超大口径全可动望远镜结构选型及精度控制

发布时间：2018-06-11 11:01

本文选题：全可动射电望远镜 + 反射面精度　；参考：《哈尔滨工业大学》2013年博士论文

【摘要】：中科院、国家发改委及新疆自治区将在奇台建造一口直径为110m的地面全可动射电望远镜。建成投入使用后，其口径将成为世界之最，性能将达到国际领先水平。然而建造如此超大跨度的望远镜，从结构技术角度最为突出的问题如下：传统结构方案存在若干不合理之处，仅自重作用就显著降低了主反射面精度（也称主反射面RMS），制约了其性能的发挥；同时迎风姿态多样造成主反射面风压分布复杂以及日照作用引起的非均匀温度场，均严重影响了主反射面RMS值；此外，电磁波在副反射面聚焦而产生的“太阳灶”效应也应引起重视。围绕上述关键科学问题，以控制主反射面RMS值为主线，提高主反射面精度为目标，本文拟从如下四方面展开研究： 1、射电望远镜结构总体方案改进与优化以提高主反射面精度为目标，首先对全可动望远镜结构工作原理及反射面RMS拟合方法进行介绍；其次分析了传统结构方案精度较低的本质原因为：主反射面存在集中荷载作用、背架结构支承方案不合理、背架结构体系空间受力性能不佳。基于此，分别对其进行改进或创新，提出了一种新型高效的全可动望远镜结构总体方案，有效的提高了反射面精度。 2、背架结构截面优化、几何参数分析与最佳安装角度的确定以主反射面精度为优化目标，引入遗传算法并进行改进，，对背架结构进行截面优化，获得了一组较优的截面尺寸；在此基础上，对除截面尺寸以外的其它几何变量进行参数分析，探讨了它们对反射面RMS的影响程度。同时，仍以提高反射面精度为目标，利用梯度法的基本思想对望远镜背架结构的最佳安装角度进行了优化确定。 3、反射面结构风荷载特性及其对精度的影响采用风洞试验和CFD数值模拟相结合的研究方案，对一类典型反射面（焦径比为0.3）结构展开各迎风姿态下的风荷载及风振响应特性分析，获得了适用于该类结构设计的风荷载取值。基于此，对既定的望远镜结构分别进行了生存风速和工作风速下的结构性能分析，评估了望远镜结构的力学可靠性，探讨了各类荷载对反射面RMS的影响，为后续反射面促动器的变形调控提供参考依据。 4、日照非均匀温度场特性及其对反射面精度的影响以主、副反射面为研究对象，采用瞬态传热有限元分析方法，建立了综合考虑太阳辐射、空气对流换热、阴影遮挡等因素的望远镜整体结构日照温度场精细化数值模型。并选取最不利工况对其进行日照作用分析，获得了望远镜变位中该作用对主反射面RMS的全过程影响，以及电磁波聚焦在副反射面产生的“太阳灶”效应的时间及空间分布特性。
[Abstract]:The Chinese Academy of Sciences, the National Development and Reform Commission and the Xinjiang Autonomous region will build an all-mobile radio telescope with a diameter of 110 meters. When built and put into use, its caliber will be the world's largest and its performance will reach the international leading level. However, the construction of such a large span telescope, The most outstanding problems from the point of view of structure technology are as follows: there are some unreasonable points in the traditional structural scheme. The precision of the main reflector is significantly reduced by self-weight only (also known as the main reflector RMSN, which restricts the performance of the main reflector); At the same time, the complex distribution of wind pressure on the main reflector and the non-uniform temperature field caused by the effect of sunlight seriously affect the RMS value of the main reflector due to the variety of upwind attitude. The "solar cooker" effect caused by electromagnetic wave focusing on the secondary reflection surface should also be paid attention to. According to the above key scientific problems, the main line is to control the RMS value of the main reflector and to improve the accuracy of the main reflector. In this paper, the following four aspects are proposed: 1. The improvement and optimization of the radio telescope structure is aimed at improving the accuracy of the main reflector. Firstly, the principle of the structure of the fully movable telescope and the RMS fitting method of the reflector are introduced. Secondly, the essential reasons of the low precision of the traditional structural scheme are analyzed: the main reflection plane has concentrated load, the backframe structure support scheme is unreasonable, and the spatial mechanical performance of the backframe structure system is not good. Based on this, this paper improves or innovates it separately, and puts forward a new and efficient overall scheme of fully movable telescope structure, which effectively improves the accuracy of reflection surface. 2. The cross-section optimization of the back frame structure. The geometric parameter analysis and the determination of the optimum installation angle take the precision of the main reflector as the optimization objective, introduce and improve the genetic algorithm to optimize the cross-section of the backframe structure, and obtain a group of better cross-section dimensions. The parameter analysis of other geometric variables except section size is carried out and the influence of them on the RMS of reflectors is discussed. At the same time, the goal is to improve the accuracy of the reflector. Using the basic idea of gradient method, the optimum installation angle of the telescope back frame structure is optimized. 3. The wind load characteristics of the reflector structure and its influence on the accuracy are studied by the combination of wind tunnel test and CFD numerical simulation. The wind loads and wind-induced response characteristics of a class of typical reflector structures with focal diameter ratio of 0.3 are analyzed under different upwind positions. The values of wind loads suitable for the design of this kind of structures are obtained. Based on this, the structural performance analysis of the established telescope structure under the survival wind speed and the working wind speed is carried out, and the mechanical reliability of the telescope structure is evaluated, and the influence of various loads on the RMS of the reflector is discussed. 4. The characteristics of inhomogeneous temperature field of sunlight and its influence on the accuracy of reflector are studied by using transient heat transfer finite element analysis method. A refined numerical model of solar temperature field of the whole telescope structure considering solar radiation, air convection heat transfer and shadow occlusion is established. The effects of this effect on the RMS of the main reflector and the temporal and spatial distribution characteristics of the "solar cooker" effect caused by the electromagnetic wave focusing on the secondary reflector are obtained.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH751

【相似文献】