Title of Dissertation: THEORETICAL AND EXPERIMENTAL STUDY OF AUTOIGNITION OF WOOD

A theoretical and experimental study of the autoignition of wood is performed. In the experiment, a wood sample (redwood) of 4 by 4 cm surface area with 4 cm thickness is exposed vertically to a heater panel in a cone calorimeter. The surface temperature is continuously measured by an infrared thermocouple and mass loss is monitored by a load cell. Incident heat flux is varied until glowing ignition could not occur. Times to glowing ignition and flaming autoignition are measured. It is found experimentally that the critical heat flux for flaming autoignition is 20 kW/m2 and for glowing ignition is 10 kW/m2. A theoretical model for autoignition of wood is developed. The model considers the processes occurring in both solid and gas phases. In the solid phase, a one-dimensional heat conduction model is employed. Char surface oxidation, which can lead to glowing ignition, is taken into account at the solid-gas interface surface. By “glowing ignition”, it means the onset of surface combustion. Criteria for glowing ignition are developed based on a surface energy balance. A numerical result shows that according to the present glowing ignition criteria, an inflection point of th