Begell House Inc.
Atomization and Sprays
AAS
1044-5110
2
2
1992
CORRECTING MALVERN PARTICLE SIZE MEASUREMENTS FOR PHASE DISTORTION
73-85
10.1615/AtomizSpr.v2.i2.10
R. A.
Pietsch
Thermal Sciences and Propulsion Center, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907
Paul E.
Sojka
Maurice J. Zucrow Laboratories (formerly Thermal Sciences and Propulsion Center), School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, 47907-2014, USA
G. B.
King
Thermal Sciences and Propulsion Center, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907
The two effects of phase distortion on particle size measurements made with a Malvern spray analyzer are identified as beam spread and a shift of the Airy pattern extrema to higher spatial frequencies. Beam spread is shown to be present regardless of the laser beam coherence length (lc), while the Airy pattern shift occurs when the size of the particle being sampled exceeds lc. A correction scheme that removes the effects of phase distortion whenever possible is outlined, and then evaluated by comparing phase-distorted particle size information with its undistorted counterpart. The enhanced agreement indicates that the proposed technique successfully removes the effects of phase distortion whenever possible. Finally, guidelines are provided for determining when phase distortion is present, and when the correction scheme can be applied.
ATOMIZATION CHARACTERISTICS OF A HIGHSPEED ROTARY-BELL PAINT APPLICATOR
87-99
10.1615/AtomizSpr.v2.i2.20
P. L.
Corbeels
Thermal Sciences and Propulsion Center, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907
Dwight W.
Senser
Thermal Sciences and Propulsion Center, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana
Arthur H.
Lefebvre
Emeritus Professor, Cranfield University, Stratford, U.K., and Purdue University, W. Lafayette, IN, USA
An experimental study was conducted on the influence of fluid properties and operational parameters on the atomization characteristics of a high-speed rotary-bell paint applicator. Drop size measurements near the bell edge were complemented with high-speed photography to investigate the filming characteristics, atomization modes, and ligament disintegration mechanisms of this type of applicator. Surface tension was varied by a factor of 2.5 and viscosity by a factor of 100. Rotational speeds ranged from 4000 rpm to 40,000 rpm, while the liquid mass flow rate was varied from 0.67 to 6.67 g/s. It was found that high-viscosity fluids film the bell very evenly and produce long regular ligaments, whereas low-viscosity fluids film incompletely and produce very irregular ligaments that disintegrate near the bell edge. Mean drop size was found to be fairly insensitive to large changes in flow rate and viscosity at bell speeds higher than 20,000 rpm.
TWIN-FLUID ATOMIZATION: FACTORS INFLUENCING MEAN DROP SIZE
101-119
10.1615/AtomizSpr.v2.i2.30
Arthur H.
Lefebvre
Emeritus Professor, Cranfield University, Stratford, U.K., and Purdue University, W. Lafayette, IN, USA
The principal factors governing the mean drop sizes produced by twin-fluid atomizers are examined. It is shown that atomization may occur by one of two different mechanisms. For both "classical" and "prompt" modes of atomization, the principal factors governing the fineness of atomization are air velocity, air/liquid ratio, and surface tension. For the classical mechanism of breakup, involving flow instabilities and wave formation, atomization occurs slowly and is strongly influenced by variations in liquid viscosity, air density, and the initial diameter (or thickness) of the liquid jet (or sheet). If atomization occurs very rapidly, these parameters have little effect on mean drop size.
WAVE CHARACTERISTICS OF LIQUID SHEETS WITH IMPINGING AIR JETS
121-135
10.1615/AtomizSpr.v2.i2.40
Norman
Chigier
Department of Mechanical Engineering,
Carnegie-Mellon University, Pittsburgh, PA 15213-3890, USA
Hasan
Eroglu
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
Spatial amplitude growth rates, average wavelengths, frequencies, and wave propagation speeds were measured for liquid sheets with co-current air streams impinging on the two opposite interfaces. High-speed photography was used to obtain the spatial amplitude growth rates and wavelengths. Wave frequencies were measured by means of a laser beam attenuation technique. The effect of viscosity on the wave frequencies was investigated by injecting glycerine-water mixtures through the two-dimensional atomizer. The spatial wave amplitude growth rate was found to decrease with increase in liquid mass flow rate but increase with increase in air velocity. The average wavelengths decreased with increase in both liquid mass flow rate and air velocity. However, the dominant frequency increased with increase in liquid mass flow rate and air velocity. The frequency also increased with a decrease in viscosity.
MORPHOLOGICAL CLASSIFICATION OF DISINTEGRATION OF ROUND LIQUID JETS IN A COAXIAL AIR STREAM
137-153
10.1615/AtomizSpr.v2.i2.50
Zoltan
Farago
DLR German Aerospace Research Establishment DLR Research Center, Germany
Norman
Chigier
Department of Mechanical Engineering,
Carnegie-Mellon University, Pittsburgh, PA 15213-3890, USA
From an analysis of over 1000 high-speed spark photographs, the modes of round liquid jet disintegration in a coaxial air stream were classified over a liquid Reynolds number range of 200 to 20,000 and over an aerodynamic Weber number range of 0,001 to 600. The observed distintegration modes are compared to the modes of spherical water drop and thin water sheet disruption in an air stream.
DROP DISTRIBUTION EFFECTS ON PLANAR LASER IMAGING OF SPRAYS
155-177
10.1615/AtomizSpr.v2.i2.60
H. M.
Ryan
Propulsion Engineering Research Center and Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania, USA
Sibtosh
Pal
Propulsion Engineering Research Center and Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania, USA
W.
Lee
Department of Mechanical Engineering and NASA Propulsion Engineering Research Center, The Pennsylvania State University, University Park, Pennsylvania 16802
Robert J.
Santoro
Propulsion Engineering Research Center and Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania
A study of the effects of drop distribution on the interpretation of light-scattering polarization ratio measurements for characterizing mean drop diameter is presented. The work focuses on the appropriateness of logarithmic-normal, Rosin-Rammler, Nukiyama-Tanasawa, and upper-limit distributions in representing the drop size distribution. Comparisons between the individual drop distributions are made on the basis of fits to experimental measurements made in a pressure-atomized water spray using the Phase Doppler Particle Analyzer (PDPA). The results from the drop size distribution comparisons indicate that care must be exercised when fitting number or volume distributions, since the diameter-weighting differences in fitting diameter number or volume distributions can significantly alter the best-fit results. In general, good fits to either diameter number or volume distributions can be obtained with the previously mentioned distributions. However, complementary transformations between the diameter number and volume distributions generally resulted in unacceptable fits. Furthermore, number density predictions were typically less satisfactory for the Rosin-Rammler distribution. Both the logarithmic-normal and Nukiyama-Tanasawa distributions were applied to the polarization ratio technique analysis for measurement of the Sauter mean diameter. Differences observed between the PDPA and polarization ratio results could not be resolved through more accurate representation of drop size distribution. In fact, direct Mie scattering calculations using the measured size distributions showed discrepancies with the observed polarization ratio measurements from the experiment. These observations eliminate size distribution as the only source of inaccuracy in the polarization ratio technique and point to examination of other light-scattering-related effects such as technique size biases.
NUMBER DISTRIBUTION FUNCTION OF DROP SIZE AND VELOCITY IN WATER SPRAYS
179-192
10.1615/AtomizSpr.v2.i2.70
Tatsuya
Yamada
Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya 466, Japan
Akira
Moriyama
Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya 466, Japan
Based on the simultaneous measurements of drop she and velocity, the experimental bivariate probability density function of their occurrence was determined over 16 sample locations in a solid-cone spray. The function was plotted in contour maps, indicating some bimodality of the size-velocity distributions. A composed form of dual logarithmic-normal distribution functions was proposed to describe the experimental function. It is concluded that the proposed function is satisfactory, since the coefficient of correlation between the calculated and the observed probability densities is close to 1. In addition, the evaluated means of drop size and velocity show good agreement with the measured values.