Begell House Inc.
Atomization and Sprays
AAS
1044-5110
19
11
2009
NEAR-WALL CHARACTERISTICS OF AN IMPINGING GASOLINE SPRAY AT INCREASED AMBIENT PRESSURE AND WALL TEMPERATURE
997-1012
10.1615/AtomizSpr.v19.i11.10
Jochen
Stratmann
Institute of Heat and Mass Transfer, RWTH Aachen University, Germany
D.
Martin
Institute of Heat and Mass Transfer, RWTH Aachen University, Eilfschornsteinstr. 18, 52062 Aachen, Germany
P.
Unterlechner
Institute of Heat and Mass Transfer, RWTH Aachen University, Eilfschornsteinstr. 18, 52062 Aachen, Germany
Reinhold
Kneer
Institute of Heat and Mass Transfer (WSA), RWTH Aachen University, Augustinerbach 6, 52056 Aa-chen, Germany
With a focus on the direct-injection gasoline (GDI) engine, this work provides near-wall spray details of the liquid phase of an impinging fuel spray at GDI engine conditions. The experiments are conducted in a constant volume pressure chamber at elevated gas pressure (pgas = 0.6 and 1.5 MPa), increased gas temperature (Tgas = 500 K), and variable wall temperature (Tw = 400 and 575 K). Using phase-Doppler anemometry, temporally and spatially resolved mean droplet sizes and velocity components are determined at distances from 0.2 to 1.0 mm above the surface. The transient behavior of the wall jet, which develops along the surface, is resolved by the measurements. The formation of a vortex at the front of this jet is observed. At its tip, large mean droplet diameters are observed that coincide with a rapid change of the wall-normal velocity. An increasing wall temperature causes the tip of the wall jet to propagate slower along the wall, which is apparently caused by a change in the local density of the gas above the surface.
GAS ENTRAINMENT CHARACTERISTICS OF DIESEL SPRAY DURING END OF INJECTION TRANSIENT
1013-1029
10.1615/AtomizSpr.v19.i11.20
Seoksu
Moon
Department of Mechanical Engineering, Inha University, Incheon, South Korea
Keiya
Nishida
Department of Mechanical System Engineering, University of Hiroshima, 1-4-1
Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan
Yuhei
Matsumoto
Department of Mechanical System Engineering, University of Hiroshima, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan
Jeekuen
Lee
Faculty of Precision Mechanical Engineering, 664-14, 1-ga, Duckjin-dong, Duckjin-gu, Jeonju, Chonbuk, 561-756, Republic of Korea
This paper reports the effect of injection parameters such as nozzle hole diameter and injection duration on gas entrainment of diesel sprays during the end of injection transient. The entrained gas flow fields of transient diesel sprays were measured using particle image velocimetry incorporated with the laser-induced fluorescence technique. To investigate the effect of injection parameters, two nozzles with different hole diameters and two injection modes (a quasi-steady injection with long injection duration and a transient injection with short injection duration) were applied. In all test cases, in order to compensate for the decreased mass inside the spray caused by the decrease in fuel supply, gas entrainment during the end of injection transient increased compared to that of the quasi-steady state. In the case of the nozzle with a larger hole diameter, the steeper decrease in fuel mass flow rate during the end of injection transient resulted in a higher rate of entrained gas flow compared to that of the nozzle with the smaller nozzle hole diameter. However, this increasing rate of gas flow rate appears similar regardless of applied injection modes, a quasi-steady injection with long injection duration and a transient injection with short injection duration, supposedly due to the similar decreasing rate of fuel mass flow during the end of injection transient. The decrease in mass inside the spray (mass disturbance) propagated from the nozzle tip region to downstream with time. This propagation speed of mass disturbance inside the spray was affected by the penetrating rate of the spray during injection, and increased through the nozzle with a larger hole diameter and quasi-steady injection with longer injection duration.
X-RAY RADIOGRAPHY MEASUREMENTS OF DIESEL SPRAY STRUCTURE AT ENGINE-LIKE AMBIENT DENSITY
1031-1044
10.1615/AtomizSpr.v19.i11.30
Alan L.
Kastengren
X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA; Combat Capabilities Development Command Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005, USA
Christopher F.
Powell
Energy Systems Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
Yujie
Wang
Physics Department, Shanghai Jiaotong University, Shanghai, China
Kyoung-Su
Im
Livermore Software Technology Corporation, Livermore, CA, USA
Jin
Wang
Argonne National Laboratory
X-ray radiography has been used to examine the dependence of the near-nozzle fuel distribution of diesel sprays on injection pressure and ambient density. Measurements of sprays from two nozzles with different geometries, one extensively hydroground and the other minimally hydroground, have been obtained to show how nozzles of different geometries respond to changes in ambient density and rail pressure. The spray penetration near the nozzle demonstrates little dependence on ambient density, but a strong dependence on rail pressure. Comparison of these results with standard correlations in the literature show that in the near-nozzle region examined in this study, the penetration is expected to show little dependence on ambient density. The spray width becomes much larger for both nozzles as the ambient density increases. Rescaling the axial position by the square root of the density ratio between the fuel and the ambient gas accounts for the trends in spray width with ambient density for both nozzles. The radiography data can also be examined to determine the relative trends in the steady-state, mass-averaged axial velocity of the spray. The velocity decays more rapidly with axial distance as the ambient density increases. Rescaling the axial position also accounts for the trend of velocity decay with ambient pressure.
ELECTROHYDRODYNAMICS AND CHARGE INJECTION ATOMIZERS: A REVIEW OF THE GOVERNING EQUATIONS AND TURBULENCE
1045-1063
10.1615/AtomizSpr.v19.i11.40
John S.
Shrimpton
Energy Technology Research Group, School of Engineering Sciences, University of Southampton,
Atomization and Sprays Research Group Dept. Mechanical Engineering, UMIST, Manchester, United Kingdom, SO171BJ
Agisilaos
Kourmatzis
School of Aerospace, Mechanical and Mechatronic Engineering, The University
of Sydney, Sydney, NSW 2006, Australia
This review paper provides an overview of the governing equations of electrohydrodynamics pertaining to dielectric liquid atomization. The majority of the paper concentrates on the governing equations of electrohydrodynamic (EHD) flow and general averaged forms and their relevance to the study of charge injection atomizers. These equations are nondimensionalized and will bring to the forefront relevant quantities that define the electroconvective problem. A time-scale based method and traditional engineering method of nondimensionalization highlight values of key numbers for several specific charge injection atomizer concepts. Finally, an overview of EHD turbulence literature is provided along with a statement of the Reynolds-averaged governing equations allowing for discussion of the unclosed terms appearing and their probable significance.
FUNDAMENTAL CLASSIFICATION OF ATOMIZATION PROCESSES
1065-1104
10.1615/AtomizSpr.v19.i11.50
Malissa
Lightfoot
Air Force Research Laboratory, USA
A device-independent framework to classify and describe atomization is developed. This framework divides atomizers into various classes based on the geometry of the liquid prior to breakup. These classes are general enough to encompass a wide array of existent atomizers while still describing important aspects of the atomization physics. Across these classes, a limited number of atomization regimes exist that are grouped based on the rate of the atomization processes (disturbance growth and breakdown). Existent classifications are reconsidered to show how they fit into the current construction of five classes (jet, sheet, film, prompt, and discrete parcel) and three modes (bulk fluid, mixed, and surface). The new framework also clarifies the underlying physics of the atomization process. This process consists of the initiation and growth of a disturbance, followed by its breakdown. Several categories of disturbance initiation and disturbance breakdown are described, supported by examples from the literature.