Influence of Downstream Distance on the Spray Characteristics of Pressure-Swirl Atomizers

Chin, J. S.; Nickolaus, D.; Lefebvre, A. H.

doi:10.1115/1.3239875

Cited by 23 publications

(10 citation statements)

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“…When a spray is formed at the outlet of an atomizer, it expands in the radial direction before developing a fully axial ow. (35) Larger particles penetrate farther in the radial direction than smaller ones and cause the formation of larger size distribution at the edge of the spray. To make the following discussion clear, a coordinate system is de ned, as shown in Figure 1.…”

Section: Discussionmentioning

confidence: 99%

Experimental Evaluation of a Mathematical Model for Predicting Transfer Efficiency of a High Volume?Low Pressure Air Spray Gun

Tan

Flynn

2000

Applied Occupational and Environmental Hygiene

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The transfer efficiency of a spray-painting gun is defined as the amount of coating applied to the workpiece divided by the amount sprayed. Characterizing this transfer process allows for accurate estimation of the overspray generation rate, which is important for determining a spray painter's exposure to airborne contaminants. This study presents an experimental evaluation of a mathematical model for predicting the transfer efficiency of a high volume-low pressure spray gun. The effects of gun-to-surface distance and nozzle pressure on the agreement between the transfer efficiency measurement and prediction were examined. Wind tunnel studies and non-volatile vacuum pump oil in place of commercial paint were used to determine transfer efficiency at nine gun-to-surface distances and four nozzle pressure levels. The mathematical model successfully predicts transfer efficiency within the uncertainty limits. The least squares regression between measured and predicted transfer efficiency has a slope of 0.83 and an intercept of 0.12 (R2 = 0.98). Two correction factors were determined to improve the mathematical model. At higher nozzle pressure settings, 6.5 psig and 5.5 psig, the correction factor is a function of both gun-to-surface distance and nozzle pressure level. At lower nozzle pressures, 4 psig and 2.75 psig, gun-to-surface distance slightly influences the correction factor, while nozzle pressure has no discernible effect.

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Section: Discussionmentioning

confidence: 99%

Experimental Evaluation of a Mathematical Model for Predicting Transfer Efficiency of a High Volume?Low Pressure Air Spray Gun

Tan

Flynn

2000

Applied Occupational and Environmental Hygiene

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“…Theoretical and experimental studies have been completed by Lefebvre's research group [2][3][4][5] in terms of spray angle, mean drop size, and radial liquid distribution, all of which are a function of fluid properties and nozzle dimensions. Similarly, Chin's group [6,7] and Som's group [8] experimentally and analytically investigated general spray characteristics downstream of a pressure-swirl atomizer for a larger range of conditions. These studies allowed general structure of the flow but more details have been obtained recently, using Phase Doppler Particle Analyzer (PDPA) by Santolaya et al [9] for a pressure swirl spray nozzle.…”

Section: Introductionmentioning

confidence: 98%

Numerical description of a pressure-swirl nozzle spray

Qin

Loth

2016

Chemical Engineering and Processing - Process Intensification

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A B S T R A C T Pressure-swirl nozzles are widely used in both industrial and experimental processes. However, the spray flow fields are difficult to predict due to the complexities of the dense break-up region. Herein, an inflow boundary condition approach is employed whereby droplets are computationally injected at 9 mm downstream of the orifice based on experimentally derived descriptions of the mean droplet and gas velocities, combined with empirical relations for turbulent kinetic energy and dissipation. The gas flow is then predicted with a Reynolds-Averaged Navier-Stokes solution while the particle trajectories are computed with a discrete random walk model. This approach was found to reasonably describe downstream spatial distribution of gas and droplet velocity, with moderate mesh resolution and CPU time. In addition, the evolution of the droplet velocity fluctuations was found to be consistent with turbulent diffusion theory based on the local Stokes numbers and turbulent kinetic energy.

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Section: Introductionmentioning

confidence: 97%

“…The effect of measurement location on measured drop sizes has been discussed by Chin et al 9 and Dodge and Moses. 10 Chin et al 9 suggest taking measurements far downstream of the atomizer (200-300 mm) to allow velocity differences between drops to equilibrate, but the solution to the problem of a representative sample of a cross section of the spray is not addressed. In fact, at these large distances from the atomizer, measurements with a laser-diffraction instrument, such as Chin et al 9 were considering in their analysis, would be both difficult and a poor representation of the spray.…”

Section: Introductionmentioning

confidence: 97%

“…10 Chin et al 9 suggest taking measurements far downstream of the atomizer (200-300 mm) to allow velocity differences between drops to equilibrate, but the solution to the problem of a representative sample of a cross section of the spray is not addressed. In fact, at these large distances from the atomizer, measurements with a laser-diffraction instrument, such as Chin et al 9 were considering in their analysis, would be both difficult and a poor representation of the spray. The difficulty arises from spray impingement on the windows or lenses of the laser-diffraction system for moderate or wide cone angle sprays.…”

Section: Introductionmentioning

confidence: 99%

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Representation of average drop sizes in sprays

Dodge

1988

Journal of Propulsion and Power

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Procedures are presented for processing drop-size measurements to obtain average drop sizes that represent overall spray characteristics. These procedures are not currently in general use, but they would represent an improvement over current practice. Clear distinctions are made between processing data for spatial-and temporal-type measurements (also referred to as concentration-sensitive and flux-sensitive, respectively). The conversion between spatial and temporal measurements is discussed. The application of these procedures is demonstrated by processing measurements of the same spray by two different types of instruments, a laser-diffraction drop sizer and a phase-Doppler particle analyzer. C J D Nomenclature fraction of total spray cross section occupied by ring j SFS instruments, drops per unit volume (number density) in y th ring TFS instruments drops per unit area (number flux) in y th ring averaging process, designated by overbar on D average diameter; integer values p and q determine averaging procedure as shown in Eq. (1) arithmetic mean diameter D 20 = surface area mean diameter 5zo, Ao 530, surface area mean diameter of drops in j th ring volume mean diameter volume mean diameter of drops in the y th ring Sauter mean diameter (SDM) (volume/surface mean _ diameter) D vo 5 = volume median diameter; that diameter for which half the spray volume is contained in drops of larger size, and half in drops of smaller size HIJ = fraction of drops measured in size class / for ring j (not equivalent for SFS and TFS instruments) Ni = number of drops sampled in the /th size class (not equivalent for SFS and TFS instruments) ,SFS ^ number of drops sampled in the /th size class, where drops are counted proportional to drops per unit volume (number density) ,TFS = number of drops sampled in the ith size class, where drops are counted proportional to drops per unit time per unit area (number flux) N c = number of drop-size classes N R = number of rings in spray cross section u t = average velocity of drops in size class /' Subscripts i = number of size class j = ring number for various annuli in .spray cross section

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Influence of Downstream Distance on the Spray Characteristics of Pressure-Swirl Atomizers

Cited by 23 publications

References 0 publications

Experimental Evaluation of a Mathematical Model for Predicting Transfer Efficiency of a High Volume?Low Pressure Air Spray Gun

Experimental Evaluation of a Mathematical Model for Predicting Transfer Efficiency of a High Volume?Low Pressure Air Spray Gun

Numerical description of a pressure-swirl nozzle spray

Representation of average drop sizes in sprays

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