A theoretical and experimental study of buoyant turbulent flames with emphasis on soot and radiation
Abstract
Accidental fires resulting from fuel spills and tank explosions commonly burn as pool fires. These fires contain large quantities of soot and radiates strongly. Computational methods have been developed to help fire safety designers reduce the hazards associated with such fires. Motivated by this, theoretical and experimental studies of buoyant turbulent diffusion flames with emphasis on soot and radiation are conducted including the measurements of soot volume fractions, spectral radiation intensities and radiative heat fluxes, and the fire dynamics simulations in both laboratory and large-scale buoyant turbulent fires. The new measurements combined with velocity and mixture fraction data from the literature are used to evaluate the fire dynamics simulation results of velocity field, scale-up capability, spectral radiation intensity and total radiative heat flux. The results of the experimental study show that: (1) the soot particles exist in thin regions, called streaks, which are wrinkled by turbulence and fluctuate strongly; (2) the soot streaks are generally aligned with the mean flow direction causing anisotropic distributions of the soot volume fractions within the fire; (3) the spectral radiation intensity is dominated by the continuum radiation from soot and the 4.3 μm band of CO2, with H2O vapor band showing only small contributions; (4) the total radiative heat fluxes are apparently affected by the fuel type and the total heat release. The results of the theoretical computations show that: (1) three-dimensional fire dynamics simulations are necessary for predicting the velocities and the scalars in buoyant turbulent flames; (2) the fire dynamics simulations with a mixture fraction based combustion model predict the velocities and scalars very well with small domain and grid effects, and can be scaled up to large-scale pool fires; (3) the fire dynamics simulations can be utilized together with wideband radiation models and a finite volume method to calculate the spectral radiation intensities from gaseous species with good accuracy and the total radiative heat fluxes reasonably well.
Degree
Ph.D.
Advisors
Gore, Purdue University.
Subject Area
Mechanical engineering
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