Begell House Inc.
Multiphase Science and Technology
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0276-1459
11
1
1999
GROUP COMBUSTION IN SPRAY FLAMES
1-18
10.1615/MultScienTechn.v11.i1.10
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
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.
THE IMPACT OF DROPS ON WALLS AND FILMS
19-36
10.1615/MultScienTechn.v11.i1.20
Cameron
Tropea
Technische Universitat Darmstadt, Institute for Fluid Mechanics and Aerodynamics, Alarich-Weiss-Str. 10, 64287 Darmstadt, Germany
Marco
Marengo
Advanced Engineering Centre, School of Computing Engineering and Mathematics, Cockcroft Building, Lewes Road, University of Brighton, Brighton BN2 4GJ, UK; Department of Engineering, University of Bergamo, Viale Marconi 5, 24044 Dalmine (BG), Italy; Department of Civil Engineering and Architecture, University of Pavia, via Ferrata 3, 27100, Pavia, Italy
This review deals with the impact of drops on solid surfaces and on liquid films. The post-impingement behaviour on solid surfaces is strongly affected by the liquid-solid contact angle. When droplets impinge on liquid films, the mode of splashing is changed. The evidence relating to drop impaction is surveyed and it is concluded that there is a general lack of experimental data though there has been a rapid development of prediction tools.
TWO-FLUID MODELS FOR SIMULATING TURBULENT GAS-PARTICLE FLOWS AND COMBUSTION
37-57
10.1615/MultScienTechn.v11.i1.30
L.
Zhou
Tsinghua University, Department of Engineering Mechanics, Haidian District, Beijing 100084, China
Systematic studies in recent years on two-fluid models for simulating turbulent gas-particle flows and combustion have been done in the Department of Engineering Mechanics, Tsinghua University, Beijing, China. New theoretical models, including the global models of turbulent reacting gas-particle flows and basic equations in the frame work of two-fluid models, models for simulating particle reaction-particle diffusion, particle turbulence-gas turbulence, and gas reaction-gas turbulence interactions were proposed. These models have been used for developing different computer codes applied in simulating 2-D and 3-D recirculating and swirling turbulent reacting gas-particle/droplet flows and combustion in practical engineering facilities. The numerical modeling using these codes has been applied as a design tool for developing innovative cyclone separators, cyclone combustors, cement kilns, liquid-fuelled ram-jet combustors, pulverized-coal burners and oil-water hydrocyclones.
MULTIPHASE FLOW: VIEWS OF THE FUTURE
59-77
10.1615/MultScienTechn.v11.i1.40
Geoffrey F.
Hewitt
Department of Chemical Engineering & Chemical Technology, Imperial College of Science, Technology & Medicine, Prince Consort Road, London SW7 2B Y, England, UK
A report on discussions at the Third International Workshop on Multiphase Flow, London, June 1992.