Radiation from Buoyant Turbulent Diffusion Flames

Orloff, L.; Ris, J. De; Delichatsios, Michael

doi:10.1080/00102209208951852

Cited by 41 publications

(29 citation statements)

References 12 publications

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“…Smoke and soot formation in laminar flames is epitomized by smoke point, which is defined as the minimum flame height (or fuel flow rate) at which the flame just begins to emit smoke (Tewarson, 2002). Smoke point has been correlated with sooting propensity (Gomez et al, 1984;Hirschler, 1985;Kent, 1986;Yao et al, 2011), combustion efficiency (Gomez et al, 1984), and flame radiation (Kent, 1986;Markstein, 1985;Orloff et al, 1992). Studies have been carried out to investigate the effects of fuel type, burner diameter, gravity, pressure, and air to fuel stream velocity ratio on the smoke point.…”

Section: Introductionmentioning

confidence: 99%

Determination of Smoke Point of Laminar Acetylene Diffusion Flames Under Subatmospheric Pressures

Wang

2014

Combustion Science and Technology

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An experimental study on smoke point of acetylene laminar jet diffusion flames was performed in a chamber with sub-atmospheric pressures of 0.03-0.1 MPa. A combined normal video and the CH filtering technique were employed in the flame image recording to facilitate determining the smoke point. The measured smoke point flame height, fuel flow rate, and residence time was found to vary with pressure to power laws. In this article, both jet inertia and buoyancy effects were considered for calculating smoke point residence time of reacting jets.

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Section: Introductionmentioning

confidence: 99%

Determination of Smoke Point of Laminar Acetylene Diffusion Flames Under Subatmospheric Pressures

Wang

2014

Combustion Science and Technology

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“…This radiation length scale characterizes the cooling of the flame gases within the flame envelope owing to the radiant losses. This observation in conjunction with numerous experimental data (Markstein, 1985;Kent, 1987;Orloff et al, 1989;Delichatsios and Orloff, 1989) in buoyant and momentum jets leads to the development of validated flame radiation scaling relationships.…”

Section: Introductionmentioning

confidence: 60%

“…(a) The radiant fraction in turbulent buoyant jet flames, XR' which is independent of the flow rate (Markstein, 1985), correlates with the laminar smoke-point heat release rate of the fuel, Q,p (Markstein, 1985), (The smoke-point heat release rate is proportional to the smoke-point height (Markstein, 1985;Kent, 1986;Markstein, 1987), Such correlation is shown in Figure I(a), where all fuels were reduced to "standard" conditions (Orloff et al 1989) ii.e. 7J = 2200 K, S = 15) by diluting the fuel and/or oxidant stream with Nitrogen (S is the mass stoichiometric oxidant to fuel ratio, and T f is the adiabatic flame temperature), One important observation from Figure I(a) is the weak dependence of the radiant fraction on the smoke-point heat release rate of the fuel.…”

Section: Physical Principles and Luminous Flame Radiation Scalingmentioning

confidence: 94%

“…Since measured maximum soot concentration in laminar flames (Markstein and de Ris, 1985); Delichatsios et al 1987;Markstein, 1985Markstein, , 1987Kent, 1986Kent, , 1987 can be related to the smoke-point heat release rate as: (c) In our extensive work using momentum controlled turbulent jet flames (Delichatsios and Orloff, 1989;Delichatsios et al, 1987), we have shown that it is the Kolmogorov time scale that controls soot concentrations in such flows and not the macroscale mixing time. Moreover, that analysis (Delichatsios and Orloff, 1989) is consistent with the relationship expressed in Eq.…”

Section: Physical Principles and Luminous Flame Radiation Scalingmentioning

confidence: 96%

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The Effects of Fuel Sooting Tendency and the Flow on Flame Radiation in Luminous Turbulent Jet Flames

Delichatsios¹,

Orloff²,

Delichatsios³

1992

GCST

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In this paper two observations are emphasized with regard to flame radiation in luminous turbulent jet flames: (a) the radianl fraction in turbulent buoyant jet flames is a weak function of the fuel sooting tendency as expressed by the laminar smoke-point heat release rate; and (b) moreover. for very sooty fuels, the radiant fraction saturates to a constant value which is independent of the laminar smoke-point heat release rate, although it depends on the adiabatic flame temperature. These observations can be explained by considering that cooling of the flames is enhanced and the effective radiation temperature drops as soot increases and thus radiant losses increase, until for very sooty fuels flame extinction in the upper part of the flames occurs. The physics of flame radiation phenomena are discussed in the light of a global similarity analysis for flame radiation together with the use of extensive experimental data. In the analysis, complementary to the usual hydrodynamic length scale for combustion. a new radiation length scale is introduced which characterizes the effects of radiant losses on the flow. Scaling relationships of the turbulent radiant fraction in terms of the laminar smoke-point heat release rate are developed first for turbulent buoyant jet flames, wherein flow effects are small, and then extended 10 momentum-dominated turbulent jet flames. The present results have direct practical significance (a) for predicting radiant fractions in fires, and (b) for the design of enhanced flame radiation burners. The physics presented here for soot concentration and radiant cooling can be incorporated in detailed k-e-g or other turbulence models.

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“…Analytical and numerical models used to describe fire radiation and flame spread often rely on the correlation between the radiant emission from buoyant turbulent diffusion flames and parameters characterizing the sooting propensity of fuels, such as the laminar smoke point and smoke yield [1][2][3][4][5][6]. Several semi-empirical smoke point based radiation sub-models are available on the basis of these correlations [7,8].…”

Section: Introductionmentioning

confidence: 99%

Radiation Characteristics of Corrugated Cardboard Flames

Zeng¹,

Chaos²,

Khan³

et al. 2014

Fire Saf. Sci.

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The relation between flame radiation, smoke yield, and smoke point of a practical solid fuel, namely corrugated cardboard, is studied experimentally. Experiments are performed using an ASTM E 2058/ISO 12136 Fire Propagation Apparatus (FPA). Corrugated cardboard flames are established in the FPA under external heat fluxes representative of those found in a large-scale fire scenario. The heat release rates for these flames are on the order of 7 to 10 kW based on calorimetry analyses. Radiation is measured using a heat flux gage located in the near field of the flame. In order to better interpret calorimetry data, effort is placed on the characterization of the chemical composition and thermodynamics of the corrugated cardboard used both in its virgin and charred states. A novel smoke point measurement system based on the FPA is also described and demonstrated. It is shown that the specific heat of combustion of volatiles released from the pyrolysis process increases with pyrolysis progress. Furthermore, flame radiant fraction, smoke point, and smoke yield are also shown to vary during pyrolysis and combustion. The variations of both the smoke point and radiant fraction with pyrolysis progress at different heating rates indicate that the volatile chemical composition continuously varies during pyrolysis. These observations are explained by faster release rates of fuel oxygen and hydrogen than that of carbon during pyrolysis.

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Radiation from Buoyant Turbulent Diffusion Flames

Cited by 41 publications

References 12 publications

Determination of Smoke Point of Laminar Acetylene Diffusion Flames Under Subatmospheric Pressures

Determination of Smoke Point of Laminar Acetylene Diffusion Flames Under Subatmospheric Pressures

The Effects of Fuel Sooting Tendency and the Flow on Flame Radiation in Luminous Turbulent Jet Flames

Radiation Characteristics of Corrugated Cardboard Flames

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