Firebrand burning under wind: an experimental study

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Abstract
Background: Spot fires play a significant role in the rapid spread of wildland and wildland–urban interface fires. Aims: This paper presents an experimental and modelling study on the flaming and smouldering burning of wood firebrands under forced convection. Methods: The firebrand burning experiments were conducted with different wind speeds and firebrand sizes. Key results: The burning rate of firebrands under forced convection is quantified by wood pyrolysis rate, char oxidation rate and a convective term. The firebrand projected area is correlated with firebrand diameter, char density, wind speed, and flaming or smouldering burning. A surface temperature model is derived in terms of condensed-phase energy conservation. We finally establish a simplified firebrand transport model based on the burning rate, projected area and surface temperature of firebrands. Conclusion: The mass loss due to wood pyrolysis is much greater than that due to char oxidation in self-sustaining burning. The burning rate is proportional to U1/2, where U is wind speed. The projected area for flaming firebrands decreases more rapidly than that for smouldering ones. The firebrand surface temperature is mainly determined by radiation. Implications: Knowledge about firebrand burning characteristics is essential for predicting the flight distance and trajectory in firebrand transport.
Funding Information
  • National Key Research and Development Program of China (2022YFC3003000)
  • China Postdoctoral Science Foundation (2021M703083)
  • Foundation of State Key Laboratory of Laser Interaction with Matter (SKLLIM2001)
  • National Natural Science Foundation of China (52321003 and 51936011)

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