A multiphase approach for pyrolysis modelling of polymeric materials

In this study, a multiphase pyrolysis model has been proposed under the large eddy simulation (LES) framework incorporating moving boundary surface tracking, char formation, and detailed chemical kinetics combustion modelling. The proposed numerical model was applied to simulate the cone calorimeter test of two kinds of materials: (i) pinewood (charring) and (ii) low-density polyethylene (non-charring). Using a cone calorimeter setup, good agreement has been achieved between the computational and the experimental results. The model is capable of predicting the formation of the char layer and thus replicating the flame suppressing thermal and barrier effects. Furthermore, with the application of detailed chemical kinetics, the fire model was able to aptly predict the generation of asphyxiant gas such as CO/CO₂ during the burning process. However, the pinewood experiments showed significant CO/CO₂ emissions post flame extinguishment attributed to char oxidation effects, which were not considered by the fire model. Despite the limitation, the fully coupled LES model proposed in this study was capable of predicting the fluid mechanics and heat transfer for the turbulent reacting flow, solid-phase decomposition, and gaseous products under flaming conditions. In the future, it can be further extended to include char oxidation mechanisms to improve predictions for charring materials. © 2021, Tsinghua University Press.