Bulk and particle properties of pine needle fuel beds - influence on combustion

This paper presents a study to assess the influence of pine needle layer characteristics on combustion for three pine species of the Mediterranean region of France. It identifies the key parameters that explain the combustion of this fuel bed component. A relationship between permeability of the litter layer, fuel bed porosity and needle geometrical properties is presented. Although permeability was found to influence the rate of heat release from the combustion of litter independent of litter species, this was not the case for litter layers with similar mass and porosity. This study also stresses the important role of particle properties on their time to piloted ignition. The surface-to-volume ratio (SVR) of the species is the essential parameter driving the time to ignition as it defines the thermal thickness of single needles. This parameter also influences the combustion dynamics of litters under forced convection. In that case, the heat release rate of pine needle litters with the same permeability increases with the SVR of the species.