Pyrolysis and Combustion Processes of Combustible Materials under External Heat Flux

Abstract

Fire behaviors of four types of combustible materials, including wood, non-charring, charring and intumescent polymers, were investigated under autoignition conditions both experimentally and numerically. This study contained three parts. In the first part, six species of wood, including pine, beech, cherry, oak, maple, and ash, were studied experimentally under autoignition conditions in a cone calorimeter. Empirical models were developed for the first time to predict autoignition time, average mass loss rate, time at 50% mass loss, and CO yield of wood samples with various moisture contents under autoignition conditions. In the second part, fire behaviors of six species of polymers, including HDPE, PP, PMMA, ABS, PET and PC, were investigated experimentally under autoignition conditions in the cone calorimeter. Ignition methods were found significant to combustion efficiency of non-charring polymers, but their influence on charring polymers was observed insignificant. Experimental results indicated that both CO and CO2 yields increased significantly when non-flaming combustion transitioned to flaming combustion. An empirical model was developed to predict thermal thickness of polymers under heat flux. In the third part, a new mathematical model, FiresCone, was developed to simulate pyrolysis and combustion processes of these four types of combustible materials. FiresCone has considered as many fire processes as possible to improve the modeling accuracy and expand its application. FiresCone was validated by experimental results from the first two parts. FiresCone provides not only a practical tool for fire risk evaluation, but also fundamental supports to full-scale fire modeling.