Study of flows induced by hot gas injection into a mechanically ventilated room - Application to fire smoke propagation in multi-rooms fire scenarios
Congress title :5th International Seminar on Fire and Explosion Hazards
Congress town :Edimbourg
Congress date :23/04/2007
This work deals with fire smoke propagation between forced ventilated rooms in the framework of a research program undertaken by the French institute "Institut de Radioprotection et de Sûreté Nucléaire" (IRSN) in collaboration with the University of Aix-Marseille. The objective is to study the mechanisms of smoke propagation in multi-rooms fire scénarios in the spécifie configuration of confined rooms (few openings) connected to a mechanical ventilation network. The smoke flows are mainly the filling in the fire room, the flow at the doorway between rooms and the spill plume in the target room. The effects of the mechanical ventilation and in particularly the renewable rate, the locations of inlet or outlet ventilation branches on smoke motions are investigated.
The study is undertaken from an expérimental approach based on real and reduced scale facilities in order to propose on the one hand a detailed description of the flow motions and on the other hand an extensive parametric analysis. Two kinds of reduced-scale models have been developed: an isothermal one and a thermal one. They both represent two rooms, equipped with a ventilation System, connected by a door and with a scale réduction of 1:5 in comparison with the real scale référence. In the isothermal model (Fig. 3 (a)), smoke production is simulated by injecting a light gaseous mixing of air and hélium, respecting the Froude number conservation. In the thermal model (Fig. 2 (a)), hydrocarbon pool fire is used as smoke source. The thermal model is aimed at obtaining addiûonal information induced by the combustion process, flame radiation and thermal losses at walls. In addition, to support reduced scale approach, real scale experiments are conducted in the DIVA facility of IRSN which represents a typical industrial configuration (Fig. 1 (a)).
The poster présents the gênerai description of the programme and the first results. Laws of similitude on which the reduced scale approach is based are presented. The behaviour of spill plume in the target room is shown from tomography laser visualisations conducted on the one hand at real scale in DIVA facility (Fig. 1 (b)) and on the other hand in the two reduced scale models (Fig. 2 (b) and Fig. 3 (b)). The flow geometry is quantified from digital image processing; information concerns the thickness of the smoke layer at the door, the spill plume trajectory (the centreline and the edges) and the location of the spill plume impact at the ceiling of target room. First results are discussed and comparison between the data obtained from the three facilities is presented.