为了测量燃烧场的热力学性质,研究了分子滤波瑞利散射技术.分子滤波瑞利散射技术采用窄线宽激光器、分子滤波器和像增强CCD相机,通过分子吸收凹陷检测激光片照射流场产生散射光的频谱,抑制背景杂散光和米散射,解析流场热力学信息.建立了分子滤波瑞利散射诊断系统和分子滤波器,根据测得的滤波图像和碘蒸气吸收光谱,获得了甲烷一空气预混火焰的温度场和密度场.测量结果显示,距离标定燃烧炉表面15 mm处火焰的密度为0.19 kg/m3,温度为(1827±84) K,与CARS法测是结果基本吻合,测温不确定度为8%.分子滤波瑞利散射技术还成功应用于水雾和高速喷流结构的诊断,获得了激光作用区的湍流结构.实验表明,分子滤波瑞利散射技术能够测量燃烧场温度和密度,并能用于流场可视化.%A molecular Filtered Rayleigh Scattering (FRS) diagnostic system was demonstrated to measure thermodynamic properties in combustion environments. The diagnostics system was composed of a narrow line width laser, a molecular/atomic absorption filter and a collection device such as ICCD. The absorption filter was used to modify the spectra of the Rayleigh scattering signal from the flow field illuminated by a laser sheet from a Nd:YAG pulsed laser. The laser was tuned to an absorption line of iodine vapor contained in the filter. This caused Mie scattering and background scattering from solid particles and strong absorption on the surface while much of Doppler broadened Rayleigh scattering was transmitted through the filter. The thermodynamic parameters were deduced from the measured transmission of the molecular Rayleigh scattering. The FRS diagnostic system and the iodine filter cell were described. On the basis of diagnosing FRS image and measuring iodine vapor absorption spectrum, the 2D temperature and density fields of methane/air premixed flame were obtained. The measured density at 15 mm above the burner surface is 0. 19 kg/m3 , and temperature is (1 827±84) K, which is good agreement with the results measured by using CARS method in the same condition. The uncertainty of temperature measurement by FRS is less than 8％. Furthermore, FRS technique was used to diagnose the atomization steam and supersonic exhaust flows. The results turbulence structures on the area of laser action were obtained. These demonstrate the abilities of the FRS technique to measure temperature and density fields and to enhance flow visualization in a combustion environment.
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