Effect of sandpaper-like small wall roughness on deflagration-to-detonation transition in a hydrogen-oxygen mixture
Effect of sandpaper-like small wall roughness on deflagration-to-detonation transition in a hydrogen-oxygen mixture
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砂纸状小壁粗糙度对氢氧混合物中爆燃到爆轰转变的影响
DOI：
10.1016/j.proci.2018.07.119
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发表时间：
2019
影响因子：
3.4
通讯作者：
Tetsuro Obara
中科院分区：
文献类型：
--
作者：
Shinichi Maeda;Masashi Fujisawa;Shogo Ienaga;Keisuke Hirahara;Tetsuro Obara
实验研究了化学计量比氢氧混合气体中的爆燃转爆轰(DDT)现象，采用砂纸状粗糙壁通道作为小阻挡。燃烧通道内横截面长486 mm，宽12 mm，高10 mm，上下壁用砂布覆盖，表面粗糙度Rz为1000微米，Ra为100微米(粗糙壁条件)。不涂砂布的槽壁(抛光墙条件)也进行了对比试验。利用高速纹影照相技术，通过侧面的光学窗口观察了从火花点火后火焰传播到爆轰转变的整个过程。虽然在抛光壁面条件下只观察到了缓慢的亚音速火焰，但壁面粗糙度大大增强了火焰的加速作用，并且在点火下游120 mm处发生了爆轰转变。在粗糙壁条件下，观察到沿通道壁的反应锋可能在火焰边缘和粗糙壁之间的多个空腔中以未反应气体的形式传播。这一反应锋最终形成了高速的郁金香火焰。在郁金香火焰前方观察到通道壁附近的突出反应锋和压缩波(预压区)的积累，使压力增加到初始压力的10-15倍，从而触发了爆轰。预压区的温度估计在600-700℃之间，不足以引发瞬时自燃。目前的观察结果可能为最终爆炸开始的可能机制提供了实验证据，这是局部自发火焰加速与紧接在火焰前沿前方的压缩波耦合的；对于高活性混合物，这是建议的(Liberman等人)。2010)。
Deflagration-to-detonation transition (DDT) in a stoichiometric hydrogen–oxygen mixture was experimentally investigated using a channel with a sandpaper-like rough wall as a small blockage. The combustion channel was 486 mm long, 12 mm wide, and 10 mm high in the inner cross-section, and the top and bottom walls were covered with a sand cloth with surface roughness of 1000 µm by Rz and 100 µm by Ra (rough wall condition). The channel wall without the sand cloth (polished wall condition) was also tested for comparison. The entire process from the flame propagation following spark ignition to the detonation transition was visualized through optical windows on the side walls by high-speed schlieren photography. Although only the slow subsonic flame was observed in the polished wall condition, the wall roughness greatly enhanced flame acceleration and the detonation transition occurred at 120 mm downstream from the ignition. In the rough wall condition, the reaction front along the channel wall, which might propagate in the unreacted gas in the many cavities between the flame edge and the rough wall, was observed. This reaction front finally developed to form the high-speed tulip flame. The prominent reaction front near the channel wall and the accumulation of compression waves (the precompression zone), which increased the pressure up to 10–15 times the initial pressure, were observed immediately ahead the tulip flame, and this triggered the detonation onset. The estimated temperature in the precompression zone of 600–700 K was not high enough to induce instantaneous self-ignition. The present observation might indicate the experimental evidence for the possible mechanism of the final detonation onset, which was local spontaneous flame acceleration coupled with the compression wave immediately ahead of the flame front; which was suggested for highly reactive mixtures (Liberman et al. 2010).