半封闭管道内瓦斯煤尘爆炸火焰传播特性试验

Experimental approach to the flame propagation features of the explosive gas and coal dust in the semi-enclosed pipeline

为了进一步探究瓦斯煤尘爆炸火焰的传播规律,在自行设计搭建的半封闭竖直管道内,选用褐煤、烟煤和无烟煤3种煤样分别进行爆炸试验,并通过改变煤尘质量浓度来观察不同煤种条件下瓦斯煤尘爆炸反应强度,研究不同煤种条件下煤尘质量浓度对瓦斯煤尘耦合爆炸火焰传播规律的影响。结果表明,在瓦斯体积分数和煤尘质量浓度相同的条件下,褐煤爆炸产生的火焰传播速度最大,无烟煤最小。这是因为褐煤的挥发分含量较高,而影响爆炸火焰传播速度的主要原因是煤尘在加热情况下释放出的可燃气量,即煤种的挥发分含量,挥发分含量越大,瓦斯煤尘爆炸火焰传播速度也就越大。褐煤和烟煤的火焰传播速度随火焰传播距离增加而增加,直至传播至管道外部;无烟煤的火焰传播速度随火焰传播距离增加呈现先上升后下降的状态。在试验中,3种煤种和瓦斯爆炸时产生火焰最大传播速度的位置距离爆炸源较远。瓦斯煤尘爆炸产生的火焰稳定性较差,在传播过程中速度变化不稳定,存在较大的波动。火焰传播速度与煤尘质量浓度不成正比,在一定范围内,适当增加煤尘质量浓度可以大大提高瓦斯煤尘爆炸的反应强度,且存在一个最佳的煤尘质量浓度50 g/m^3,使火焰传播速度达到最大。

The given paper has done separate tests with the semiclosed vertical pipeline designed and built up by the authors ourselves so as to push further the exploration of the propagation regularities of the gas and coal dust explosion flames of the 3 coal types,i.e.the lignite coal,the bituminous coal and the anthracite one.By changing the mass concentration rate of the coal dust,and examining the intensity of the gas coal dust explosion reaction of the different coal types under study,we have traced and determined the impact of the coal dust mass concentration on the regularity of the gas-dust coupled explosive flame propagation under the different coal types.The results show that,under the same conditions of the gas mass fraction and the coal dust mass concentration,the flame propagation speed produced by the lignite explosion tends to be greater whereas the anthracite has to be the smallest.This can be attributed to the high evaporation of the lignite.The main reason that may affect the propagation speed of the explosion flame is the amount of the gas released by the coal dust under the great heat,that is,the volatile content of the coal species.Actually,the greater the said volatile content rate,the greater the propagation speed of the gas and coal dust explosion flame would be.Meanwhile,the flame propagation velocity of the lignite and bituminous coal tends to increase with the increase of the flame propagation distance,up to until it spreads to the outside of the pipeline.And,then,the flame propagation velocity of the anthracite may turn to decrease first and then disperse with the propagation distance of the flame going on.Moreover,the position of the maximum propagation velocity of the 3 kinds of coal species involving the gas explosion in the experiment can be made far away from the explosion source,with the flame stability produced by the gas coal dust explosion strength getting on less and less.Furthermore,with the velocity change being unstable in the propagation process,the great fluctuation can be found due to the speed disproportional to the flame propagation to the coal dust mass concentration.And,in a certain range,proper increase of the coal dust quality concentration can help to improve the reaction strength of the gas coal dust explosion greatly.Thus,there may exist an optimal qualified coal dust concentration rate of 50 g/m^3,which can help the flame propagation to reach its maximized speed.