Hele-Shaw通道内瓦斯爆炸火焰特性试验研究

Experimental study on gas premixed flame characteristics in Hele-Shaw channel

为探究甲烷/空气预混气体当量比对Hele-Shaw通道内火焰爆燃特性的影响,自行设计搭建尺寸(长×宽×厚)为950 mm×200 mm×6 mm的透明有机玻璃瓦斯爆炸管道试验平台。通过改变试验平台厚度研究通道间隙对甲烷/空气预混气体火焰结构与传播特性的影响。结果表明,不同的通道厚度和当量比对火焰锋面结构和火焰传播动态特性有显著影响。当通道厚度为6 mm时,最大火焰传播速度发生在化学当量比下,为12.84 m/s,且在该工况下火焰最先到通道末端,时间为518.57 ms。当量比为0.8的贫燃状态时,在火焰不稳定性的作用下,火焰传播后期出现二次振荡现象及手指形的火焰锋面。随着通道厚度的减小,火焰到达通道末端的时间逐渐变长,对火焰整体传播速度有明显的抑制作用。

To explore the influence of the equivalent ratio of methane/air mixture on the flame deflagration characteristics in the Hele-Shaw channel,a transparent plexiglass gas explosion pipeline experimental platform with a size of 950 mm×200 mm×6 mm was designed and built.The effect of the gap on the flame structure and propagation characteristics of methane/air premixed gas was studied by changing the pipe thickness.The results show that different pipe thicknesses and equivalent ratios have significant effects on flame propagation characteristics.When the pipe thickness was 6 mm,the maximum flame propagation velocity occurred at the stoichiometric ratio of 12.84 m/s.Furthermore,under this working condition,the flame reached the end of the pipe first,and the time was 518.57 ms.Under the studied equivalence ratio conditions,flames all presented three typical propagation stages.The flame front spread smoothly,small-scale folds and large-scale phases corresponded to different propagation speeds.When the equivalence ratio was 0.8,a second oscillation image and a finger-shaped flame front appeared in the later stage of flame propagation under the effect of TA instability.The oscillation amplitude can reach 5 mm.Under the condition of the same equivalence ratio,the decrease of the channel thickness led to the volume to surface ratio.The heat loss of the combustion products to the surrounding wall will also increase,and it'll take longer for the flame to reach the end of the combustion chamber.Under the same conditions,as the thickness decreased to 5 mm and 4 mm,the time to reach the end of the pipe increased from 923 ms to 980 ms and 1152 ms,an increase of 57 ms and 173 ms,respectively.It can be seen that as the thickness of the channel decreases,it has a significant inhibitory effect on the overall flame propagation speed.Finger-shaped flame fronts and late oscillations only appear when h=6 mm.Therefore,reducing the thickness of the passage contributes to the suppression of the occurrence.