Influence of standing sound waves on droplet combustion

Tanabe, Mitsuaki; Morita, Tomoaki; Aoki, Kiyoshi; Satoh, Kimiyoshi; Fujimori, Takahiro; Sato, Junichi

doi:10.1016/s0082-0784(00)80308-2

Cited by 33 publications

(47 citation statements)

References 7 publications

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“…The augmentation of droplet evaporation rate in non reacting pulsating flow was reported earlier by Raithby [35]. An increase of evaporation rate was also observed in case of droplet burning in pulsating flow [10][11][12]. In the present case augmentation of heat and mass transfer is not as significant, since the difference between ambient temperature and peak droplet flame temperature is relatively small.…”

Section: Frequency Domainsupporting

confidence: 86%

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Numerical Investigation of the Time Scales of Single Droplet Burning

Beck

Koch

Bauer

2008

Flow Turbulence Combust

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The effect of gas phase velocity fluctuations on single droplet burning is investigated numerically. The main objective of this study is to understand the effect of gas phase turbulence on nitric oxide formation in single droplet flames. Since the interaction of gas phase velocity fluctuations with droplet burning is of sequential character, a separate investigation of droplet momentum coupling and droplet burning is performed. Momentum coupling controls droplet relaxation against changes of the gas phase velocity along the droplet trajectory and, thereby, determines to what extend gas phase velocity fluctuations translate into droplet slip velocity fluctuations. This coupling effect acts as a high pass filter with a cutoff frequency determined by the droplet Reynolds number and diameter. In the simulation of single droplet burning detailed models for chemical reaction, diffusive species transport and evaporation are used. A significant effect of slip velocity fluctuations on the mean values of NO formation rate is observed. The effect of slip velocity fluctuations on the mean NO formation rate is frequency dependent. The frequency response of the droplet flame is similar to that of a low pass filter. The droplet flame time scale characterizing the response to slip velocity fluctuations is found to correlate with chemical time scales. This time scale is not affected by droplet diameter.

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Section: Frequency Domainsupporting

confidence: 86%

“…Experimental investigations of single droplet burning in pulsating flow have been performed at ambient temperature and pressure in a zero gravity environment [10][11][12]. In these studies, slip velocity fluctuations are generated by placing the droplet at the pressure node of an acoustic field.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Time Scales of Single Droplet Burning

Beck

Koch

Bauer

2008

Flow Turbulence Combust

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“…One of the interaction pathways for the case of spray combustion is the heat release variation of fuel droplet due to the transfer variation caused by acoustic oscillation. To clarify this, droplet combustion experiments had been done in standing acoustic fields (Tanabe et al 2000;Okai et al 2000;Tanabe et al 2005;Dattarajan et al 2006). Microgravity environments have been employed for this purpose since this decade.…”

Section: Introductionmentioning

confidence: 99%

Drop Tower Experiments and Numerical Modeling on the Combustion-Induced Secondary Flow in Standing Acoustic Fields

Tanabe

2010

Microgravity Sci. Technol.

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From the microgravity experiments on single fuel droplet combustion and on spark-ignited premixed flame in acoustic field, that have been done in this decade, secondary flow has been confirmed. The flow occurs only when combustion occurs and always in the direction to the neighboring node of velocity oscillation in standing acoustic field. This flow is thought to be driven by a kind of acoustic radiation force that arises from density non-uniformity due to combustion. According to the hypothesis, the driving force is expected to be very similar to buoyancy, being a volumetric force proportional to density difference. Since the mechanism tells that only the density difference due to combustion is the requirements for the occurrence of the secondary flow, a simpler system is employed for the hypothesis validation. A hot wire in a standing acoustic field gives a local temperature rise and the secondary flow is successfully reproduced. To avoid buoyancy that covers the radiation force, microgravity conditions are used. Through direct-and modeled numerical simulations and with drop tower experiments, the validity of the hypothesis is checked out. As a result, the supposed radiation force is found to be able to explain well the characteristics of the secondary flow. It is found that adding an acoustic radiation force term determined from acoustic parameters into conventional CFD calculation, one can sufficiently reproduce and predicts the behavior of the secondary flow numerically.

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“…The other is convective transport. Acoustically induced thermal convection that is driven by a kind of acoustic radiation force in a standing acoustic field has been previously found (Tanabe et al, Proc Combust Inst 28:1007-1013, 2000. The burning rate of an isolated single droplet is promoted by this thermal convection.…”

mentioning

confidence: 86%

Influence of Acoustic Perturbation and Acoustically Induced Thermal Convection on Premixed Flame Propagation

Yano

Takahashi

Kuwahara

et al. 2009

Microgravity Sci. Technol.

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Interference between an acoustic field and premixed flame is investigated. Two kinds of transport processes are considered to cause combustion promotion in the acoustic field. One is diffusive transport. It has long been considered that the acoustic oscillation promotes diffusion, like turbulence does. The other is convective transport. Acoustically induced thermal convection that is driven by a kind of acoustic radiation force in a standing acoustic field has been previously found (Tanabe et al., Proc Combust Inst 28:1007-1013, 2000. The burning rate of an isolated single droplet is promoted by this thermal convection. In this report, the influence of the acoustic oscillation on the premixed flame propagation was examined through experiment and numerical simulation. The gravitational force was not taken into account since it complicates the combustion phenomena. The experiment and numerical simulation were done in microgravity condition. Each influence of turbulent diffusion and thermal convection were evaluated from the burning velocity, flame shape and flame speed, since the diffusive effect has been considered to have an influence on the burning velocity, while the convective effect has an influence on the flame speed and flame shape. As a result, it was clarified that the diffusive effect has a minor influence on the

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Influence of standing sound waves on droplet combustion

Cited by 33 publications

References 7 publications

Numerical Investigation of the Time Scales of Single Droplet Burning

Numerical Investigation of the Time Scales of Single Droplet Burning

Drop Tower Experiments and Numerical Modeling on the Combustion-Induced Secondary Flow in Standing Acoustic Fields

Influence of Acoustic Perturbation and Acoustically Induced Thermal Convection on Premixed Flame Propagation

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