Microgravity experiments of single droplet combustion in oscillatory flow at elevated pressure

Ogami, Yasuhiro; Sakurai, Satoru; Hasegawa, Shota; Jangi, Mehdi; Nakamura, Hisashi; Yoshinaga, Kentaro; Kobayashi, Haruo

doi:10.1016/j.proci.2008.05.008

Cited by 11 publications

(20 citation statements)

References 8 publications

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“…(3d) includes that conducted into the particle and especially the re-radiation losses from the surface, which are very important for large solid particles (>5 mm here) compared to the small droplets (less than 1 mm) usually investigated in the literature [1][2][3][4][5][6][7][8][9][10][11]. Based on Eqs.…”

Section: Luminancementioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10]), gases (e.g. [11][12][13]) and even solid combustibles [14][15][16][17][18][19][20].…”

Section: Introductionunclassified

“…Yozgatligil [8] has revealed the sooting behavior of ethanol droplet combustion under micro-gravity conditions through the 2.2-s drop tower at NASA Glenn Research Center. Ogami [10] and Takahashi [11] have investigated the droplet combustion and flame extinguishment behavior under different flow conditions. For solid combustible, Yang [14] has carried out experiments in NASA DC-9 and the KC-135 Reduced Gravity Aircraft to investigate the burning behavior of thermoplastic spheres.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on diffusive solid combustion behavior during transition from normal- to reduced-gravity

Delichatsios

et al. 2012

International Journal of Heat and Mass Transfer

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a b s t r a c tExperiments are carried out in a simplified drop system, which can provide a 2.3 s 10 À2 g reduced gravity period, to investigate the transition of solid material combustion behavior from normal-to reduced-gravity. A CCD camera records the diffusion flames produced by a solid fuel, Methenamine (C 6 H 12 N 4 ), which easily sublimes and decomposes to flammable CH 4 and H 2 . The temperature distribution within the flame is analyzed by a monochromatic line of sight CCD measurement calibrated by a thermocouple measurement. It is revealed that during the transition period from normal-to reduced-gravity, the change of the flame shape, from tall and thin (pear like) to spherical, is faster than that of the luminance which represents the radiation intensity, indicating a relatively shorter adjustment time scale of dynamical gas flow buoyancy than that of the heat transfer when subjected to such a sudden change of gravity condition. It is also found that owing to the change of the flow affecting the oxygen and heat supply, the luminance of the flame as well as the burning rate, which was deduced based on projected area of the solid fuel according to d 2 -law, first decreases followed by an increment near the end of the drop where the gravity level slightly increases. The flame temperature gradually decreases, as the flame suddenly goes into reduced-gravity. Interpretation based on analysis of heat transfer balance and pyrolysis rate as well as the experimental results both indicate that the transitional effect is less pronounced for a smaller fuel particle than for a larger one, where buoyancy is stronger under normal-gravity whereas the flame has a larger standoff distance with increasing importance of the radiation losses from the fuel particle surface under reduced-gravity. The present work is relevant in assessing fire hazards of solid material during space travel as gravity levels change.

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Section: Luminancementioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10]), gases (e.g. [11][12][13]) and even solid combustibles [14][15][16][17][18][19][20].…”

Section: Introductionunclassified

Section: Introductionmentioning

confidence: 99%

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Experimental study on diffusive solid combustion behavior during transition from normal- to reduced-gravity

Delichatsios

et al. 2012

International Journal of Heat and Mass Transfer

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“…Figure 1 shows a schematic of their model. Several experiments under microgravity conditions were performed later in the same research team as Mitsuya et al in order to observe the behavior of 1-butanol fuel droplets in the presence of upstream velocity oscillations [15][16][17]. Based on the results of the experimental data, Jangi et al [16] have shown the classical quasi-steady model [18], which is film-theory based, [19] cannot predict the hysteresis and drastical enhancement of the burning rate during the combustion of a 1-butanol fuel droplet when upstream velocity oscillates.…”

Section: Introductionmentioning

confidence: 99%

“…The experimental data available in the literature [15][16][17] are the base for verification of the validity of the numerical results. The main proposes of this study are to demonstrate and characterize the role of a new mechanism that is responsible for the enhancement of the burning rate and deviation from those behaviors which are predicted by quasi-steady model.…”

Section: Introductionmentioning

confidence: 99%

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Jangi

Shaw

Kobayashi

2009

Flow Turbulence Combust

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Numerical studies on the behaviors of combustion of 1-butanol fuel droplet at presence of upstream velocity oscillation are performed. Fuel droplet has an initial diameter of 1.25 mm and ambiance pressure and temperature are 0.4 MPa and 300 K, respectively. These conditions are those in which the microgravity experiments in literature conducted. In the excellent agreement with the experimental data, numerical results show a significant enhancement of the burning rate of droplet compared to what is predicted by quasi-steady film theory models. The mechanism of the enhancement of burning rate is clarified then by observation of a new mechanism that is named thermal-drag, TD. It is shown, depending on the amplitude and frequency of the upstream velocity oscillation, the flame in wake region of droplet can move toward the droplet surface by the force of vortex flow motions produced by the TD mechanism. It is verified that such movement of the flame is responsible for the enhancement of the burning rate and deviation of the response of the evaporation process form the predictions of the quasi-steady model. Frequency analysis of the burning rate reveals that at low frequency and amplitude the FFT diagram of the burning rate contains of only one main peak synchronies with the frequency of upstream velocity oscillation, which implies a quasi-steady response. However; at high frequency and amplitude the diagram includes of wide range of 98 Flow Turbulence Combust (2010) 84:97-123 frequencies beside of the main peak that readily shows deviation from the quasisteady conditions. In the latter, the study on the response of the combustion to the upstream velocity fluctuations in which the fluctuations contains of three wave numbers shows the amplification of the effects of low frequency fluctuations rather than that of damping of the effects of high frequency fluctuations on the evaporation processes.

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Droplet combustion in presence of airstream oscillation: Mechanisms of enhancement and hysteresis of burning rate in microgravity at elevated pressure

Jangi¹,

Kobayashi²

2010

Combustion and Flame

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Microgravity experiments of single droplet combustion in oscillatory flow at elevated pressure

Cited by 11 publications

References 8 publications

Experimental study on diffusive solid combustion behavior during transition from normal- to reduced-gravity

Experimental study on diffusive solid combustion behavior during transition from normal- to reduced-gravity

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Droplet combustion in presence of airstream oscillation: Mechanisms of enhancement and hysteresis of burning rate in microgravity at elevated pressure

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