Characterization of flammability and species yields for PMMA burning at constant equivalence ratios in a fire propagation apparatus

Abstract

A new method for the measurement of the heat release rate and products of combustion at constant global equivalence ratios (GERs) was developed. This method was based on a modified Fire Propagation Apparatus (FPA) equipped with O₂, CO₂, CO, total hydrocarbons (THC), particulate matter (PM), NO, and HCN sensors. The control of GER was achieved by administering precisely calibrated, time-varying air flow to the combustion zone. To demonstrate this method's capabilities, the combustion of poly(methyl methacrylate) (PMMA) was investigated at GER ranging from 0.63 to 1.96. The CO₂ yield, expressed as mass of species per mass of pyrolyzate, and heat of combustion were found to monotonically decrease from 2.04 to 1.05 and from 23.6 kJ g⁻¹ to 15.1 kJ g⁻¹, respectively, with increasing GER. Conversely, CO, PM, and THC yields increased from 0.019 to 0.263, from 0.015 to 0.051, and from 0.006 to 0.301, respectively, with increasing GER. Good carbon balance, within ±5 %, was achieved across the entire GER range. The characteristic time the combusting mixture spends in the FPA's test section was identified as another key parameter, alongside GER, that affected both species production and heat release. An empirical model was developed and validated to fully capture these dependencies.