The effects of pulsating wind on the transition from smouldering to flaming combustion

Abstract

Smouldering and flaming of solid fuels both originate after the pyrolysis reaction, and fires often transition between the two types of combustion. Smouldering-to-flaming (StF) transition introduces a sudden increase of the fire hazard in terms of temperature, spread rate, and power. The literature has studied the effect of wind on StF but only with continuous wind. Here, we show for the first time the influence of pulsating wind by studying the StF transition on wood samples that have been ignited and where smouldering is spreading. The time to StF transition with pulsating wind takes place, on average, ∼39% earlier than continuous wind, and it is highly repeatable, which is unusual for the previous literature. Pulsating wind enhances the transition by temporarily eliminating the cooling and dilution effects of the wind. This study contributes to the fundamental understanding of StF transition for pulsating wind that often occurs in real conditions but had not been studied before.