Abstract
Effects of radiative energy absorption via decomposed gaseous products on spontaneous gas-phase ignition over a combustible solid heated by external radiation are studied numerically. Numerical model includes time-dependent heat and mass transport and chemical reactions of gas- (exothermic) and solid-phase (endothermic) in three-dimensional domain. PMMA is considered as solid combustibles since rich physical/chemical data is available. Ignition characteristics are examined in different absorption coefficients of MMA vapor and in various orientations of the solid combustibles. It is shown that the ignition delay time gives complex responses in various orientations of the sample (sometimes delays, but sometimes enhances the ignition), while is rarely affected qualitatively by the absorption coefficients, 0.1∿0.2 (atm)^<-1>(cm)^<-1>, considered in the present study. Since the dynamic motion of the 'energy-absorbed-HOT-gases' plays an important role in the prior process of the ignition, precise 3-D transport processes must be considered for an understanding of the absorption effects.
