Propagation of the ignition front in beds of wood particles

The speed of the propagation of the ignition front downwards against the air flow in a fixed bed of burning wooden particles has been studied. The ignition speed reaches a steady state soon after ignition at the surface, if the inlet air temperature is the same as the initial temperature of the fixed bed. Modeling of the quasi-steady-state speed of propagation of the ignition front is considered. The effects of the flow rate of air, moisture, particle size, density, and wood species on the velocity of the ignition front and on the maximum temperature in the bed are studied experimentally and interpreted by modeling. A maximum speed of propagation was observed with a specific air rate. Correlations for estimating the velocity of the ignition front and maximum temperature in the bed are presented. (C) 2000 by The Combustion Institute.