Quantifying the controlling mechanisms of opposed flow flame spread: Influence of orientation, material, and external heating

The contribution of gas-phase and solid-phase heat transfer on opposed flow flame spread was quantified under a range of experimental conditions. The thermal gradient ahead of the flame front was determined using a temperature reconstruction method from time resolved temperature data. In all conditions tested, both gas phase and solid phase heat transfer displayed significant contributions to heating ahead of the flame front. PMMA samples were tested in three orientations - downward, horizontal, and lateral. It was found that the lateral configuration displayed the highest rate of flame spread (3.54 mm/min) compared to downward (2.67 mm/min) and horizontal (2.54 mm/min). Lateral spread also exhibited a lower magnitude of solid phase heat transfer compared to the other orientations. Trials that were externally heated showed lower contributions of solid phase heat transfer as the applied surface heat flux was increased. Both PMMA and POM samples were used to compare the effects of the presence of a sooting or non-sooting flame. The methodology provided in this work quantifies the relative contributions of gas-phase and solid-phase heat transfer in opposed flame spread scenarios.