Begell House Inc.
Atomization and Sprays
AAS
1044-5110
24
8
2014
CHARACTERISTICS OF ADHESION DIESEL FUEL ON AN IMPINGEMENT DISK WALL PART 2: DROPLET WEBER NUMBER AND ADHERED FUEL MASS
651-671
10.1615/AtomizSpr.2014008445
Mohd Zaid
Akop
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan
Yoshio
Zama
Division of Mechanical Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, Japan, 376-8515
Tomohiko
Furuhata
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan
Masataka
Arai
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan; Tokyo Denki University
Weber number
diesel spray
impingement disk
adhered fuel
inclined wall
impingement distance
injection pressure
Behavior of adhesion diesel fuel spray impinging on a flat wall was investigated experimentally. Nonevaporated diesel spray was injected into a high-pressure vessel. A flat wall disk set vertically or inclined to the spray axis was prepared as an impingement surface. The mass of the disk with adhered fuel was measured using an electronic balance, and the fuel mass adhered to the disk surface was evaluated. It was found that the adhered mass was greatly affected by the Weber number which was obtained with impingement velocity and the Sauter mean diameter of the spray. To evaluate quantitatively the Weber number effect on adhered mass, a modified adhered mass ratio concerning the diameter of the impingement disk and its inclined angle was introduced. The modified adhered mass ratio rapidly decreased when the Weber number increased beyond 1000. Finally empirical relationships among the adhered mass ratio, the thickness of the adhered fuel film and the Weber number were derived.
EFFECT OF GEOMETRIC VARIATIONS ON THE SPRAY DYNAMICS OF AN ANNULAR FUEL SHEET IN A HYBRID ATOMIZER
673-694
10.1615/AtomizSpr.2014008656
Souvick
Chatterjee
Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India
Mithun
Das
Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India
Achintya
Mukhopadhyay
Department of Mechanical Engineering, Jadavpur University, Kolkata-700032,
West Bengal, India
Swarnendu
Sen
Department of Mechanical Engineering, Jadavpur University, Kolkata 700032, India
atomization
breakup length
coswirl
counterswirl
prefilming
breakup length
fractal dimension
Sustained improvement of the efficiency of the atomization process demands development of advanced and innovative injectors followed by detailed investigation of the spray characteristics. In this work, a hybrid atomizer that combines the characteristics of a pressure swirl and airblast injector has been fabricated and thoroughly investigated. The atomizer in the current study, in which an annular liquid sheet is sandwiched between an outer and an inner airstream, deploys a swirling flow field such that the three streams of fuel, inner air, and outer air are injected tangentially. Additionally, the inner air channel possesses certain flexibilities in the form of reversal of swirl orientation and also can be recessed, leading to a prefilming configuration. The high-speed images obtained for these different geometric variations at varied hydrodynamic conditions are processed to measure different quantitative parameters such as breakup length, the sheet expansion parameter, and fractal dimension, each providing insights regarding the atomization process. The sheet is found to be most stable at a moderate air flow, as is evident from a higher breakup length and lower fractal dimension. A counterswirling inner air is found to increase the instability of the sheet with a lower breakup length and higher fractal dimension. While the presence of prefilming is found to augment the atomization at high outer air flow rates, the reverse trend is observed at lower flow rates.
MECHANISMS, EXPERIMENT, AND THEORY OF LIQUID SHEET BREAKUP AND DROP SIZE FROM AGRICULTURAL NOZZLES
695-721
10.1615/AtomizSpr.2014008779
Anthony
Altieri
Cornell University, Department of Chemical and Biological Engineering, Ithaca, New York 14850, USA
Steven
Cryer
Dow AgroSciences, LLC
Lipi
Acharya
Dow AgroSciences Information Technology and Data Analysis, Statistics/Mathematics, Indianapolis, Indiana 46268, USA
agriculture
stability
liquid sheet
multiphase
Spray nozzles operate by discharging a liquid sheet or jet which subsequently breaks up into droplets. Droplets which are too small can become entrained in ambient air currents and carried off target, while larger droplets often reduce coverage and efficacy. Many agricultural chemicals are formulated as an oil-in-water emulsion. In this study, single-phase (water) and two-phase (oil-in-water) emulsion were investigated photographically, experimentally, and theoretically to isolate the relevant mechanisms of sheet disintegration and representative droplet size. Three distinct mechanisms of sheet breakup were observed and parameterized by different scaling of the Weber number. Mechanisms include wave growth, rim breakup, and hole growth. Wave and rim breakup were found to dominate in single-phase sprays, while formation of holes within the liquid sheet and hole growth was dominant when an immiscible second phase was introduced. Existing models for wave growth and rim breakup leading to atomization, along with a novel model for hole expansion and subsequent sheet destruction, compare favorably with droplet diameters obtained experimentally. Although the exact mechanism for hole creation is not definitively established, several possibilities are discussed and inferred from experimental observations. It appears that a second immiscible phase, if low- or nonwetting, creates the necessary precursor for hole formation within the liquid sheet leading to sheet breakup. If this mechanism is indeed correct, it should be possible to control the spray droplet size distribution from spray nozzles given the size and wettability (hydrophobic nature) of solid or liquid immiscible particles/droplets within a two-phase system.
EXPERIMENTAL STUDY ON VELOCITY DISTRIBUTION OF POSTIMPINGEMENT DIESEL SPRAY ON A WALL. PART 1: EFFECT OF IMPINGEMENT ANGLE ON FLOW PATTERN
723-746
10.1615/AtomizSpr.2014010321
Yoshio
Zama
Division of Mechanical Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, Japan, 376-8515
Kazuma
Sugawara
Department of Mechanical System Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, Japan, 376-8515
Mohd Zaid
Akop
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan
Tomohiko
Furuhata
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan
Masataka
Arai
Division of Mechanical Science and Technology, Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515, Japan; Tokyo Denki University
postimpingement diesel spray
velocity field
wall impingement
impingement angle
PIV
High pressure and split fuel injection have been equipped commonly in DI (direct injection) diesel engines, and fuel impingement to the combustion wall becomes a major spray behavior for controlling engine performance. However, there is little information concerning the velocity field of postimpingement spray. In this study, the velocity field of an impingement diesel spray was measured with time-resolved particle image velocimetry (PIV). To obtain a two-dimensional tomographic image, diesel spray was impinged to a slender bar instead of a flat wall. As a result, velocity distribution of the impingement diesel spray in time series was obtained for various impingement angles. According to sequential tomographic images of the postimpingement spray, a high-density spray cloud rolled up inside the postimpingement spray. It was caused by secondary breakup of the liquid film on the wall. By analyzing the mean velocity field of the postimpingement spray, substantial impingement mass seems to decrease with an increase of the inclination angle of the impingement disk. Moreover, it was found that there was high velocity and a low-turbulence sublayer near the wall in the postimpingement spray.