在各种新型发动机技术研究中，燃烧室内燃气温度分布是评估发动机性能和预测发动机寿命的重要依据。在多种测温技术中，光学方法以其不干扰流场的显著优点引起了研究人员的广泛关注。从可视化的角度而言，光学成像技术具有高时间、空间分辨率等优势，适用于具有高湍流度的瞬态流场诊断；从波长分辨的角度而言，火焰的发射光谱通常由化学自发光分子谱辐射、高温热致分子谱辐射以及微颗粒的宽带灰体辐射组成。化学发光结合计算层析算法可以表征火焰的三维结构和释热率的分布，对于发动机内燃烧组织和燃烧效率优化具有重要价值。燃烧产物中气态组分的准平衡态热致辐射能够表征火焰经典热力学温度，可以为燃气温度测量方法提供新手段。更进一步的，该方法能够与计算层析算法结合实现多维度温度测量，可能为发动机地面实验研究提供关键的温度场数据。

本文基于火焰自发辐射光谱特征，分别针对成像技术和光谱技术开展测试方法研究并给出典型应用，具体包括：

在成像技术研究方面，重点研究基于内窥式光纤束的多维成像方法和辐射功率的多维量化方法，首先研制了多视角内窥式光纤束成像系统，利用钨灯、黑体等标准光源对成像系统存在的光纤传输衰减、相机响应不均匀性及非线性等系统误差逐一进行了评估和修正，基于代数迭代算法(Algebraic Reconstruction Technique , ART)高精度重建火焰三维结构；其次，建立了相机输出灰度值与化学自发光辐射强度之间的映射关系，将三维火焰重建技术由定性研究火焰结构提升至定量测量辐射功率分布。

将多视角内窥成像技术应用于搭载于力学所JF24高焓激波风洞平台的超燃冲压发动机实验，测量了Mach 10圆截面超燃冲压发动机内部火焰结构。实验窗口内径仅8 mm，克服了圆形截面燃烧室内部成像难题。分束成像最大限度的降低了测试系统复杂度和成本，以一台高速相机实现20 kHz帧频的6个视角同步辐射成像。结合可调谐吸收光谱技术(Tunable Diode Laser Absorption Spectroscopy , TDLAS)研究了该脉冲试验台的有效试验时间，初步分析了氢气燃料在支板和壁面喷注两种模式下的超声速火焰脉动的特性。

在光谱技术研究方面，本文计算了燃烧气态产物的准平衡态热致分子辐射光谱，提出并发展了一种宽波段发射光谱积分比测温方法，分析了自吸收效应导致的光谱变化以及其对温度测量的影响。该方法最大限度降低了系统复杂度，测温上限也拓展至3000K以上。首先，计算分析了可见光-中红外的宽波段燃气辐射光谱特性，证实水蒸气光谱的高信噪比，并研究了900 nm~2500 nm的H₂O光谱结构、强度与气体温度的关联性；其次，利用甲烷\氧气平面层流火焰开展测温方法验证，在富氧、富燃和当量燃烧三种工况测量了不同高度燃气温度，证明了该方法的极高测温灵敏度；最后，在超燃直连台加热器内实测了2MPa下氢氧火焰温度，证实了该方法在高压环境的适用性。

将该测温技术拓展至多维测量。首先提出了自吸收光谱投影计算方法，模拟分析不同参数对测温精度的影响，发现大尺寸火焰和高压力会致使自吸收效应强化，进而使得温度测量结果严重偏离真值；其次，分析对比了非线性重建算法和线性重建算法，提出了一种基于代数迭代算法（ART）的多次线性重建方法，实现了较高重建精度，解决了自吸收下多维精确测温难题；最后，基于宽波段发射光谱积分比与多次线性重建方法，利用平移旋转束实验方案，测量了甲烷\氧气预混层流火焰及非预混射流火焰在不同工况下的多截面二维温度分布，在2000-2700K的温度范围内，该方法均展现出了高达10K的温度分辨能力。

In the study of various new engine technologies, the gas temperature distribution in the combustion chamber is an important basis for assessing engine performance and predicting engine life. Among the various temperature measurement techniques, optical methods have attracted a lot of attention from researchers for their remarkable advantage of not disturbing the flow field. From the perspective of visualization, optical imaging techniques have the advantages of high temporal and spatial resolution, and are suitable for the diagnosis of transient flow fields with high turbulence. In terms of wavelength resolution, the emission spectrum of a flame usually consists of chemically self-luminous molecular spectral radiation, high-temperature thermogenic molecular spectral radiation, and broadband gray-body radiation of micro-particles. Chemiluminescence combined with computational tomography algorithms can characterize the three-dimensional structure of flames and the distribution of heat release rates, which are of great value for the optimization of combustion organization and combustion efficiency in engines. The quasi-equilibrium thermogenic radiation of the gaseous component of the combustion products can characterize the classical thermodynamic temperature of the flame and can provide new means for gas temperature measurement methods. Further, the method can be combined with computational laminar algorithms to achieve multidimensional temperature measurements, which may provide critical multidimensional temperature data for engine experiments.

In this paper, based on the characteristics of flame spontaneous radiation spectrum, the test method research is carried out and typical applications are given for imaging and spectroscopic techniques, respectively. Specifically, it includes the following:

In the imaging technology research, the focus is on the multidimensional imaging method based on the endoscopic fiber bundle and the multidimensional quantification method of radiation power. Firstly, a multi-view endoscopic fiber bundle imaging system was developed, and the system errors such as fiber transmission attenuation, inhomogeneity and nonlinearity of camera response of the imaging system were evaluated and corrected one by one using standard light sources such as tungsten lamp and blackbody, and the three-dimensional structure of the flame was reconstructed with high precision based on the algebraic iterative algorithm (ART). Secondly, the mapping relationship between the camera output grayscale value and chemical self-luminous radiation intensity is established, and the 3D flame reconstruction technique is upgraded from qualitative study of flame structure to quantitative measurement of radiation power distribution.

The multi-view endoscopic imaging technique was applied to the JF24 test bench of the Institute of Mechanics, Chinese Academy of Sciences to measure the internal flame structure of Mach 10 circular-section scramjet engines. The experimental window has an inner diameter of only 8 mm, thus overcoming the challenge of imaging the interior of a circular-section combustion chamber. The split-beam imaging minimizes the complexity and cost of the test system and enables simultaneous radiometric imaging of six views at 20 kHz frame rate with a single high-speed camera. The effective test time of this pulsed test bench was investigated in combination with tunable absorption spectroscopy (TDLAS), and the characteristics of the supersonic flame pulsation of hydrogen fuel in both branch plate and wall injection modes were initially analyzed.

In the study of spectroscopic techniques, this paper calculates the quasi-equilibrium state thermogenic molecular radiation spectra of combustion gaseous products, proposes and develops a broad-band emission spectral integral ratio temperature measurement method, and also analyzes the spectral changes due to self-absorption effects and their effects on temperature measurement. The method minimizes the complexity of the system and extends the upper limit of temperature measurement to more than 3000K. First, the broad-band gas radiation spectral properties in the visible-mid-infrared are calculated and analyzed, confirming the high signal-to-noise ratio of the l water vapor spectrum, and the correlation between the structure and intensity of the H₂O spectrum from 900 nm to 2500 nm and the gas temperature is investigated. Secondly, the validation of the temperature measurement method was carried out by using methane \ oxygen plane laminar flow flame, and the gas temperature at different heights was measured in three working conditions of oxygen-rich, combustion-rich and equivalent combustion, and the extremely high temperature measurement sensitivity of the method was proved. Finally, the hydrogen-oxygen flame temperature at 2 MPa was measured in the heater of scramjet direct-connected bench to confirm the applicability of the method in high-pressure environments.

The temperature measurement technique is extended to multi-dimensional measurements. Firstly, a self-absorption spectral projection calculation method is proposed to simulate and analyze the effects of different parameters on the temperature measurement accuracy, and it is found that the self-absorption effect is intensified by large flame size and high pressure, which makes the temperature measurement results deviate from the true value seriously. Secondly, we analyzed and compared the nonlinear reconstruction algorithm and linear reconstruction algorithm, and proposed a multiple linear reconstruction method based on the algebraic iterative algorithm (ART), which achieves high reconstruction accuracy and solves the problem of accurate multidimensional temperature measurement under self-absorption. Finally, based on the integration ratio of broadband emission spectra and multiple linear reconstruction methods, combined with the translational rotating beam experimental scheme, the multi-sectional two-dimensional temperature distributions of methane-oxygen premixed laminar flame and non-premixed jet flame were measured under different working conditions, and the method showed a temperature resolution of up to 10 K in the temperature range of 2000-2700 K.