Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen–oxygen mixture
Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen–oxygen mixture
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DOI：
10.1007/s00193-016-0660-1
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发表时间：
2016-05
期刊：
影响因子：
2.2
通讯作者：
S. Maeda;S. Minami;D. Okamoto;T. Obara
中科院分区：
文献类型：
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作者：
S. Maeda;S. Minami;D. Okamoto;T. Obara
研究了70 kPa下高反应性化学计量比氢氧混合物在100 mm方形截面通道中的燃烧转爆轰过程。5mm宽和5、10和15mm高的障碍物在通道底部等距间隔60mm。这一现象主要是通过时间分辨纹影可视化从两个正交方向使用高速摄像机。爆炸转变发生在一个非常短的距离内，只有三个或四个重复的障碍物。就在爆震转变之前的全局火焰速度远低于燃烧产物的声速，并且对于具有5 mm和10 mm的障碍物高度的测试，没有达到初始未反应气体的声速。这些结果表明，爆震过渡并不总是需要全球火焰加速超过音速的高活性可燃混合物。这种爆震引发的一种可能的机制是未反应的和反应的气体在每个障碍物后面存在的涡流回旋的火焰前缘附近的混合，以及由冲击波形成的热点。爆轰的最后开始起源于未反应的气袋，这是由障碍物下游面和通道壁包围。
The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.