Just Accepted
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Experimental study on the ignition of fuel beds by two firebrands in tandem arrangement under wind conditions
Abstract
Background: In wildland fires, the multiple firebrands deposited on the fuel beds are likely to exhibit small separation distances and have the potential to ignite the fuel bed that cannot be ignited by a single firebrand or accelerate the fuel ignition compared to a single firebrand. Aims: This research provided a combined experimental and analytical study on the ignition behavior of pine needle fuel beds by two cylindrical firebrands in tandem arrangement. Methods: A small-scale wind tunnel was used for the ignition and heat flux measurement experiments with wind speeds up to 4 m/s. Key results: The heat fluxes produced by the firebrands and the ignition probability of fuel beds increased, while the ignition delay time of fuel beds decreased with increasing wind speed. The two tandem firebrands can accelerate the ignition of the fuel bed within the critical separation distance. Conclusions: A semi-empirical model for the ignition delay time of the fuel bed was derived based on the energy balance concept, which coupled the separation distance and the wind speed. Implications: This work demonstrates the cooperative ignition effect of two firebrands and is valuable for future research on the ignition behavior of fuel beds by more nearby firebrands.
WF24133 Accepted 28 April 2025
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