Tilt of Flame from an Item Burning Close to a Wall

摘要

To model the flame tilt angle toward wall surface, experimental and theoretical studies were carried out. Cubical-shaped flexible polyurethane foam having 0.5 m edge length was burned at a position close to a wall made of ceramic fiber board. The separation distance between wall and specimen surfaces was in the range of 0.01 m to 0.2 m. Flame tilt angle increased with separation distance, but ceased at more than certain separation distance. To develop a mathematical model for flame tilt angles, the ratio of buoyancy force to inertia of entrainment air was considered. A virtual cylinder with a radius of n-times of fire source diameter was considered as an entry of entrained air flow. The effect of blocking by wall surfaces was considered by the angle between wall ends seen from fire source. In case of flames collided with wall surface, the flame tilt angle was calculated assuming that flame bends along with wall surface while keeping the same total flame length as in open configuration. Flame tilt angle increased with separation distance in case of flame collide on wall surface. The prediction results were compared with experimental data and existing models. The proposed model could predict the changes of flame tilt according to the separation distance fairly well. As an overall comparison, the proposed model is in better agreement with experimental data than existing models.