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Journal ArticleDOI

Experimental Study of the Effects of Side-Edge Burning in the Downward Flame Spread of Thin Solid Fuels

13 Mar 2012-Combustion Science and Technology (Taylor & Francis Group)-Vol. 184, Iss: 4, pp 489-504
TL;DR: In this paper, a comparison between the downward flame spread rate for thermally thin samples with one or two inhibited edges is done in multiple situations, and the effects of atmospheric composition as well as the width and thickness of a cellulosic-type fuel are tested experimentally.
Abstract: A comparison between the downward flame spread rate for thermally thin samples with one or two inhibited edges is done in multiple situations. The effects of atmospheric composition as well as the width and thickness of a cellulosic-type fuel are tested experimentally. We have found that the normal velocity to the inclined flame front in a side-edge burning is very similar to the downward flame front speed when the sample is inhibited by both edges. Also, the effect of locating a sidewall close to the free edge of the sample is investigated. All these results may be important in order to validate or refute possible models of downward flame spread that take into account side effects.
Citations
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Journal ArticleDOI
TL;DR: In this article, the orientation effects during inclined downward flame spread processes were thoroughly investigated by experimental and theoretical methods, and the mechanism of orientation effect during the flame spread process was qualitatively analyzed in detail, and simplified expressions of flame spread rate of the two insulation materials with different orientations were deduced.

83 citations

Journal ArticleDOI
01 Mar 2019-Energy
TL;DR: In this paper, the effects of fuel depth and ullage height on liquid flame spread of diesel and 5% ethanol-diesel blends were studied in a set of experiments.

56 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of vertical channel with various structure factors (α) on downward flame spread over extruded polystyrene (XPS) foam is investigated, and a model is established to predict the total, convective and radiative heat fluxes transferred to preheating zone.

27 citations

Journal ArticleDOI
TL;DR: In this article, side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments were investigated. But the results showed that the flame spread rate is controlled by ignition along the side-Edge, rather than at the center of the samples, for experiments with both single and two parallel slabs.

26 citations

Journal ArticleDOI
TL;DR: In this article, the effects of sample thickness (d), sidewalls and atmospheric pressure (p) on the flame spread of extruded polystyrene (XPS) are studied.
Abstract: An experimental study on the characteristics of downward flame spread of extruded polystyrene (XPS) is presented. The parameters investigated include average mass loss rate per unit of thickness ( $$ \dot{m}^{'} $$ ), average flame height (H f), average flame spread rate (v f), and mass growth rate ( $$ \dot{m}_{1} $$ ) of molten XPS. The effects of sample thickness (d), sidewalls and atmospheric pressure (p), and the combined effects of these factors on the flame spread are studied. The larger sample thickness corresponds to larger $$ \dot{m}^{'} $$ and higher flame upon most occasions. As d rises, v f and $$ \dot{m}_{1} $$ increase under all conditions; v f and d follow the equation: $$ {\text{v}}_{\text f} = A ( 1- {\text{exp(}} - {\text{Cd))}} $$ . The dimensionless heat release rate: $$ \dot{Q}^{*} \propto { \exp }( - 0. 3d) $$ . $$ \dot{m}^{'} $$ , v f , and $$ \dot{m}_{1} $$ obtained without sidewalls are higher than those with sidewalls. $$ \dot{m}^{'} $$ , v f, and H f obtained on the plain (p = 100.8 kPa) are larger than those obtained on the plateau (p = 65.5 kPa). $$ \dot{m}_{1} $$ obtained on the plain is lower than that on the plateau. In most cases without sidewalls, $$ \dot{m} \propto p^{{\text n_{0}} } $$ , where 1.9 < n 0 < 2, and $$ H_{\text f} = a + \mu p^{{\text n_{0} }} $$ . H f obtained in the cases without sidewalls is larger than that with sidewalls when the sample thickness is small, while the opposite is true for thicker samples. When sidewalls are absent, on the plain, with a rise in thickness, the increase of v f is significant for thin samples while the variation is not considerable for thick samples; on the plateau, this increase is significant for all thicknesses tested. The experimental results agree well with the theoretical analysis.

21 citations


Cites result from "Experimental Study of the Effects o..."

  • ...This is consistent with the conclusion of Comas and Pujol [21]....

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References
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Journal ArticleDOI
01 Jan 1969
TL;DR: In this article, a theoretical description of a laminar diffusion flame spreading against an air stream over a solid- or liquid-fuel bed is presented, where both a thin sheet and a semi-infinite fuel bed are considered.
Abstract: A theoretical description is presented for a laminar diffusion flame spreading against an air stream over a solid- or liquid-fuel bed. Both a thin sheet and a semi-infinite fuel bed are considered. The burning process is described as follows: The hot flame heats the unburned fuel bed, which subsequently vaporizes. The resulting fuel vapor reacts with the oxygen supplied by the incoming air, thereby producing the heat that maintains the flame-spread process. The formulated model treats the combustion as a diffusion flame, for which the details of the reaction kinetics can be ignored by assuming infinite reaction rates. The model includes the chemical stoichiometry, heat of combustion, gas-phase conductive heat transfer, radiation, mass transfer, fuel vaporization, and fuel-bed thermal properties. The radiation is mathematically treated as a heat loss at the flame sheet and a heat gain at the fuel-bed surface. The calculated flame-spread formulas are not inconsistent with available experimental data. These results reveal much of the physics involved in a spreading, flame. For instance, the flame-spread rate is strongly influenced by (1) the adiabatic stoichiometric flame temperature, and (2) the fuel-bed thermal properties, except for the fuel-bed conductivity parallel to the propagation direction.

356 citations


"Experimental Study of the Effects o..." refers background or methods or result in this paper

  • ...Note that Figure 6 is a log-log plot where data do not exactly follow a 1 slope, as suggested from the analytical expression of de Ris (1969)....

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  • ...Later, Markstein and de Ris (1975) studied flame spreading from a point source of ignition on the edge of textile and plastic samples. They found that under all conditions examined, all with environmental air atmosphere, the downward velocity along the edge Vd was faster than the velocity normal to the flame front VN and assumed that both velocities could be related as VN1⁄4Vd sinh, where h is the angle between the vertical side edge and the inclined flame front. Creeden and Sibulkin (1976) studied the downward flame propagation on PMMA sheets with an uninhibited side edge, and they found that after a transient phase, h remained constant (h 30 in air). They compared the downward flame spread rate Vd with flame front velocities V of PMMA sheets with two edges inhibited found in the literature and obtained that, in all conditions studied, VN1⁄4Vd sinh coincided with V within a 20% interval. After that, Vedha-Nayagam et al. (1986) found a relationship between the angle h and the downward spread rate Vd based on the exothermic surface reaction model of Sirignano (1974). However, their measurements for various atmospheric concentrations and total pressure were only carried out for free-side paper samples, and only the angle h was reported. Mell and Kashiwagi (2000) and Mell et al. (2000) worked experimentally and with three dimensional (3-D) numerical simulations to find out what happened when a horizontal sample with two free edges was ignited in the middle with forced flow, mainly in microgravity conditions but also in normal gravity....

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  • ...Thus, we can calculate the influence of the flame temperature on the front spread rate by using de Ris’s (1969) formula, V kg=(qscsss)(Tf Tv)=(Tv Ta), where Tf is the flame temperature, Tv is the temperature of vaporization, and Ta is the ambient temperature....

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  • ...There have been many theoretical and experimental studies that have investigated downward flame spread, where the flame spreads vertically down against gravity (e.g., Altenkirch et al., 1980; de Ris, 1969; Delichatsios, 1986; Fernandez-Pello and Williams, 1977; Greenberg and Ronney, 1993)....

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  • ...Later, Markstein and de Ris (1975) studied flame spreading from a point source of ignition on the edge of textile and plastic samples. They found that under all conditions examined, all with environmental air atmosphere, the downward velocity along the edge Vd was faster than the velocity normal to the flame front VN and assumed that both velocities could be related as VN1⁄4Vd sinh, where h is the angle between the vertical side edge and the inclined flame front. Creeden and Sibulkin (1976) studied the downward flame propagation on PMMA sheets with an uninhibited side edge, and they found that after a transient phase, h remained constant (h 30 in air). They compared the downward flame spread rate Vd with flame front velocities V of PMMA sheets with two edges inhibited found in the literature and obtained that, in all conditions studied, VN1⁄4Vd sinh coincided with V within a 20% interval. After that, Vedha-Nayagam et al. (1986) found a relationship between the angle h and the downward spread rate Vd based on the exothermic surface reaction model of Sirignano (1974). However, their measurements for various atmospheric concentrations and total pressure were only carried out for free-side paper samples, and only the angle h was reported....

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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
01 Jan 1981
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.

173 citations


"Experimental Study of the Effects o..." refers background in this paper

  • ...In most of these experimental studies, samples were rectangular, held by the two long vertical sides and burned from the top horizontal side to the bottom one (e.g., Fernández-Pello et al., 1981; Frey and T’Ien, 1976; Lastrina et al., 1971; Zhang et al., 1992)....

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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


"Experimental Study of the Effects o..." refers background in this paper

  • ...There have been many theoretical and experimental studies that have investigated downward flame spread, where the flame spreads vertically down against gravity (e.g., Altenkirch et al., 1980; de Ris, 1969; Delichatsios, 1986; Fernandez-Pello and Williams, 1977; Greenberg and Ronney, 1993)....

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Journal ArticleDOI
TL;DR: In this paper, a theory for predicting the steady rate of spread of a flame over the surface of a solid in directions ranging from downward to horizontal is developed. But the model is based on a diffusion flame in a boundary layer downstream from a point of flame inception, heat transfer by natural convection from this flame to the gasifying fuel which supports it, heat conduction through the solid to the cooler fuel ahead of the flame, generation of an upstream boundary layer due to entrainment into the flame plume, upstream gasification and diffusion of fuel into this boundary layer,

104 citations


"Experimental Study of the Effects o..." refers background in this paper

  • ...There have been many theoretical and experimental studies that have investigated downward flame spread, where the flame spreads vertically down against gravity (e.g., Altenkirch et al., 1980; de Ris, 1969; Delichatsios, 1986; Fernandez-Pello and Williams, 1977; Greenberg and Ronney, 1993)....

    [...]