Self-Sustained Flaming Combustion and Ignition of Single Wood Pieces in Quiescent Air

ABSTRACT

Single wood pieces in quiescent air were ignited by an electric coil which was removed shortly after. There was found some critical size, specimens smaller than which would be ignited, burn with a flame and, produce a carbonaceous residue (sometimes glowing). Thin pieces burned more easily than thick ones but the duration of flaming combustion depended on the specimen size. Pieces thicker than the critical size did not sustain a flame. Simplified theoretical analysis based on pure one-dimensional transient heat conduction gave a satisfactory description of the evolution of the pyrolysis process and the surface gas flux. There also existed a minimum heating rate that led to piloted ignition; the heating process with a rate lower than this minimum would simply result in carbonization without flame. Calculations on piloted ignition of thin samples showed that thinner pieces need higher heating rates than thicker ones, which agreed with experimental measurements.

Key Words:

• Wood combustion
• flame over wood
• burning of wood
• forced ignition of wood
• pyrolysis of wood
• heat transfer in wood blocks