纵向通风对全尺寸巷道火灾燃烧特性和烟气温度分布的影响研究

    Study on effects of longitudinal ventilation on combustion characteristics and flue gas temperature distribution in full-scale roadway fires

    • 摘要: 为探究纵向通风对矿井巷道火灾演化特性的影响规律,开展了全尺寸巷道火灾实验,分析不同通风风速(0.5、1.0、1.5和2.0 m/s)下火灾燃烧特性和烟气温度分布。结果表明:在低风速下火焰受热浮力驱动呈微倾斜状,风速增大后,受到气流水平推力与热浮力的耦合作用,火焰形态转变为明显的倾斜射流状,燃烧强度随之增强;在火焰核心区,不同通风风速下温度峰值均稳定在1 200 ℃,而温度时序曲线存在明显差异,低风速(0.5 m/s)下曲线的波动幅度显著大于高风速工况;随着风速的提高,CO2体积分数达到峰值所需时间由1 200 s缩短至600 s,而O2体积分数并未与CO2体积分数完全同步变化,在0.5 m/s风速下O2体积分数在600 s率先降至最低值;风速增大至1.5和2.0 m/s后,O2体积分数降至最低点的时间滞后至1 200 s;CO体积分数曲线呈“多峰”分布特征,其峰值随通风风速增大逐渐降低,同时φ(CO)/φ(CO2)比值曲线在风速为0.5 m/s和1.0 m/s时先后出现2次明显突增,分别发生在燃烧初期和衰减阶段,而风速提高至1.5 m/s和2.0 m/s时,φ(CO)/φ(CO2)比值峰值显著下降,仅为风速0.5 m/s条件下对应峰值的51%和41%;不同高度烟气温度随与火源距离的增加均呈先快速下降后趋于平缓的变化趋势,且在15 m区域内烟气温度衰减最快。建立了考虑通风风速影响的巷道顶棚烟气温度纵向衰减预测模型,预测值与实测值的相对误差基本控制在15%以内。

       

      Abstract: To investigate the influence law of longitudinal ventilation on the fire evolution characteristics of mine roadways, full-scale roadway fire experiments were carried out. The combustion characteristics and flue gas temperature distribution under different ventilation wind speeds (0.5, 1.0, 1.5 and 2.0 m/s) were analyzed. The results show that the flame is slightly inclined driven by thermal buoyancy at low wind speeds. With the increase of wind speed, under the coupling effect of horizontal airflow thrust and thermal buoyancy, the flame evolves into an obviously inclined jet shape, accompanied by the rise of combustion intensity. In the flame core zone, the peak temperature remains stable at 1 200 ℃ under all ventilation wind speeds, whereas the time-history temperature curves differ significantly. The fluctuation range of the temperature curve under the low wind speed of 0.5 m/s is remarkably larger than that under high wind speed conditions. As the wind speed rises, the time required for the volume fraction of CO2 to reach its peak shortens from 1200 s to 600 s. However, the variation of O2 volume fraction is not completely synchronized with that of CO2. At the wind speed of 0.5 m/s, the O2 volume fraction first drops to the minimum value at 600 s; when the wind speed increases to 1.5 m/s and 2.0 m/s, the time for O2 volume fraction to reach its minimum is delayed to 1200 s. The volume fraction curve of CO presents a multi-peak distribution characteristic, and its peak value gradually decreases with the rising ventilation wind speed. Meanwhile, the φ(CO)/φ(CO2) ratio curve exhibits two distinct sharp surges successively at wind speeds of 0.5 m/s and 1.0 m/s, which occur in the initial combustion stage and decay stage respectively. When the wind speed is increased to 1.5 m/s and 2.0 m/s, the peak values of the φ(CO)/φ(CO2) ratio decrease significantly, which are only 51% and 41% of the corresponding peak value under the wind speed of 0.5 m/s. At different heights, the flue gas temperature drops rapidly at first and then tends to be gentle with the increase of the distance from the fire source, and the fastest temperature attenuation occurs within the area of 15 m. A longitudinal attenuation prediction model for roadway ceiling flue gas temperature considering the influence of ventilation wind speed is established, and the relative error between predicted and measured values is basically controlled within 15%.

       

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