大口径地基太阳望远镜主动温控技术研究

发布时间：2018-12-14 05:59

【摘要】：随着口径的增大和开放式结构的采用,热光阑和主镜的主动温控技术成为了地基开放式太阳望远镜的关键技术之一。由于我国首台大口径开放式地基太阳望远镜——1.8米口径中国大型太阳望远镜(Chinese Large Solar Telescope,CLST)研制项目的立项,亟需针对大口径地基太阳望远镜主动温控技术开展相关研究。本文围绕地基开放式太阳望远镜主动温控技术和CLST主动温控系统实施需求,开展了深入的理论和应用研究。第一,对热光阑内部视宁度效应进行了理论研究,提出了一种内部视宁度效应定量计算方法。该方法首先基于计算流体动力学理论,获得过热热光阑加热后的空气温度场;然后,利用相关公式将温度场转化为折射率场;最后,基于几何光学理论,获得光束经过折射率场后形成的畸变波前,实现对热光阑内部视宁度效应的定量计算。本文将该方法应用于CLST热光阑内部视宁度效应定量计算,获得了热光阑温升与望远镜成像像质间的定量关系,并给出了CLST热光阑温控指标。第二,对热光阑冷却结构设计方法进行了理论研究,提出了一种基于射流冷却原理的新型热光阑冷却结构设计方法。通过流固耦合仿真,证明该新型冷却结构设计方法有效提升了热光阑冷却腔内流固耦合面的换热系数,能够显著提高热光阑的冷却效率。第三,对太阳望远镜镜面视宁度效应进行了定量计算,建立了镜面温升、环境风速和望远镜成像像质间的定量关系,并给出了CLST主镜镜面温控指标。第四,建立了太阳望远镜主镜传热理论模型,该模型可应用于主镜热分析。相比于传统有限元法,该方法具有快速、准确的优势。第五,基于站址环境温度数据和局部视宁度效应分析结果,给出了主动温控系统设计指标。结合热光阑及主镜传热特性,完成了主动温控系统设计。基于600mm口径开放式太阳望远镜实验样机(Prototype of Open Solar Telescope,POST),搭建了主动温控系统实验平台,对主动温控系统分别进行了极限能力测试、室内和外场温控实验。实验结果表明,POST主动温控系统满足各项设计指标,其中,热光阑和主镜主动温控系统的平均温控误差分别为0.31K和0.288K。此外,还对热光阑热分析方法和主镜传热理论模型进行了实验验证。针对大口径地基太阳望远镜主动温控这一关键技术,本文进行了深入研究,对大口径地基太阳望远镜主动温控技术所涉及的一些理论和工程问题提出了具体的解决方法和方案;同时,为我国CLST主动温控系统的实施提供了完整的技术路线。
[Abstract]:With the increase of aperture and the adoption of open structure, the active temperature control technology of thermal diaphragm and primary mirror has become one of the key technologies of the ground-based open solar telescope. Because of the establishment of the development project of the first large-caliber open ground-based solar telescope, the 1.8-meter Chinese large Solar Telescope (Chinese Large Solar Telescope,CLST), Research on active temperature control technology for large-caliber ground-based solar telescope is urgently needed. This paper focuses on the requirements of active temperature control technology for ground-based open solar telescope and CLST active temperature control system. Firstly, a quantitative calculation method for the internal apparent nailing effect of thermal diaphragm is proposed, which is based on the theoretical study of the internal apparent nailing effect. Based on the computational fluid dynamics theory, the air temperature field of the superheated diaphragm is obtained, and then the temperature field is transformed into the refractive index field by using the correlation formula. Finally, based on the theory of geometrical optics, the distorted wavefront formed by the beam passing through the refractive index field is obtained, and the quantitative calculation of the internal viewing effect of the thermal aperture is realized. In this paper, the method has been applied to the quantitative calculation of the apparent Nine effect in the thermal aperture of CLST. The quantitative relationship between the temperature rise of the thermal aperture and the imaging image quality of the telescope has been obtained, and the temperature control index of the thermal aperture of the CLST has been given. Secondly, the design method of thermal diaphragm cooling structure is studied theoretically, and a new design method of thermal diaphragm cooling structure based on jet cooling principle is proposed. Through the fluid-solid coupling simulation, it is proved that the new cooling structure design method can effectively enhance the heat transfer coefficient of the fluid-solid coupling surface in the thermal diaphragm cooling cavity, and can significantly improve the cooling efficiency of the thermal diaphragm. Thirdly, quantitative calculation of the effect of mirror apparent Nine on the solar telescope is carried out, and the quantitative relationship among mirror temperature rise, ambient wind speed and imaging image quality of the telescope is established, and the CLST primary mirror surface temperature control index is given. Fourthly, a theoretical model of heat transfer in primary mirror of solar telescope is established, which can be applied to thermal analysis of primary mirror. Compared with the traditional finite element method, this method has the advantage of rapidity and accuracy. Fifthly, the design index of active temperature control system is given based on the temperature data of site and the result of local visual effect analysis. The active temperature control system is designed based on the heat transfer characteristics of the thermal diaphragm and primary mirror. Based on the experimental prototype of 600mm open solar telescope (Prototype of Open Solar Telescope,POST), the experimental platform of active temperature control system is set up. The limit capability of active temperature control system and the temperature control experiment of indoor and external field are tested respectively. The experimental results show that the POST active temperature control system meets the design requirements, and the average temperature control errors of the thermal diaphragm and primary mirror active temperature control system are 0.31K and 0.288K, respectively. In addition, the thermal analysis method of thermal diaphragm and the theoretical model of primary mirror heat transfer are verified experimentally. Aiming at the key technology of active temperature control of large aperture ground-based solar telescope, this paper makes a thorough study, and puts forward some theoretical and engineering solutions to the active temperature control technology of large aperture ground-based solar telescope. At the same time, it provides a complete technical route for the implementation of CLST active temperature control system in China.
【学位授予单位】：中国科学院研究生院(光电技术研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH743

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