Assessing the effect of oxidizer on flame geometry and effluent composition from burning solids

The combustion chemistry and geometry of a diffusion flame are dictated by the transport of a fuel and an oxidizer towards a flame sheet. To enable the independent assessment of the impact of an oxidizer on a diffusion flame, the fuel injection rate must be controlled independently of the airflow. Through the independent control over the burning rate of the synthetic polymers polymethylmethacrylate (PMMA) and polyoxymethylene (POM), it is demonstrated that flame geometry can be systematically varied as a function of the oxygen environment. Both polymers were studied in the Fire Propagation Apparatus using a constant mass loss rate (MLR) under varying oxidative environments (177 L min⁻¹, 0 – 20.9 % vol O₂). This study draws upon frameworks developed for co-flow burners, allowing the characteristics of a diffusion flame to be established as a function of the oxidative environment. Flames sustained under lower oxidative environments displayed decreased luminosity and anchoring, with the heat flux from the POM flame decreasing by 14.7 kW m⁻² as the oxygen concentration decreased from 20.9 % to 9.25 %. By relating combustion emissions to the flame geometry, through the use of a constant MLR, the processes controlling the emissions from the burning of solids have been studied in a novel manner.