Begell House Inc.
Atomization and Sprays
AAS
1044-5110
21
11
2011
SPRAY CHARACTERISTICS OF DIESEL FUEL CONTAINING DISSOLVED CO2
883-892
10.1615/AtomizSpr.2012003294
M.
Karaeen
Ben-Gurion University of the Negev, Beer-Sheva, Israel
Eran
Sher
Faculty of Aerospace Engineering, Technion-Israel Institute of Technology,
Haifa, Israel
diesel fuel
dissolved CO2
flash-boiling
The effect of adding CO2 to diesel fuel has been studied by several groups that used tailor-made injection systems to achieve notable low Sauter mean diameters (SMDs). In the present study, we use a real commercial fuel injection system and study the effect of the amount of dissolved CO2 on the resulting spray characteristics. In this case, when the mixture enters the injector and flows downstream through the variable cross-section passage toward the discharge orifice, partial nucleation of the dissolved gas is expected to occur at different locations along the duct, which transforms the mixture into tiny bubbles that grow fast downstream. When the mixture is driven out through the discharge orifice, these bubbles undergo a rapid flashing process that results in an intensive disintegration of the liquid bulk into small droplets. In the present study, we present an experimental study of the atomization process of diesel fuel containing dissolved CO2 that occurs in steady flow conditions. An extensive study was performed to map the effect of the CO2 content on the spray SMD and droplet distribution at different locations downstream the discharge orifice. It is concluded that the atomization of diesel fuel containing dissolved CO2, is significantly promoted by the flash-boiling phenomenon, which results in low SMD sprays, low D0.1 droplets, a faster breakup mechanism, and a more uniform droplet size distribution.
DROPLET SIZE AND VELOCITY MEASUREMENTS AT THE OUTLET OF A HOLLOW CONE SPRAY NOZZLE
893-905
10.1615/AtomizSpr.2012004171
Arnaud
Foissac
IRSN, DSU/SERAC/LEMAC, BP 68, F-91192 Gif-sur-Yvette Cedex, France
Jeanne
Malet
IRSN; UJV Rez, Hlavni 130, PSC 250 68, Czech Republic
Maria Rosaria
Vetrano
Department of Mechanical Engineering, KU Leuven, Celestijnenlaan 300A, 3001 Leuven, Belgium
Jean-Marie
Buchlin
von Karman Institute for Fluid Dynamics, Rhode-St-Genese, Belgium
Stephane
Mimouni
Electricite de France, R&D Division, MFEE, 6 Quai Watier, 78400 Chatou, France
Francois
Feuillebois
LIMSI
Olivier
Simonin
Institut de Mecanique des Fluides de Toulouse, IMFT, Universite de Toulouse, CNRS - Toulouse,
FRANCE
spray
phase-Doppler anemometer
droplet size distribution
droplet velocity distribution
air entrainment
CFD numerical input data
During the course of a severe accident in a nuclear pressurized water reactor (PWR), hydrogen may be produced by reactor core oxidation and distributed into the containment. Spray systems are used in order to limit overpressure, enhance the gas mixing, avoid hydrogen accumulation, and wash out fission products. In order to simulate these phenomena with computational fluid dynamics codes, it is first necessary to know the droplet size and velocity distributions close to the outlet nozzle. Furthermore, since most of the phenomena relative to droplets (condensation, gas entrainment, and collisions) are of particular importance in the region just below the nozzle, accurate input data are needed for real-scale PWR calculations. The objective is, therefore, to determine experimentally these input data under atmospheric conditions. Experimental measurements were performed on a single spray nozzle, which is routinely set up in many PWRs. This nozzle is generally used with water at a relative pressure supply of 3.5 bar, producing a mass flow rate of approximately 1 kg/s. At a distance of 20 cm, in which under ambient conditions atomization is just achieved, it is found that the geometric mean diameter varies from 280 to 340 μm, the Sauter mean diameter varies from 430 to 520 μm, and the mean axial velocity varies from 14 to 20 m/s. The radial velocity is around 7 m/s, whereas the orthoradial velocity is almost equal to zero at this distance of the nozzle. Gas velocity measurements around the spray are also performed.
MONO- AND MULTI-COMPONENT DROPLET COOLING/HEATING AND EVAPORATION: COMPARATIVE ANALYSIS OF NUMERICAL MODELS
907-931
10.1615/AtomizSpr.2012004194
A. E.
Elwardany
Sir Harry Ricardo Laboratories, School of Computing, Engineering and Mathematics, Faculty of Science and Engineering, University of Brighton, Brighton BN2 4GJ UK
I. G.
Gusev
Sir Harry Ricardo Laboratories, Centre for Automotive Engineering, School of Computing, Engineering and Mathematics, Faculty of Science and Engineering, University of Brighton, Brighton, BN2 4GJ, UK
Guillaume
Castanet
UMR 7563, LEMTA, Universite de Lorraine, ENSEM, Vandoeuvre-les-Nancy, TSA 60604-54518 Vandoeuvre CEDEX, France
Fabrice
Lemoine
Laboratoire d'Energetique et de Mecanique Theorique et Appliquee, Institut National Polytechnique de Lorraine, Universite Henri Poincare - Nancy I 2, Avenue de la Foret de Haye BP 160, F-54504 Vandoeuvre-les-Nancy Cedex, France
Sergei S.
Sazhin
Advanced Engineering Centre School of Architecture, Technology and Engineering
University of Brighton Cockcroft Building, room C302b,
Lewes Road Brighton BN2 4GJ UNITED KINGDOM
droplets
acetone
ethanol
multi-component fuel
heating
cooling
evaporation
diffusion equation
heat conduction
moving boundary
The results of a comparative analysis of the predictions of various models for mono- and multi-component droplet cooling/heating and evaporation in ambient air are presented. The finite thermal conductivity and species diffusivity inside droplets are taken into account along with the effects of recirculation inside droplets. The effect of the deviation from the Raoult law (non-ideal mixtures) is taken into account. It is pointed out that the predictions of the models based on the analytical and numerical solutions to the heat transfer and species diffusion equations inside droplets (the location of the droplet surface was fixed during the timestep in both models) are almost identical for the one-way solution, which gives confidence in both solutions. At the initial stage of droplet cooling/heating and evaporation, the coupled solution predicts visibly lower droplet temperatures, compared with the predictions of the one-way solution. At the later stage of droplet cooling/heating and evaporation, the coupled solution predicts higher droplet temperatures, compared with the predictions of the one-way solution. At the initial stage of droplet evaporation, the predictions of the models, taking and not taking into account the effects of the moving boundary during the timesteps on the solutions to the heat transfer and species diffusion equations, are very close. At the same time, the difference in the predictions of these models needs to be taken into account when the whole period of droplet evaporation up to the complete evaporation of droplets is considered. The effect of the moving boundary is shown to be much stronger for the solution to the species diffusion equations than for the solution to the heat conduction equation. The effect of the choice of the approximation of the binary diffusion coefficient for the ethanol/acetone mixture in air is shown to be small and can be ignored in most engineering applications. The modeling results are compared with experimental observations of acetone/ethanol mono- and multi-component droplet cooling/heating and evaporation where appropriate.
SPRAY PROCESS MODELING IN METAL MATRIX COMPOSITE POWDER PRODUCTION
933-948
10.1615/AtomizSpr.2012004487
Xinggang
Li
Department of Particles and Process Engineering, University of Bremen; Foundation Institute of Materials Science, Badgasteiner Str. 3, D-28359 Bremen, Germany
L.
Heisteruber
Department of Particles and Process Engineering, University of Bremen; Foundation Institute of Materials Science, Badgasteiner Str. 3, D-28359 Bremen, Germany
Lydia
Achelis
Particles and Process Engineering Department, Faculty of Production Engineering, University Bremen, Bibliothekstr. 1, 28359 Bremen, Germany; Foundation Institute of Materials Science, Badgasteiner Str. 3, D-28359 Bremen, Germany
Volker
Uhlenwinkel
Department of Particles and Process Engineering, University of Bremen; Foundation Institute of Materials Science, Badgasteiner Str. 3, D-28359 Bremen, Germany
Udo
Fritsching
Particles and Process Engineering Department, Faculty of Production
Engineering, University Bremen, Bibliothekstr. 1, 28359 Bremen, Germany; Leibniz Institute for Materials Engineering IWT, Badgasteiner Str. 3, 28359
Bremen, Germany
swirl pressure gas atomization
metal matrix composite
spray process
three-phase flow
multi-scale model
Swirl pressure gas atomization is used to produce metal matrix composite powders in a spray process. Here, solid particulate material (typically ceramic particles) is co-injected together with the atomization gas to be impacted on the liquid metal lamellas/droplets in flight. Thus, a three-phase spray flow is formed. The spray process is simulated based on a multi-scale model. On the macro-scale, an Eulerian-Lagrangian-Lagrangian model is employed. According to the simulation results, high gas velocity (above 100 m/s) and particle number concentration (in the order of 102/mm3) can be maintained in the secondary atomization region, e.g., 30−40 mm below the nozzle, where the metallic droplets and ceramic particles have been mixed fully. Numerical results from the macro simulation provide a background and initial conditions for the meso-scale simulation. On the meso-scale, the particle-laden gas flow around a metallic droplet is investigated based on an Eulerian-Lagrangian model. The particle-droplet impact efficiency, found related to relative Stokes number (St) and Reynolds number (Re), should be always above 90% for a spherical droplet of 125 μm diameter along its flight path, due to high St and Re (both in the order of 102−103). The interaction between the metallic droplets and the ceramic particles is described quantitatively based on a particle-droplet (spherical) impact model. However, the particle incorporation rate into the metal droplets is overpredicted in comparison to experimental findings, probably due to neglecting particulate reinforcement penetration efficiency and the influences from the metallic lamella/droplet deformation and break-up.
ATOMIZATION OF GELLED PROPELLANTS FROM SWIRL INJECTORS WITH LEAF SPRING IN SWIRL CHAMBER
949-969
10.1615/AtomizSpr.2012004646
Li-Jun
Yang
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine,
School of Medicine and Engineering, Beihang University, Beijing 100083,
China
Qing-Fei
Fu
School of Astronautics, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, School of Medicine and Engineering, Beihang University, Beijing 100083,
China; School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, United Kingdom
Wei
Zhang
School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100191
Ming-long
Du
School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing, China, 100191
Ming-Xi
Tong
Beijing Institute of Astronautical Systems Engineering, China Academy of
Launch Vehicle Technology, Beijing, China
spray characteristics
power-law fluid
gelled propellant
swirl injector
leaf spring
Gelled propellants behave as non-Newtonian fluids and are promising for future aerospace application because they combine the advantages of solid propellants with those of liquid propellants. Spray formation of gelled propellants from swirl injectors in which a leaf spring was installed was described by carrying out experiments in a spray test facility and then comparing them with the spray behavior of water. Safety being a consideration, a water-based gel simulant was used in the experiments instead of the gelled propellant. The rheological characteristics of the gel simulant were tested. A high-speed camera was used to record detailed information about the liquid sheet breakup process and spray development. The experiments were performed with injectors of different configurations and leaf springs to test the effect of injector geometry and leaf spring on the spray characteristics. It was found that the spray patterns of gel simulant were qualitatively different from those of Newtonian liquid (water). The identified spray patterns for the gel simulant were columnar jet, twisted swirling sheet, fluid web, and fully developed hollow cone. The spray cone pulsated under some conditions. A nondimensional frequency parameter was defined as the product of the geometric characteristics constant of a swirl injector and Strouhal number. This parameter for both injectors collapses to one constant under different Reynolds numbers. Adding a leaf spring in the swirl chamber tended to decrease the spray angle of the conical liquid sheet and increase the discharge coefficient and mass flow rate. The breakup length of the gel simulant from injectors with a leaf spring was longer than that from injectors without a leaf spring in the measured range of pressure drops; the mean diameter of droplets of water from the injectors with a leaf spring was larger than that from injectors without a leaf spring.