飞火点燃是导致森林与城市及其交界域火灾发生的重要潜在路径。飞火颗粒接触森林或建筑可燃物，可引发其直接明火或阴燃点燃行为，而自维持阴燃可转化为明火。然而，现有飞火点燃研究关注直接明火点燃行为，缺乏对阴燃点燃及其诱发明火点燃行为的研究。本项目系统研究飞火颗粒与环境风耦合作用下，不同热解动力学特性可燃物阴燃点燃及其诱发明火点燃行为，建立可燃物飞火点燃的临界条件；通过分析典型特征参数（点燃延滞时间、颗粒周围温度分布、点燃临界参数），采用传热传质、热解动力学和流体力学理论，揭示可燃物点燃过程的热量输运机制，阐明颗粒温度/能量、可燃物特性及环境风对可燃物阴燃点燃及其诱发明火点燃控制机理的影响；基于飞火点燃的气相化学反应本质，发展耦合可燃物热解反应和热解气氧化燃烧的可燃物阴燃点燃及其诱发明火点燃数值模型；最终揭示飞火颗粒、环境及可燃物交互作用中的传热传质机理。项目成果将促进对飞火颗粒点燃行为的科学认识。

The spotting ignition by firebrands is an important pathway by which wildland and urban (including WUI) spot fires are started. Upon impacting with combustible materials, such as natural fuels or building materials, firebrands can initiate spot fires by direct flaming or smoldering ignition，and self-sustained smoldering can transition to flaming. However, available studies on the firebrand ignition process mainly concentrate on the flaming ignition behavior and the knowledge on the smoldering and transition to flaming ignition behavior is limited. The current project aims to systematically investigate the smoldering and transition to flaming ignition of the various recipient fuels with the coupling effects of wind and firebrands, and capture the critical conditions for firebrand ignition. Analyses of typical characteristic parameters (ignition delay time, temperature distribution around particle, critical ignition parameters) and theories based on heat/mass transfer, pyrolysis kinetics and fluid mechanics, are to be used to uncover the heat transfer during the ignition process and clarify the effects of the particle temperature/energy, the recipient fuel properties and wind on the control mechanism of the smoldering and transition to flaming ignition. Then, a numerical model for the smoldering and transition to flaming ignition of recipient fuel, associated with the coupling the pyrolysis kinetics of recipient fuel and the oxidation reaction of pyrolysis gases, will be proposed based on the nature of firebrand ignition. Finally, the heat/mass transfer mechanism between the firebrands, atmosphere and recipient fuel during the ignition process will be revealed. The research of this project will promote the scientific understanding of spot fire phenomenon.