水平燃料填充床反向阴燃传播及其熄灭分析

Analysis of reverse smoldering propagation and its quenching in a horizontally packed bed of fuel

根据单步反应机理(仅包括燃料的氧化),建立了一维非稳态燃料填充床反向阴燃的数学模型。通过简化模型参数及大活化能渐近分析,得出了定性描述燃料反向阴燃传播的两个方程。结果表明:随着空气流量的增大,阴燃温度是不断上升的,但由于受到反向空气风流的影响,阴燃温度的增长幅度是逐渐变小的;阴燃传播速度却呈现出先增大后减小直至熄灭的变化趋势。这种变化趋势与前人的实验结果相一致。通过定性分析得出:在气体流量为零的情况下,燃料仍然可以发生阴燃,而维持阴燃不断传播所需要的氧气量源于反应区域周围气体的扩散。此外,也分析了燃料特性参数(如密度、孔隙率、比热、导热系数及活化能)对燃料阴燃温度和阴燃速度传播的影响。

Based on a one-step kinetic mechanism（only including fuel oxidation）,a one-dimensional,unsteady,numerical model is presented for reverse smoldering propagation in a horizontally packed beds of porous media.By simplifying the model parameters and using asymptotic methods,two simplified equations are obtained to qualitatively depict the reverse smoldering propagation.The results show that the smoldering temperature increases with increasing the gaseous mass flux,but the increasing amplitude is reduced due to the convective cooling of preheat zone.With increasing the gaseous mass flux,the smoldering velocity increases to a maximum and decreases until quenching occurs at the maximum inlet airflow velocity.The evolution behavior of reverse smoldering propagation is well consistent with the experimental observations by Ohlemiller et al.and Torero et al.The qualitative analysis shows that the smoldering wave is also sustained by the oxygen already present in the porous medium through the diffusion of gaseous species though the supplied airflow is zero,namely,Mg=0.Moreover,the effects of fuel properties（including density,porosity,specific heat,conductivity,activation energy） are studied on the reverse smoldering combustion.