非对称多火源燃烧交互受限卷吸特性与传热机理研究

Forest and town fires are usually caused by jump fires or high temperature radiations igniting the adjacent combustibles thus forming multiple fires burning and eventually developing into large scale mass fires. The current research on multi-fire behaviors is mainly based on the fire array way in which the sizes of all fires are identical and the fires are placed symmetrically. While in actual mass fire scenarios, the sizes of fire sources are diverse. The characteristics of the asymmetric air entrainment and heat feedback would result in an unsuitable use of the theory based on the symmetric multiple fires to the asymmetric multiple fires. In this project, experimental study, theoretical analysis and numerical simulation methods will be adopted to systematically study the air entrainment and heat transfer behaviors of the asymmetric multiple fires under different fuel types, fire sizes and array ways. The evolution of flame shape will be elucidated firstly to establish the air entrainment model and flame shape model of asymmetric multiple fires. Then, by analyzing evolutions of the wall conduction, flame convection and flame radiation of each pool, the model of the controlling heat feedback mechanism for the burning rate of asymmetric multiple fires will be proposed. Finally, the flame radiation characteristics under different fuel types will be revealed, then the global flame radiation model for asymmetric multiple flames will be established. This study can develop the theory of interaction restricted behavior of asymmetric multiple fire plumes, and provide theoretical guidance and technical support for the monitoring, early warning and prevention of forest and town mass fires. It has great theoretical significance and practical value.

森林和城镇大火往往是由着火点附近可燃物被飞火直接点燃或高温辐射引燃形成多火源燃烧并最终发展成为大规模群发性火灾所致。目前的多火源燃烧行为研究主要基于火阵列中各个火源尺度相同且对称放置。而在实际的群发性火灾场景中，火源尺度大小各异，呈现非对称空气卷吸和热反馈特性，导致基于对称多火源的机理和规律不再适用。本项目拟采用实验研究、理论分析和数值模拟相结合的方法，系统研究不同燃料类型、火源尺度和分布特征下非对称多源的空气卷吸和传热特性：阐明火焰形态演化规律，建立非对称多火羽流的空气卷吸和火焰形态模型；分析各个火源壁面传导、火焰对流和火焰辐射三项热反馈演变规律，建立非对称多火源燃烧的热反馈主控机制模型；揭示不同燃料种类的火焰辐射特性，建立非对称多火焰全局对外辐射模型。本研究可发展非对称多火羽流交互受限行为理论，为森林和城镇群发性发火灾监测预警和防控提供理论指导与技术支撑，具有重要的理论意义和实用价值。

森林和城镇大火往往是由着火点附近可燃物被飞火直接点燃或高温辐射引燃形成多火源燃烧并最终发展成为大规模群发性火灾所致。目前的多火源燃烧行为研究主要基于火阵列中各个火源尺度相同且对称放置。而在实际的群发性火灾场景中，火源尺度大小各异，呈现非对称空气卷吸和热反馈特性，导致基于对称多火源的机理和规律不再适用。本项目拟采用实验研究、理论分析和数值模拟相结合的方法，系统研究开放空间和隧道受限空间中不同燃料类型、火源尺度和分布特征下非对称多源相互作用燃烧的空气卷吸和传热特性。首先，开展了开放空间双火源相互作用燃烧行为研究，揭示了双矩形火源在不同火焰融合阶段的火焰形态、火焰高度和竖向气体温度分布规律，分析了大小双方形气体火源在不同火源功率和间距下的火焰融合行为，揭示了非对称火焰脉动卷吸特性，研究了大小双圆形油池火在不同火源直径和间距下的燃烧行为，揭示了各个火源燃烧速率演化规律和热量反馈主控机制。其次，研究了自然通风隧道内大小双火源在不同火源功率和间距下的相互作用火焰形态，揭示了不同火焰融合状态下顶棚纵向气体温度分布规律，并建立了相关参数物理预测模型，由此确定了引燃相邻可燃物的临界安全距离。最后，研究了纵向通风隧道内大小双火源在不同通风速度、火源功率和间距下的火焰倾斜、融合行为，揭示了火焰倾角与纵向通风作用力、火源自身热浮力以及火源间相互作用力之间的耦合关系；研究了纵向通风隧道内障碍物对双火羽流运动特性的影响，揭示了纵向通风和障碍物条件下的隧道纵向温度分布以及顶棚下方最高温度演化规律。本研究可发展非对称多火羽流交互受限行为理论，为森林和城镇群发性发火灾监测预警和防控提供理论指导与技术支撑，具有重要的理论意义和实用价值。