- Author
- Fleischmann, C. M. | Pagni, P. J. | Williamson, R. B.
- Title
- Backdraft Experiments.
- Coporate
- California Univ., Berkeley
- Sponsor
- National Institute of Standards and Technology, Gaithersburg, MD
- Contract
- NIST-GRANT-60NANB1D1168
- Keywords
- experiments | computer programs | simulation | backdraft | gravity current
- Identifiers
- FIRST
- Abstract
- Backdraft is defined as a rapid deflagration following the introduction of oxygen into a compartment filled with accumulated excess pyrolyzates. A scenario describing the physical and chemical fundamentals underlying backdraft phenomena is presented. A half-scale apparatus, designed to avoid dangerous over-pressures, is used to obtain data from backdraft experiments. A gas burner supplies a 150 kW natural gas fire in a 1.2 m high, 1.2 m wide, 2.4 m long compartment with a small, 2.5 cm high 30 cm wide, vent at floor level. Significant excess pyrolyzates accumulate in 180 sec, when a hatch covering a 0.4 m high 1.2 m wide vent, centered on a short wall, is opened, simulating a window breaking due to thermal stresses. The propagation across the compartment of the cold density driven flow, which now enters through the vent, is called a gravity current. The gravity current carries a flammable mixed layer, formed in the shear layer at the interface with the hot fuel-rich layer, to a spark located by the burner on the opposite wall. The rapid deflagration which then results is a backdraft. The average total travel time of the gravity current and the deflagration, in and out of the compartment respectively, is 5.4 ± 0.9 sec. The FIRST compartment fire model is used to calculate conditions in the compartment prior to the backdraft. The hypothesized scenario is confirmed. Future work will provide more quantitative species and flow data and will extend this study to more common fire fuels.