An Experimental Investigation of Evaporative Sprays in Axial Acoustic Fields

Gurubaran, R. Kumara; Sujith, R. I.

doi:10.2514/6.2008-4769

Cited by 2 publications

(5 citation statements)

References 16 publications

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“…In an acoustically compact domain, the number density wave, as reported previously in the works of Gurubaran et al 15 and Gajan et al 16 , results from the interaction of the pulsating flow with the droplets at the injection time. When droplets are continuously injected into a pulsating flow, droplets at an asymptotic state (after a long time) convect at mean flow speed u false¯ c and oscillate around that for a given frequency, amplitude of oscillation, droplet size and fluid and gas properties.…”

Section: Droplet Dynamicssupporting

confidence: 57%

“…Previous studies have observed droplet clustering 15 and the formation of a droplet density wave 23,16 downstream of the injector through experiments and simulations. Achury and Polifke 24 proposed a theoretical approach to study the response of a single droplet to acoustic oscillations.…”

Section: Introductionmentioning

confidence: 99%

“…The Sauter mean and arithmetic mean diameters of the spray were seen to decrease in the presence of an acoustic field by 15% and 20%, respectively, due to enhanced evaporation rate of the spray. Gurubaran et al 15 observed droplet clustering and a variation of droplet mean diameter downstream of the injector and concluded that the acoustic pressure amplitude has a significant effect on the particle size distribution. Gajan et al 16 experimentally investigated the behaviour of a spray downstream of an aero-engine injector submitted to acoustic excitation and noticed the formation of a spray droplet density wave.…”

Section: Introductionmentioning

confidence: 99%

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Response of spray number density and evaporation rate to velocity oscillations

Kulkarni

Silva

Polifke

2022

International Journal of Spray and Combustion Dynamics

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A theoretical investigation of the effect of gas velocity oscillations on droplet number density and evaporation rate is presented. Oscillations in gas velocity cause a number density wave, i.e. an inhomogeneous, unsteady variation of droplet concentration. The number density wave, as it propagates downstream at the mean flow speed, causes modulation of the local evaporation rate, creating a vapour wave with corresponding oscillations in equivalence ratio. The present work devises an analytical formulation of these processes. Firstly, the response of a population of droplets to oscillations in the gas velocity is modelled in terms of a number density wave. Secondly, the formulation is extended to incorporate droplet evaporation, such that an analytical expression for the evaporation rate modulation is obtained. Subsequently, the droplet 1D convection-diffusion transport equation with the calculated evaporation source term is solved using an appropriate Green’s function to determine the resulting equivalence ratio perturbations. The dynamic response of equivalence ratio fluctuations to velocity oscillations is finally characterized in terms of a frequency-dependent transfer function. The aforementioned analytical approach relies on a number of simplifying approximations, nevertheless it was validated with good agreement against 1D Euler-Lagrange CFD simulations.

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Section: Droplet Dynamicssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Response of spray number density and evaporation rate to velocity oscillations

Kulkarni

Silva

Polifke

2022

International Journal of Spray and Combustion Dynamics

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“…1 The particular spray dynamics that results from the interaction with a pulsating or oscillating carrier flow is what we call here spray response. Although different scenarios of sprays interacting with unsteady flows have been studied experimentally, [2][3][4][5] by means of computational fluid dynamics (CFD), 6,7 and analytically, 8,9 there is to the best of our knowledge no proper and comprehensive classification of different types of spray responses in the literature. The problem of making a rigorous classification lies in the fact that, depending on the scenario under investigation, various mechanisms are more or less dominant.…”

Section: Introductionmentioning

confidence: 99%

“…It is argued in that study that the origin of the ND wave is related to two factors: the atomization process itself and the fluctuating transport of small droplets. Gurubaran and Sujith have also performed experimental investigations in non-evaporating 2 and evaporating sprays 5 submitted to an axial acoustic field. They found that the spray velocity oscillates with the same frequency as the excitation signal, but out of phase.…”

Section: Introductionmentioning

confidence: 99%

Modulation of spray droplet number density and size distribution by an acoustic field

Achury

Polifke

2017

The Journal of Computational Multiphase Flows

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Multiple interactions may occur when a poly-disperse spray is exposed to an acoustic field. In the context of spray combustion instabilities, acoustic agglomeration, the formation of a droplet number density wave and the modulation of the droplet size distribution are interesting effects. A droplet number density wave, i.e. preferential concentration of droplets in space, may result from size-dependent, one-way momentum coupling between the acoustic field and the spray. The modulation of the droplet size distribution, which has been evidenced in the experimental work of Gurubaran and Sujith (AIAA 2008-1046), is thus a consequence of the droplet number density wave formation. In the present work, the mechanisms that produce these effects are simulated and analyzed in depth by means of computational fluid dynamics. The spray is modeled with both Lagrangian (particles mass-point approach) and Eulerian (continuous phase approach) descriptions. The particular Eulerian method used is a variant of the presumed density function method of moments, which allows to account for the effects of poly-dispersity, in particular the size-dependence of particle velocity. Both the Lagrangian and Eulerian models are validated against experimental data for spray dynamics and spray response to an acoustic field.

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An Experimental Investigation of Evaporative Sprays in Axial Acoustic Fields

Cited by 2 publications

References 16 publications

Response of spray number density and evaporation rate to velocity oscillations

Response of spray number density and evaporation rate to velocity oscillations

Modulation of spray droplet number density and size distribution by an acoustic field

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