Experimentally producing firebrands showers from disparate fuels to represent the combustion of structural and vegetative fuels simultaneously

Abstract

A laboratory-scale firebrand generator, developed by the authors, has been used to generate a new set of firebrand distributions to replicate firebrand shower processes from cedar building materials and mixed, disparate Douglas-fir/cedar wood species. Douglas-fir (DF) wood pieces were intended to represent firebrands from vegetative fuel combustion, such as shrubs or trees, and were cut into the dimensions, average (± standard deviation) of 7.9 (± 1) mm (thickness), 7.9 (± 1) mm (width), and 12.7 (± 1) mm (length) with the mass of 0.50 (± 0.05) g. Western Red Cedar (WRC) wood pieces, intended to represent firebrands from burning buildings, were made from Red Cedar wood shingle siding, and cut into the dimensions, average (± standard deviation), of 40 (± 2) mm (length), 40 (± 2) mm (width), and 6.9 (± 1.8) mm (thickness) with the mass of 3.59 (± 0.91) g. Glowing firebrand distributions were produced by feeding these wood types in the firebrand generator using three methods: DF only at 80 g/min, WRC only at 80 g/min, and a mix of DF at 40 g/min and WRC at 40 g/min. For each feeding scenario, results are reported on the spatially resolved number distribution, as well as detailed size, mass, and exit velocity of the generated firebrands. For the first time, it is possible to simultaneously produce glowing firebrands representative of vegetative combustion and building combustion in the same shower.