Optical Analysis of Flat Spray Nozzles
used in Coating Applications
En’Urga Inc.
1291-A Cumberland Avenue, West Lafayette, IN 47906
765-497-3269 765-463-7004
http://www.enurga.com
®
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Abstract
One of the key requirements for assuring a
uniform coating thickness is a good nozzle that
has no streaks or voids, and provides a uniform
pattern distribution. This presentation will focus
on a method of optical patternation that can be
used to ensure nozzle quality.
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Importance of Spray Uniformity
Spray quality is a necessary determinant of
finish quality, film thickness uniformity
Avoid “fingers” and voids in the pattern
Nozzle design and development
Nozzle quality control
Finding matched tips
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Current Methods for Spray Uniformity
Spraying onto a substrate
– Analyze pattern after paint dries
Capturing an image of the spray
– Analyze photos/digital images of pattern
Mechanical patternation
– Measures flow rate in sectors of the pattern
Visualization of spray pattern
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Disadvantages of Current Methods
Time consuming
Labor intensive
Limited spatial resolution
Not suitable for on-line QC
Digital imaging: 2-D used to measure a 3-D
pattern
Visualization: highly subjective
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Statistical Extinction Tomography (SETScan®)
Path integrated extinction of laser sheets
Multiple view angles for non-axisymmetric
turbulent flows
Multiple slices to obtain high spatial
resolution
Local extinction coefficients obtained by
statistical de-convolution
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SETScan® Patternator
Can be mounted vertically for horizontal spray
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Interpretation of Extinction Coefficients
Extinction coefficient is equivalent to total surface
area of all droplets within a specific volume
(surface area/unit volume ~ mm –1) when:
• Drop sizes > 1 µ
• Obscuration > 0.005 and < 0.98
• Particles are spherical
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SETScan® Features
Immune to environmental lighting
Transient spray capture at speeds up to 10 KHz
High accuracy (+/- 2%)
High repeatability (+/- 5% on patternation number)
Angular resolution up to 5 degrees
Spatial resolution up to 0.25 mm
Alignment of nozzle not critical
Easily operated by technician
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Typical Measured Parameters
Spray angle (major and minor for flat spray)
Pattern displacement from nozzle center
Horizontal integration (along the x-axis)
Surface area distribution
– Radial
– Angular
Color contour plot indicating absolute value
of surface area per unit volume (mm-1)
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Results
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“Good” Flat Spray Nozzle
400 psi; 3.5 inches from nozzle
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“Good” Nozzle vs. Pressure
3.5” from measurement plane
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“Good” Flat Spray Nozzle vs. Distance
400 psig vs. distance
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controlnozzle ®
Horizontal Integration
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Spray Angles
Nozzle Major angle Minor angle
(degrees) (degrees)
“Good” 56.25 17.53
“Worn” 58.03 18.29
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Summary
SETScan® Patternator can be used to quickly
quantify the spray patterns using
– Color contour plots of S.A./volume (mm-1)
– Horizontal integration
– Spray angles
– Patternation number
– Angular or radial surface area/volume
distributions
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