【作者】 张虎；

【导师】 戴景民；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2010， 博士

【摘要】 尾焰温度是火箭发动机性能评估的重要参考依据,推进技术发展的需要对火箭发动机尾焰温度测量提出了越来越高的要求。然而当前固体火箭发动机尾焰温度测量的研究比较多,对液体火箭发动机透明尾焰温度测量的研究还比较少。本课题主要研究可用于液体火箭发动机尾喷焰研究的相干反斯托克斯拉曼散射(CARS: Coherent Anti-Stokes Raman Spectroscopy)火焰温度测量技术,为评估液体火箭发动机燃烧效率、分析燃烧机理进而改进发动机设计提供参考。在对CARS信号光强理论、理论光谱计算、测量方法及测量方案设计进行研究的基础上,将结合参考光路的单脉冲双泵浦CARS测量方法应用于燃烧火焰温度测量研究中,并对影响测量准确性的可能因素进行了分析。主要完成了以下几方面的研究工作:1.设计了单脉冲双光路双泵浦BOXCARS测量系统,具备对温度梯度大、不稳定燃烧火焰流场进行实时测量的能力,并能够抑制非共振背景信号,提高信噪比。双泵浦方法保证了多组分的测量能力,在适当调整可调谐光源输出频率的前提下,能够同时得到两种成分的CARS光谱,不但可以通过与理论光谱的拟合得到温度信息,理论上还能通过与非共振背景信号的对比得到目标组分浓度信息。以检验CARS测量设备准确性为出发点,提出了CARS校准系统设计方案。2.在对CARS基本理论进行深入阐述的基础上,对已有CARS理论模型进行了适度简化和改进。从非线性光学基础理论出发,导出了CARS信号光强度的耦合波方程,给出了CARS光强表达式,对影响到信号光强度的光源线宽、光源线型、相位匹配条件、相干长度以及三阶非线性极化率分别进行了探讨。给出了通过解密度矩阵的方法推导三阶非线性极化率的数学模型的过程。阐述了非共振极化率在信号光形成中的影响及抑制方法,重点讨论了共振极化率的光谱计算。对三阶非线性共振极化率表达式中拉曼线宽、拉曼散射截面及跃迁能级之间的粒子数密度差的计算分别进行了详细讨论。3.在CARS经典理论模型的基础上,对基于传统CARS测量方法拓展的多色CARS方法及电子共振增强(ERE: Electronic-Resonance-Enhanced)CARS方法进行了深入讨论。对双泵浦CARS及双宽带CARS方法从原理上进行了探讨,并给出了理论模型。针对双泵浦方法存在的问题,提出了改进方法,扩展了适用范围,并给出了基于双泵浦方法的测量方案。对双宽带方法的相位匹配关系进行了详细计算,证明了在双光束过程相位匹配关系成立的情况下,三光束过程的相位匹配关系也是必然成立的。对ERE-CARS基本原理进行了讨论,对一氧化氮分子的ERE-CARS方法下的三阶非线性极化率模型进行了推导,并设计了可用于极低浓度一氧化碳CARS测量的ERE-CARS测量方案。4.以火焰喷枪PT-500产生的丁烷/空气扩散火焰为测量对象,以氮气为探针分子进行了CARS温度测量实验研究,并将测量结果与热电偶测量结果进行了对比,对可能影响两者之前存在差值的因素进行了分析。实验结果表明,CARS温度测量误差在800K以上约为70K,在500K~800K之间约为40K。论文研究成果对火箭尾焰温度场测量具有一定的理论意义和实用价值。更多还原

【Abstract】 Flame temperature is important for rocket engine evaluation. With the development of propulsion technology, higher demand for flame temperature measurement is put forward. This paper is to develop a Coherent Anti-Stokes Raman spectroscopy (CARS) temperature measurement system which can be used for estimating combustion efficienty of the liquid-propellant rocket engine, analyzing combustion mechanism, and providing modified design for rocket engine.Relative theory, methods and theoretical calculations of spectra are systematically studied. On this basis, the single-pulse dual-pump CARS technique combining reference optical system has been successfully applied to the measurement of temperature field for high-temperature combusting flame, with in-depth analysis of the impact of possible factors that may affect the measurement accuracy. The main researches are listed as follows:1. For the needs of this research, we have developed a single-pulse double-pumped BOXCARS measuring device include the reference optical circuit, which can perform real-time measurement of high-temperature combusting flame flow field with very high temperature gradient and great instability, and also can conduct effective suppression of non-resonant background noise. Since dual-pump methods ensure a multi-component measurement capability, with the premise of appropriate adjustments in the output frequency of the light source, we can obtain two components of the CARS spectra simultaneously. Then we can not only obtain the temperature information by fitting with the theoretical spectrum, but also can obtain the concentration information by comparing with non-resonant background signal. Finally we proposed to design CARS measurement equipment for testing the accuracy of the equipments.2. After in-depth analyzing the basic theory of CARS, we also simplified and developed the theoretical model of CARS appropriately: From the basis of nonlinear optical theory, we have derived the coupled-wave equations of CARS signal intensity, presented the expression of CARS light signal intensity, and also discussed the factors that may affect the light signal intensity such as light source linewidth, light source linetype, phase-matching conditions, coherence length and third-order nonlinear polarizability. Then we derived the mathematical model of third-order nonlinear polarizability by using density matrix. By comparison of resonant polarizability with non-resonant polarizability, the role of non-resonant polarization in the formation of optical signal is analyzed, focusing on the calculation of spectral resonance polarizability. Also we have elaborated the calculation of Raman linewidth, Raman scattering cross section, transitions between energy levels of the particle number density difference that are crucial in the third-order nonlinear susceptibility expressions.3. Based on the theoretical model of CARS, we have in-depth discussed the multi-color CARS method extended from the traditional CARS measurement method and the Electronic-Resonance-Enhanced method (ERE). The principles of dual-pump CARS and dual-broadband CARS approaches are investigated, followed by the analysis of its feasibility and advantages over traditional methods before the final theoretical model is given. In terms of the existing problems of dual-pump methods, we have designed the methods to improve the performance and extend the applicable scope, as well as the dual-pump-based measurement methods. Based on the detailed calculation of phase matching based on dual-broadband methods, it is proved that the three-beam phase matching relationship is bound to hold provided that the two-beam phase matching relationship holds. Based on the discussion of principles of ERE-CARS, we have elaborated the advantages and applications of ERE-CARS and also derived the third-order nonlinear polarizability model of nitric oxide molecules based on the ERE-CARS method, as well as designed the scheme of ERE-CARS measurement that can be applied to measuring carbon monoxide in extremely low concentration circumstances based on CARS measurements.4. For the experiment object of butane / air diffusion flame that is generated by flame spray gun PT-500, we have carried out the experiments with nitrogen as the probe molecular. The measurement results of the proposed method and that of thermocouple measurement are compared and the factors that may contribute to the difference were analyzed. The experimental results show that, the CARS measurement error of temperature is about 70K when the temperature is higher than 800K and about 40K when the temperature is between 500K and 800K.Researches in this paper are valuable for rocket flame temperature distribution determination.更多还原