Numerical study on the effect of oxygen concentration on the piloted ignition of PMMA in reduced pressure atmospheres

摘要

Purpose - This study aims to investigate the controlling mechanisms of ambient oxygen and pressure on piloted ignition of solid combustibles under external radiant heating. Design/methodology/approach - The numerical simulation method was used to model the influence of ambient oxygen concentration on the piloted ignition of a thermally irradiated solid sample in reduced pressure atmospheres. The solid phase decomposition and gas phase kinetics were solved simultaneously. Findings - It was determined that the elevated oxygen atmospheres resulted in a higher flame temperature and a thicker temperature profile over the solid surface. Also, increasing oxygen and reducing pressure had a similar effect in the decrease of the ignition delay time. The shorter ignition time in reduced pressure was mainly because of the decreasing of convective heat losses from the heated solid. As oxygen was reduced, however, ignition occurred later and with a greater mass loss rate because more volatiles of solid fuel at transient ignition were required to sustain a complete reaction under an oxygen-poor condition. Research limitations/implications - The results need to be verified with experiments. Practical implications - The results could be applied for design and assessment of fire-fighting and fire prevention strategies in reduced pressure atmosphere. Originality/value - This paper shows the effect mechanism of ambient oxygen and pressure on piloted ignition of solid combustibles.