Transient Analysis of Fire-Induced Heat Transfer in Cylindrical Sealed Space
The main objective of the present work is an investigation of the heat transfer induced by the fire in a cylindrical sealed space. The thermal smoke flow geometry characteristics in cylindrical sealed space were discussed, LES and mixture fraction methods were applied to conduct numerical transient analysis. Computed results has validated the smoke flow course in simulation experiments. The study indicates that the heat transfer faster upper the fire source than around it. When the fire source location is near the wall, the smoke layer distributing were not distinct far from the fire source, and the heat transfer faster in transverse than longitudinal direction. Keywords—heat transfer , fire, cylindrical sealed space, numerical simulation.
Air entrainment into buoyant jet flames and pool fires
Abstract A simple model for the fire dynamics of turbulent fires is proposed and then used to derive correlations for air entrainment into turbulent jet fires and pool fires. Five parameters are identified to control the fire dynamics: the pool diameter D, the total buoyancy flow B∞, a buoyancy force per unit mass at the adiabatic stoichiometric temperature ( ΔT ad T ∞ )g , the ambient density ϱ∞, and the stoichiometric mass air to fuel ratio S. These parameters lead by dimensional arguments to correlations for air entrainment rates, which are further refined by using a simplified physical model. Three distinct regimes for air entrainment are identified in turbulent pool fires: (a) close to pool surface where entrainment rates vary as Z 1 2 (where Z is the vertical distance from the source), (b) near the neck-in area where entrainment rates vary as Z 3 2 , and (c) farther downstream but below the flame tip where entrainment rates vary as Z 5 2 . The proposed correlations are used to plot experimental data from which proportionality coefficients are determined. It is shown, also, that there is a relationship between entrainment rates up to the flame tip and visible flame feights; such a relationship would allow one to estimate entrainment rates by measuring visible flame heights.
Some experiments on buoyant diffusion flames
Abstract In flames produced by freely burning fuel, buoyancy may play an important role in determining the speed of the gases in the flame zone and hence the flame height. Measurements have been made of the height of flames from burning cribs of wood on a square horizontal base and a few for two other arrangements. The results are consistent with a dimensionless analysis, leading, for one particular fuel system, to the functional equation L/D = f(Q2/gD5), where L is the flame height, D the linear dimension of the fire or orifice, Q the volumetric flow rate of gaseous fuel at ambient temperature and g the acceleration due to gravity. In turbulent fuel jets L/D is a constant for a given fuel which is shown theoretically to be a limiting case of this relation.