The objective of this study is to examine the feasibility of two combustion models combined with a large-eddy simulation for a full-scale ventilated tunnel fire. The numerical model solves 3D, time-dependent Navier—Stokes equations, coupled with submodels for soot formation and thermal radiation transfer. Turbulent combustion process is modeled by an eddy dissipation concept (EDC) and mixture fraction (MF) approach by using two chemical reaction steps to CO prediction. The predicted temperature in the smoke and flame shape was compared through a Blind method to the experimental data of Apte et al. [Apte VB, Green AR and Kent JH. Pool fire plume flow in a large-scale wind tunnel. Proceedings of the Third International Symposium on Fire Safety Science, July 8-12, Edinburgh, UK: Elsevier; 1991, pp. 425—434] and Fletcher et al. [Fletcher DF, Kent JH, Apte VB and Green AR. Numerical simulations of smoke movement from a pool fire in a ventilated tunnel. Fire Safety J 1994; 23(4): 305—325]. The predicted results of Fletcher et al. [Fletcher DF, Kent JH, Apte VB and Green AR. Numerical simulations of smoke movement from a pool fire in a ventilated tunnel. Fire Safety J 1994; 23(4): 305—325] with k-ε model and of Gao et al. [Gao PZ, Liu SL, Chow WK and Fong NK. Large eddy simulations for studying tunnel smoke ventilation. Tunn Undergr Sp Tech 2004; 19(6): 577—586] with large-eddy simulation, both based on a single chemical reaction, are also included. Two boundary conditions, such as adiabatic wall and heat loss inside wall, were applied on the tunnel structure. Both the EDC and MF approaches are shown to possess the ability to predict the general behavior of the experimentally determined temperature field as the heat loss inside the tunnel walls is taken into account. While, it is felt that EDC is more convenient for simulation of a large-scale under-ventilated tunnel fire where the CO and soot yields required by using MF approach, vary significantly with the air to fuel ratio by mass.

This numerical study focuses on the fire phenomenology associated with the presence of a composite-type aircraft immersed, at one particular location and orientation, within a large aviation-fuel fire in a moving fluid medium. An extension of the eddy dissipation concept is incorporated, allowing one to investigate the roles of the wind speed and its direction on the fire growth, heat flux distribution and smoke products, such as carbon monoxide and soot. The predicted flame shape compares well with the measurements for an intermediate-scale fire. The outcome of the study is interesting, and the interaction model between turbulence and combustion is indeed adequate. The prediction indicates that interaction between the large object and fire environment combined with the influence of wind conditions dramatically affects the continuous flame shape. The increase of the wind speed results in an alteration of the distribution of the incident heat fluxes to the engulfed fuselage skin for a case where the fire and fuselage are of comparable size. The highest heat flux occurs on the windward side of the fuselage for the low and medium winds, but on the leeward side of the fuselage for the high wind. The peak in heat flux to the medium or high wind is almost equal in magnitude, but about a factor four increase of that to the low wind.

This numerical study focuses on the fire phenomenology associated with the presence of a cylindrical object immersed, at one particular location and orientation, within a large aviation-fuel fire in a moving fluid medium. An extension of the eddy dissipation concept is incorporated, allowing to investigate the roles of the wind speed and its direction on the fire growth, heat flux distribution and smoke products, such as carbon monoxide and soot. The predicted flame shape compares well with the measurements. Moreover, the study has shed new light on the effect of the variation, which is erratic in nature, from the average wind direction on the heat flux distribution. The outcome of the study is interesting, and the interaction model between turbulence and combustion is indeed adequate. The prediction indicates that the interaction between the large object and fire environment combined with the influence of wind conditions affects the location of the continuous flame zone dramatically. The increase in the wind speed results in an alteration of the distribution of the incident heat fluxes to the surface of the engulfed cylinder for a case where the fire and object are of comparable size. The highest heat flux occurs on the windward side of the cylinder for the low and medium winds but on the leeward side of the cylinder for the high wind. The peak heat fluxes to the medium or high wind are almost equal in magnitude but about 50% beyond the ones to the low wind.

The molecular species composition of major toxic species, such as soot, CO and unburnt hydrocarbons from a boundary layer diffusion flame over heptane or dodecane surface at microgravity is numerically investigated. A two-step global reaction model for gas-phase chemistry and a simplified soot model consisting of laminar smoke point type for soot inception are used. Thermal radiation is calculated using the discrete-ordinates method coupled with a non-grey model for the radiative properties of CO, CO₂, H₂O and soot. The numerical results provide further insights into the intimate coupling between burning rate, flame length, thermal radiation, and toxic products at reduced gravity level. The importance of oxidizer flow speed to the flame structure, soot formation and thermal radiation at microgravity is demonstrated. The amount of soot from the microgravity heptane/dodecane flames augments with an increase of oxidizer flow velocity from 0.1 to 0.3 m/s due to an enhancement of burning rate. This finding is contrasted to the case with porous gas burners relative to toxic species production from microgravity flames. For the burning of various liquid fuels, the radiative loss fraction in general increase in a range of 0.5 to 0.7 due to enhanced soot formation with augmentation of the oxidizer flow velocity.