A flaming transition of smoldering thin-rod biomass in low pressure

A flaming transition behavior of smoldering porous specimen was carefully observed in low-pressure chamber under higher oxygen concentrations at Yo = 0.53. The low-pressure experiment reproduced the transition behavior with high accuracy that the transition occurs at a certain distance within 0.6 mm in standard deviation. The varied pressure range of the present work is 1.0 - 100 kPa and atmospheric gas is a mixture of dried nitrogen and oxygen in this experiment. A 2-mm-rod-shaped biomass stick is considered as the burning specimen. The specimen was located vertically and forced ignition was made at the top to achieve the following downward propagation. Two transition modes were identified: one is the transition before ash disappears (Transition regime ?), the other is the transition caused by randomly disappearing ash (Transition regime II). The length of the smoldering region when the transition occurred in the transition regime ? was measured. From the relationship between the length of smoldering and the partial pressure of oxygen in the transition regime I; the trigger of the transition is expected to have the strong relation with the total heat release from the luminescence region.