【作者】 杨超；

【导师】 黄向东；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2024， 硕士

【摘要】 叶尖间隙作为航空发动机装配过程中的一个重要的测量指标,其大小对发动机的安全性、燃料利用率和工作效率等有着重要的影响,实现发动机叶尖间隙的精确、快速测量是一项重要的研究课题。光谱共焦测量是一种新兴的光学测量方法,其具有精度高、测量范围大、非接触等优点,近年来在电子和半导体、汽车、金属、电池、薄膜和医疗等领域有着越来越广泛的应用,本课题围绕光谱共焦测量叶尖间隙应用过程中探头体积过大、光能利用率低的问题展开了以下光纤式光谱共焦测量技术的研究:(1)为缩小光谱共焦探头体积,本文提出基于自聚焦透镜的色散探头的研究,通过自聚焦透镜成像理论研究,得到透镜成像过程中数值孔径、物像关系和色散模型,同时基于菲涅尔衍射理论得到成像过程中的光场分布,进而得到透镜的共焦模型,结合色散模型得到自聚焦透镜的光谱共焦模型,依据该模型和发动机叶尖间隙的测量需求,设计得到了基于自聚焦透镜的双透镜结构色散物镜,并对其进行集成化探头设计,探头在500nm-650nm的光谱范围下的各项测量指标为工作距2.7mm,测量范围3mm,探头外形尺寸为6mm×37mm,以上各项指标能够较好的满足发动机叶尖间隙的测量需求。(2)为提高光纤式光谱共焦光能利用率,开展了基于自聚焦透镜的光纤耦合的研究,包括LED光学模型建立、LED-阶跃式光纤耦合模型的建立,得到通过增大最大耦合角度可以提高耦合效率的结论,基于该结论和凸面自聚焦透镜的成像性质,设计基于凸面自聚焦透镜的耦合光路,并对该光路进行消色差优化,减小因波长差异而造成的耦合效率不一致的问题,最终耦合数值孔径达到0.65。(3)通过基于凸面自聚焦透镜、平面自聚焦透镜和无自聚焦透镜的耦合光路的对比实验,在535nm波长下,两种基于自聚焦透镜的耦合光路耦合效率分别提升32%、30%,在635nm波长下,耦合效率分别提升38%、34%。通过实验验证基于自聚焦透镜色散探头的各项性能指标,探头工作距2.75mm,通过在测量范围内进行多项式曲线拟合方法,矫正非线性误差,拟合所得测量特性曲线的拟合误差为0.4μm;通过双透镜、单透镜结构探头的对比实验,证明增大探头像方数值孔径,可提高系统的分辨力,双透镜探头分辨力达到0.7μm;进一步测试了基于自聚焦透镜探头的光谱共焦测量系统的短时稳定性和重复性,短时稳定性实验标准差为0.1μm;重复性实验标准差0.2μm,实验结果符合发动机叶尖间隙测量的需求。更多还原

【Abstract】 The tip clearance is an important measurement indicator during the assembly process of aviation engines,and its size has significant effects on engine safety,fuel efficiency,and operational efficiency.Achieving precise and rapid measurement of the tip clearance is an important research topic.Spectral confocal measurement is an emerging optical measurement method with advantages such as high precision,large measurement range,and non-contact capability.In recent years,it has been increasingly applied in various fields such as electronics and semiconductors,automotive,metals,batteries,thin films,and medical.This study focuses on the application of spectral confocal measurement in measuring tip clearance and addresses the issues of probe volume and low optical utilization.The following fiber optic spectral confocal measurement techniques are researched:(1)To reduce the volume of spectral confocal probes,this study proposes research on dispersion probes based on GRIN lenses.By studying the imaging theory of GRIN lenses,the numerical aperture,object-image relationship,and dispersion model during lens imaging are obtained.Based on Fresnel diffraction theory,the light field distribution during imaging is derived,and the confocal model of the lens is obtained.Combining the dispersion model,the spectral confocal model of the GRIN lens is derived.Based on this model and the measurement requirements of engine tip clearance,a dual-lens structure dispersion objective based on GRIN lenses is designed.Integrated probe design is performed,and the performance indicators of the probe in the spectral range of 500nm-650 nm are: working distance 2.7mm,measurement range 3mm,and probe outer dimensions 6mm × 37 mm.These indicators can effectively meet the measurement requirements of engine tip clearance.(2)To improve the optical utilization efficiency of fiber optic spectral confocal,research on fiber coupling based on GRIN lenses is conducted.This includes establishing LED optical models and LED-step fiber coupling models.It is concluded that increasing the maximum coupling angle can improve coupling efficiency.Based on this conclusion and the imaging properties of convex GRIN lenses,a coupling optical path based on convex GRIN lenses is designed.Chromatic aberration optimization is performed on this optical path to reduce the problem of inconsistent coupling efficiency caused by wavelength differences.The numerical aperture of the coupling reaches 0.65.(3)Through comparative experiments of coupling optical paths based on convex GRIN lenses,planar GRIN lenses,and no GRIN lenses,at a wavelength of 535 nm,the coupling efficiency of the two GRIN lens-based coupling optical paths increased by 32%and 30%,respectively.At a wavelength of 635 nm,the coupling efficiency increased by38% and 34%,respectively.The performance indicators of the GRIN lens dispersion probe are validated through experiments.The working distance of the probe is 2.75 mm.By using polynomial curve fitting within the measurement range,non-linear errors are corrected,and the fitting error of the measured characteristic curve is 0.4μm.Through comparative experiments of dual-lens and single-lens structure probes,it is demonstrated that increasing the numerical aperture of the probe can improve the system’s resolution.The resolution of the dual-lens probe reaches 0.7μm.Furthermore,the short-term stability and repeatability of the spectral confocal measurement system based on GRIN lens probes are tested,with a standard deviation of 0.1μm for short-term stability and 0.2μm for repeatability.The experimental results meet the requirements of engine tip clearance measurement.更多还原