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Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2000, Volume10

108 pages

Issue price - $75.00

EULER/LAGRANGE CALCULATIONS OF TURBULENT SPRAYS: THE EFFECT OF DROPLET COLLISIONS AND COALESCENCE

M. Ruger
INVENT Computing GmbH, Erlangen, Germany

S. Hohmann
Rheinisch Westfalische Technische Hochschule Aachen Institut fur Warmeubertragung und Klimatechnik, Aachen, Germany

M. Sommerfeld
Martin Luther Untversitat Halle-Wittenberg Institut fur Verfahrenstechnik, Halle (Saale), Germany

G. Kohnen
Martin Luther Untversitat Halle-Wittenberg Institut fur Verfahrenstechnik, Halle (Saale), Germany

ABSTRACT

The Euler/Lagrange approach is a powerful numerical tool for the prediction of poly disperse two-phase flows. In the present article this method is applied to the calculation of spray evolution by taking into account the two-way coupling between the phases, i.e., the gas and droplet phases, and droplet evaporation. Moreover, a new stochastic droplet-droplet collision model based on the kinetic theory of gases was developed. The model takes into account grazing and coalescing collisions, which are found to be very important even for the low-speed turbulent spray considered.
For validating the numerical results with regard to the spray evolution and the effects of droplet coalescence, detailed experimental studies were performed for two hollow-cone spray nozzles. In order to provide the required information concerning the spray characteristics sufficiently resolved, i.e., gas velocities, droplet size distributions, droplet mass fluxes, and droplet velocities, phase Doppler anemometry was applied.
The comparison of measurement and prediction showed excellent agreement for the profiles of the mean properties of both phases and the local droplet size distributions and size-velocity correlations. Moreover, the calculations revealed that the frequently observed increase of the integral droplet Sauter mean diameter along the spray is due mainly to coalescence, white the impact of droplet evaporation is of minor importance.