SUMMARYThe lattice Boltzmann method (LBM) is becoming an effective numerical technique of computational fluid dynamics (CFD). In this study, with some new thermal LBM schemes being proposed, the LBM is used to simulate the gravity current prior to backdraft (a particular and hazardous phenomenon in compartment fire) within laminar restrictions. The dimensionless time for gravity current traveling from the opening to the rear wall of a bench-scale compartment is calculated under different opening geometries, respectively, including: full end opening, upside-slot end opening, middle-slot end opening, downside-slot end opening, and slot ceiling opening. The application is very successful and the results show that the dimensionless time under the slot ceiling opening is the longest. Among the slot end openings, similar dimensionless time has been obtained for the upside-slot and middle-slot end openings, which is shorter than the downside-slot end opening. For the full end opening, the shortest dimensionless time is obtained. Finally, some valuable advices are given for fire protection engineering.

Current assessment models and experimental tests on gas toxicities in a fire hazard are mainly based on the hypothesis that uniform smoke and gas layers exist in the compartment. This study, through experiments conducted in a reduced-scale compartment—corridor model, examines the assumption and explores the characteristics of spatial distribution of toxic gases in smoke transport from a fire hazard. The results suggest that the toxic gases in the upper layer in the corridor are characterized by uniform expansion, while those in the lower layer are not. It has also been found that evolutions of the gases in different layers are not synchronous, while they are identical at the same height where the densities are close. Further analyses indicate that the formation of CO from the deoxidization of O2, CO 2, and the unburned hydrocarbon in the smoke movement delays the time of the maximum concentration.