基于激光光解诱导荧光技术实现燃烧反应区及中间产物CH_3瞬态可视化

实现火焰反应区和不同中间组分的在线二维瞬态成像,在湍流燃烧的基础研究中具有十分重要的意义。用Nd∶YAG激光器的5倍频输出(212.8nm)作为光源,通过激光光解诱导荧光技术在甲烷/空气预混火焰中,成功实现了火焰反应区的瞬态成像,并首次采用该技术实现了CH_3的在线瞬态成像测量。分析了该方法同其他荧光标示物在反应区二维瞬态成像方法的优势,并研究了火焰燃烧过程中其他燃烧中间产物和不同燃空比对CH_3单脉冲成像的影响,讨论了现有条件下该技术的应用范围。根据实验结果,在燃空比Φ=1.2的条件下,在反应区我们获得了信噪比约为8的单脉冲成像,分析火焰中CH_3的单脉冲成像结果可知火焰燃空比在1.0~1.4之间时,或者火焰中CH_3的浓度大于9.3×1015 molecules·cm-3信噪比较好。该项技术在动力机械及其他研究领域的应用有十分重要的参考价值。

Instantaneous Imaging of Reaction Zone and CH3 Radicals in Flames Using Laser Photodissociation-Induced Fluorescence

Online instantaneous two-dimensional imaging of reaction zone and different intermediate species in flames are important and fundamental in the research of turbulence combustion.In methane/air premixed flames,the instantaneous imaging of flame reaction zone is achieved using laser photodissociation-induced fluorescence technique with the 5th harmonic (212.8 nm) of an Nd ∶ YAG laser as excitation source.The online instantaneous imaging of CH3 radicals was accomplished for the first time with this technique.The advantage of this technique was analyzed over other typical PLIF techniques in terms of visualization of flame reaction zone.The influences of other combustion intermediates and flame equivalence ratio to the single-shot imagining of CH3 were studied,and the application range of the technique was also discussed.The result shows that single shot imaging of reaction zones in our measurement with a signal-to-noise ratio (SNR) of 8.Single shot imaging of CH3 has better SNR by LPIF in premixed methane/air flames with the equivalence ratio from 1.0 to 1.4,or when the concentration of CH3 is higher than 9 × 1015 molecules · cm-3.The results provide very important information for the application of this technology in power machinery and other field.