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Multiphase Science and Technology
SJR: 0.183 SNIP: 0.483 CiteScore™: 0.5

ISSN Imprimer: 0276-1459
ISSN En ligne: 1943-6181

Multiphase Science and Technology

DOI: 10.1615/MultScienTechn.v11.i1.10
pages 1-18

GROUP COMBUSTION IN SPRAY FLAMES

Sebastien Candel
CNRS, Ecole Centrale de Paris Laboratoire E.M2.C, F-92295 Chatenay Malabry, Cedex France
Francois Lacas
Laboratoire EM2C, C.N.R.S., Ecole Centrale Paris, Grande Voie des Vignes, 92295 Châtenay-Malabry, France
Nasser Darabiha
Ecole Centrale Paris CNRS, UPR 288, Laboratoire EM2C Grande Voie des Vignes 92290 Chatenay-Malabry, France
Juan-Carlos Rolon
Laboratoire EM2C du CNRS (UPR 288) et de l'ECP, École Centrale, France

RÉSUMÉ

Experiments as well as theoretical and numerical work indicate that spray burning is most often controlled by collective effects. The burning of a single droplet is seldom observed in practical situations whilst there are many examples of combustion of groups of droplets. In such circumstances the droplets vaporize collectively and combustion takes place in a flame located around the cloud. Group combustion is widespread and constitutes a central problem. This is illustrated in this article by a set of examples of fundamental and practical nature. In the first case we consider the structure of a laminar spray flame formed in a counterflow. This stagnation point flame is remarkably stable and may be studied in great detail. The flame structure features a vaporization front and a reactive front separated by a small distance typifying group combustion behavior in the simplest geometry. In the second case we consider the ignition of a dense droplet cloud in a hot oxidizing atmosphere. A model of this configuration assuming droplet group vaporization reveals the possible ignition regimes and provides a description of the dynamics of the process. In the third example, the spray is formed by a shear coaxial injector fed with liquid oxygen and gaseous hydrogen. The flame established in this configuration has been extensively studied with a variety of optical diagnostics and image processing techniques. The data indicate that a highly corrugated flame surrounds the dense spray of droplets formed by the liquid core break-up. Because the flame is turbulent, the mean flame appears as a thick shell shrouding the LOX spray and oxygen vapor.


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