Visualization of Organized Structures in Buoyant Diffusion Flames

Schönbucher, Axel; Brötz, Walter; Balluff, Ch.; Riedel, G. L.; Kettler, A.; Schieß, Norbert

doi:10.1002/bbpc.19850890608

Cited by 7 publications

(6 citation statements)

References 11 publications

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“…Puffing has also been 6 observed to play an important role in flame and wildfire spread-7 ing [2,3] . Pool-fire puffing has been studied extensively in the lit-8 erature, by means of experiments [4][5][6][7][8][9][10][11][12][13] , numerical simulations 9 [14][15][16][17][18][19][20] , and scale modeling [21][22][23][24][25] . Extensive reviews on pool 10 fires can be found in [26][27][28][29] .…”

Section: Introductionmentioning

confidence: 99%

“…where T is the temperature scaled with T * A , and Y F and 6) and (7) , re-129 spectively, where c * p denotes the specific heat at constant pressure, 130 assumed to be constant in the following analysis. The parameter S , 131 of order S = 15 in hydrocarbon combustion, represents the amount 132 of air needed to burn the unit mass of fuel.…”

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confidence: 99%

“…The presence of soot is noticeable in most liquid-pool flames, 137 enhancing heat losses through radiation. Since this effect is antic-138 ipated to be moderately small for the small-size flames associated 139 with the onset of puffing, no radiation term is included in (7) . In-140 stead, its effect on the peak flame temperature will be approxi-141 mately accounted for by slightly lowering the value of the dimen-142 sionless heat release q .…”

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On the critical conditions for pool-fire puffing

Moreno-Boza

Coenen

Carpio

et al. 2018

Combustion and Flame

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Pool fires are known to undergo a bifurcation to a globally unstable puffing state driven by baroclinic and buoyant vorticity production. Although the supercritical puffing regime away from the bifurcation has been studied extensively in the literature, no detailed account has been given of the critical conditions for its onset, that being the purpose of the present paper. For the relevant canonical case of round liquid pools without swirl, aside from the inherent thermochemical and transport parameters associated with the fuel, pool-fire puffing is governed by a single dimensionless number, the Rayleigh number, which scales with the cube of the pool diameter. Consequently, for a fixed fuel and under fixed ambient conditions, there is a critical fuel pool diameter, associated with a critical value of the Rayleigh number, above which the flame starts puffing. A global linear stability analysis that accounts for the axisymmetry of the prevailing instability mode is developed here to describe the bifurcation. The mathematical formulation employs the limit of infinitely fast reaction, with account taken of the nonunity Lewis number and vaporization characteristics of typical liquid fuels. Predictions of critical puffing conditions, including critical diameters and puffing frequencies, are provided for methanol and for heptane pool fires, and the results are compared with results of new small-scale experiments under controlled laboratory conditions, reported here, yielding reasonably good agreement.

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Section: Introductionmentioning

confidence: 99%

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On the critical conditions for pool-fire puffing

Moreno-Boza

Coenen

Carpio

et al. 2018

Combustion and Flame

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“…In large-scale fires, the flames are more turbulent and the fires exhibit large, lowfrequency oscillations that are initiated in the continuous flame zone near the surface of the fuel and persist up through the intermittent flame zone and well into the thermal plume which has been qualitatively described elsewhere, cf. [2,3].…”

Section: Introductionmentioning

confidence: 98%

An experimental study of acoustically driven medium-scale pool fires

2011

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A set of experiments has been conducted on a medium-scale propane fueled pool fire acoustically forced in order to facilitate repeatable measurements defining the flame's transient behavior. The fuel flow was slightly perturbed at the pool fire's natural frequency by a sine waveform driven with a loudspeaker which was installed under the burner. As a result of the perturbation, the puffing behavior of the pool fire and the fire shape were modified. As the magnitude of the sine wave was increased larger perturbations were clearly observed, based on the measurement of the radiative heat flux and image analysis. Temperature and soot volume fractions were measured along the center line and throughout a slice of the flame. The soot volume fractions in the flame region are in good agreement with the data of other researchers. The reproducibility of these measurements was established through several experiments. The acoustically driven flame provides the possibility of more repeatable measurements of the transient behavior of these pool fires.

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“…Besonders interessant f i r die sicherheitstechnische Anwendung ist die neue, unproblematische Definition der Flammenkontur als BuRerste, geschlossene Aquidensite der statischen Aquidensitenstruktur des Feuers. Die statischen Aquidensitenstrukturen sind definiert abhangig vom Tankdurchmesser und vom eingesetzten Brennstoff[24].…”

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Erforschung von Schadenfeuern flüssiger Kohlenwasserstoffe als Beitrag zur Sicherheit von Chemieanlagen

Schönbucher

Brötz

Balluff

et al. 1985

Chemie Ingenieur Technik

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Das Gefahrenpotential von Schadenfeuern in Chemieanlagen wird am Beispiel von Tank-und Pool-Flammen aufgezeigt. Die Bedeutung und Funktion fluiddynamischer, organisierter Strukturen fur die Verbrennungsvorgange in Schadenfeuern wird dargelegt. Kurz erlautert werden die angewandten experimentellen Methoden zur Sichtbarmachung organisierter Strukturen. Ausfiihrlich behandelt werden die Einfliisse dieser Strukturen auf die sicherheitstechnisch relevanten GroBen Abbrandgeschwindigkeit und Warmezone, maximaler Basisdurchmesser eines Schadenfeuers, Flammenlange und -Neigung sowie Strahlungswarmestrom in die Umgebung. Zur Berechnung der entfernungsabhangigen Bestrahlungsstarke eines Schadenfeuers wird neben dem Punktquellenmodell und dem Zylinder-Flammenstrahlungsmodell ein neues Modell, das Ballen-Strahlungsmodell, vorgestellt. Es beriicksichtigt die iiberlagerte Warmestrahlung von Flammenballen (hot spots) und RulSballen sowie den Blockierungseffekt kalter Brennstoffballen. Die Anwendung dieses Modells fiihrt auf zeitlich gemittelte, maximale Bestrahlungsstarken von E -4 W/cm2, die fur Schadenfeuer mit einem Pool-Durchmesser >14 m bei den meisten Brennstoffen gemessen werden. Diese Werte liegen etwa urn den Faktor 3 niedriger als die mit dem Zylinder-Flammenstrahlungsmodell berechneten Bestrahlungsstarken. Die sich daraus ergebenden Konsequenzen, z. B. fur die Sicherheitsabstande benachbarter Tanks, werden diskutiert. Investigation of hazardous fires of liquid hydrocarbons ascontribution to the safety of chemical plants. This article illustrates the danger potential of hazardous fires, such as pooland tank fires in chemical plants. The importance and the role of fluid dynamic organized structures for the combustion processes are presented. Experimental methods used for the visualization of these organized structures are also explained. The influence of such structures on the safety data, burning rate, maximum pool fire diameter, flame height and flame tilt, and the total radiative power is dealt with in detail. The point source model and the solid flame radiation model are discussed for calculation of the distance-dependent irradiance of a pool fire. A new model, the parcel-radiation model, considers the radiation of hot spots, soot parcels, and the effect of radiation blockage by cooler, unburnt fuel parcels. Application of the parcel-radiation model leads to a calculated maximum irradiance of E -4 W/cm2, which is verified experimentally for most pool fires with diameters > 14 m. These irradiances are three times smaller than the values calculated by the solid flame radiation model. The consequences for safe separation distance between two adjacent pools are discussed.

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Visualization of Organized Structures in Buoyant Diffusion Flames

Cited by 7 publications

References 11 publications

On the critical conditions for pool-fire puffing

On the critical conditions for pool-fire puffing

An experimental study of acoustically driven medium-scale pool fires

Erforschung von Schadenfeuern flüssiger Kohlenwasserstoffe als Beitrag zur Sicherheit von Chemieanlagen

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