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Development of a Two-dimentional Measurement System for Supersonic Flow using LIUVF

利用 LIUVF 开发超声速流二维测量系统

基本信息

批准号：
04555043
负责人：
FUJIMOTO Tetsuo
金额：
$ 10.5万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-04555043/
关键词：
LIUVF Oxygen Molecule Temperature Measurement Two-dimensional Measurement Visualized Image Rarefied Gas Flow Laser Sheet Picture Processing 超音速流

项目摘要

Oxygen molecules have the absorption bands in the broad range from 114 in the ultra violet to 1580 nm in the infrared. The dominant Schumann-Runge absorption band system corresponds to the transition of the ground state X^3SIGMA_g^- to the excited state B^3SIGMA_u^-, and has the discrete absorption bands from 175 to 250 nm and the continuum ones from 130 to 175 nm. The B state has been known to be crossed by many repulsive potential curves and to be predissociated. Since the strong predissociation rate makes the lifetime of the fluorescence short in the order of 10^<-12> seconds, it is possible to assume that the fluorescence yields prior to the intermolecular collision.In this study, we investigate the capability of imaging of rarefied gas flow using O_2-LIPF (Laser-Induced Predissociative Fluorescence). Since oxygen is one of main component of air, O_2-LIPF may make it possible to visualize the air flow in the high speed wind tunnel without the tracer. However, because the visualization of the flow field below the room temperature using O_2-LIPF is very difficult, is has been applied only to the high entalpy and combustion flow^<(1)>, not to high speed flow with low temperature. In this study, the rarefied oxygen flow is visualized by O_2-LIPF, using an ArF excimer laser (193 nm) and a high-sensitive CCD camera. If long exposure time (1200 seconds) of the CCD camera is set and the scattered laser beam is suppressed sufficiently, the oxygen flow below the room temperature using O_2-LIPF can be imaged successfully.

氧分子在从紫外线的114 nm到红外线的1580 nm的宽范围内具有吸收带。主要的舒曼-龙格吸收带系统对应于基态X^3 SIGMA_g ^-到激发态B^3 SIGMA_u ^-的跃迁，在175 ~ 250 nm有离散吸收带，在130 ~ 175 nm有连续吸收带。已知B态被许多排斥势曲线穿过并被预解离。由于强的预解离速率使得荧光寿命短于10^s量级<-12>，因此可以假设荧光产生于分子间碰撞之前。由于氧气是空气的主要成分之一，O_2-LIPF可以使高速风洞中的空气流动在无示踪剂的情况下可视化成为可能。然而，由于O_2-LIPF在室温以下的流场显示上的困难，它只适用于高焓和燃烧流场，而不适用于低温高速流场。本研究采用ArF准分子激光器（193 nm）和高灵敏度CCD摄像机，利用O_2-LIPF对稀薄氧气流进行了可视化。如果CCD摄像机的曝光时间长（1200秒），并充分抑制激光散射，O_2-LIPF可以成功地对低于室温的氧气流成像。