星载光学系统遮光罩消杂光结构优化设计方法

本文对星载光学系统遮光罩消杂光结构的优化设计做了初步探讨。提出了遮光罩和挡光环消杂光设计的基本原则。给出了一种二级遮光罩结构寸的优化设计方法和一种遮光罩内壁上挡光环位置优化设计方法,并对一级和二级遮光罩进行了初步的分析比较。     

星载光学系统遮光罩消杂光结构优化设计方法

本文对星载光学系统遮光罩消杂光结构的优化设计做了初步探讨。提出了遮光罩和挡光环消杂光设计的基本原则．给出了一种二级遮光罩结构寸的优化设计方法和一种遮光罩内壁上挡光环位置优化设计方法，并对一级和二级遮光罩进行了初步的分析比较。     

近红外成像光学系统设计

为了明确近红外成像光学系统对杂散光的抑制能力,设计了一个光谱为0.75 m ~1 m,焦距12.002 mm,F/1.8,视场1515的光学系统,其结构为改进型的双高斯结构。实验结果表明:设计的光学系统的各视场光斑在艾瑞斑内,焦移量最大为4.9 m,球差约为1 m,垂轴像差最大为3 m,MTF接近衍射极限。对设计的光学系统进行了杂散光评估和杂散光抑制,得到了杂散光抑制前后的点源透射比。分析结果表明:与未加遮光罩相比,加入遮光罩的光学系统PST值下降了76.6%~87.5%。     

高分辨率空间相机遮光罩结构参数的有限元分析

根据经典薄壳振动理论,利用有限元法对高分辨率空间相机遮光罩的结构参数进行了分析。将正交试验法与有限元法相结合,定量地分析了加强筋的数量和形状对遮光罩动力学特性的影响程度;根据模态分析的结果,考察了单个加强筋的参数对其动力学特性的影响。结果表明,加强筋的高度对结构刚度的影响最大,遮光罩的固有频率随着加强筋的数量和高度以及周向加强筋厚度的增加而增加,随着轴向加强筋的厚度的增加而减小。分析结果为高分辨率空间相机遮光罩的结构设计提供了必要的指导。     

空间光学遥感器遮光罩结构方案选择

利用有限元工程分析技术对空间光学遥感器的遮光罩结构方案进行了选择。应用MSC.Patran/Nastran软件对遮光罩进行了模态分析,应用TMG软件对遮光罩进行了热分析。根据模态分析和热分析的结果对遮光罩材料的铺层方式、遮光罩的结构形式和遮光罩的长度进行了优选。结果表明,[-45°/90°/45°/0°]s交叉对称铺层方式、一条轴向筋和1mm厚度、200mm长度的四棱台式遮光罩的结构方案是合理可行的。其结果为遮光罩的结构设计提供了必要的指导。     

离轴三反光学遥感器遮光罩的设计与试验验证

遮光罩是空间光学遥感器的重要组成部分,是抑制空间光学遥感器杂散光的首要措施。遮光罩削弱杂散光效果的好坏直接影响到光学遥感器光学系统的成像品质。本文设计了一种满足离轴三反空间光学遥感器要求的大尺寸碳纤维/环氧复合材料遮光罩,并结合有限元分析、杂散光分析及力学试验、光学系统传递函数检测手段来验证该遮光罩是否满足航天使用要求。结果显示,各视场光学系统传递函数检测结果基本一致,均在0.2以上。表明该大尺寸遮光罩具备良好的结构的稳定性、可靠性,能够满足空间应用要求。     

R-C系统外遮光罩挡光环的程序化设计及锥状内遮光罩的改进

基于几何作图法推导出R-C系统外遮光罩内挡光环顶点的坐标公式,利用C语言编程实现程序化设计挡光环.在中心遮光比确定的情况下,推导出内遮光罩的顶点坐标公式,并将通常使用的主镜一级锥状遮光罩改进为二级锥状遮光罩,以高速摄影系统的R-C型折反式主物镜为例,对其主镜和次镜内遮光罩进行设计,并给出设计结果.当轴角为70°,遮光罩为二级和一级时,到达像面的杂散光照度分别为1.082 3×10-12 W/m2和1.661 4×10-10 W/m2,相差二个数量级,证明改进的二级遮光罩优于一级遮光罩,能有效抑制杂散光.最后,设计了主、次镜间镜筒内壁上等高挡光环,进一步抑制了R-C系统的杂散光.     

大视场空间相机轻型遮光罩的研制

空间相机遮光罩既能遮挡杂光进入相机镜头,又可利用遮光罩长度和遮光罩内的光栅及表面材料特性,吸收已进入遮光罩的杂散光,能够保证相机获得较高的信噪比。具有优良性能指标的碳纤维复合材料应用于空间相机中能够满足空间相机的结构设计指标,并能大大降低相机的重量。针对某空间相机进行了遮光罩的设计,通过利用有限元模拟仿真分析与试验验证相结合的方法,验证了碳纤维作为遮光罩材料的可行性和是否能够提高光学系统的信噪比。结果表明,碳纤维复合材料应用于空间相机遮光罩的设计是完全可行的。     

R-C系统遮光罩的最优化设计

在作图方法的基础上 ,推导出 R- C系统遮光罩尺寸和口径的约束条件 ,利用最优化方法得到 R- C系统遮光罩尺寸和口径的数值解。克服了传统作图方法不足 ,能够和系统的光学设计同时进行 ,有助于获得系统的最优结构。     

遮光罩内壁蜂窝结构单元的双向反射特性

内壁蜂窝结构是决定遮光罩杂散光抑制性能的主要因素,掌握其各向异性辐射传输特性对遮光罩的杂散光分析和优化设计具有重要意义.针对蜂窝结构单元,建立辐射传输模型,导出了表面双向反射分布函数的离散表达式;通过蒙特卡罗法模拟蜂窝结构单元的辐射传输过程,分析了几何参量和涂层反射率对等效面反射特性的影响;根据模拟所得双向反射分布函数数据库,建立了用于遮光罩杂散光分析的蜂窝结构等效面的反射特性概率模型.分析结果表明,蜂窝结构对杂散光呈现很强的后向散射特征,等效面的反射特性概率模型与直接模拟结果符合很好,可用于遮光罩杂散光分析和设计.     

漩涡阻止器水力性能的PIV试验分析及其机理研究

漩涡阻止器是用来防止或减少漩涡发生的特殊装置,它具有特殊的几何形状,能够优化水力机械内部的流动。在水泵吸水池内部,尤其在吸入口的周围存在着较大的漩涡,在吸入口的下方,安装一个“T”型的漩涡阻止器,应用PIV技术测出安装漩涡阻止器前后吸水池内部的流场分布,并对其流动特性进行深入分析,证明了该阻止器能够有效的减小漩涡发生。对这种“T”型漩涡阻止器的作用过程进行深入的研究发现,能够用摩阻理论来解释它的作用机理。     

弓形折流板换热器中折流板对换热器性能的影响

本文采用Bell-Delaware换热器设计方法研究了传统弓形折流板换热器加热轻油时在不同管束排列角度下,改变换热器壳侧折流板间距以及改变折流板的窗口高度对管壳式换热器的壳体内径、换热管数目、壳侧换热系数及壳侧压降的影响.     

齿形中心扩锥对旋流燃烧器气固流动影响的PDA试验研究

1前言旋流燃烧器依靠高温回流区做为稳定的热源，使煤粉气流及时着火并稳定燃烧，燃烧器单独组织燃烧，不互相影响，燃烧器区域的气固流动特性决定了燃烧器的性能。燃烧器的喷口结构对其气因流动特性有重要影响山。本文提出了齿形中心扩锥结构（如图l所示）。2实验方法及结果分析试验采用三维激光粒子动态分析仪（简称三维PDA），实验台系统主要由送风机、吸风机、给粉机、燃烧器模型、试验段、旋风分离器等组成，试验段为一竖直放置的筒体，直径为4800mm，燃烧器模型安装在简体上部中心位置，最外层扩口端部与筒体内壁平齐，沿射流流动方…     

FREE VIBRATION ANALYSIS OF BAFFLED LIQUID-STORAGE TANKS BY THE STRUCTURAL-ACOUSTIC FINITE ELEMENT FORMULATION

In fluid-structure interaction systems, baffles as a dynamic damping device are being widely used to suppress the fluid sloshing motion. Meanwhile, natural and dynamic behaviors of such systems are significantly influenced by the baffle parameters, such as the baffle number, the installation location, the inner-hole diameter and the liquid fill height. This paper intends to numerically investigate the parametric eigen characteristics, by the coupled structural-acoustic finite element method (FEM), of baffled cylindrical liquid-storage tank. According to the symmetric two-field formulation, a test FEM program is developed, in which the reduced integration for avoiding the shear and membrane locking and the modified shear correction factor as well as degenerated 8- and 6-node shell elements and 3-D trilinear acoustic elements are used. Through the comparison with the available analytic solutions of no-baffled axisymmetric tank, the validity of the test program and theoretical work is verified. Next, with the verified test FEM program, various combinations of major baffle parameters are intensively examined, in order for the parametric baffle effects on the natural frequency of baffled tanks.     

空气-水蒸气流经扰流圈的冷凝传热强化

本文对含高浓度不凝组分存在条件下水蒸汽冷凝传热强化进行了机理分析和实验．结果表明,扰流圈能大大增加气液边界层的湍动强度,具有优越的强化传热、传质效果．在实验范围内,其冷凝传热膜系数是光滑管的１．９～３．５倍．     

Experimental investigation of the flow inside a saxophone mouthpiece by particle image velocimetry

An experimental study of the flow inside a saxophone mouthpiece in playing conditions is carried out by means of particle image velocimetry at high acquisition rate. Planar velocity measurements on the midsection of a Plexiglas tenor saxophone mouthpiece are performed, respectively, in the mouthpiece baffle and in the reed channel. Sequences of velocity fields inside the mouthpiece baffle and around the reed tip are shown for one reed duty cycle. Maxima of the velocity fluctuations are observed at the upper surface of the mouthpiece at a distance between five and ten reed apertures from the tip. The proper orthogonal decomposition analysis reveals that almost 50% of the kinetic energy in the baffle is distributed in the first two modes displaying a periodic behavior at the fundamental frequency, the rest being turbulent flow behavior. The measured dynamical vena contracta coefficient at the inlet is reasonably constant around the value of 0.6 for reed positions far from closure. This is in agreement with existing steady flow analytical models and previous experimental results.     

STUDY OF THE IMPINGEMENT OF IMPULSE WAVE UPON A FLAT PLATE

The impulse wave is made by the weak normal shock discharge from an open end of a shock tube. In order to understand the dynamic characteristics of the impulse wave impinging upon a flat plate, experiments are performed over the shock Mach number range from 1·01 to 1·20. A flat plate is placed downstream, normal to the axis of the shock tube, to simulate the impulse wave impingement on an object. The distance between the exit of the shock tube and flat plate is changed. The baffle plate is installed at the exit of the shock tube. The sizes of the baffle plate and impinging flat plate are varied to investigate the magnitude of the impulse wave impinging upon the flat plate. Computational analysis is applied to model the flow field subject to unsteady, axisymmetric, inviscid, compressible, equations. Computational results well predict the experimented dynamic behavior of the impinging impulse wave. The impulse wave impinging upon the flat plate has a sharp peak of very short rising time and its magnitude decreases with distance from the center of the flat plate. The magnitude of the impulse wave impinging upon the flat plate can be predicted by the empirical equations that are developed in the present study.     

FREE-VIBRATION ANALYSIS OF LIQUID-FILLED TANK WITH BAFFLES

The natural frequencies of liquid in a liquid-filled cylindrical rigid tank without and with baffles are evaluated. An annular plate is used as a baffle, which is fitted to the inner periphery of a cylindrical tank. Both rigid and flexible baffles are considered. Finite elements are used to discretize both the liquid and the structural domain. The slosh frequencies of liquid are computed for different dimensions, thicknesses and positions of baffles, both rigid and flexible considering the circumferential wave number as one. The axisymmetric and other asymmetric modes are not studied. The results obtained for rigid baffle case are comparable with the existing results. The coupled vibration frequencies of the tank-flexible-baffle system are computed considering the effect of sloshing of liquid.     

圆柱形通道结构橡胶声障板

本文介绍了具有圆柱通道的橡胶水声反声障板的机理，通过静态近似得到此种橡胶声学参数的计算公式，测试了相关材料的动态力学性能，并对障板的声学特性进行了理论计算和分析，给出了不同频率下的反声性能随材料损耗因子、剪切模量及厚度的变化规律，并对模型进行了试验验证。