Pyrolysis and piloted ignition of thermally thick PMMA exposed to constant thermal radiation in cross forced airflow

Impact of cross forced airflow on pyrolysis and piloted ignition of PMMA (Poly methyl methacrylate) under constant heat flux is experimentally, analytically and numerically addressed in this study. Experimental setup consisting of a heating and blowing units was employed to provide the target constant heat flux and airflow velocity. Surface temperature and ignition time were measured in tests to examine the combined effect of forced airflow and heat flux. No ignition was observed when the heat flux and air velocity were 11.53 kW/m² and 1.43 m/s combined, indicating a critical airflow velocity dominates ignition. An analytical model and a solid phase numerical model were developed to predict and validate the experimental measurements. Both surface and in-depth absorption of thermal radiation were considered in the models. The results showed both the critical temperature and ignition time increase with airflow velocity. Radiation reducing was found to be enhanced by increasing airflow velocity. Both the analytically and numerically predicted results employing either pure surface or in-depth absorption of thermal radiation matched the experimental measurements at acceptable levels, but the agreement between the calculations of in-depth absorption and measurements was better.