Begell House Inc.
Atomization and Sprays
AAS
1044-5110
1
4
1991
WAVE CHARACTERISTICS OF LIQUID JETS FROM AIRBLAST COAXIAL ATOMIZERS
349-366
10.1615/AtomizSpr.v1.i4.10
Hasan
Eroglu
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Norman
Chigier
Department of Mechanical Engineering,
Carnegie-Mellon University, Pittsburgh, PA 15213-3890, USA
Results of wavelength and frequency measurements are presented for liquid jets issuing from airblast coaxial atomizers. The liquid jet surface wavelengths were measured from the photographs for liquid jet velocity ranges of 1.1−18.2 m/s and air velocity ranges of 45.8−130 m/s. Frequencies were measured using a laser beam attenuation technique. The results show that wavelengths decrease with the liquid and gas jet velocities. The frequency band of the jet surface oscillations increased with the liquid jet velocity. Average frequencies were found to increase with both the liquid and the gas jet velocities. The resulting wave propagation velocities were insensitive to the variation of these velocities.
A MODEL OF THE EVAPORATION OF BINARY-FUEL CLUSTERS OF DROPS
367-388
10.1615/AtomizSpr.v1.i4.20
K.
Harstad
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Josette
Bellan
Department of Mechanical and Civil Engineering, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
A formulation has been developed to describe the evaporation of dense or dilute clusters of binary-fuel drops. The binary fuel is assumed to be made of a solute and a solvent whose volatility is much lower than that of the solute. Convective flow effects, inducing a circulatory motion inside the drops, are taken into account, as well as turbulence external to the cluster volume. Results obtained with this model show that, similar to the conclusions for single, isolated drops, the evaporation of the volatile is controlled by liquid mass diffusion when the cluster is dilute. In contrast, when the cluster is dense, the evaporation of the volatile is controlled by surface layer stripping, that is, by the regression rate of the drop, which is, in fact, controlled by the evaporation rate of the solvent. These conclusions are in agreement with existing experimental observations. Parametric studies show that these conclusions remain valid with changes in ambient temperature, initial slip velocity between drops and gas, initial drop size, initial cluster size, initial liquid mass fraction of the solute, and various combinations of solvent and solute. The implications of these results for computationally intensive combustor calculations are discussed.
GRAY LEVEL FACTORS USED IN IMAGE PROCESSING OF TWO-DIMENSIONAL DROP IMAGES
389-400
10.1615/AtomizSpr.v1.i4.30
Sang Yong
Lee
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology,
291, Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
Byung Suh
Park
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Kusong-Dong, Yusong-Gu, Taejon, 305-701, Korea
In Goo
Kim
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Kusong-Dong, Yusung-Gu, Taejon 305-701, Korea
This paper describes how the threshold gray level should be chosen for accurate measurements of polydispersed spray drops in using image sensing or image processing techniques. For this purpose, reference pictures were prepared to simulate the photographs of spray drops with various sizes based on the Rosin-Rammler and upper-limit distribution functions. Graphical correlations between the optimum threshold level and the distribution parameters are proposed, and a guideline for using those results is provided.
ATOMIZATION AND EVAPORATION OF DIESEL SPRAYS IN HIGH-PRESSURE AND HIGH-TEMPERATURE ENVIRONMENTS
401-419
10.1615/AtomizSpr.v1.i4.40
C.
Noviello
D.I.M.E.(Dipartimento di Ingegneria Meccanica per l’Energetica), Universitá Federico II, Naples, Italy
Antonio
Cavaliere
Dipartimento di Ingegneria Chimica, Università di Napoli "Federico II", Naples, Italy
Raffaele
Ragucci
CNR
A.
D'Alessio
Departimento di Ingegneria Chimica — Universita di Napoli "Federico II" Piazza V. Tecchio, 80-80125 Napoli, ITALY
The influence of fuel pressure on diesel spray evolution into a quiescent environment at two temperatures (300 and 800 K) has been analyzed by means of a laser light scattering technique. Two-dimensional measurements have been made of scattering intensity and its polarization state on cross sections of the spray. The theoretical and experimental aspects of the technique and the interpretation of the measured quantities are presented. The results indicate that a wide variation of the conditions of fuel injection into a room-temperature environment (fuel peak pressure from 500 to 1400 bar) does not change the liquid surface area significantly between 7 and 14 mm from the nozzle. However, the same variation of fuel pressure influences the spray evolution very much in the same spatial region for injections into a high-temperature environment. In this case a high injection pressure (peak pressure of 1400 bar) results in an increase of the liquid surface area along the spray, whereas a relatively low pressure (peak pressure of 500 bar) results in a decrease. Some reasonable explanations of this behavior are discussed, considering the possible effects due to atomization, evaporation, coalescence, turbulent dispersion, and inertial evolution of the spray.
PRIMARY BREAKUP IN LIQUID-GAS MIXING LAYERS
421-440
10.1615/AtomizSpr.v1.i4.50
P.-K.
Wu
Department of Aerospace Engineering, The University of Michigan, Ann Arbor, Michigan, USA
G. A.
Ruff
Department of Aerospace Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2140
G. M.
Faeth
Department of Aerospace Engineering, the University of Michigan, Ann Arbor, Michigan 48109-2140, USA
An experimental study of primary breakup in the near-injector region of large-diameter (5.0 and 9.5 mm) liquid jets in still air is described. Holography was used to provide drop and liquid surface characteristics for initially nonturbulent liquids (water, n-heptane, and various glycerol mixtures) having various jet exit velocities. Drop sizes after primary breakup satisfied Simmons' universal root normal distribution and can be characterized solely by their Sauter mean diameter (SMD). The SMD increased with distance from the jet exit and then remained nearly constant within a fully developed primary breakup region. SMD measurements in the fully developed regime did not agree with existing expressions based on unstable surface wave growth. However, an expression based on stripping-type breakup due to boundary layer growth in the liquid along the windward side of surface waves yielded a reasonably good correlation of present SMD measurements. The nature of this primary breakup correlation implies that secondary breakup is a dominant feature of liquid-gas mixing layers.
MEASUREMENT AND MODELING OF DIESEL SPRAYS
441-465
10.1615/AtomizSpr.v1.i4.60
This paper presents an overview of aspects of a long-term computational and experimental investigation related to the in-chamber flow of direct-injection diesel engines. The pulsed sprays formed by a single-hole diesel injector are investigated as a function of gas pressure, temperature, cross-flow velocity, and turbulence level. The impaction of the sprays on a wall is also examined. Cyclic variations of the spray structure, from pulse to pulse, are reported and measurements of the spray breakup length are made as a function of time after needle lift and also of the spray environment. These are compared with measurements obtained by various techniques in previous work. The experiment program is carried out in parallel with the development of a computational fluid dynamics (CFD) model of the spray and of spray-gas flow and spray-wall interaction. There is generally good agreement with the predictions of a CFD model of the pulsed spray, and areas for further development of the CFD model are isolated.
Contents, Index of Volume 1
467-478
10.1615/AtomizSpr.v1.i4.70