热颗粒和热辐射共同作用阴燃点燃松针燃料床:数值研究

Smoldering ignition of pine needle fuel bed under the coupled effect of a hot particle and thermal radiation:A numerical study

建立了热颗粒和热辐射共同作用下阴燃点燃松针燃料床的二维数值模型,计算得到了热颗粒和热辐射单独点燃以及共同作用点燃的临界条件,分析了燃料床的点燃过程。与前人实验数据对比表明数值模型能够较好预测临界点燃条件。金属热颗粒单独作用时点火所需的临界温度与颗粒直径呈双曲线关系。金属热颗粒与热辐射共同作用时,临界辐射热通量呈现出随颗粒温度和直径的增加而显著减小的趋势。热辐射持续供热能有效维持表层炭氧化反应,两者共同作用下点燃危险性增加。研究同时发现,燃料含水率对共同作用下的临界辐射热通量有较大影响。

In this paper,a two-dimensional numerical model of smoldering ignition of a pine needle fuel bed under the coupled effect of a hot particle and thermal radiation is established.The numerical simulation predicts the critical conditions for the ignition by the hot particle and radiation individually and together,and the ignition process is analyzed.The comparison with the previous experimental data shows that the numerical model can predict the critical ignition conditions well.The critical temperature required for ignition when a hot particle act alone has a hyperbolic relationship with the particle diameter.When a hot particle and thermal radiation act together,the critical radiant heat flux decreases significantly with the increase of the particle temperature and diameter.Continuous heating of thermal radiation can effectively promote the maintenance of surface carbon oxidation reaction,and increases the ignition risk.It is also found that the moisture content of fuel has a great influence on the critical radiant heat flux.