is performed to determine electric fields through the windings. The method has been examined employing power frequency and impulse voltages. We have also demonstrated successful application of the method to a transformer and have verified the computed results by comparison with measured results.     

浅析杂散光对分光光度计的影响

分光光度计是理化分析中最常用的仪器,杂散光是分光光度计检定中的一个重要指标,其大小对于分光光度计测量结果有很大的影响,决定仪器的合格与否。本人依据计量检定规程技术要求,结合实际工作出现的问题,对其进行了全面的总结和分析。     

排气消声器温度场数值仿真与分析

建立消声器和外界环境的耦合传热计算模型,并使用Fluent软件计算简单膨胀腔消声器的温度场,分析消声器内外温度分布的形成原因及气流速度对温度场的影响。在此基础上,计算双进口消声器在某一工况下的温度分布。     

单轴式声悬浮的实验研究及数值模拟分析

采用自行研制的单轴式声悬浮装置,实现了密度为7.9g/cm3的钢球的稳定悬浮.采用有限元方法对两种不同形状谐振腔的声场进行了数值计算和模拟,结果表明采用凹球面形反射面能有效提高悬浮性能;同时解释了实验过程中小球沿凹球面壁运动的现象,对进一步研究声悬浮装置结构对悬浮性能的影响有一定的借鉴意义.     

Experimental and Numerical Analysis of Inserts in Sandwich Structures

In aeronautics, sandwich structures are widely used for secondary structures like flaps or landing gear doors. In the case of landing gear doors, the junction is made by a local reinforcement called an insert. This insert is made by a resin molded in the Nomex sandwich core. Such structures are still designed mainly using test results and the lack of an efficient numerical model remains a problem. The purpose of this study is on the one hand to perform experiments in order to be able to identify the failure modes and on the other hand to propose an efficient numerical model. Pull-out tests with cycling were conducted and 3D displacement measured by optical methods. The potential failure modes are numerous (delamination, local fiber breaking, skin/core debonding, core crushing, core shear buckling, potting failure, etc.). Experiments demonstrated that, for the lower loads, the non-linearity and the hysteresis are mainly due to core shear buckling. From this observation, the nonlinear behavior of the core is identified by a 3 point-bending test. The shear-modulus damage law is then implemented on a non-linear finite element model and an acceptable correlation of the tests is achieved. As a consequence, some improvements of the technology will be proposed, manufactured and tested.     

雾化气体淬火过程耦合流场数值模拟及实验研究

运用计算流体动力学(CFD)的方法在FLUENT平台上建立雾化气体淬火的三维非稳态模型,对介质不同速度工况下淬火过程中试件温度场、流体速度场、流体温度场和流体压力场进行了流固热耦合数值模拟,并将模拟结果与边界条件实验结果进行了对比分析。结果表明,同等工况下,介质进口速度越大,流体的速度也越大;同截面上200m/s速度工况下试件上下表面两区域的压力差值比100m/s速度工况下大;试件放在淬火区淬火80s后,200m/s速度工况下试件的最高温度为299.5℃,100m/s速度工况下试件的最高温度为336℃,由此得出淬火介质进口速度越大,淬火试件的温度下降越快,试件冷却速度越快,冷却效果越好。     

杂散辐射率超标的原因分析及改进措施

本文通过对一例可见分光光度杂散辐射率超标的原因进行分析进而谈到对出现此类情况的可见分光光度计设计上的改进措施。     

船舶冷藏集装箱内温度场数值分析及优化

为研究和改善载货后船舶集装箱内温度分布的不均匀性,以20 ft冷藏集装箱为研究对象,对现有T型槽道送风方式进行改进和优化,提出了一种新型局部送风方式;利用ICEM-CFD软件建立模型并进行仿真计算,揭示冷藏集装箱内温度分布特性,与原始模型进行对比分析,结果表明:在箱门附近引入局部送风系统可有效改善箱内温度分布,有效控制箱内温差1~2K,减小局部高温区域面积。局部送风系统还可以延迟装载货物时箱内温度上升速率,有效降低箱内能量损失。文章对进一步开展船舶冷藏集装箱内温度控制和节能优化具有借鉴意义。     

《转子-轴承-密封系统非线性动力学理论和试验研究》

采用理论分析和试验研究相结合的方法,研究油膜力和密封力联合作用下转子轴承密封系统的非线性动力学特性和稳定性。将转子轴承密封试验台系统等效为Jeffcott系统,采用短轴承理论建立油膜力的非线性模型,采用Muszynska模型建立非线性的密封力。通过数值仿真研究在不同转子转速下密封力对系统非线性特性和稳定性的影响。将试验结果与理论计算进行比较,两者基本一致。     

Numerical and Experimental Analysis of Welding Deformation in Thin Plates

The use of welding to permanently join plates is common in industry due to its high efficiency. But welding creates thermal stresses, which can lead to residual stresses and physical distortion. This phenomenon directly influences the buckling stiffness of the welded structure. The welding distortion not only makes difficult the erection of the project, but also influences the final quality and cost of production. In this research, the thermo-elastic-plastic conditions were simulated by a three-dimensional (3D) finite element model (FE). Mechanical and thermal properties of the material were applied to the model, leading to eigenvalue analysis of the thermal and longitudinal stress distribution, buckling during welding and global. The research was performed on thin plates welded by butt joints and T-joints. A birth and death method depending on time was also used to model the molten pool. Since welding is a thermo-mechanical process, a coupling method was used to obtain results for nonlinear transient thermal analysis and introduce them in the structure analysis in order to investigate the buckling phenomenon. A comparison of our numerical results with those obtained from our experiments showed that the models can help predict when and where local buckling can occur. This method can also help predict the heat distribution and deformation during and after welding.     

风流脉动下采空区流场数值模拟与实验研究

针对矿井内风流脉动的特性,基于矿井通风理论、流体力学理论、空气动力学 理论、传热传质学理论、多孔介质渗流理论,建立了矿井风流脉动下采空区流场的计算模型;通 过数值模拟,研究了脉动风流作用下采空区流场的分布特点,并通过实验对其进行了测试和 验证。结果表明所建立的采空区非稳定流场的数学模型可用于研究采空区流场分布状态,并 为采空区火灾防治提供有效的手段。      

1L慢烤燃装置温场分布数值模拟与试验研究

建立了一种1L慢烤燃装置模型,通过数值模拟分析其内部温场分布的影响因素和机理,通过改变模型中隔板尺寸、导流板形状、风扇数量和风扇转速等条件,研究了各种工况下烤燃装置内烧瓶周围温场分布。模拟结果表明,风扇数量与转速、隔板尺寸、导流板形状均会影响烧瓶周围温场分布的位置,但仅有风扇转速会影响温场响应的灵敏度、温场达到稳定所需时间和温场分布均匀性。理想的慢烤燃装置可实现的温场分布性能为:响应时间低于1 s,达到稳定时间低于30 s,均匀度在0.2℃左右。建立试验装置,在烧瓶外侧布置温度传感器,所得温场分布和温场均匀度与模拟结果一致。     

卡塞格伦望远镜系统杂散光分析

白天强背景光将通过望远镜系统对后续观测系统产生很强的杂散光。在这种条件下，卡塞格伦望远镜系统杂散光成对称分布，主要来源于望远镜筒壁的漫反射光、马蹄镜的直接反射光和次镜支架的漫反射光。理论分析和数值模拟表明，系统结构中马蹄镜和次镜的作用最大，而观测视场角的增大将导致杂散光通量的急剧上升。     

离心泵蜗壳效应数值模拟与分析

利用FLUENT软件结合有限元体积法和Navier—Stokes方程,通过数值模拟方法研究离心泵蜗壳内的二维流场情况。根据分析结果表明离心泵的蜗壳壁面随着与叶轮距离的增大,受到的冲击越小。蜗壳出口处的壁面位置会存在低压区,对离心泵的内部流场造成能量损耗。利用数值模拟的方法,对离心泵蜗壳的设计优化提供了理论依据。     

Inverted and Forward Preisach Models for Numerical Analysis of Electromagnetic Field Problems

This paper discusses the use of the inverted ($B$-based) Preisach model and its incorporation into the finite-element method (FEM). First, the$B$-based Preisach model is studied thoroughly along with the forward ($H$-based) Preisach model, highlighting the advantages and disadvantages of both models. The study confirms that, in addition to the main purpose of the$B$-based model—to compute the magnetic field$H$directly—the$B$-based model can overcome the congruency problem. Thus, the$B$-based model proves to be more accurate than the$H$-based model. Second, the paper suggests that incorporating the$B$-based Preisach model into FEM models results in relatively accurate, computationally efficient simulations. The method has been validated by simulating hysteresis torque in a high-speed induction motor, and a comparative investigation of the effectiveness, accuracy, and efficiency of the models has been conducted.     

带限位倒摆的实验与数值研究

设计研制一个带限位的倒摆实验系统,建立 该系统的力学模型,通过实验与数值分析的研究,讨论周期与随机激励情况下的各种响应,证实所建立模型的正确性,揭示该系统存在复杂的非线性动力学行为,并指出噪声对系统非线性动力学行为的影响。研究结果将为带有间隙结构的设计和间隙结构动力学分析提供参考。     

Experimental and Numerical Studies of the Magnetic Field Transfer of a Magnetic Cylinder Coated with Superconductor

A novel concept of cloaking, concentration and transferring of the static magnetic fields by the combination effect of the superconductor (SC) and ferromagnet (FM) has been recently presented. The performance of these hybrid structures strongly depends on the properties of the involved materials as well as its geometrical parameters. In this work, we have practically demonstrated a magnetic hose, which is developed by a FM core wrapped by a SC layer. Meanwhile, a finite-element simulation with experimentally derived permeability of both SC and FM constituents was also established. Based on the verified simulation, further investigations were carried out to systematically examine the dependence of the transfer efficiency of the magnetic hose on its dimension and magnetic properties of the involved materials, both of which are difficult to be varied in practical case, especially for the magnetic properties.