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Journal ArticleDOI

Flame spread in an opposed forced flow: the effect of ambient oxygen concentration

01 Jan 1981-Vol. 18, Iss: 1, pp 579-589
TL;DR: In this article, the velocity of flame propagation over the surface of thick PMMA and thin paper sheets has been measured as a function of the velocity and oxygen concentration of a forced gas flow opposing the direction of the flame propagation.
Abstract: The velocity of flame propagation over the surface of thick PMMA and thin paper sheets has been measured as a function of the velocity and oxygen concentration of a forced gas flow opposing the direction of flame propagation. It is shown that although for thin fuels the flame spread rate always decreases as the opposed flow velocity increases, for thick fuels the dependence of the spread rate on the gas velocity is also a function of the ambient oxygen concentration. For low oxygen concentrations the flame spread rate decreases as the velocity of the gas flow increases. For high oxygen concentrations, however, the spread rate increases with the flow velocity, reaches a maximum and then decreases as the gas velocity increases. The velocity of the opposed flow at which the maximum occurs is a function of the oxygen concentration, decreasing as the concentration decreases. Following phenomenological considerations and simplified descriptions of the primary mechanisms occurring during the flame spread process, the experimental results are correlated by two non-dimensional parameters, one describing the gas phase kinetic effects and the other describing the process of heat transfer from the flame to the fuel. Such a correlation provides a powerful means of predicting the flame spread prcess as well as physical insight into the mechanisms controlling the propagation of the flame.
Citations
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Journal ArticleDOI
TL;DR: In this paper, heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation.
Abstract: Recent advances in the experimental study of the mechanisms controlling the spread of flames over the surface of combustible solids are summarized in this work. The heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation. The realization that, in most practical situations, the spread of fire in opposed gas flows occurs at near extinction or non-propagating conditions is particularly significant. Under these circumstances, gas phase chemical kinetics plays a critical role and it must be considered if realistic descriptions of the flame spread process are attempted. In the concurrent mode of flame spread, heat transfer from the flame to the unburnt fuel appears to be the primary controlling mechanism. Although gas phase chemcial kinetics is unimportant in the flame spreading process, it is important in the establishment and extension of the diffusion ...

266 citations

Journal ArticleDOI
TL;DR: A review of modeling and experiments of the ignition and flame spread over liquid fuel pools for separate regimes defined by the initial pool temperature relative to the fuel flash point is given in this paper.

130 citations

Journal ArticleDOI
TL;DR: This paper will stress the many aspects of Fire Science not yet complete or in some cases not even started as well as various levels of modeling, aided by the modern computer.
Abstract: Since there have been many review articles on many aspects of Fire Science and its applications (1-10), this paper will stress the many aspects of Fire Science not yet complete or in some cases not even started. By now (1985), it has become broadly accepted that the way of the future in Fire Engineering is through various levels of modeling, aided by the modern computer. A number of models exist for various aspects of a fire in an enclosure (11-14) the most advanced of which are gradually becoming sufficiently general (15-21) to include a fire in any of man's structures. These include both zone and field mOdels. At the same time the U.S. Forest Service has developed a fire model sufficiently accurate to have been incorporated into a special hand held calculator usable in the field (22).

92 citations


Cites background from "Flame spread in an opposed forced f..."

  • ...We know the general nature of the energy feedback system which heats and ignites material ahead of an advancing flame front and many special cases have been studied (40-51)....

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Journal ArticleDOI
TL;DR: The aim of this work was motivated by the research of sample width and thickness effects on upward flame spread behavior, including flame spread rate during acceleration propagation for different sample thickness and width, theoretical global mass loss prediction based on Emmons's hypothesis, and dimensionless flame height scaling with dimensionless heat release rate for steady stage burning.

87 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarized recent advances in the experimental study of the mechanisms controlling the spread of flames over the surface of combustible solids are summarized in this work, and the heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spreading of flames in oxidizing flows that oppose or concur with the direction of propagation.
Abstract: Recent advances in the experimental study of the mechanisms controlling the spread of flames over the surface of combustible solids are summarized in this work. The heat transfer and gas phase chemical kinetic aspects of the flame spread process are addressed separately for the spread of flames in oxidizing flows that oppose or concur with the direction of propagation. The realization that in most practical situations, the spread of fire in opposed flows occurs at near extinction or non-propagation conditions is particularly significant. Under these circumstances, gas phase chemical kinetics plays a critical role and it must be considered if realistic descriptions of the flame spread process are attempted. In the concurrent mode of flame spread, heat transfer from the flame to the unburnt fuel appears to be the primary controlling mechanism. Although gas phase chemical kinetics is unimportant in the flame spread process, it is important in the establishment and extension of the diffusion flame that generates the spread process. The current experimental observations, although still in need of further verification, provide insight toward the development of accurate descriptions of the flame spread process.

75 citations

References
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01 Mar 1976
TL;DR: Computer program is described for numerical solution of chemical equilibria in complex systems by using nonlinear algebraic equations using free-energy minimization technique.
Abstract: A detailed description of the equations and computer program for computations involving chemical equilibria in complex systems is given. A free-energy minimization technique is used. The program permits calculations such as (1) chemical equilibrium for assigned thermodynamic states (T,P), (H,P), (S,P), (T,V), (U,V), or (S,V), (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. The program considers condensed species as well as gaseous species.

1,221 citations

Journal ArticleDOI
TL;DR: In this paper, the structure of steady state diffusion flames is investigated by analyzing the mixing and chemical reaction of two opposed jets of fuel and oxidizer as a particular example, and an Arrhenius one-step irreversible reaction in the realistic limit of large activation energies.

792 citations

Journal ArticleDOI
TL;DR: In this paper, the steady-state flame spread over a thermally thin solid fuel is investigated, and qualitative agreement is obtained with experimental results in the near-extinction limit region.

183 citations

Journal ArticleDOI
TL;DR: In this article, the authors show that buoyancy influences the downward spread rate of flames consuming thermally thin fuel beds, and that a small change in orientation with respect to the vertical is equivalent to a change in the magnitude of gravity in the direction of spread.

131 citations