The effect of moisture content and thermal behaviour on the ignition of

Abstract

Fuel moisture content is one of the key parameters controlling the flaming ignition of wildland fuel. However, the role of fuel moisture content in assessing the flammability of different fuel curing (dead and live fuel) is still not well understood. This paper presents the results of ignition tests of fuel beds consisting of dead and live Eucalyptus saligna leaves under a wide range of moisture contents. External heat flux and fuel moisture content are shown to significantly influence time to ignition and mass loss rate at the ignition of Eucalyptus saligna leaves, thus illustrating distinctive heating processes in the fuel bed. The thermal behaviour of the leaf bed before ignition is analysed using the analytical solution to the heat conduction equation, as the classical ignition correlations yield inconclusive results. This approach allows identification of thermally thick and thin behaviours for distinct ranges of heating, with the transition (thermally intermediate) region observed at higher external heat fluxes for higher moisture content. Additionally, a flammability assessment based on time to ignition confirms the inadequacy of the common assumption that live fuel can be considered as moist dead fuel.