Begell House Inc.
Atomization and Sprays
AAS
1044-5110
16
6
2006
TEMPERATURE MEASUREMENTS IN POLYDISPERSE SPRAYS BY MEANS OF LASER-INDUCED FLUORESCENCE (LIF) ON THREE SPECTRAL BANDS
599-614
10.1615/AtomizSpr.v16.i6.10
M.
Bruchhausen
LEMTA, CNRS-UMR 7563, 2 avenue de la Forêt de Haye, BP160, F-54504 Vandæuvre-lès-Nancy, France
A.
Delconte
LEMTA, CNRS-UMR 7563, 2 avenue de la Forêt de Haye, BP160, F-54504 Vandæuvre-lès-Nancy, France
D.
Blondel
DANTEC Dynamics, Tonsbakken 16-18, 2740 Skovlunde, Denmark
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
The characterization of the local temperature of the liquid phase of a polydisperse spray is an important problem in many engineering applications. This article presents a new technique to measure the temperature of the liquid phase in polydisperse sprays, even under evaporation. The technique is based on the use of laser-induced fluorescence of a dye tracer (sulfo-rhodamine B) added to the liquid. The fluorescence emission is detected simultaneously on three spectral bands in order to eliminate the dependency of the fluorescence emission on the concentration of the tracer, on the dimensions of the probe volume, on the laser intensity, and on the optical layout and also to correct for the wavelength-dependent scattering of the fluorescence. This effect is due to the interaction of the fluorescence photons with the spray environment. As an example, application to a heated water polydisperse spray is presented.
FLOW PATTERN OBSERVATIONS OF GASOLINE DISSOLVED CO2 INSIDE AN INJECTOR
615-626
10.1615/AtomizSpr.v16.i6.20
A.
Rashkovan
The Pearlstone Center for Aeronautical Studies, Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
Eran
Sher
Faculty of Aerospace Engineering, Technion-Israel Institute of Technology,
Haifa, Israel
Spray formation by fuel-dissolved gas atomization is studied. The geometry of the injector, which consists of two orifices separated by an expansion chamber, was optimized to produce spray with minimal Sauter mean diameter (SMD). Special attention is drawn to the flow pattern inside the expansion chamber and on its significant impact on the resultant spray quality. Three possible characteristic regimes were identified: all liquid flow, stratified two-phase flow, and well-mixed bubbly flow. The latter regime results in the lowest SMD sprays. The necessary operation conditions and injector geometry in order to reach the well-mixed bubbly flow regime were mapped. A possible explanation for the optimal value of about 0.7 for the orifice diameter ratio has been proposed. When optimizing an injector of this type, it is anticipated that the pressure of the expansion chamber plays an important role. The pressure is primarily determined by the orifice diameter ratio. A lower pressure enhances both the nucleation rate at the inlet orifice and the bubble growth rate inside the chamber. Conversely, a higher pressure enhances the discharge velocity and the bubble growth rate downstream of the discharge orifice; both result in a better secondary droplet breakup. In an attempt to find an empirical criterion for the optimal orifice diameter ratio, we examined various combinations of the relevant parameters. The product of the void fraction and the pressure drop across the discharge orifice has been found fairly useful over the entire range of the present experimental conditions.
TRANSPORT OF HIGH BOILING POINT FIRE SUPPRESSANTS IN A DROPLET-LADEN HOMOGENEOUS TURBULENT FLOW PAST A CYLINDER
627-656
10.1615/AtomizSpr.v16.i6.30
Cary
Presser
NIST
C. Thomas
Avedisian
Sibley School of Mechanical & Aerospace Engineering, Cornell University, Ithaca, New York 14853
Liquid agent transport was investigated around unheated and heated horizontal cylinders (to a near-surface temperature of approximately 423 K, i.e., well above the water boiling point) under ambient conditions. Experimental results are presented for a well-characterized, droplet-laden homogenous turbulent flow field, using water, methoxy-nonafluorobutane (i.e., HFE-7100, C4F9OCH3, with a boiling point of 334 K), and 1-methoxyheptafluoropropane (i.e., HFE-7000, C3F7OCH3, with a boiling point of 307 K). Phase Doppler interferometry and visualization techniques were used to explore the thermal effects on spray surface impingement, vaporization, and transport around and downstream behind the cylinder by providing information on droplet size and velocity in the vicinity of the cylinder. For water, results indicated that impinging droplets larger than about 35 μm generally coat the unheated cylinder surface, with few droplets rebounding back into the free stream. Downstream, in the wake region of the cylinder, smaller size droplets (generally, of less than 35 μm) are entrained into the recirculation zone. Heat transfer reduces droplet mean size and velocity significantly in the vicinity of the heated cylinder. For the two HFE agents, liquid coating and dripping (observed for water) were eliminated due to vaporization. Droplet mean size increases and velocity decreases with increasing agent boiling point. These variations may also be explained by the changes in agent physical properties. It is improbable that shattering occurs for the droplet sizes and velocities encountered for the given operating conditions, although it could conceivably occur for a few individual impinging droplets.
PRIMARY BREAKUP OF ROUND AERATED-LIQUID JETS IN SUPERSONIC CROSSFLOWS
657-672
10.1615/AtomizSpr.v16.i6.40
Khaled A.
Sallam
School of Mechanical and Aerospace Engineering, Oklahoma State University, Tulsa, OK 74106, USA
C.
Aalburg
Department of Aerospace Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2140, USA
G. M.
Faeth
Department of Aerospace Engineering, the University of Michigan, Ann Arbor, Michigan 48109-2140, USA
K.-C.
Lin
Taitec, Inc., Beavercreek, OH 45430, USA
C. D.
Carter
Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA
Thomas A.
Jackson
Air Force Aero-Propulsion Laboratory, Fuel and Lubrication Division, WRDC/POSF, Wright Patterson Air Force Base, Ohio, USA
An experimental investigation of the primary breakup properties of round aerated-liquid jets in the annular flow regime exposed to a supersonic crossflow is described. Single- and double- pulse shadowgraphy and holography were used to study the properties of the conical liquid sheet that extends from the jet exit for finite degrees of aeration as well as the outcomes of primary breakup in the dense-spray region near the liquid jet itself. The results show that the gas jet along the axis of the annular flow leaving the injector passage is underexpanded so that the excess pressure of the flow in this region forces the annular liquid sheet into a conical shape that extends from the injector exit. Primary breakup occurs in a similar manner along both the upstream and downstream sides of the liquid jet (relative to the crossflow), which suggests that there are relatively weak aerodynamic effects due to the crossflow near the jet exit. Surface velocities of the liquid sheet were measured and were used to develop correlations for the liquid sheet thickness. The sizes of ligaments and drops were measured along the liquid surface and were found to have constant diameters of 29 and 43 μm, respectively, independent of position along the liquid sheet for the wide ranges of aeration levels, liquid/gas momentum flux ratios, injector exit passage diameters, and liquid properties considered during the present investigation. Finally, drop size distributions satisfied Simmons's universal root-normal drop size distribution function with mass median drop diameter (MMD)/Sauter mean diameter (SMD) = 1.07, which implies more nearly monodisperse drop size properties after aerated-liquid jet primary breakup than is encountered for other primary breakup processes.
MODELING DROPLET SIZE DISTRIBUTION NEAR A NOZZLE OUTLET IN AN ICING WIND TUNNEL
673-686
10.1615/AtomizSpr.v16.i6.50
Laszlo E.
Kollar
CIGELE/INGIVRE, University of Québec at Chicoutimi, 555 Boulevard de l'Université, Chicoutimi, Québec G7H 2B1, Canada
Masoud
Farzaneh
CIGELE/INGIVRE, University of Québec at Chicoutimi, 555 Boulevard de l'Université, Chicoutimi, Québec G7H 2B1, Canada
Anatolij R.
Karev
CIGELE/INGIVRE, University of Québec at Chicoutimi, 555 Boulevard de l'Université, Chicoutimi, Québec G7H 2B1, Canada
The median volume diameter (MVD) and the droplet size distribution (DSD) in an aerosol cloud under icing conditions are investigated. The procedure involves experimental observation of aerosol size distributions in an icing wind tunnel, computing the MVD by applying an empirical formula, and matching a distribution function to experimental data so as to estimate the DSD. Some of the nozzle dynamic parameters (NDPs), i.e., nozzle water and air pressure, are varied throughout the experiments, and droplet diameter is measured near the nozzle outlet. A new empirical formula is proposed that expresses the relationship between the MVD and the NDPs and, compared to previous studies, provides wind tunnel operators with a more convenient technique to estimate the MVD in the operational range of the selected nozzles. Moreover, the least squares fitting technique is used to find the best-fitting distribution function among published empirical relationships intended to model the DSD for nozzle-generated aerosol. The MVD and DSD obtained by this procedure, together with the NDPs and the thermodynamic parameters, may be used to model and control two-phase flows in icing wind tunnels.
STUDY OF AMBIENT TURBULENCE EFFECTS ON DIESEL SPRAYS IN A FAN-STIRRED VESSEL
687-704
10.1615/AtomizSpr.v16.i6.60
Tamas
Jakubik
Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, 616 69 Brno, Czech Republic
Malcolm
Lawes
Institute of Engineering Thermofluids, Surfaces and Interfaces, School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom
Robert M.
Woolley
School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, United Kingdom
Miroslav
Jicha
Brno University of Technology, Faculty of Mechanical Engineering, Department of the
thermodynamics and environmental engineering, Technická 2896/2, 616 69 Brno, Czech Republic
This study investigates the influence of the ambient turbulence on a pressure-atomized diesel-like spray in the well-characterized and controlled turbulence flow field of a fan-stirred experimental vessel. Injections were performed into nitrogen at 15 bar and 400 K under four turbulent conditions, with RMS velocities ranging from 0.5 up to 5.5 m/s. Mie scatter laser sheet and Schlieren techniques were applied to visualize the liquid and the vapor phase of the spray. With increasing turbulence, there was increasing formation of droplet clusters and ligaments, which resulted in a reduced detection of droplet vapor along the whole penetration length of the spray. From considerations of the Stokes numbers for the droplet-turbulence interaction, it is concluded that the microlength scales of the ambient turbulence were the probable source of this droplet clustering.
IMPINGEMENT OF HIGH-PRESSURE GASOLINE SPRAYS ON ANGLED SURFACES
705-726
10.1615/AtomizSpr.v16.i6.70
J. M.
Nouri
School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V0HB
Jim H.
Whitelaw
Thermofluids Section, Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, London SW7 2BX, United Kingdom
A combination of visualization and local measurements of velocity and droplet size characteristics of normal and angled impinging sprays at an injection pressure of 80 bar, chamber pressures of atmospheric and 12 bar, and injection duration of 3.2 ms has shown the formation of a spray moving along the wall after impingement. Angled plates at 80° and 45° produced nonuniform wall sprays, with the difference between maximum and minimum radii from impingement increasing with plate angle. The penetration of the wall spray was less at the higher chamber pressure, and much of the injected fuel appeared to form a liquid film on the surface, although this could not be verified from the images. The velocities of the droplets inside the wall spray showed that its thickness was less at the higher chamber pressure with smaller velocities and larger diameters. The average droplet diameter was smaller than that in the spray prior to impingement for both chamber pressures so that they were better able to follow the induced airflow circulation. The results also showed that the 45° impingement resulted in similar droplets to those of normal impingement. In general, the droplets forming the jet wall spray with both angles were mainly transported from the main spray, with contributions from splashing and reatomization closer to the main spray and from stripping of the liquid film farther downstream, where the wall spray tended to turn upward.