中文摘要：

飞火是城市火灾特别是城市震后火灾的重要蔓延方式之一，它可以使火灾在相距较远的离散可燃物之间进行跳跃式蔓延，从而增加了扑救难度，威胁扑救人员的安全。因此，对飞火蔓延现象的认识和飞火蔓延距离的计算是降低飞火危险性的前提。基于Baum-McCaffrey火焰羽流模型，重点研究在城市火灾羽流中球形飞火颗粒的上升行为和环境风影响下颗粒的蔓延过程，给出了计算飞火蔓延距离的方法和飞火颗粒在火焰羽流中能够上升的直径区间，并探讨了火灾热释放速率、环境风速和颗粒燃烧特性等因素对飞火蔓延距离的影响。

英文摘要：

Spotting is one of important propagation mechanisms for large〉scale urban fires, especially for post-earthquake urban fires. Firebrands can start new ignitions beyond the continuous fire zone and lead to fire spreading in a non-continuous way, so it can impend fire controlling and threaten to firefighters＇ safety. Understanding the propagation distance of firebrands is the premise for reducing the risk of spotting fire. Based on research results of Baum McCaffrey fire plume structure, this work is an effort to study firebrands lofting in large-scale fires and transporting in ambient wind. In this work, one model for predicting the maximum propagation distance of firebrands is proposed and the factors affecting this distance, including heat release rate of fire, wind speed and firebrand combustion characteristics, are analyzed.