瓦斯/煤尘爆炸初期复合火焰加速及灾害强化机制分析

Analysis on the Acceleration of Composite Flame and the Strengthening Mechanism of Disaster in the Initial Stage of Gas/Coal Dust Explosion

为了探明瓦斯/煤尘耦合爆炸灾害强化的产生机制,采用20 L球、高速纹影和PIV对瓦斯/煤尘爆炸初期复合火焰加速特性、压力变化进行了实验研究,并对其爆炸瞬间的流场特征进行了分析。结果表明:相比甲烷/空气爆炸,同一甲烷浓度下,瓦斯/煤尘爆炸初期火焰传播速度稍有降低,焰胞状结构减少,火焰上浮现象几乎消失;马克斯坦长度随甲烷浓度的增大而减小且均为正值,表明爆炸初期复合火焰发展趋于稳定,有利于煤尘粒子参与燃烧反应。甲烷浓度接近最佳当量浓度、煤尘粒径越小或煤尘质量浓度增加接近最佳浓度时能诱发复合火焰加速,导致爆炸威力增强。低浓度瓦斯/煤尘复合体系对煤尘质量浓度的提高更敏感,而随着煤尘浓度的增大,甲烷浓度对瓦斯/煤尘复合体系的影响逐渐降低。初始爆炸强度对瓦斯/煤尘复合体系有重要影响。9%瓦斯/煤尘爆炸体系由于初始爆炸强度高,复合火焰中心负压使多数煤尘粒子做向心运动,火焰前锋周围聚集了大量煤尘粒子,同时在火焰前锋周围形成的大量方向相反的大涡量旋涡,促进了煤尘表面与氧气的快速接触,加剧了燃烧反应。研究结果将为瓦斯/煤尘耦合爆炸灾害防治提供指导。

In order to clarify the strengthening mechanism of gas/coal dust coupling explosion disaster,20 L spherical,a high-speed schlieren and a PIV were used to study acceleration characteristics and pressure change of composite flame in the initial stage of gas/coal dust explosion,and the flow field characteristics of the explosion moment were analyzed.The results show that compared with the methane/air explosion,at the same methane concentration,the flame propagation speed in the initial stage of the gas/coal dust explosion is slightly reduced,the flame cell structure is reduced,and the flame floating phenomenon almost disappears.The Markstein length decreases with the increase of methane concentration and are all positive,indicating that the development of composite flame tends to be stable in the initial stage of explosion,which is conducive to the participation of coal dust particles in combustion reaction.When the concentration of methane is close to the best equivalent concentration,the smaller the particle size of coal dust or the increase of the mass concentration of coal dust is close to the best concentration,the composite flame can be accelerated,resulting in the increase of the composite explosion power.The low concentration gas/coal dust composite system is more sensitive to the increase of coal dust mass concentration,and with the increase of coal dust concentration,the influence of methane concentration on the gas/coal dust composite system gradually decreases.The initial explosion intensity has an important influence on the gas/coal dust composite system.Due to the high initial explosion intensity of 9%gas/coal dust explosion system,the negative pressure in the center of the composite flame makes most of the coal dust particles do centripetal movement,and a large number of coal dust particles gather around the front of the flame.At the same time,a large number of large vortices in opposite directions are formed around the front of the flame,which promotes the rapid contact between the coal dust surface and oxygen,and intensifies the combustion reaction.The research results will provide guidance for the prevention and control of gas/coal dust coupling explosion disaster.