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基于双光子吸收激光诱导荧光(TALIF)技术,在纯净的高焓流场环境中,将脉冲激光从垂直于流场方向射入流场,并通过布置在风洞试验段外与流场和激光形成的平面向垂直方向上的ICCD测量获取到了二维氧原子的荧光信号,该信号可以反映氧原子相对浓度。为保证实验中使用到的激发激光波长为最佳激发波长,分别对氧原子基态处在不同角量子数的情况进行了测试,最终确定J=2时,波长为225.584nm为最终实验激发波长,为了保证所获取的氧原子荧光信号在非饱和线性区,在同种状态下,将激发激光能量从小到大调整并进行荧光信号的测试,获取了激光能量在3.4mJ以下的线性区域。为确保获取清晰对比度最优的ICCD荧光图像,选择了Nikon f=105mm F/2.8镜头为实验测试镜头,同时将50次曝光的累计结果作为图像输出。对所获取的荧光图像进行分析,实验结果可以清晰地看到超声速流场中压缩波形成的距中心线约±50mm位置处左右各一个的小峰,亚声速流场中中心处氧原子浓度有一个约60mm宽的均匀区域,区域以外氧原子浓度急剧下降,这些结果符合实验风洞特性,此测试方法可以很好地运用到流场测量中。
Based on the two-photon absorption laser-induced fluorescence (TALIF) technique, a pulsed laser is injected into the flow field perpendicular to the flow field in pure high-enthalpy flow field environment. The flow field and the laser beam The resulting planar CDMA measurements of the vertical direction obtained the fluorescence signal of the two-dimensional oxygen atom, which can reflect the relative concentration of oxygen atoms. In order to ensure that the excitation laser wavelength used in the experiment is the optimal excitation wavelength, the ground state of oxygen atoms at different angular quantum numbers were tested respectively. Finally, when J = 2, the wavelength was 225.584 nm as the final experimental excitation wavelength, In order to ensure that the obtained fluorescence signal of oxygen atoms is in a non-saturated linear region, under the same condition, the excitation laser energy is adjusted from small to large and the fluorescent signal is tested. The linear region with the laser energy below 3.4 mJ is obtained. In order to ensure a clear and contrast-optimized ICCD fluorescence image, a Nikon f = 105mm F / 2.8 lens was chosen as the experimental test lens, and the cumulative result of 50 exposures was output as an image. The obtained fluorescence images are analyzed. The experimental results can clearly see that the compression peak in the supersonic flow field forms a small peak at about ± 50 mm from the center line. The concentration of oxygen atoms in the center of the subsonic flow field is one About 60mm wide and uniform area, the region outside the oxygen concentration dropped sharply, these results in line with experimental wind tunnel characteristics, this test method can be well applied to the flow field measurements.