过热表面烟草粉尘阴燃实验研究

Experimental study of tobacco dust smoldering on superheated surface

为了研究烟草粉尘阴燃发生的影响因素,运用锥形量热仪测定粉尘的热释放速率,改进现有的粉尘层最低着火温度测试仪,将3组不同粒径的的烟草粉尘置于热表面上进行阴燃实验研究。结果表明:制丝粉、切片粉、卷包烟末热释放速率峰值分别为90、91、75 k W/m2,切片粉火焰传播速度最快。峰值最低的卷包烟末于50 s左右率先热释放,切片粉制丝粉随后分别于75、80 s左右进行热释放;阴燃过程可进行阶段性分析,其中水分蒸发燃料氧化放热阶段粉尘温度相对稳定攀升,于氧化放热阶段温度突变,因此控制阴燃的产生,必须于水分蒸发燃料氧化放热阶段之前控制其发展趋势,做出相应有效的预警方案;粉尘顶层率先发生阴燃,随后阴燃逐渐向下传播直至粉尘完全燃尽;粉尘层达到阴燃温度时,顶层升温速率最高,中层底层在未发生阴燃时,顶层阴燃有预热作用;阴燃时间和实验持续时间都是随着粒径的增大而增大;粒径越小阴燃各阶段持续时间越短,致使阴燃越迅速越难控制。

To study the influencing factors on the occurrence of burning, the cone calorimeter was used to test the determination of dust＇s heat release rate and improve the existing test device for ignition temperature of dust layer, 3 groups of the tobacco dusts in different particle sizes smoldering on the surface of the heat were studied through experiments. The result shows that the heat release rate peaks of sliced tobacco dust, picadura dust and rolled tobacco powder are 90, 91 and 75 k W/m^2 respectively and the flame propagation speed of the picadura dust is the fastest. The rolled tobacco powder whose peak is the lowest begins to smoke around50 s, taking the lead among these three tobacco dusts in heat release, then the picadura dust and sliced tobacco dust release the heat at 75 s and 80 s respectively. The smoldering process can be analyzed in stages,in the stage of water evaporation and fuel oxidation, the dusts＇ temperature rise stably, and the temperature jumps in the stage of exothermic oxidation. Thus, to control the smoldering, we must take measures and make the corresponding effective early warning scheme to control the trend of its development before the stage of water evaporation and fuel oxidation; The first occurrence of dust smoldering is on the top layer, then the smoldering spread down until the dust completely burnt out, when the dust layer reached the smoldering temperature, the top layer＇s heating rate is the highest, when the middle and bottom layers are not smoldering, the top layer preheats them. The smoldering time and duration of experiment are increased with the increase of particle size, each stage＇s smoldering duration decreases with the decreasing of particle size which make the dust smolder faster and harder to control.