平面双光子激光诱导荧光技术在高焓气流氧原子测量中的初步应用

Preliminary application of planar two-photon LIF measurements of atom O in high-enthalpy flow field

基于双光子吸收激光诱导荧光(Two-photon absorption laser-induced fluorescence,简称TALIF)技术,在纯净的高焓流场环境中进行测量,获得氧原子的荧光信号。为了获取更大区域内的流场信息,将激发激光整形成80mm宽的薄片状激光。通过对测试镜头的优化选择和对ICCD参数的合理设置,实现了对距离镜头大于1.2m超远目标的清晰成像。对所获取的荧光图像进行分析,在测试结果中可以清晰地看到超声速流场中在模型头部形成的弓形激波,亚声速流场中氧原子浓度在距头部30~50mm处最强,靠近模型头部处浓度较前方偏弱,这些结果符合实验预期。测试方法将在下一步运用到流场定量测量中。

The high-enthalpy ICP wind tunnel is one of the most reliable ground test facilities to test the thermal protection material for space vehicles.For good understanding the flow field,flow parameters need to be known.Due to high temperature nonequilibrium effects,the life of the thermal protection material can be directly influenced by the density of atom O.Therefore,the knowledge of the O density becomes important.The two-photon absorption laser-induced fluorescence（TALIF）technology is a good way to measure atom O.In this paper,the atom O fluorescent signal has been measured based on TALIF in a pure high-enthalpy flow field.To obtain information in a broader region,the laser beam is transformed into a plane with 80 mm width.A clear image of the object with a distance of 1.2meters from the lens has been got when lens and ICCD parameters are properly set.After the analysis of fluorescent images,the experimental result shows that there is an obvious bow shock wave in front of the model in the supersonic flow field.The concentration of atom O exhibits a maximum value in the area of 30 to 50mm away from the head in the subsonic flow field,and decreases near the surface.These phenomena are consistent with expected result,so the method can be applied to flow parameters measurement in the future.