The influence of wall roughness on detonation limits in hydrogen–oxygen mixture
The influence of wall roughness on detonation limits in hydrogen–oxygen mixture
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DOI：
10.1016/j.combustflame.2016.05.003
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发表时间：
2016-07
影响因子：
4.4
通讯作者：
Bo Zhang
中科院分区：
文献类型：
--
作者：
Bo Zhang
在本研究中，通过插入不同钢丝直径(δ)和螺距(LS)的Shchelkin螺线来产生壁面粗糙度。粗糙度定义为δ/LS之比。系统地研究了管壁粗糙度对化学计量比氢氧混合物爆轰极限的影响。爆速是由沿管子每隔10厘米间隔的光纤和激波销确定的。用烟熏薄片记录了极限附近的蜂窝爆轰结构。实验结果表明，在爆轰极限范围内，光滑段和粗糙段的爆轰波均可自持，并能以稳定的速度传播。然而，当爆轰波进入粗壁管时，爆速会降低。在粗糙度较大的管内，由于爆轰反应区与激波后形成的边界层的相互作用，速度亏损更为明显。在粗壁管中，当爆轰接近极限时，观察到单头旋转结构。在发生单头旋转现象的最小初始压力以下，爆轰失效并衰减为爆燃，最小速度约为0.4VcJ。研究发现，壁面粗糙度对爆轰传播极限既有促进作用，也有抑制作用。当粗糙度小于0.231时，人们认为粗糙度产生的湍流促进了爆轰，并扩大了爆轰极限。但当粗糙度大于0.333时，低速行为对爆轰起主要抑制作用，说明一定粗糙度以上对爆轰极限有不利影响。
In this study, wall roughness is generated by inserting a Shchelkin spiral with different wire diameter (δ) and pitch (Ls). Roughness is defined as the ratioδ/Ls. The effect of tube wall roughness on the detonation limits in stoichiometric hydrogen–oxygen mixture is systematically examined. The detonation velocity is determined from optical fibers and shock pins spaced at 10 cm intervals along the tube. Smoked foils are employed to record the cellular detonation structure near the limits. The experimental results indicate that detonation in both smooth and rough sections can be self-sustaining and can propagate with a steady velocity as the conditions are well within the detonation limits. However, the detonation velocity decreases as it transmits into the rough-walled tube. The velocity deficit is more significant in tubes with larger roughness due to the interaction of the detonation reaction zone and the boundary layer formed behind the shock. Single-headed spinning structure is observed as the detonation approaches the limits in the rough-walled tube. Below the minimum initial pressure at which single-headed spinning phenomena occur, detonation fails and decays to deflagration, and the minimum velocity is approximately 0.4VCJ. It is found that wall roughness can either promote or prohibit the detonation propagation limits. When the roughness is smaller than 0.231, it is believed the turbulence generated from the roughness facilitates detonation and extends the detonation limits. However, when the roughness is larger than 0.333, low-velocity behavior plays a dominant role in prohibiting the detonation, which indicates that roughness above a certain level has a negative effect on detonation limits.