Spray Droplet Sizing – Understanding the Basics · Take Home • At equal volume: – Halving the...
Transcript of Spray Droplet Sizing – Understanding the Basics · Take Home • At equal volume: – Halving the...
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Spray Droplet Sizing –Understanding the Basics
Brad FritzUSDA ARS
Aerial Application Technology Research Unit
College Station, Texas
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Droplet Diameter
DD = droplet diameterV = droplet volume
At equal volume with droplets of ½ diameter
8X the # Droplets
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Droplet Volume in the Spray Cloud
One 400 µm drop
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Droplet Volume in the Spray Cloud
8 - 200 µm drops
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Droplet Volume in the Spray Cloud
64 - 100 µm drops
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Total Spray VolumeCharacteristics of total spray volume.
NumberDistribution
Or
VolumeDistribution
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Volume vs Number
1X 400µm
8X 200µm
64X 100µm
Total Spray Volume of:V400 + 8(V200)+ 64(V100)
V400 = 64 x V100= 8 x V200
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We have a total Volume V. V400 + 8*V200 + 64*V100 = V
Why Volume vs Count?Count Distribution
We have a total of 73 drops. 1 + 8 + 64
400 µm =
200 µm =
100 µm =
Volume Distribution
400 µm =
200 µm =
100 µm =
Amount of active product:Volume of spray droplets
NOT Number of droplets
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Volume Distribution
• DV10 or DV0.1• DV50 or DV0.5 or VMD• DV90 or DV0.9• %Vol<100µm• %Vol<200µm• How do we get to the numbers we typically
deal with?• Using some measurement system, the
percentage of the total spray volumethat is in each droplet size range is determined.
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Review• DV10, DV50 or VMD, DV90
• The diameter for which 10% of the total spray volume is made up of droplets of equal or lesser diameter.
100% 10%DThis diameter is the DV10
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Review
100%50%
This diameter is the VMD
D
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150 µm 370 µm 634 µm
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4.7%
17.2%
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Relative Span
An indicator of the width of distribution.
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RS = 0.67
RS = 1.4
RS = 2.2
VMD = 300µm
DV10200 µm
DV90400 µm
DV10165 µm
DV90435 µm
DV1090 µm
DV90510 µm
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Take Home
• At equal volume:– Halving the diameter creates 8X droplets– Quartering creates 64X droplets
• The smaller the diameter, the greater the number of droplets, and the less control you have over them.
• Volume Distribution corresponds to available product and efficacy– DV10, DV50 (VMD), DV90, RS, %<100µm, etc…
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Spray Measurement
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Measurement
Groundspeed?
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It’s All About How You Measure…
Likely Will Get Different Exact
Numbers
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It’s All RelativeSlowest
Fastest
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Same Concept
SMALL
MEDIUM
LARGE
While Numerical Diameters may differ, Relative Size will be consistent
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Reference Sprays• Establish Reference Nozzles/Sprays
VF/F F/M M/C C/VC VC/XC
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Reference Nozzle Curves
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MEDIUM SprayDV10: 80 to 110 um
DV50: 190 to 280 um
MEDIUM SprayDV10: 105 to 155 umDV50: 230 to 350 um
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Be Cautious with NumbersASABE S572 Standard
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Labels – Beware of Conflict
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Take Home
• Droplet Size Number can vary from lab to lab, company to company….
• BUT
• Droplet Size Classification is consistent.
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Differences Within a ClassMEDIUM Spray – USDA ARS Current Nozzle Models
141
180
280
429
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2 MEDIUM SpraysMedium #18°, 60 psi and 150 mphDV10 = 184VMD = 322DV90 = 543%<100um = 2.7%
Medium #238°, 60 psi and 150 mphDV10 = 146VMD = 282DV90 = 433%<100um = 5.6%
CP11TT with 4015 FF
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2 MEDIUM Sprays
141
180
280
429
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What Happens in the Field?
Downwind Drift
Medium #11.6%
Medium #2 2.4%
AGDISP
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Take Home
Consider Size Class first.Then
Optimize setups to decrease fines.
RememberNot all MEDIUM or COARSE sprays are equal