Effect of fuel bed size and moisture on the flammability of Eucalyptus saligna leaves in cone calorimeter testing

摘要

The effect of the fuel bed size and moisture content on the flammability of Eucalyptus saligna leaves was investigated using the Cone Calorimeter. Tests were carried out using modified cylindrical shape ?closed? sample holders with various diameters. This specific type of sample holder did not allow mass transfer through the sample boundaries and minimised the convective heat transfer from the sides. Leaves were conditioned to three different states, i.e. oven-dried, natural-dried, and fresh samples resulting in different values of moisture content. Flammability criteria such as time to ignition, burning rate, heat release rate, and heat of combustion were measured and analysed in every test condition. The results show an evident influence of the sample diameter, as well as fuel moisture content, on the flammability. The values of burning rate and heat release rate increase at a diameter range of 5?12.5 cm and slightly decrease until the 17.5 cm diameter. Thus, the sample size used in the cone calorimeter must be explicitly considered to get comparable results. The study also shows the importance of adequate testing method and sample preparation in small-scale flammability study of wildland fuel.