大口径水冷式激光腔镜热畸变分析与构型设计

发布时间：2018-06-11 14:05

本文选题：高能激光器 + 热畸变　；参考：《大连理工大学》2015年硕士论文

【摘要】：为保证激光器输出光束质量,必须将激光反射镜的反射面热畸变降低到允许范围内。主动水冷方式是抑制反射面热畸变的主要手段。但随着高能激光器的发展,常规水冷镜的结构形式已经难以满足针对大口径腔镜越来越高的要求。因此,有必要对高使役精度的大口径水冷镜进行研究。本文首先使用有限元方法对直流道水冷镜的常规结构进行分析,提出了镜体结构关键设计尺寸的设计原则。在单流道简化模型的基础上,研究出一种基于温度更新的计算方法,使用这种方法计算得到的温度场分布结果无论在趋势上,还是在数值上都与计算流体动力学(CFD)数值计算结果相差无几。随后,对直流道水冷镜的常规结构进行优化,设计出一种新型优化结构,可在流道换热能力有限的条件下,将镜面热畸变控制在较低的水平。对于大口径直流道水冷镜流阻大、散热不均的问题,本文又提出一种具有交指型流道结构的水冷镜新构型。针对新构型流场结构特点,从理论上推导出其设计准则。通过建立流热固耦合分析模型,对Φ150 mm水冷镜反射面的温度场和热变形进行了研究,并分别在总流量和总压降恒定两种条件下,将新构型与常规结构的性能进行了对比。数值模拟结果表明,新构型各冷却流道换热系数的一致性较好,当总流量恒定时,其镜面最大热变形相比直流道水冷镜下降约1/3,而x和y方向上的变形峰谷值则分别减小40%和60%。另外,新结构的流阻很小,在恒定压降条件下,可获得3倍于常规结构的冷却水流量,在降低镜面变形方面的优势更为显著。这为解决大尺寸激光镜的热变形问题提供了一个可行方案。为验证使用CFD数值方法分析Φ150 mm新构型流场的有效性,设计了通水实验以测试压力和流速。通过对比实验结果,可以认为数值分析结果具有足够的准确性。本文的研究内容为研制高使役精度的大口径激光水冷镜提供了可行的设计方案,后续还要对其制作工艺进行深入研究。
[Abstract]:In order to ensure the laser output beam quality, the thermal distortion of the reflection surface of the laser mirror must be reduced to the allowable range. Active water cooling is the main method to restrain the thermal distortion of reflection surface. However, with the development of high energy lasers, the structure of conventional water-cooled mirrors has been difficult to meet the increasing requirements for large aperture mirrors. Therefore, it is necessary to study the large diameter water-cooled mirror with high precision. In this paper, the finite element method is used to analyze the conventional structure of the DC channel water-cooled mirror, and the design principle of the key design dimensions of the mirror structure is presented. On the basis of the simplified model of single channel, a new method based on temperature update is developed. The results of temperature field distribution are calculated by using this method, regardless of the trend. The numerical results are almost the same as those obtained by CFDs (Computational fluid Dynamics). Subsequently, the conventional structure of the DC channel water-cooled mirror is optimized, and a new type of optimization structure is designed, which can control the thermal distortion of the mirror at a lower level under the condition of limited heat transfer capacity of the flow channel. For the problem of large diameter DC channel water-cooled mirror with large resistance and uneven heat dissipation, a new configuration of water-cooled mirror with intersecting channel structure is proposed in this paper. According to the characteristics of the new configuration flow field, the design criteria are deduced theoretically. The temperature field and thermal deformation of the reflecting surface of 桅 150mm water-cooled mirror are studied by establishing a fluid-thermal-solid coupling analysis model. The performance of the new configuration is compared with that of the conventional structure under the condition of constant total flow rate and constant pressure drop. The numerical simulation results show that the heat transfer coefficients of each cooling channel of the new configuration are consistent. When the total flow rate is constant, the maximum thermal deformation of the mirror is about 1 / 3 lower than that of the DC channel water-cooled mirror, while the peak and valley values of deformation in the x and y directions are reduced by 40% and 60%, respectively. In addition, the flow resistance of the new structure is very small, under the condition of constant pressure drop, the cooling water flow rate of the new structure can be obtained 3 times than that of the conventional structure, and the advantages of the new structure in reducing the deformation of the mirror surface are more obvious. This provides a feasible scheme for solving the problem of thermal deformation of large size laser mirror. In order to verify the validity of the CFD numerical method for analyzing 桅 150mm new configuration flow field, a water diversion experiment was designed to measure the pressure and velocity of flow. By comparing the experimental results, it can be concluded that the numerical results are accurate enough. The research content of this paper provides a feasible design scheme for the development of large aperture laser water-cooled mirror with high precision.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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