Ignition threshold for impact‐generated fires
Ignition threshold for impact‐generated fires
复制标题
撞击引起的火灾的点燃阈值
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
D. Kring
中科院分区：
文献类型：
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作者：
D. Durda;D. Kring
[1]大规模撞击事件发生后，高能、富含蒸汽的羽流物质重新积聚造成大气加热，可能会产生大面积火灾。本文研究了不同类型植被自燃和引燃所需的阈值辐照度，并确定了三种具体的研究情况：（1）51 kW/m ~ 2持续至少2 min自燃点燃木材;（2）20 kW/m ~ 2持续至少20 min点燃木材;和（3）28 kW/m2，持续至少1 min，以点燃树叶、腐烂的木材和森林凋落物。整个大陆范围内木材自燃的喷射羽流质量阈值为102至6 × 1015公斤，与撞击位置无关，但取决于喷射物速度分布的细节。木材整体自燃的临界喷出羽流质量在1001 ~ 2 × 10 ~（16）kg之间。全大陆范围和全球范围火灾的阈值羽流质量与引导点燃木材的阈值羽流质量非常接近，而全大陆范围和全球点燃树叶和森林凋落物的阈值羽流质量则低得多，低2至3倍。要产生大陆规模的火灾，撞击坑的直径至少要达到85公里，要产生全球规模的火灾，撞击坑的直径必须达到135公里。
[1] Widespread fires can be generated after large impact events by atmospheric heating caused by the reaccretion of high-energy, vapor-rich plume material. We examine the threshold irradiance levels necessary for spontaneous and pilot ignition of various types of vegetation and define three specific cases for investigation: (1) 51 kW/m2 for a period of at least 2 min to spontaneously ignite wood; (2) 20 kW/m2 for a period of at least 20 min to ignite wood in the presence of an ignition source; and (3) 28 kW/m2 for a period of at least 1 min to ignite foliage, rotten wood, and forest litter. The threshold ejected plume mass for continent-wide spontaneous ignition of wood is ∼2 to 6 × 1015 kg, independent of impact location but dependent on the details of the ejecta speed distribution. The threshold ejected plume mass for global spontaneous ignition of wood is in the range ∼1 to 2 × 1016 kg. The threshold plume masses for continent-wide and global fires are very nearly the same for piloted ignition of wood, while the threshold plume masses for continent-wide and global ignition of leaves and forest litter are significantly lower, by a factor of ∼2 to 3. Impact craters of at least 85 km diameter are needed to produce continental-scale fires, and craters of ∼135 km diameter are needed for global-scale fires.