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Effects of atmospheric oxygen on horizontal peat smoldering fires: experimental and numerical study

Author(s): Jiuling Yang, Naian Liu, Haixiang Chen, Wei Gao, Ran Tu
Year Published: 2019

The smoldering combustion of natural organic layers such as peatlands leads to the largest and most persistent wildland fires on the Earth. The atmospheric oxygen concentration (mass fraction of oxygen: ) significantly influences the smoldering characteristics of peatlands. This work investigates the effects of on horizontal peat smoldering behaviors by experimental and numerical means. The experimental results indicate that as increases, the upper surface of the dry peat undergoes a transition from weak charring (without combustion) to surface glowing combustion. The smoldering peak temperature increases with increasing , and when YO2 is beyond a certain value (35% in this work), the surface smoldering spread rate starts to deviate from the centerline smoldering spread rate. The decrease in the averaged volume ratio of and with increasing manifests the rise in CO2 production owing to intense surface oxidation reactions. For the first time, the model predicts the overhang structure of peat during horizontal smoldering spread. A theoretical criterion for the transition to surface glowing combustion is proposed as the onset of the second surface β-char oxidation, which needs sufficient oxygen and high enough surface temperature. Finally, two nonlinear transition thresholds varying with oxygen concentration and wind velocity are predicted.

Citation: Yang, Jiuling; Liu, Naian; Chen, Haixiang; Gao, Wei; Tu, Ran. 2019. Effects of atmospheric oxygen on horizontal peat smoldering fires: experimental and numerical study. Proceedings of the Combustion Institute 37(3):4063-4071. https://doi.org/10.1016/j.proci.2018.06.218
Topic(s): Fire Effects, Ecological - Second Order, Soils, Fire & Fuels Modeling
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 19396
FRAMES RCS number: 57603
Record updated: Apr 16, 2019