Study of airborne particles produced by normal impact of millimetric droplets onto a liquid film |
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Authors: | C Motzkus E Géhin F Gensdarmes |
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Institution: | 1. Institut de Radioprotection et de S?reté Nucléaire/Service d’Etudes et de Recherches en Aérodispersion des polluants et en Confinement, B.P 68, 91192, Gif-sur-Yvette Cedex, France 2. Centre d’Etudes et de Recherches en Thermique, Environnement et Système, Université Paris XII, 61 av. du Général de Gaulle, 94010, Créteil Cedex, France
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Abstract: | The aim of this work is to carry out an experimental investigation into the generation of airborne microparticles when millimetric
droplets of aqueous solutions impact onto a liquid film. Impact experiments using 3.9 mm diameter droplets were carried out
for Weber numbers between 159 and 808, with a fixed Ohnesorge number of 2 × 10−3 and film parameters S
f (the ratio between the thickness of the liquid film h
film and the diameter of the impacting droplet d
i) between 0.3 and 1. Observed results show that the deposition/splashing threshold is independent of the parameter S
f in agreement with the data in the literature. The aerosol measurement results demonstrate the production of solid particles
from the evaporation of secondary microdroplets with diameters less than 30 μm formed when splash occurs. The median diameter
of these microdroplets is around 20 μm, corresponding to a value of d
50/d
i = 5 × 10−3. Taken together, the results show that the mass and the number of particles emitted increase as the Weber number increases.
Moreover, at a Weber number of 808, the results show that the mass and number of particles emitted increases as the parameter
S
f decreases. In this case, the mean number of microdroplets emitted per impact is equal to 14 for S
f = 1 and equal to 76 for S
f = 0.3. |
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Keywords: | |
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