Operational limits of ignition front propagation against air flow in packed beds of different wood fuels

Propagation of the ignition front against airflow in packed beds of different wood fuels has been studied. The results of experiments carried out with pellets and mixtures of wood chips and sawdust are presented and compared with earlier experiments with different wood fuels. Increase in particle density and size was found out to widen the range of possible airflow rates, and transfer the maximum rate of ignition front propagation toward fuel lean conditions. Increase in the average sphericity of particles decreases the porosity of the bed. Mixing of small and large particles seems to be advantageous for combustion so that small particles change the optimum airflow rate to fuel rich conditions and large particles widen the usable range of airflow rates. A correlation was found for the maximum rate of ignition front propagation in beds of wood fuels