在实际矿井下，瓦斯泄漏后往往在巷道密闭空间内形成分层的、含体积分数梯度的甲烷-空气混合物。目前，国内外研究大多集中在均匀预混瓦斯爆炸火焰传播特性方面。为探究非均匀预混瓦斯爆炸火焰传播特性，通过自主搭建的小尺寸爆炸实验平台，对比研究了管道内甲烷不同自由扩散时间下，甲烷沿管道体积分数梯度分布及非均匀预混甲烷/空气爆炸火焰传播特性。实验通过浓度传感器、高速摄像机、压力传感器获取不同工况下非均匀甲烷爆炸过程中的甲烷体积分数分布、火焰传播结构、甲烷爆炸超压等数据，并进一步分析得出火焰传播速度、爆炸压升曲线等。结果表明:甲烷在管道内泄漏后，受浮力作用沿管道顶部横向传播，同时受体积分数差向底部纵向扩散，形成横向及纵向的体积分数梯度场，且自由扩散时间越短，体积分数梯度越大。体积分数梯度场对管道内非均匀甲烷爆炸火焰传播结构与爆炸超压有显著影响。甲烷体积分数梯度场下形成的非均匀预混火焰在管道内传播经历球形、指形、三重火焰、拉伸三重火焰4个阶段。当甲烷沿管道形成纵向体积分数梯度时，管道内出现三重火焰，且体积分数梯度越大，三重火焰结构愈发明显，三重火焰形态出现后，火焰传播速度、爆炸超压迅速下降，管道内甲烷纵向体积分数分布为16%—4.6%—0时，三重火焰稳定传播时火焰速度约为4.8 m/s。随三重火焰继续传播，火焰传播速度、爆炸超压略有上升趋势。管道内甲烷空气非均匀预混时爆炸超压呈现2个峰值，后波峰压力峰值约为前波峰2/3，压力峰值间隔时间随体积分数梯度减小而减小，且在不同体积分数梯度下，甲烷体积分数越接近当量比时火焰传播速度越快，爆炸超压越高。

In an actual roadway,stratified methane air mixtures with concentration gradient are often formed in the closed space of roadway after gas leakage.At present,most of the researchers focus on the flame propagation characteristics of uniform premixed gas explosion.In order to explore the propagation characteristics of non uniform premixed gas explosion flame,the methane concentration gradient distribution and the flame propagation characteristics of non uniform premixed gas explosion flame in the pipeline under different methane diffusion time were compared through the self built small size explosion experiment platform.The methane concentration distribution,flame propagation structure and the maximum explosion pressure were collected by the concentration sensor,high speed camera system and the pressure collection system respectively in the experiment.The flame propagation velocity and explosion pressure increase curve were obtained by further analysis.The results show that after methane leakage in the pipeline,it spreads along the top of the pipeline under the action of buoyancy,and at the same time,the concentration difference diffuses longitudinally to the bottom,forming a transverse and longitudinal concentration gradient field.The shorter the free diffusion time,the greater the concentration gradient.The concentration gradient field has a significant effect on the flame propagation structure and overpressure of non uniform premixed methane explosion in the pipeline.The non uniform premixed flame formed under the concentration gradient field propagates through four stages:sphere,finger shape,triple flame and stretch triple flame.When methane forms longitudinal concentration gradient along the pipeline,the triple flame appears in the pipeline,and the larger the concentration gradient is,the more clear the triple flame structure becomes.After the appearance of the triple flame form,the flame propagation velocity and explosion overpressure decrease rapidly.When the longitudinal concentration of methane in the pipeline is between 16%—4.6%—0,the flame velocity is about 4.8 m/s when the triple flame propagates steadily.With the continuous propagation of triple flame,the flame propagation velocity and explosion overpressure rise slightly.In the case of non uniform premix of methane air in the pipeline,the explosion overpressure presents two peaks,the pressure of the back peak is about 2/3 that of the front peak,and the time between the pressure peaks decreases with the decrease of concentration gradient.Moreover,the closer the methane concentration is to the volume equivalent ratio,the faster the flame propagation speed is,and the higher the explosion overpressure is.

1 实验部分

   1.1 实验装置

   1.2 实验方案

2 结果与讨论

   2.1 管道内甲烷体积分数梯度分布

   2.2 火焰传播结构分析

   2.3 火焰传播速度分析

   2.4 爆炸超压分析

3 结论