Under-Ventilated Wall Fire Behaviour during the Post- Flashover Period

Abstract

This work is aimed the evolution of the behaviour of a strongly contained wall fire in an enclosure during the postflashover period. It has characterised the fire intensity decay up to extinction of a wall fire by lack of oxygen and the effects of a sudden door opening on the formation of an air gravity wave capable to bring the backdraft phenomenon. To better understand these two sequential fire scenarios, the study was divided into two complementary parts performed in the same laboratory scale experimental setup. The first part consists to stabilise a steady wall fire at the rear of the compartment and to follow its evolution when a door closes the aperture leaving only a thin slot opened to limit the air entering. It has been observed the formation of a ghosting flame moving through the compartment before dying at the aperture. By supposing the continuation of the fuel solid pyrolysis after flame extinction due to the radiation of the hot environment, fuel vapours continue to fill the compartment. The second part will study the effects of a reopening of the door. It has been observed and characterised the formation and the propagation of a gravity wave through the enclosure. This is representative of the development of the first stage of the backdraft. Tests are performed to measure the aerodynamic properties of the flow behaviour.