SELF-SUSTAINED FLAMING COMBUSTION AND IGNITION OF SINGLE WOOD PIECES IN QUIESCENT AIR

Single wood pieces in quiescent air were ignited by an electric coil w hich was removed shortly after. There was found some critical size, sp ecimens smaller than which would be ignited, burn with a flame and, pr oduce a carbonaceous residue(sometimes glowing). Thin pieces burned mo re easily than thick ones but the duration of flaming combustion depen ded on the specimen size. Pieces thicker than the critical size did no t sustain a flame. Simplified theoretical analysis based on pure one-d imensional transient heat conduction gave a satisfactory description o f the evolution of the pyrolysis process and the surface gas flux. The re also existed a minimum heating rate that led to piloted ignition; t he heating process with a rate lower than this minimum would simply re sult in carbonization without flame. Calculations on piloted ignition of thin samples showed that thinner pieces need higher heating rates t han thicker ones, which agreed with experimental measurements.