Ignition of solid fuel by thermal radiation in a confined rectangular enclosure: Experiment and numerical analysis

In this study, the experimental and numerical analyses have been performed to study the ignition of solid fuel (PMMA) in the rectangular enclosure, wh en it is suddenly exposed to a radiative source with high emissivity. Exper imentally, a high-speed camera has been used to record the flame initiation and propagation in the enclosure for various radiative heat source tempera tures, while the ignition delay time as well as the gas phase temperature w as measured. Numerical analysis has also been performed in a two-dimensiona l geometry by taking account of the effects of gas radiation due to fuel va por. In general the ignition delay time decreased, as the radiative source tempe rature increased, while the ignition location shifted from the upper corner region of hot wall to the upper corner region of fuel wall in the rectangu lar enclosure. Thereby, the ignition mechanism seemed to be changed from th e mixing and transported controlled ignition to the thermally controlled ig nition. While the numerical ignition delays were in good agreement with the experimental ones for the former, numerical result under-predicted experim ental one for the latter since the thermal pyrolysis of PMMA became more im portant than the heat and mass transfer process in the whole ignition proce ss. Usage of numerical simulation was found to be also quite successful in examining and discussing flame behavior after onset of ignition, when the r adiative heat source temperature was varied.