Successful Imaging of a the Preheat-zone of a Lean (Φ< 0.6) Flame: A The Potential Capability of Acetone-OH Simultaneous PLIF to Diagnose Flames at the Near-extinction Limit
Successful Imaging of a the Preheat-zone of a Lean (Φ< 0.6) Flame: A The Potential Capability of Acetone-OH Simultaneous PLIF to Diagnose Flames at the Near-extinction Limit
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稀薄 (Φ< 0.6) 火焰预热区的成功成像：A 丙酮-OH 同步 PLIF 诊断接近熄灭极限火焰的潜在能力
DOI：
10.1007/s12650-012-0134-1
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发表时间：
2012
影响因子：
1.7
通讯作者：
M. Hirota and T. Saito,
中科院分区：
文献类型：
--
作者：
Y. Nakamura;Y. Yamada;M. Hirota and T. Saito,
摘要提出了一种利用丙酮-羟基同时脉冲激光诱导函数成像非常稀薄的层流预混火焰(当量比ϕ为0.6)预热区的策略。在283 nm和266 nm处的激发是通过一台YAG-Dye激光器和来自进入燃料流动的丙酮和燃烧生成的OH的荧光信号一起由一台ICCD相机检测到的。即使在非常贫瘠的条件下，火焰在没有火焰稳定器的情况下被吹灭，这些来源之间的清晰的“非信号区”也可以成功地成像。为了与测量的一维荧光信号分布进行比较，进行了包括七步丙酮分解反应在内的详细化学的一维数值模拟。这些比较清楚地表明，可观察到的“无信号区”的厚度比预测的丙酮和羟基都不存在的区要宽得多。研究发现，这种偏差是由于丙酮荧光信号强烈的温度依赖性造成的。这一特征表明，可观测到的“无信号区”应对应于未燃烧区温度的空间变化区，即预热区。结果表明，可观测到的“无信号区”与通过数值模拟得到的预热区在一定范围内的温度分布符合得很好(ϕ>；)。因此，丙酮-羟基同时PLIF被认为是一种很有前途的技术，能够在不知道温度分布的情况下可视化预热区，即使在接近消光的极限。
AbstractA strategy to image the preheat zone of a very lean, laminar premixed flame (whose equivalence ratio,ϕ, is <0.6) is proposed using acetone-OH simultaneous PLIF. A combination of excitation at 283 and 266 nm is accomplished by a YAG-Dye laser and fluorescence signals from the acetone seeded into the fuel flow and the combustion-generated OH together detected by a single ICCD camera. Clear “non-signal zone” between these sources is successfully imaged even under very lean conditions, where the flame is blown off without a flame holder. 1-D numerical simulations with detailed chemistry, including seven-step acetone-decomposition reactions are performed for comparison with measured 1-D fluorescence signal distributions. These comparisons clearly indicate that the thickness of the observable “non-signal zone” is much wider than the zone where neither the predicted acetone nor the OH exists. It is found that this deviation is caused by the strong temperature dependence of the acetone fluorescence signal. This feature suggests that the observable “non-signal zone” should correspond to the region with the spatial variation of temperature in the unburned zone; namely, the preheat zone. In fact, it is shown that the observable “non-signal zone” agrees well with the preheat zone obtained by numerically simulated temperature profiles over a range of imposed very lean condition (ϕ> 0.54). Therefore, acetone-OH simultaneous PLIF presents itself as a promising technique capable of visualizing the preheat zone without knowledge of the temperature distribution, even at the near-extinction limit.Graphical Abstract