Basic Study on Backdraft. Mass Loss Rate of Wood Combustion on the Low Oxygen Concentration Condition.

Abstract

In this study, we measured pyrolysis and combustion characteristics of wood with a view to make clear premix and ignition mechanism of backdraft. Cone calorimeter was used to measure heat release rate(HRR)curves and mass loss rate(MLR)curves for 18 mm thick Lauan woods at an incident heat flux of 50 kW/m2. Lauan has two peaks in the HRR and MLR curve. First sharp peak comes soon after ignition and a second peak appears near the end of the flaming combustion period. We also measured MLR curves and oxygen concentration curves for 18 mm thick Lauan woods in constant temperature, low oxygen concentration furnace. In low oxygen condition, MLR was de-creased because heat feedback from flame was decreased. In order to explain the second peak observed in the HRR and MLR curve, a simple calculation was carried out by considering wood and char properties and wood pyrolysis rate. It was found that the second peak is the result of a rapid rise in the bulk temperature of the remaining wood. The second peak is primarily dependent on the un-exposed face conditions.