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Agricultural Aviation Technology
Dennis R. Gardisser, PhD, P.E.WRK of Arkansas
Robert E. Wolf, PhDKansas State University
Application Altitude
• High
• Low
• Window
10ft – 14 ft
Drift potential vs. Height
Example
Aircraft Boom Design
• Location relative to the wing
• Nozzle setup & orientation on the boom
• Microfoil booms
• Positive action shutoff
• Boom suck back
Boom length/location
Distance below trailing edge of wing
Wing
Boom
Perpendicular
Must be >= 10 inches
Spray outlet
ASABE Standard S572
• Explanation of Dv.1, Dv.5 or VMD, Dv.9, & RS (Relative Span)
• Meaning of key words (Fine, Medium, etc.)
• Need to limit amount of small droplets or fines
• Practicality of regulation requiring 600 VMD droplet spectrum
Important Droplet Statistics:
Operational Area
RS = (Vd.9 – Vd.1)/VMD
Relative Span
RS = (Vd.9 – Vd.1)/VMD
ASABE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer
• Very Fine (VF) < 182µm• Fine (F) 183-280µm• Medium (M) 281-429µm• Coarse (C) 430-531µm• Very Coarse (VC) 532-655µm• Extremely Coarse (XC) >656µm
*USDA ARS College Station, TX
Droplet Spectra Classification (DSC)
Droplet SizeRange
Droplet Spectrum Generation
• Pressure effects– Low pressure– High pressure
• Aerodynamic effects• Nozzle type effects
– Flat fan– Deflector– Sheet– Disc & Core– Straight stream– Electrostatic– Rotary
Cutting Droplet Size in
Half
Results in ?? Times the Number of Droplets
==2 more droplets fill in the sphere
500Microns
500Microns 250
Microns
Air Temp 85F
Canopy top 105F or more!
Canopy Floor 75F
Hot air goes which direction?
Size
• 290/250 = 1.16
• 290 micron droplet is 16% larger than 250
• This may not appear to be a big change, but???
Droplet Data• 250 v. 290 micron droplet
• Change in size?
• Change in Volume or Weight?
Volume or Weight• Remember that this is a cube root relationship.
• If it was twice as big we would multiply
• 2 * 2 * 2 = 8 times heavier
• For 290/250 = 1.16
• 1.16 * 1.16 * 1.16 = 1.56
• Implies that a 290 micron droplet is 56% heavier than a 250!
0.125 orifice,300 deflector
0
100
200
300
400
500
600
700
100 110 120 130 140 150 160
MPH
DV
0.5
0
2
4
6
8
10
12
14
16
V<
10
0µ
m
20psi 40psi 60psi 20psi 40psi 60psi
Pressure Effects
0.125 orifice,50 deflector
0
100
200
300
400
500
600
700
100 110 120 130 140 150 160
MPH
DV
0.5
0
2
4
6
8
10
12
14
16
V<1
00µm
20psi 40psi 60psi 20psi 40psi 60psi
Pressure Effects
300 deflector, 40psi
0
100
200
300
400
500
600
100 110 120 130 140 150 160
mph
DV
0.5
0
2
4
6
8
10
12
14
16
V<
10
0µ
m
0.061 0.078 0.125 0.171 0.061 0.078 0.125 0.171
Orifice Size Effects
Use of models
• USDA
• AgDrift
• Australia
USDA Aerial Nozzle Atomization Models
Model Input Screen
Weather
• Wind Speed
• Wind Direction
• Relative Humidity
• Evaporation Potential
• Inversions
Recognizing Inversions:• Under clear to partly cloudy
skies and light winds, a surface inversion can form as the sun sets.
• Under these conditions, a surface inversion will continue into the morning until the sun begins to heat the ground.
Strong Inversion
Cloud of 5-25 u oil droplets generated under unstable conditions
105 foot temperature monitoring tower
8’ 41°F
16’ 41°F
32’ 40°F
64’ 40°F
105’ 38°F
8’ 33°F16’ 36°F32’ 37°F64’ 38°F
105’ 38°F
.5 mph wind
2.5 mph wind
Shallow surface inversionSTABLE conditions up to 64’ NEUTRAL conditions at 105’
Cloud is dispersing
Courtesy – George Ramsay, Dupont
Record Keeping
• Frequency
• Where to take measurements
• Usefulness of weather offsite (ie. Local airports)
• Utilization of smoke or other visual references
Flight Pattern
• Upwind
• Downwind
• Speed (Slow v. Fast)
• Helicopter v. Fixed wing
Surfactants
• Expected effects
• Potential to make the situation worse
• Clean out concerns
Desired Effect from Additives
Actual Effect from Additives
Air Temp 85F
Canopy top 105F or more!
Canopy Floor 75F
Hot air goes which direction?
Questions??