DeLuca Nicholas J, Miles Richard B, Jiang Naibo, Kulatilaka Waruna D, Patnaik Anil K, Gord James R
Appl Opt. 2017 Nov 1;56(31):8632-8638. doi: 10.1364/AO.56.008632.
We report the use of femtosecond laser electronic excitation tagging (FLEET) for velocimetry at a 100-kHz imaging rate. Sequential, single-shot, quantitative velocity profiles of an underexpanded supersonic nitrogen jet were captured at a 100-kHz rate. The signal and lifetime characteristics of the FLEET emission were investigated in a methane flame above a Hencken burner at varying equivalence ratios, and room temperature gas mixtures involving air, methane, and nitrogen. In the post-flame region of the Hencken burner, the emission lifetime was measured as two orders of magnitude lower than lab air conditions. Increasing the equivalence ratio above 1.1 leads to a change in behavior, with a doubled lifetime. By measuring the emission in a cold methane flow, a short-lived signal was measured that decayed after the first microsecond. As a proof of concept for velocimetry in a reacting environment, the exhaust of a pulsed detonator was measured by FLEET. Quantitative velocity information was obtained that corresponded to a maximum centerline velocity of 1800 m/s for the detonation wave. Extension of FLEET to larger scale, complex flow environments is now a viable option.
我们报告了使用飞秒激光电子激发标记（FLEET）以100千赫的成像速率进行测速。以100千赫的速率捕获了欠膨胀超声速氮气射流的连续、单次定量速度剖面。在亨肯燃烧器上方不同当量比的甲烷火焰以及包含空气、甲烷和氮气的室温气体混合物中，研究了FLEET发射的信号和寿命特性。在亨肯燃烧器的火焰后区域，测得的发射寿命比实验室空气条件下低两个数量级。将当量比提高到1.1以上会导致行为发生变化，寿命加倍。通过测量冷甲烷流中的发射，测得一个短寿命信号，该信号在第一微秒后衰减。作为在反应环境中进行测速的概念验证，用FLEET测量了脉冲雷管的排气。获得了定量速度信息，对应于爆轰波的最大中心线速度为1800米/秒。现在将FLEET扩展到更大规模、更复杂的流动环境是一个可行的选择。
