| 题名 | 有限元方法在高功率激光驱动装置中的应用 |
| 作者 | 任志远 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 朱健强 |
| 关键词 | 有限元方法 放大器 流场分析 热恢复 偏振片 支撑方式 |
| 其他题名 | The Application of Finite Element Method to the High Power Laser Facility |
| 中文摘要 | 激光惯性约束核聚变（Inertial Confinement Fusion，简称ICF）为世界提供了一个产生几乎无限清洁的可持续能源的方式。对本世纪愈来愈严重的的能源危机的解决方案有着深远的应用价值和科学研究意义。同时利用激光惯性约束聚变创造的条件，可在实验室开展有关高能量密度物理和国防科技应用的研究工作。由于核聚变过程中需要足够大的能量才可将靶丸压缩到高温高压的状态产生聚变反应。随着高功率激光驱动装置研究的深入，装置朝大型化、模块化和精密化的方向发展的趋势越来越明显。由于激光驱动ICF装置是一个大型的超精密光学系统，涉及的光学元件多，结构复杂，对结构的稳定性和环境的要求非常高。光学元件由于结构本身的因素以及外界的影响受到的力、热等因素的影响产生的变形，都将会影响到高能激光驱动装置的能量密度以及光束质量。 由于高功率激光驱动装置结构复杂，对高功率激光驱动系统内部的放大器等关键器件的流场及热恢复的的要求高；同时对光学元件的支撑系统要求严格。如果采用传统的设计方法，不仅需要大量的计算工作，甚至有些工作无法完成。而有限元方法为高功率激光驱动装置中的有关力学及热学问题提供了一种行之有效的解决方案。在高功率激光驱动装置中，无论是预放大系统中的棒状放大器还是主放大系统的组合式片状放大器，在工作过程中由于泵浦的关系都会产生一定的热量，因此这两种放大器的冷却系统的性能的优劣直接影响到打靶物理试验的成功。而由于在ICF驱动装置中需要高能量的激光光束，因此在装置中大型镜片的安装与支撑成为影响光束质量的重要因素。因此，对高功率激光驱动装置的关于热学及力学方面的有限元分析是非常重要的环节。而正确的建模是有限元方法的关键。 基于有限元方法，本文主要围绕高功率激光驱动装置的关键部件，对棒状放大器的冷却系统的流场，片状组合放大器的流场及热管理以及偏振片的支撑方式进行了优化。 首先，本文针对棒状放大器的冷却系统建立了有限元分析的物理模型和计算模型，分析了直流式进口，斜流式进口的冷却系统的流场。在对这两种进口方式的流场分析基础上，提出了棒状放大器的冷却系统的流场的优化模型，即采用改进的分流圈的进出口结构，使流体在冷却系统内形成环绕棒状放大器流动的环形流动，这种流动方式不仅有利于流场的压力分布的匀匀，而且对换热效果有明显的改善效果。在改进的环流流动中，正旋流动的流场又优于逆流流动的流场。 其次，片状组合放大器的热管理问题一直是高功率激光驱动装置中制约打靶频率及光束质量的瓶颈。本文在分析影响片状组合放大器热恢复因素的基础上，首次提出了在不增加冷却气体进气流量的基础上加速片状组合放大器的热恢复时间的方法。通过改变气体种类、进气喷嘴与壁面相对位置、进气温度、进气速度、喷嘴数量以及进气方式，系统的研究了影响片状放大器的各个因素对换热效果的影响。并且提出了换热均匀度的概念，利用均匀度公式可以有效科学的衡量换热效果的优劣。 最后，本文以倾斜放置偏振片作为有限元力学分析的一个典型例子，以板变形理论及支撑方式对变形的影响作为理论基础，分析了偏振片的长宽比，径厚比及支撑点数量对偏振片面型变化的影响。由于改变支撑点数量或者位置均无法改变偏振片的大变形区域与通光区域重合的问题，因此，本文创新性的提出一种边缘施加载荷的支撑方式，将镜片的最大变形区域由通光口径中心转移到通光口径以外的边缘区域，这种偏振片的支撑方式使通光区域的变形值远远小于传统的支撑方式。 本论文的工作为高功率激光驱动装置的热学和力学问题提供了一种有限元分析的方法。将这种方法应用于高功率激光驱动装置的关键部件的优化，为棒状放大器尤其是片状放大器冷却系统的流场分布及优化提供了有效的手段，首次从保持冷却流体体积流量恒定的情况下分析各个因素对热恢复的影响；在力学分析中，通过施加边缘预载的方式将偏振片的最大变形区域转移到通光口径以外。本论文的研究工作不仅在我国的高功率驱动装置的设计中具有指导意义，同时对国内外的高功率驱动装置也具有普遍的应用价值。 |
| 英文摘要 | Laser-driven Inertial Confinement Fusion (ICF) produced by the Fusion can provide the world with a produces an almost unlimited clean sustainable energy. In this century, It is far-reaching application value and scientific research significance for the more and more serious energy crisis solution. At the same time, research about the application of high energy density physics and the national defense science can be carried out in laboratory with laser inertial confinement fusion. The process of nuclear fusion need enough energy to pellet compressed to a state of high temperature and high pressure to produce fusion reaction. It is more and more obvious that the devices toward large-scale, modularization along with the development of high power laser drive. Because laser driver for ICF devices is a large ultraprecision optical system, optical element with more complex structure needs more stable and the environmental requirement is strict. the deformation produced by the structure itself and the influence of the environment such as force, heat, which will affect the energy density of high-energy laser driving device and the beam quality. Because of the high power laser driving device is more complicated, the requirements for the support system and the the flow field and heat recovery of key parts is strict. Using traditional design methods, not only need a lot of work, or even unable to complete some work. The finite element method for high power laser drive mechanics and thermodynamics provides an effective solution to the problem. In high power laser driving device, whether in the preamplifier system such as rod amplifier or four-pass amplification system, there will produce temperature gradient produced by the process of pump, so the performance of the cooling system directly affect the target of physical test. And the high-energy laser beam is needed in ICF driver device, so installation and support system for the lenses become the important factor of influence the beam quality. Therefore, the high power laser drivers device on mechanical and thermal finite element analysis is a very important. Based on finite element method, this article mainly around the key components in high power laser driving device, the cooling system of a rod amplifier of the flow field, flow field and the thermal management of disk amplifier and support system are optimized. At first, the finithe element model is established for the cooling system of the rod amplifier. The flow field of the cooling system with straight flow and oblique flow inlet.. Based on these flow field analysis, optimization model of flow field is put forward for the the cooling system of rod amplifier. with improvement for the inlet and outlet structures at the distributary circle, the fluid flows looply in the cooling system around the rod amplifier. there are better flow distribution field and coefficient of heat-exchange. Secondly, thermal management problem on the multi-segment amplifier restrict shooting frequency and the beam quality in the high power laser driver. Based on the analysis of influencing factors for the multi-segment amplifier in the process of heat recovery, the solution is presented to accelerate the thermal recovery time without increasing the cooling gas inlet flow at the first time. By changing the gas type, inlet nozzle with wall position, inlet temperature, inlet velocity, nozzle number and inlet mode, the research about the heat convection coefficient is study systematically. And put forward the concept of heat uniformity and evenness formula which can be used to effectively scientific measure of the heat transfer coefficient. Finally, based on plate deformation theory and the finite element method, tilt polarizer is study with different support way. And analyze the deformation with different length-width ratio, diameter thick and the number of support. The problem of coincide with the deformation position and the clear apeture can not influece the result with the change of number of support and the positon. therefore, in this paper, the way of preload on the mirror edge is put forward innovativly, which make the clear apeture deformation much smaller than traditional way of support. The work provides a kind of finite element analysis method for high power laser driving device of thermal and mechanical problem. This method was applied to the optimization of key components in high power laser driver devices, such as amplifier, especially multi-segment amplifier flow field distribution of the cooling system. Put forword the way of analysis of various factors to accerate the thermal recovery at the same cooling fluid flow at the first time. In mechanics analysis, the maximum deformation area is not coinciding with the clear apeture by applying preload at the edge of polarizer. Research of this paper not only has guiding significance for the design of high power laser drive device, at the same time has general application value for the high power laser device. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15751]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 任志远. 有限元方法在高功率激光驱动装置中的应用[D]. 中国科学院上海光学精密机械研究所. 2013. |
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