Firebrands are a widely observed phenomenon in wildland fires, which can transport for a long distance, cause spot ignition in the wildland–urban interface (WUI) and increase the rate of wildfire spread. The flame attached to a moving firebrand behaves as a potential pilot source for ignition, so extinguishing such a flame in the process of moving can effectively minimize its fire hazard. In this work, firebrands were represented by a dry wood ball with a diameter of 20 mm and a weight of 2.9 g, which carried a flame with the heat release rate of 250 W. The firebrand was held by a pendulum system to adjust the velocity. Results showed that there is a minimum sound pressure to extinguish the firebrand flame, which increases slightly with the sound frequency. As the firebrand velocity increases from 0 m/s to 4.2 m/s, the minimum sound pressure for extinction decreases significantly from 114 dB to 90 dB. The cumulative effect of firebrand motion and acoustic oscillation was found to facilitate flame extinction. A characteristic Damkohler number (~ 1), with the ratio of the fuel residence time to the flame chemical time, is used to quantify the extinction limit of the flaming firebrand. This work provides a potential technical solution to mitigate the hazard of firebrand flame and spotting ignition in WUI and helps understand the influence of acoustic waves on the flame stability on the solid fuel.

中文翻译：

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野地-城市交界处防火移动火标上火焰的声学熄灭

火把是野火中广泛观察到的现象，它可以长距离传播，在野地-城市界面（WUI）引起点状点火并增加野火蔓延的速度。附着在移动的火把上的火焰是潜在的引火源，因此在移动过程中扑灭这种火焰可以有效地将其火灾危险降到最低。在这项工作中，火把由一个直径为 20 毫米、重量为 2.9 克的干木球代表，其携带的火焰的热释放率为 250 W。火把由摆锤系统固定以调节速度. 结果表明，有一个最小声压可以扑灭火种火焰，该声压随声频的增加而略有增加。随着火种速度从 0 m/s 增加到 4.2 m/s，消光的最小声压从 114 dB 显着降低到 90 dB。发现火炬运动和声波振荡的累积效应有助于火焰熄灭。一个特征性的 Damkohler 数 (~ 1)，以及燃料停留时间与火焰化学时间的比值，用于量化燃烧火种的熄灭极限。这项工作提供了一种潜在的技术解决方案，以减轻 WUI 中火种火焰和点状点火的危险，并有助于了解声波对固体燃料火焰稳定性的影响。用燃料停留时间与火焰化学时间的比值来量化燃烧火种的熄灭极限。这项工作提供了一种潜在的技术解决方案，以减轻 WUI 中火斑火焰和点状点火的危险，并有助于了解声波对固体燃料火焰稳定性的影响。用燃料停留时间与火焰化学时间的比值来量化燃烧火种的熄灭极限。这项工作提供了一种潜在的技术解决方案，以减轻 WUI 中火斑火焰和点状点火的危险，并有助于了解声波对固体燃料火焰稳定性的影响。