Quenching mechanism study of oscillating flame in micro channels using phase-locked OH-PLIF
Quenching mechanism study of oscillating flame in micro channels using phase-locked OH-PLIF
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DOI：
10.1016/j.proci.2010.05.041
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Yong Fan;Yuji Suzuki;N. Kasagi
中科院分区：
文献类型：
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作者：
Yong Fan;Yuji Suzuki;N. Kasagi
本文介绍了锁相OH-PLIF成像系统的研制和OH 2线火焰温度测量，用于研究外加热石英微通道内振荡火焰的熄灭机理。振荡火焰是一个周期性的火焰在通道出口处自燃、传播和上游熄灭的过程。振荡火焰的CH_3化学发光强度的周期性变化由光电倍增管捕获，并且该信号用于产生具有延迟的输出触发，用于振荡火焰的同步OH-PLIF成像。振荡火焰的锁相OH-PLIF图像显示，火焰前缘具有与微通道中的稳定火焰相似的凹形形状。在上游传播的第一阶段，火焰前缘在出口中心处先扩展，然后沿流向和展向扩展。研究发现，火焰尾部先熄灭，火焰头部后熄灭;局部最高温度的火焰前锋尾部扩展到侧壁后，又被“弹”回中心线，使得局部最低温度的火焰前锋头部温度更高，沿流向扩展速度更快。因此，在传播的最后阶段，火焰前锋被拉伸的收缩火焰尾部的中心和火焰头部的加速。由OH 2-线法测量的火焰温度也表明，有一个温度上升后点火和减少在上游传播的壁热损失，其次是另一个小的温度上升，最后降低导致火焰淬熄。用时间分辨化学发光成像测量的火焰速度也证明了火焰传播到振荡火焰淬灭的减速。
This paper presents the development of phase-locked OH-PLIF imaging system and OH 2-line flame temperature measurement for the investigation of quenching mechanism of oscillating flame in external heated micro quartz channels. The oscillating flame is a periodic process of flame auto-ignition at the channel exit, propagation and quenching upstream. The periodic change of CH∗ chemiluminescence intensity of the oscillating flame is captured by a photomultiplier, and the signal is used to produce output trigger with delays for synchronized OH-PLIF imaging of the oscillating flame. The present phase-locked OH-PLIF images of an oscillating flame reveal that the flame front has a similar concave shape as that of the steady flame in the micro channel. Flame initializes at the center of the exit, and then the flame front expands in both the streamwise and spanwise directions during the first stage of the upstream propagation. It is found that the flame tails quenches first, and then the flame head; after the tails of the flame front with local maximum temperature expands to the sidewalls, they are ‘bounced’ backwards to the centerline, which makes the head of the flame front with local minimum temperature hotter and expand faster in the streamwise direction. Therefore, during the final stage of the propagation, the flame front is stretched by the shrinkage of the flame tail to the center and the acceleration of the flame head. Flame temperature measured by the OH 2-line method also shows that there is a temperature rise after the ignition and a decrease during upstream propagation by wall heat losses, followed by another small temperature rise, and finally a decrease leading to flame quenching. Flame velocity measured with time-resolved chemiluminescence imaging also demonstrated the deceleration of flame propagation to quenching of the oscillating flame.