Experimental studies of autoignition events in unsteady hydrogen–air flames
Experimental studies of autoignition events in unsteady hydrogen–air flames
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DOI：
10.1016/j.combustflame.2015.05.008
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发表时间：
2015-09
影响因子：
4.4
通讯作者：
B. Johannessen;A. North;R. Dibble;T. Løvås
中科院分区：
文献类型：
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作者：
B. Johannessen;A. North;R. Dibble;T. Løvås
为了研究混合区自燃事件的统计可能性，对稀预混氢燃烧热燃烧产物共流中的非定常n2 -in- h2射流火焰进行了实验研究。非定常射流火焰具有快速点火后逐渐熄灭的特点。采用录音和纹影成像高速视频对非定常火焰进行了研究。研究了井喷重燃事件发生频率与氮气稀释摩尔分数（yn2 = 0.180 ~ 0.566）、共流等效比（Φ cf= 0.20 ~ 0.27）和射流速度（V射流= 300 ~ 500 m/s）的关系。录音和纹影成像结果表明，自燃为主，重燃为主。点火频率随着氮气稀释度的增加而增加，达到最大值后，随着氮气稀释度的进一步降低。为了增加等效比，射流中需要更高的氮稀释度，以使火焰变得不稳定。氮稀释的影响主要是通过反应速率的降低和射流动量的增加来解释的。此外，结果表明，重燃速率是由化学和湍流混合控制的。录音结果与纹影成像视频吻合较好，验证了录音对非定常氢射流火焰的诊断作用。
An experimental study is presented of unsteady N 2-in-H 2 jet flames in a co-flow of hot combustion products from lean premixed hydrogen combustion for investigation of the statistical likelihood of autoignition events in the mixing region. The unsteady jet flame is characterized by rapid ignition followed by a gradual blowout of the flame. Audio recordings and Schlieren imaging high speed videos are used in investigating the unsteady flame. The frequency of the blowout re-ignition event is investigated as a function of nitrogen dilution mole fraction (Y N 2= 0.180–0.566), co-flow equivalence ratio (Φ cf= 0.20–0.27) and jet velocity (V jet= 300–500 m/s). The results from the audio recordings and Schlieren imaging indicate that autoignition dominates the re-ignition. The frequency of ignition increase with increasing nitrogen dilution until a maximum is reached after which it decreases with further nitrogen dilution. For increasing equivalence ratios a higher nitrogen dilution is needed in the jet for the flame to become unsteady. The effect of the nitrogen dilution is explained primarily through a reduction in reaction rates and increased jet momentum. Furthermore, the results suggest that the re-ignition rates are controlled by both chemistry and turbulent mixing. The results from the audio recordings and the Schlieren imaging videos correspond well which validates the use of audio recordings as a diagnostic for studying of unsteady hydrogen jet flames.