【作者】 李麦亮；

【导师】 周进；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2004， 博士

【摘要】 本文针对发动机燃烧机理研究的需要,以燃烧流场的温度和组分浓度测量为主要目标,系统地研究了相干反斯托克斯拉曼光谱（CARS:Coherent Anti-Stokes Raman spectroscopy）技术,激光诱导荧光光谱（LIFS:Laser-Induced Fluorescence Spectroscopy）技术和平面激光诱导荧光（PLIF:Planar Laser-Induced Fluorescence）技术,尤其对于CARS的单脉冲测量、CARS测温的准确性以及LIFS测量转动温度等进行了重点研究。在此基础上,将激光光谱诊断技术应用于超燃机理研究和火箭发动机燃烧过程研究,对超燃火焰结构的形成机理、凹腔的作用机理等进行了深入探讨。 在阐述了CARS的理论要点之后,对CARS光谱的理论仿真方法和实验测量方法进行了研究。通过对激光能量分配、激光模式控制、空间滤波和相位匹配等进行分析,提出了对这些实验设置进行优化的方法,实现了CARS的单脉冲（高时间分辨）测量。通过与热电偶的比较,研究了CARS测温的准确性。对CARS和热电偶在平面火焰中测温结果存在偏差的原因进行了深入分析,提出了层流预混火焰中可能存在的热力学非平衡会对氮气Q支CARS测温准确性产生影响的假设。 研究了基于双线扫描激发、谱积分求取宽带荧光强度的LIFS测温方法。从基本的激光诱导荧光理论出发,推导了该方法的测量原理。通过激发氢氧基A²∑←X²Π（1,0）跃迁的Q₁（8）和Q₁（5）线,得到了LIFS测量的平面火焰氢氧基转动温度。测量结果支持关于所研究的平面火焰中存在热力学非平衡的假设。 研究了利用单线激发PLIF技术测量氢氧基组分分布的方法,通过激发对温度变化不敏感的氢氧基A²Σ←X²Π（1,0）跃迁的Q₁（8）线得到了火焰的氢氧基分布图像。将氢氧基分布的PLIF图像与自发发射图像对比,分析了几种典型火焰的特点。 使用氢氧基PLIF技术研究了氢气/空气超燃火焰的结构,分析了可能影响燃烧性能的主要因素,特别指出湍流扩散是该超声速火焰的主要控制过程。对PLIF测量结果与数值仿真结果进行了对比,发现使用氢氧八方程化学反应模型和标准双方程k-ε湍流模型的数值仿真可以模拟超燃火焰的主要结构特征,但难以模拟湍流火焰的细节。 利用氢氧基PLIF技术,研究了氢气横喷的超燃流场中凹腔促进点火和稳定火焰的机理,发现凹腔的安装位置与燃料喷注位置的关系对发挥其促进点火的功能有影响,并且凹腔是通过持续“点燃”主流发挥其稳定火焰的作用的。研究了凹腔长深比、后缘倾角对超声速燃烧火焰结构的影响,发现火焰结构对于后缘倾角较为敏感。分析了燃料喷注方式,流动干扰对超声速燃烧过程的影响,结果显示对凹腔附近的剪切层施加干扰可有效改变燃料的混合扩散,进而改善燃烧效果。研究了氢气引燃的酒精超声速燃烧火焰,分析了酒精更多还原

【Abstract】 For the purpose of the temperature and species concentration measurement, Coherent Anti-Stokes Raman Spectroscopy (CARS), Laser-Induced Fluorescence Spectroscopy (LIFS) and Planar Laser-Induced Fluorescence (PLIF) were studied systemically. Emphases of these studies were put on the single pulse CARS measurement, the accuracy of CARS and the rotational temperature measurement using LIFS. On the basis of above studies, laser spectroscopy technologies were applied to supersonic combustion diagnosis and research on combustion in the rocket engine. And then, mechanisms of the formation of flame structure in supersonic combustion, influence of cavities and so on were discussed.After the theory of CARS and methods of theoretical simulation of CARS spectrum were summarized. The experimental measurements were studied and improved. After setups of some key parameters of CARS system have been optimized, the single pulse measurement of temperature of CARS was realized. Results of temperature measurement using single pulse and multi-pulse mode nitrogen Q-branch CARS were then studied in detail. The accuracy of measurements was discussed as an emphasis. Discrepancy between temperature measured respectively by thermocouple and CARS in a plane flame was discussed. It was found that accuracy of temperature measurements of CARS in flames is probably influenced by the state of thermal equilibrium in area where reaction is still going on. This is a new theory hypothesis of CARS measurements.It was studied that the method of temperature measurement using LIFS. It was proposed that a new method based on that double lines were excited by means of laser wavelength scanning and intensity of broad band fluorescence was expressed with spectral integral. The measurement principle of this method was deduced from basic theory of Laser-Induced Fluorescence (LIF). The rotational temperature of OH in the plane flame was measured by LIFS after line Q1(5) and Q1(8) of transition A2∑ ← X2 (?) (1, 0) were excited. The LIFS measurement supported the hypothesis about that the accuracy of CARS measurements could be influenced by the thermal non-equilibrium state of the flame.The PLIF technology to measure the distribution of OH by means of the single transition being excited was studied. After Q1(8) of the transition A2∑← X2 (?) (1 , 0) of OH had been excited, PLIF images of OH distribution in flames were got. While such PLIF images of OH in several kinds of typical flames were compared to the spontaneous emission images of radicals,flame structures of these typical flames were analyzed.The OH PLIF technology was then used to study the flame structure of H2/air supersonic combustion. Those important factors that maybe influence the combustion performance were analyzed. Especially, it was concluded that the turbulent diffusion is the most significant process of this supersonic combustion. While the flame structure was analyzed, comparison was done between the PLIF image and the CFD result. It is found that simulation using the 8 equations model of hydrogen and oxygen reaction and the standard double equations turbulent model can describe the main topologic structure of supersonic flame. However, it can not describe the detail and instantaneous structure of turbulent flame.The mechanism of the cavity to improve ignition performance and to hold the flame in the supersonic combustion flow was studied using OH PLIF technology. It is believed that the relation between the location of the cavity being installed and the location hydrogen being sprayed will probably influence the performance of cavity to ignite the flame. And also, it is believed that cavities hold the flame by means of "igniting" the main flow continuously. The influenc of the ratio of length to depth and obliquity of back edge of the cavity were studied. It is found that the flame structure is sensitive to the obliquity of back edge of the cavity. Influenc of the scheme of fuel injection and the disturbance on flow were analyzed with OH PLIF images. The results of analyses showed that disturbance on shear layer near cavity can effectively change mixing and diffusing process of the fuel, and then improve combustion. Research was conducted on alcohol/air supersonic combustion ignited by the hydrogen flame. Impacts upon ignition and forming of flame structures of alcohol injection, evaporation and so on were studied.Temporally-resolved temperature measurements were carried out in a H2/air supersonic combustion using the single pulse N2 Q-branch CARS. In comparison with the measurement results in the stable flame, temperature in the supersonic flame is obviously fluctuating. The measurements also manifested that temperature is not equivalent spatially.By means of the comparison being done among OH PLIF images, spontaneous emission images and CFD results, distribution of OH radicals and temperature of plume were studied. PLIF images showed that processes of the hydrogen/oxygen combustion and the hydrogen/-oxygen/alcohol combustion are under the different controlling mechanism respectively. The intensive spontaneous emission of flames in the rocket engine makes it possible to diagnose combustion using the spontaneous emission. At the mean time, flame structures of the combustion of the different combination of kerosene, alcohol, oxygen and hydrogen were studied using the ultraviolet spontaneous emission. The feasibility of CARS measurements was demonstrated in a model tri-propellant rocket engine. Measurement results of nitrogen Q-branch CARS showed that temperature and species concentration will be affected by the hydrogen massflowrate in the model tri-propellant rocket engine.The work of this paper can be divided into two parts: studies of laser spectroscopy technologies and studies of application of these technologies to combustion diagnosis in a jet engine. Both parts of work concluded some innovative results, especially in researches on optimization of CARS measurements, CARS measurement accuracy, temperature measurements using LIFS, mechanism of the supersonic combustion, and so on.更多还原