Spray Characteristics of Plain-Jet Airblast Atomizers

1984 ◽  
Vol 106 (3) ◽  
pp. 634-638 ◽  
Author(s):  
N. K. Rizk ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Air Pressure ◽  
Liquid Viscosity ◽  
Liquid Ratio ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Test Range ◽  
Scattering Technique ◽  
The Mean ◽  
Light Scattering Technique

The effects of air and liquid properties and atomizer dimensions on the spray characteristics of plain-jet airblast atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light scattering technique. The test range includes wide variations in air velocity, air pressure, air/liquid ratio, and liquid viscosity. The experimental data generally confirm the results of previous studies on prefilming types of airblast atomizers. They show that increases in air velocity, air pressure, and air/liquid ratio all tend to produce a more uniform spray and a lower mean drop size. It is also observed that any change in air properties, liquid properties, and atomizer geometry that lowers the mean drop size also produces a more uniform distribution of drop sizes in the spray.

scholarly journals Spray Characteristics of Plain-Jet Airblast Atomizers

1983 ◽  
Author(s):  
N. K. Rizk ◽  
A. H. Lefebvre
Keyword(s):  
Drop Size ◽  
Air Pressure ◽  
Liquid Viscosity ◽  
Liquid Ratio ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Test Range ◽  
Scattering Technique ◽  
The Mean ◽  
Light Scattering Technique

The effects of air and liquid properties, and atomizer dimensions, on the spray characteristics of plain-jet airblast atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light scattering technique. The test range includes wide variations in air velocity, air pressure, air/liquid ratio, and liquid viscosity. The experimental data generally confirm the results of previous studies on prefilming types of airblast atomizers. They show that increases in air velocity, air pressure and air/liquid ratio all tend to produce a more uniform spray and a lower mean drop size. It is also observed that any change in air properties, liquid properties and atomizer geometry that lowers the mean drop size also produces a more uniform distribution of drop sizes in the spray.

Influence of Downstream Distance on the Drop Size Characteristics of an Evaporative Liquid Spray in a Convective Gaseous Medium

1992 ◽  
Vol 114 (1) ◽  
pp. 70-74 ◽  
Author(s):  
S. P. Sengupta ◽  
A. K. Mitra ◽  
S. K. Dash ◽  
S. K. Som
Keyword(s):  
Drop Size ◽  
Free Stream ◽  
Axial Distance ◽  
Numerical Studies ◽  
Spray Axis ◽  
Mean Diameter ◽  
Liquid Spray ◽  
Initial Drop ◽  
The Mean ◽  
Light Scattering Technique

Numerical studies have been made to evaluate the interdependence of drop size characteristics and evaporation histories of an atomized liquid spray in a convective medium of uniform free stream at high temperature. With the help of a discrete droplet evaporation model, both the actual drop size distribution and the apparent one, that could have been obtained in practice by light-scattering technique, have been determined numerically at different downstream locations perpendicular to the spray axis. Variations of actual and apparent mass mean diameter and the evaporation rate with the axial distance of the spray have been established. Finally, the influences of pertinent input parameters, namely, the initial Reynolds number of the spray, the ratio of free stream to initial drop temperature and the ratio of free stream to initial drop velocity on the mean diameter and evaporation histories have been recognized.

scholarly journals Experimental Study on Atomization of Plain Jet Injector Under High Pressure Co-Axial Air Flow

1987 ◽  
Author(s):  
Gui Xiang Yang ◽  
J. S. Chin
Keyword(s):  
Experimental Study ◽  
High Velocity ◽  
Drop Size ◽  
Air Flow ◽  
Test Chamber ◽  
Back Pressure ◽  
Air Pressure ◽  
Working Fluid ◽  
Air Velocity ◽  
Pressure Drops

An experimental study has been conducted on the effect of high back pressure on the spray characteristics of a plain jet injector under coaxial high velocity air flow. The air pressures tested range from 1 to 16 atm, the range of air velocity is 60–120 m/s, the pressure drops of injector tested are 200–2000 kpa. Working fluid is water. Injector hole diameter is 0.5 mm. The key feature of the experiment is using a convergent-divergent nozzle to maintain a high air pressure inthe test chamber and at the same time to maintain a high velocity air flow in the atomization zone. Such an experimental arrangement totally eliminates air and droplets recirculation in the test chamber and problem related to slow droplet settling in a commonly used pressurized vessel for high back pressure atomization research. The results show that SMD decreases monotonicly with the increase of back pressure or air velocity, at different air velocities, the effect of air pressure is different. The drop size distribution parameter N in Rosin-Rammler distribution decreases slightly with increase of back pressure or air velocity.

Optical Measurement of Wet Steam in Turbines

1998 ◽  
Vol 120 (4) ◽  
pp. 867-871 ◽  
Author(s):  
N. N. Wang ◽  
J. M. Wei ◽  
X. S. Cai ◽  
Z. W. Zhang ◽  
G. Zheng ◽  
...  
Keyword(s):  
Optical Measurement ◽  
Droplet Diameter ◽  
Turbine Blades ◽  
Optical Probe ◽  
Wet Steam ◽  
Full Size ◽  
Power Stations ◽  
Scattering Technique ◽  
The Mean ◽  
Light Scattering Technique

The wetness fraction of steam causes dangerous erosion of turbine blades and other components, and decreases efficiency of stages. The instrumentation of wet steam has, therefore, attracted growing interest from the point of safety and economical operation of power stations. Based on the light scattering technique, a method is presented that is capable of measuring the wetness fraction of steam, the mean water droplet diameter as well as their full size distribution. An optical probe has been constructed that can be used in the turbines in operation. Its main characteristic and features are discussed in this paper. Experimental results in a 200 MW condensing steam turbine are also given.

Effect of Injector Geometry Variables Upon the Spray Performance of a Plain-Jet Airblast Atomizer

1985 ◽  
Author(s):  
S. G. Shaw ◽  
A. K. Jasuja
Keyword(s):  
Atmospheric Pressure ◽  
Drop Size ◽  
Laser Light ◽  
Laser Light Scattering ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Scattering Technique ◽  
Atomization Performance ◽  
Light Scattering Technique ◽  
Quality Measurements

This paper presents the results of a study into the effect that liquid orifice orientation and scale have upon the drop-size performance of a plain-jet airblast atomizer featuring the injection of multiple liquid jets into a swirling airstream. Tests were conducted on water at near atmospheric pressure and temperature conditions using the well-established laser light scattering technique for spray quality measurements. The results presented in the paper reveal that the angular orientation of the liquid orifice, both in longitudinal and radial directions has a noticeable impact upon the atomization performance and exhibits scope for attaining further worthwhile reductions in drop-size relative to the multiple, transversely injected liquid jet configuration.

scholarly journals Energy Considerations in Twin-Fluid Atomization

1990 ◽  
Author(s):  
Arthur H. Lefebvre
Keyword(s):  
Drop Size ◽  
Sheet Thickness ◽  
Ambient Air ◽  
Liquid Sheet ◽  
Air Pressure ◽  
Air Velocity ◽  
Atomization Process ◽  
Flow Situation ◽  
Heating Oil ◽  
Main Factor

With certain types of prefilming airblast atomizers, the manner in which the atomizing air impinges on the liquid sheet prohibits the wave formation that normally precedes the breakup of a liquid sheet into drops. Instead, the liquid is shattered almost instantaneously into drops of various sizes. This prompt atomization process is characterized by a broad range of drop sizes in the spray and by a lack of sensitivity of mean drop size to variations in liquid viscosity, atomizing air pressure, and initial liquid sheet thickness. Evidence is presented to show that which of these two different modes of atomization will occur in any given flow situation is largely dependent on the angle at which the atomizing air impinges on the liquid sheet. An equation for mean drop size, derived from the assumption that the main factor controlling prompt atomization is the ratio of the energy required for atomization to the kinetic energy of the atomizing air, is shown to provide a good fit to experimental data acquired from atomization studies on water and heating oil, carried out over wide ranges of air velocity, air/liquid ratio, and ambient air pressure.

Simulation of Paint Transfer in an Air Spray Process

1995 ◽  
Vol 117 (4) ◽  
pp. 713-719 ◽  
Author(s):  
P. G. Hicks ◽  
D. W. Senser
Keyword(s):  
Drop Size ◽  
Separated Flow ◽  
Transfer Efficiency ◽  
Significant Advance ◽  
Direct Effects ◽  
Air Velocity ◽  
Velocity Fluctuations ◽  
Spray Process ◽  
The Mean ◽  
Physical Phenomena

A methodology for simulating drop transport and deposition in air-spray, paint-application processes is presented. Simulation of the complex physical phenomena involved is made possible through a number of key assumptions based on measurements of typical air paint sprays. The significant advance is the inclusion of the direct effects of turbulent air velocity fluctuations on the trajectories of paint drops via a stochastic separated flow approach. The model accurately predicts the mean air velocity field, paint transfer efficiency, and drop transfer efficiency. Owing to increased inertia, the mechanisms controlling drop transport shift with increasing drop size.

Spray Characteristics of a Spill-Return Airblast Atomizer

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
X. F. Dai ◽  
A. H. Lefebvre ◽  
J. Rollbuhler
Keyword(s):  
Drop Size ◽  
Cone Angle ◽  
Working Fluid ◽  
Air Velocity ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Liquid Distribution ◽  
Spray Cone ◽  
Liquid Injection ◽  
Bypass Ratio

The spray characteristics of a spill-return airblast atomizer are examined using water as the working fluid. Measurements of mean drop size, drop size distribution, spray cone angle, and circumferential liquid distribution are carried out over wide ranges of liquid injection pressures and atomizing air velocities. Generally it is found that an increase in nozzle bypass ratio worsens the atomization quality and widens the spray cone angle. Increase in airblast air velocity may improve or impair atomization quality depending on whether it increases or decreases the relative velocity between the liquid and the surrounding air. Airblast air can also be used to modify the change in spray cone angle that normally accompanies a change in bypass ratio.

Influence of Ambient Air Pressure on Pressure-Swirl Atomizer Spray Characteristics

2001 ◽  
Author(s):  
Arvind K. Jasuja ◽  
Arthur H. Lefebvre
Keyword(s):  
Gas Turbines ◽  
Drop Size ◽  
Cone Angle ◽  
Ambient Air ◽  
Air Pressure ◽  
Spray Characteristics ◽  
Spray Cone ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

A single-component PDPA is used to evaluate the spray characteristics of a simplex pressure-swirl atomizer when operating at high liquid flow rates and elevated ambient air pressures. Attention is focused on the effects of air pressure on mean drop size, drop-size distribution, mean velocity, volume flux, and number density. Using a constant flow rate of 75 g/s, measurements are carried out along the spray radii at a fixed distance downstream from the atomizer face of 50 mm. The air pressures of 1, 8, and 12 bars chosen for these tests correspond to air densities of 1.2, 9.6, and 14.4 kg/m3. The purpose of the investigation is to supplement the existing body of information on pressure-swirl spray characteristics, most of which were obtained at normal atmospheric ambient pressures, with new data that correspond more closely to the conditions prevailing in the primary combustion zones of modern gas turbines. The results obtained are explained mainly in terms of the influence of air pressure on spray structure, in particular spray cone angle and Weber number.

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