飞火和热辐射耦合作用点燃松针的实验研究

飞火颗粒点燃和火焰辐射引燃是森林-城镇交界域火灾两种主要引燃方式。已有很多研究关注单种引燃方式,但缺乏二者耦合作用下的引燃机理研究。实验研究了热颗粒与热辐射耦合作用下松针燃料床的点燃行为,分析了热颗粒尺寸、温度及辐射热通量对点燃特性的影响。实验结果表明:热颗粒和热辐射耦合作用的点燃危险性远远高于热颗粒或者热辐射单独作用下的点燃危险性。耦合作用时,点燃概率随颗粒尺寸、温度和辐射热通量增大而增大,热颗粒临界点燃温度以及临界辐射热通量均随热颗粒尺寸增大而降低;阴燃向明火转变的点燃时间随辐射热通量增大而降低,但与颗粒状态呈现出较为复杂的关系。

Experimental study on the ignition of pine needles by the coupled effect of firebrands and thermal radiation

Firebrands and flame radiation are the two major ignition sources in the Wildland-Urban Interface fires. Ignition of combustibles by firebrands or flame radiation has been studied separately in the literature, however, their coupled effect on ignition has not been investigated. In this work, experiments were conducted to investigate the coupled effect of firebrands and thermal radiation on the ignition of pine needles. The effects of particle diameter, temperature and external radiative heat flux were analyzed. Results revealed that the coupled ignition risk is much higher than either independent ignition risk. Ignition probability increases with the increase of particle diameter, temperature and external radiative heat flux. The critical temperature of hot particle and radiative heat flux for sustained ignition decrease with the increase of particle diameter. Ignition time of smoldering-to-flaming transition is reduced with the increase of radiative heat flux. However, the relationship between the ignition time and hot particle is complicated.