煤矿火灾诱发瓦斯爆炸危险性预测

针对高瓦斯易自燃煤层火区封闭与启封过程中常发生的瓦斯爆炸问题,采用20 L爆炸装置,在实验研究环境温度为25~200℃和CO体积分数为1%~10%的条件下进行瓦斯爆炸极限测定,发现CO体积分数升高,瓦斯爆炸上限、下限均下降,温度升高,爆炸上限升高、下限下降;温度与CO气体耦合作用下,瓦斯爆炸上限升高、下限下降,瓦斯爆炸危险性增加,爆炸上限、下限与温度和CO气体体积分数呈二次多项式变化趋势。初始温度和CO气体对爆炸极限的耦合影响比单一因素影响大,其对爆炸上限的影响更为显著。在此基础上,基于变化瓦斯爆炸三角形与曲线拟合理论,研究了火区封闭过程中次生瓦斯爆炸危险性演化过程,根据曲线相交原则反演求出CH4体积分数与O2体积分数,结合CH4体积分数与O2体积分数随时间变化关系,求出可能发生瓦斯爆炸时间t。若可能爆炸点M(XM(CH4),YM(O2))点的O2体积分数小于临界点E的O2体积分数,即YM(O2)<YE(O2),则O2体积分数不足,不爆炸。若O2体积分数大于临界点E的O2体积分数YM(O2)>YE(O2),O2充足,发生瓦斯爆炸时间依据CH4体积分数变化的爆炸时间t(CH4)确定,并分析了瓦斯易爆点监测位置及变化趋势。以水平巷道煤巷底板火灾事故为例,在前期建立50 m×4 m×3 m(长×宽×高)的长方体巷道数值模型基础上,应用瓦斯、O2拟合曲线与变化爆炸三角形理论对火区封闭过程中瓦斯爆炸时间进行估算,得到了瓦斯爆炸发生时间,为现场应急抢险救援提供借鉴。

Influence analysis of flow rule in mine fire during injecting inert gases

According to the action law of gas flow during injecting inert gases as the research main line, and hydromechanics and thermodynamics theories, the characteristic of gas delamination that was caused by injecting inert gases to closed fire zone was analyzed. The criterion was brought forward, which could scale disappearing probability of turbulent state. Formation mechanism of gas layer in turbulent state was discussed primarily. Simultaneously, the condition was pointed out, which could makc the gas in turbulent state by injecting different gases. The mathematical model about dynamic changes of oxygen and methane concentration in the process of injecting gases was erected. The mixture mechanism about injecting different flow inert gases and flammable gas layer in closed fire zone was revealed.