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Computational Thermal Sciences: An International Journal
ESCI SJR: 0.249 SNIP: 0.434 CiteScore™: 1.4

ISSN Print: 1940-2503
ISSN Online: 1940-2554

Computational Thermal Sciences: An International Journal

DOI: 10.1615/ComputThermalScien.v1.i3.30
pages 289-308

ON THE USE OF DNS TO ANALYZE HEAT AND MASS TRANSFERS IN A DROPLET-LADEN TURBULENT JET

Zakaria Bouali
UMR 6614 CNRS CORIA, Rouen University, bp 12−Site universitaire du Madrillet, 76801 St Etienne du Rouvray, France
Bruno Delhom
CORIA, University of Rouen, France
Karine Truffin
Institut Français du Pétrole - R102 1&4 avenue Bois Préau 92852 Rueil Malmaison, France
Hicham Meftah
CORIA, University of Rouen, France; Ibn Zohr University, GEMS Laboratory, ENSA, B.P 1136, Agadir-Morocco
Julien Reveillon
CORIA-UMR 6614 – Normandie Université, CNRS-Université et INSA de Rouen, Campus Universitaire du Madrillet, 76800 Saint Etienne du Rouvray, France

ABSTRACT

Nowadays, it is fundamental to decrease fuel consumption and pollution generated by cars by improving engine efficiency. The characterization, the prediction, and the control of the physical phenomena interacting within the combustion chamber are necessary if one wants to improve the current systems and to develop new technologies. This is why it is important to understand and control the whole of the physical processes taking place from the liquid injection and atomization down to combustion phenomena and gas exhaust. In direct-injection engines, modeling the evaporation of the liquid fuel is a very difficult phase. Experimental results have shown that the droplet presence amplifies the temperature fluctuations and modifies the mixing between the vapor of fuel and the oxidizer. If, up to now, the effects of evaporation on the equivalence ratio and the velocity fluctuations have been taken into account in engines modeling, temperature exchanges between the spray and the gas phase have not been clearly evaluated. These fluctuations, however, could play a considerable role in the process of self-ignition and then pollutant formation. The main objective of this work is to carry out direct numerical simulation (DNS) of an evaporating gasoline spray in order to estimate the effects of the droplets on the energy field and to study temperature and enthalpy fluctuations. We focus mainly on the vaporization sources terms found in the balance equation of the variance of the sensible enthalpy. DNS is a useful tool that allows exactly solving the Navier-Stokes equations by considering all the characteristic scales of the flow. When two-phase flows are considered, only a DNS of the carrier phase is carried out, whereas a Lagrangian model is necessary to describe the liquid phase. The droplets are considered as local sources of vapor, momentum, and energy; a two-way coupling is considered.


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