Scaling Sub-Surface Layer Circulation Induced by Pulsating Flame Spread over Liquid Fuels

Takahashi, Kozue; Ito, Akihiko; Kudo, Yuji; Konishi, Tadashi; Saito, Kozo

doi:10.1007/978-1-4020-8682-3_12

Cited by 4 publications

(5 citation statements)

References 8 publications

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“…Schlieren images show that the convection layer does not have uniform thickness; most of the layer is only about 2 mm thick, whereas the layer is about 8 mm thick at the surface flow front for a thick fuel layer. For an oil thickness beyond 8 mm, the ratio of the thickness of the convection layer to the length of the convection layer remains nearly constant, which is consistent with Takahashi et al's results [6] of thick butanol layers.…”

Section: Mechanism Of Flame Spreadsupporting

confidence: 90%

“…Therefore, it is necessary to study the phenomena and mechanism of flame spread over floating oil. Flame spread over liquid fuel has been a hot topic of combustion theory and fire safety science since the 1960s and has been investigated experimentally and numerically [1][2][3][4][5][6][7][8][9]. Such researches have mainly focused on the effects of parameters such as the initial fuel temperature and tray width on the rate of flame spread and on the qualitative analysis of surface convection.…”

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confidence: 99%

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Experimental study of flame spread over oil floating on water

Guo

Zhou

et al. 2012

Chin. Sci. Bull.

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The phenomena and mechanism of flame spread over oil floating on water were studied using temperature measurements made by fine thermocouples and an infrared camera, schlieren images of surface convection and video recordings of flame spread. The experimental results reveal that the floating-oil depth greatly affects the average rate of flame spread and average flame pulsation wavelength. The surface tension effect is the main cause of surface convection, which controls flame spread. Momentum loss and heat loss from forward-flowing hot oil to water play an important role in retarding flame spread for oil thicknesses less than about 8 mm. With the development of the exploitation of offshore oil and marine transportation, there have been frequent fires resulting from oil spills. Because of the quick diffusion of oil leaked on water and the fast spread of flames over an oil surface, such fires usually have catastrophic consequences. Although flame spread is only a short process during a fire, it determines the direction of flame spread and the best time to put out fires. On the other hand, controlled combustion is an important way to clean up floating oil, but the precondition is that the flame can spread over the floating oil. Therefore, it is necessary to study the phenomena and mechanism of flame spread over floating oil. Flame spread over liquid fuel has been a hot topic of combustion theory and fire safety science since the 1960s and has been investigated experimentally and numerically [1][2][3][4][5][6][7][8][9]. Such researches have mainly focused on the effects of parameters such as the initial fuel temperature and tray width on the rate of flame spread and on the qualitative analysis of surface convection. However, little has been done to study flame spread over floating oil, which has the distinguishing characteristics that the floating oil is usually thin and water greatly affects the flame-spread phenomena. Mackinven et al.[10] experimented with decane floating on water and found that the average rate of flame spread increased with an increase in fuel thickness. Neil et al. [11] confirmed that fuel thickness has a large effect on the rate of flame spread. However, the researchers [10,11] obtained only qualitative results, and the reason why fuel thickness affects the phenomena of flame spread remains unclear till now. In the present study, the flame spread over different thicknesses of aviation kerosene (with a flash point of about 66C) floating on water was investigated simultaneously employing a schlieren system, an infrared camera, fine thermocouples and charge-coupled device (CCD) cameras. The paper presents the variation in the average rate of flame spread with floating oil thickness, gives reasons why the oil thickness affects the flame spread rate and presents the mechanism of flame spread.

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Section: Mechanism Of Flame Spreadsupporting

confidence: 90%

mentioning

confidence: 99%

Experimental study of flame spread over oil floating on water

Guo

Zhou

et al. 2012

Chin. Sci. Bull.

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“…The temperature coefficient of surface tension and other physical properties are treated as constants. Our instability analysis is based on the previous study [31][32][33][34]. A schematic of subsurface layer flow is shown in Figure 3.…”

Section: Basic Equationmentioning

confidence: 99%

“…To benefit from all these experimental and numerical studies both under normal gravity and microgravity and to update the theory of flame spread over liquids formulated International Journal of Chemical Engineering 3 by Williams [30], we conducted stability based on the basic reference [31] and scaling analyses on these results in the hope of finding a unified theoretical framework within which to relate them [32][33][34]. Our instability analysis was focused on the liquid subsurface layer ahead of a flame's leading edge, where a surface wave is initiated and a cold temperature valley is created.…”

Section: Introductionmentioning

confidence: 99%

Scaling Analysis on Pulsating Flame Spread over Liquids

Takahashi

Ito

Kudo

et al. 2008

International Journal of Chemical Engineering

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Scaling analyses based on subsurface layer instability were performed to explore the role of three independent (surface tension, gravity, and viscosity) influences on the mechanism of pulsating flame spread under normal and microgravity conditions. These three influences form two independent pi-numbers: the Marangoni (Ma) number and Grashof (Gr) number, which include the characteristic length scale ratio (depth of subsurface circulation)/(horizontal length of preheated liquid surface). The Prandtl (Pr) number was introduced to compensate for the different thermal diffusivity and kinematic viscosity of different liquids. Also a nondimensional flame spread rate, V/V D (= Vδ/D, where δ is the quenching distance and D is the diffusivity of fuel vapor) was introduced. Using these nondimensional parameters, the flame spread mechanism was divided into two separate regimes: for the shallow liquid pool the nondimensional flame spread rate was correlated with {Gr 0.2 /(Ma·Pr)} 1.0 , while for the deep liquid pool it was correlated with {Gr 0.2 /(Ma·Pr)} 1.5 .

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“…Although flame spread is only a short process of combustible liquid fires, it determines the flame spread direction and the best time for putting out fires. So, preventing flame spread over a spill of liquid fuel has been a hot problem of combustion theory and fire safety science, which was investigated extensively in the past decades [1][2][3][4][5][6] . Akita [7] and Degroote et al [8] found that when the initial temperature of liquid fuel is lower than a certain value, subsurface flow plays an essential role in flame spread.…”

Section: Introductionmentioning

confidence: 99%

Flame spread over aviation kerosene with an obstacle in liquid phase

Guo

et al. 2011

J. Therm. Sci.

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The phenomena of flame spread over aviation kerosene with an obstacle in liquid phase are investigated experimentally through surface temperature measurement by using infrared camera, schlieren images of subsurface flow in front of and behind obstacle and residence time of flame obtained from video recording. Experimental results reveal that obstacle has no effect on gas phase controlled flame spread. But for liquid phase controlled flame spread, flame can be stopped by an obstacle with its top edge flush with oil surface, and the residence time decreases with the increase of initial temperature of fuel. That conduction and radiation only play a subsidiary role in flame spread over liquid fuel was proved by schlieren images and surface temperature profiles.

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Scaling Sub-Surface Layer Circulation Induced by Pulsating Flame Spread over Liquid Fuels

Cited by 4 publications

References 8 publications

Experimental study of flame spread over oil floating on water

Experimental study of flame spread over oil floating on water

Scaling Analysis on Pulsating Flame Spread over Liquids

Flame spread over aviation kerosene with an obstacle in liquid phase

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