The influence of small mass loss rate peaks on the rate of spread of predictive flame spread simulations: A theoretical study

Abstract

Peaks in the mass loss rate (MLR) curve derived from thermogravimetric analysis (TGA) are commonly used to infer the pyrolysis rates of solid fuels. While the main peaks are often modelled, smaller MLR fluctuations are typically neglected, leading to discrepancies between models and experiments. The impact of these small fluctuations on key simulation predictions, however, remains unclear. This study systematically explores a specific scenario in which a small MLR fluctuation significantly affects the predicted rate of spread (ROS) of a simplified flame spread simulation. The MaCFP-recommended pyrolysis model for poly(methyl methacrylate) (PMMA) is adapted to incorporate a small MLR peak accounting for 0.5 % to 2 % of the sample’s total mass. Results from sensitivity analyses show that the peak position has the greatest impact on the ROS, followed by the peak mass fraction, while the peak width has negligible effect. Adding a small peak at lower temperatures increased the ROS by up to 6 % to 13 %, depending on the peak’s mass fraction, whereas peaks at higher temperatures had little to no effect. These results indicate that fluctuations at lower temperatures, w.r.t. the main peak, could significantly enhance the predicted spread rates and should be considered in flame spread simulations.