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How boiling happens in nanofuel droplets

Pandey, Khushboo and Basu, Saptarshi (2018) How boiling happens in nanofuel droplets. In: PHYSICS OF FLUIDS, 30 (10).

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Official URL: http://dx.doi.org/10.1063/1.5048564

Abstract

We report detailed analyses of evaporation and atomisation characteristics of nanofuel droplets in a contactless environment (acoustic levitation) under external radiative heating. Two base fuels, ethanol and n-dodecane with a significant difference in their respective vapour-pressures, are considered. Nanoparticles (NPs) of cerium oxides (CeO2) are utilised as nano-additives at a dilute particle loading rate (PLR) of 0%-0.5% by weight. Pure ethanol droplets vaporise at a faster rate than pure dodecane droplets and do not exhibit any secondary atomisation. However, pure dodecane droplets exhibit two modes of secondary breakup; Kelvin-Helmholtz instability induced stripping and catastrophic breakup beyond a certain threshold value of the initial droplet size. Nanofuel droplets of ethanol neither exhibit any significant change in the vaporisation rate nor exhibit secondary atomization. Contrarily, dodecane-based nanofuels show enhanced vaporisation due to heat absorption by nanoparticles and consequently different modes of secondary breakup. Interestingly, dodecane-based nanofuel droplets exhibit internal boiling induced atomization. A time scale analysis considering orthokinetic NP aggregation, evaporation lifetime, and bubble growth rate is presented to elucidate the mechanism of such internal boiling. The theoretical non-dimensional time scale (tau*) so coined is extended to estimate the minimum value of the droplet size necessary for exhibiting boiling. The analysis shows excellent agreement with the experimental observations. Furthermore, we propose a unique three-dimensional regime map to correlate the breakup modes with droplet sizes, PLR, and heating rates. Published by AIP Publishing.

Item Type: Journal Article
Additional Information: Copy right for this article belong to AMER INST PHYSICS
Department/Centre: Division of Interdisciplinary Research > Interdisciplinary Centre for Energy Research
Division of Mechanical Sciences > Mechanical Engineering
Depositing User: Id for Latest eprints
Date Deposited: 22 Nov 2018 15:03
Last Modified: 22 Nov 2018 15:03
URI: http://eprints.iisc.ac.in/id/eprint/61123

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