Flame Extensions Under a Curved Ceiling

Abstract In this paper, the factors affecting flame extension under curved ceilings are presented. An experimental campaign in reduced scale was carried out in Lund University’s Fire Lab using a propane gas burner and heptane pool fire in different positions and heat release rates within a curved ceiling setup. A flame recognition script was developed to identify the flame length in the videos taken for each test. The flame length data was then compared with flame length models found in the literature which have only been developed from buoyancy driven flows. The results show that the curved geometry affects flow, enhancing it and resulting in longer flames. This is particularly clear in the tests with the propane gas burner. When positioned flush against the side wall, the reduced air entrainment and the gas’s momentum cause unburnt fuel to travel further along the ceiling, thereby extending the flame length. In the case of pool fires, proximity to the wall reduces the heat release rate which in turn limits the flame extensions. Consequently, momentum dominated flows such as those produced by the propane burner, result in longer flame extension compared to the buoyancy dominated flows characteristic of pool fires. The greatest difference between the experimental data presented in this study and flame extension models found in the literature is attributed to the omission of the flow’s buoyancy component in these models. Additionally, the type of fire, whether buoyancy or momentum dominated, and its position within the test setup impact the flame extensions. To address these limitations, this work introduces adaptations of previously published models.