Flow Visualization & Measurement of Two-dimensional Temperature Field in the Rarefied Gas Flow Using LIF (Laser Induced Fluoresence)

提出了一种稀薄气体流动温度定量成像的方法。流场可视化的平面激光诱导荧光（PLIF）的载气中接种的碘分子。碘分子在可见光区有多条吸收线，并发出强烈的荧光。荧光强度与激光束激发的能级中的分子数量成正比。根据该数值对温度的依赖性，可以根据通过照射具有不同波长的激光束获得的两个可视化图像的荧光强度的比率来确定局部温度。这种方法允许通过激光片和高灵敏度的摄像机成像的二维温度分布的流场。将该方法应用于温度剧烈变化的超声速自由射流流场的温度测量。结果表明，利用P（16）/R（18）[514.720 nm]和P（26）/R（28）[514.942 nm]吸收谱线测量的B（v '= 43）X（v”=0）跃迁射流温度分布与理论值符合得很好。

A method for quantitative imaging for temperature in the rarefied gas flow has been developed. The flow field is visualized by planar laser-induced fluorescence (PLIF) of iodine molecules seeded in carrier gas. Iodine molecules have many absorption lines in visible region and radiate intense fluorescence. The fluorescence intensity is proportional to the number of molecules in the energy level excited by the laser beam. From the dependence of this number on the temperature, the local temperature can be decided from the ratio of the fluorescence intensities of two visualized images which are obtained by irradiations of laser beams with different wave length. This method allows to image the two-dimensional temperature distribution of the flow field by means of a laser sheet and a high sensitive vidicon camera. This method is applied to the temperature measurement of the flow field of a su personic free jet in which temperature varies drastically. It is found that the temperature distribution of the jet measured by P(16)/R(18) [514.720 nm] and P(26)/R(28) [514.942 nm] absorption lines in the transition of B(v'=43) X(v"=0) agrees well the theoretical one.