温度分层环境下火灾烟气羽流上升高度公式分析

Analysis of the increasing equation of fire smoke plumes in temperature stratified ambient

对小尺度空间温度分层环境下柴油有焰火及棉绳阴燃火烟气运动进行了实验和数值模拟。结果表明,在分层环境下,烟气与环境空气温度差造成的浮力在某一高度消失并转为负值,致使烟气停止上升而向横向扩展。Morton积分公式低估了烟气羽流上升的最大高度,且在相同出口条件及分层环境下,柴油烟雾比棉绳烟雾下降趋势快,上升高度小,其原因在于积分公式中自相似卷吸及烟气为空气假设。引入烟气密度修正系数和自相似修正系数,对Morton公式进行了修正和讨论。

The present paper has done an investigation and analysis of the movements of smoldering cotton wick smoke and flaming diesel oil smoke phtmes in a temperature stratified ambient in a small scale environment through experimental measurements and CFD simulations. The results indicate that in a stratified environment, the temperature difference between the plume and the ambient may eventually vanish and reverse the sign, thus forming a horizontal layer with the plume ceasing to smolder on. Actually, the Morton equation might have been proved to underestimate the actual maximum height of a fire smoke plume. In fact, the diesel oil smoke can be getting decreased faster and rising at a smaller maximum height with the same outlet and stratification conditions. The situation may come to pass at the Morton integral model assumption that the plume is itself similar and the fire smoke is air. By introducing the smoke density factor and self-similarity factor, the Morton equation has thus been discussed and improved.