TY - JOUR
T1 - Extinction of Wood Fire
T2 - A Near-Limit Blue Flame Above Hot Smoldering Surface
AU - Lin, Shaorun
AU - Huang, Xinyan
AU - Gao, Jian
AU - Ji, Jie
N1 - Funding Information:
This work is supported by the National Key Research and Development Plan under Grant no. 2020YFC1522800, the National Natural Science Foundation of China (No. 51876183, 51806230), and the SKLFS Open Fund (No. HZ2019-KF02).
Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
PY - 2021/7/7
Y1 - 2021/7/7
N2 - Abstract: Timber is cost-effective and environmentally-friendly, which is a potential material for sustainable buildings, but its fire safety is still a significant concern. In this work, we investigate the burning behaviors of different types of woods and their self-extinction mechanism under external radiation. A unique near-limit flame is observed when the irradiation is above a critical value of about 40 kW/m2. Such a near-limit flame is weak, blue, and discrete that tends to attach to the wood residue surface, different from the normal buoyancy-controlled sooty yellow flame. If the irradiation is low (< 40 kW/m2), the yellow flame extinguishes and transits directly to smoldering at the mass flux of about 4 g/m2 s. However, above the critical irradiation level, the yellow flame transits to the blue flame that does not extinguish until the mass flux of around 1 g/m2 s, extending the flame extinction limit of timber materials. The near-limit blue flame may appear only if the char surface temperature exceeds 700°C. Two critical conditions are hypothesized for this unique blue flame, (I) in-depth pyrolysis (mainly lignin) sustained by the internal smoldering combustion, and (II) the hot surface maintained by large external radiation to extend the flammability limit. This unique blue flame may play an essential role in the transition between flaming and smoldering and help evaluate the fire risk of timber materials under real fire scenarios. Graphical abstract: [Figure not available: see fulltext.]
AB - Abstract: Timber is cost-effective and environmentally-friendly, which is a potential material for sustainable buildings, but its fire safety is still a significant concern. In this work, we investigate the burning behaviors of different types of woods and their self-extinction mechanism under external radiation. A unique near-limit flame is observed when the irradiation is above a critical value of about 40 kW/m2. Such a near-limit flame is weak, blue, and discrete that tends to attach to the wood residue surface, different from the normal buoyancy-controlled sooty yellow flame. If the irradiation is low (< 40 kW/m2), the yellow flame extinguishes and transits directly to smoldering at the mass flux of about 4 g/m2 s. However, above the critical irradiation level, the yellow flame transits to the blue flame that does not extinguish until the mass flux of around 1 g/m2 s, extending the flame extinction limit of timber materials. The near-limit blue flame may appear only if the char surface temperature exceeds 700°C. Two critical conditions are hypothesized for this unique blue flame, (I) in-depth pyrolysis (mainly lignin) sustained by the internal smoldering combustion, and (II) the hot surface maintained by large external radiation to extend the flammability limit. This unique blue flame may play an essential role in the transition between flaming and smoldering and help evaluate the fire risk of timber materials under real fire scenarios. Graphical abstract: [Figure not available: see fulltext.]
KW - External radiation
KW - Extinction limit
KW - Flaming-to-smoldering transition
KW - Timber fire
UR - http://www.scopus.com/inward/record.url?scp=85109690257&partnerID=8YFLogxK
U2 - 10.1007/s10694-021-01146-6
DO - 10.1007/s10694-021-01146-6
M3 - Journal article
AN - SCOPUS:85109690257
SN - 0015-2684
JO - Fire Technology
JF - Fire Technology
ER -