CUTTING EDGE TECHNIQUES TO MEASURE DROPLET SPECTRUM AND CHEMICAL DEPOSITION OF PESTICIDE SPRAY...
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Transcript of CUTTING EDGE TECHNIQUES TO MEASURE DROPLET SPECTRUM AND CHEMICAL DEPOSITION OF PESTICIDE SPRAY...
CUTTING EDGE TECHNIQUES TO MEASURE DROPLET SPECTRUM AND CHEMICAL DEPOSITION OF
PESTICIDE SPRAY
Muhammad Farooq
US Navy Entomology Center of Excellence, Jacksonville, FL
Disclaimer
The views expressed in this presentation are those of the author and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the U. S. Government.
Spray Application
Droplet generationDroplet Characterization
Dispersion
FluxDeposition Measurement
Transport
DepositionDeposition Measurement
Droplet Size
Measurement
Intrusive Non Intrusive
Collection
Direct Indirect
Photographic Optical
Intrusive Methods
Coated SlidesCoated with MgO, teflon, gelatin, petroleum,
resins
Impressions or stains are measured
Droplet size determined indirectly
Mainly suitable for laboratory measurements due to
handling issues
Intrusive Methods
Water Sensitive paper
Oil Sensitive paper
Coated Films
Glossy Paper
Leaf Surfaces
Liquid Media
Intrusive Methods
Cascade Impactors
Air sampled
Droplets segregated by inertial separation
Amount on each stage related to droplet size
Source:www.envcoglobal.com
Air
sp
eed
in
crea
ses
and
d
rop
let
size
dec
reas
es
Intrusive Methods
Fibrous MediaDroplets captured on fibers
Droplet size measured directly
Research on ways to measure droplets on fibers lead to development of Army Insecticide Measurement System then DCIII
Source: CAB International, 1993
DCIII Portable Droplet Counter
Enhancement of Analysis Techniques for Intrusive Methods
• Reading slides Manually using microscope
• Drop Vision System that scans slide in to computer that measures the droplet sizes
Drop Vision
Slide Microscope with digital image processor
Droplet Image Analysis software
Graphing & Reporting software
Sensitive Paper Reading System
Cards Scanned as Bitmap
Image analyzed with Stainalysis or with WRK Image Analyzer
• Droplet size
• Droplet density
• Percent coverage of card surface
Reading of Collected Droplets by Photography
Source: Aalborg University, Denmark, Website
Non-Intrusive Methods
Photographic Measurements
Holographic
Optical Array Spectrometer
Light Scattering
Laser Doppler droplet sizing
Photographic Measurements
Frozen image byShort duration high intensity light
Mercury vapor lamp, electric spark and flash => 1 ms duration
Laser pulses => order of ns
High speed camera
Images read by image analysis programs
Two pulses => Droplet size and velocity
Frozen Image
Photomicrography
Rathburn & Miserocchi, JEE, Feb. 1967
Laser Imaging
Source: www.oxfordlasers.com
Image Analysis for Size and Velocity
Sou
rce:
w
ww
.oxf
ord
lase
rs.c
om
Frozen Image of fast moving object
Source: www.oxfordlasers.com
Interferometric Mie Imaging
Fringe pattern produced by out of focus imaging
Number of fringes related to droplet size
Droplet size and 3-D VelocityNumber density Mass FluxSize-Velocity correlation
Source: www.LaVision.de
Shadography
High Magnification Image for visualization
Sizing by image analysis
Droplet size, shape and 2-D Velocity
Number density, Mass Flux
Size-Velocity correlation Source: www.LaVision.de
Particle Image Velocity
6-10 ns image100 ns time between images
Source: www.LaVision.de
Digital Image Correlation
Source: www.LaVision.de
Systems Developed
Particle MasterSize and Velocity of droplets
Spray MasterVisualization of spray
Flow MasterStudy of flows
Strain masterDeformation of flows or materials under stress
Holography
The image can be reproduced with laser to measure droplets
Optical Array SpectrometersPrinciple
Source: CAB International, 1993
Number of obscured diodes related to droplet size
Light Scattering Methods
Light Intensity Technique
Forward scattering spectrometer probe (FSSP)
Laser Diffraction Technique
Malvern droplet sizing system
Sympatec droplet sizing system
Light Intensity Technique
Source: CAB International, 1993
Laser Diffraction Technique Principle
Source: CAB International, 1993
Laser Diffraction Technique
Location of droplet in the beam does not effect the size determination
Source: www.sympatec.com
Use He-Ne class 3, 632.8 nm laser
Spatial measurement systems
Easy to set-up and align
Provide volume distribution of droplet size
Data Rate up to 10 kHz
Size range
Malvern: 0.1 to 2000 mm with two lenses
Sympatec: 0.1 to 3500 mm with 8 lenses
Laser Diffraction Technique
Measurement volume
Laser Doppler Droplet SizingPrinciple
Laser
Beam splitter
Measurement /probe volume
Detector 1
Detector 2
Detector 3
• Filtered signal
• Frequency of the signal related to droplet velocity
• Phase shift related to droplet size
Doppler Signal
Laser Doppler Droplet SizingPrinciple
General Features of PDPA
•The PDPA is a flux sampling instrument (single particle counter) •Provides simultaneous measurement of velocity and size of spherical particles•Particle size between ca. 0.5 µm and several millimetres•Can analyze many spray characteristics. The most important are:
–Droplet number distribution–Droplet volume distribution–Droplet velocity distribution–Droplet concentration and Liquid Water Content–Turbulence intensity–Droplet size velocity correlation
Droplet Size-Velocity Correlation
0 20 40 60 80 100-5
0
5
10
15
20
Diameter (um)
Velo
city
(m/s
ec)
Dia (m) V (m/s) Dia (m) V (m/s) Dia (m) V (m/s)
0.01 5.46 0.17 8.13 0.44 5.51
0.03 10.17 0.18 7.95 0.46 9.03
0.05 4.26 0.22 8.28 0.46 3.68
0.05 7.72 0.25 6.79 0.46 7.10
0.07 7.97 0.29 6.40 0.47 6.69
0.08 5.44 0.33 1.95 0.48 7.51
0.09 8.46 0.33 8.03 0.50 7.42
0.10 6.51 0.35 4.18 0.50 3.66
0.12 7.00 0.37 6.94 0.50 1.87
0.12 8.42 0.38 3.55 0.50 1.93
0.13 11.85 0.39 4.19 0.52 8.65
0.13 3.60 0.39 1.47 0.54 6.18
0.14 5.24 0.41 4.19 0.55 2.57
0.16 6.02 0.43 9.41 0.56 3.67
Data Extraction
xqLWC (g/m3)Volume Flux X (cc/cm2 s)Volume Flux Y (cc/cm2 s)Volume Flux Z (cc/cm2 s)PVC Volume 1% (um)PVC Volume 10% (um)PVC Volume 50% (um)PVC Volume 90% (um)PVC Volume 99% (um)Total Particle Conc.(1/cc)
16.194.620.25340.002375920.001639350.000000006.9110.2214.7019.9925.13205.7088
Summary Data
Air contamination studies
Air suction system
Laser-based or centrifugal impaction
Droplet size range: 0.3 – 20.0 µm
Flow rate: Up to 100 L/min
Solid particles in gases or liquids
Looking for one to measure liquid droplets in air
Portable Particle Counters
PDI Flight probe
Funded by US Navy for cloud and plane icing studies
Based on Laser Doppler sizing principle
Design being optimized Source: Artium Technologies Inc.
Spray Application
Droplet generationDroplet Characterization
Dispersion
FluxDeposition Measurement
Transport
DepositionDeposition Measurement
Why Deposition?
Fundamental part of sprayer evaluations in agriculture
Practices in public healthBio-assays
Droplet size characteristics
These techniques do not:Approve or disapprove the delivery system
Elucidate the shortcomings of the equipment being tested
Lead to improvements for meeting the objective
Deposition Measurement
Sampling
Quantification may include extraction
sampler of area Collection
extracted material of AmountDeposition
Samplers
Indicating SamplersPlant species for herbicides
Sensitive Paper
Water sensitive
Oil sensitive
Samplers
Passive SamplersCylindrical collectors
Paper
Mylar Sheet
Plant Leaves
Cotton squares
Filter papers
Plastic tapes
Cotton ribbons
Useful for course high volume agricultural sprays
Active samplers
Air Samplers
Rotating samplers
Samplers
Useful for sub-micron particles and ULV space sprays
Air Samplers
Air drawn over a filter medium
Flow rate known
Sampling time recorded
Quantity of spray determined analytically.
Result: Concentration of spray in air
Concentration is a measure of flux
Air Sampler Settings
Source: CAB International, 1993
Rotary Samplers
Rotorod Sampler
Rotary Samplers
Rotating slide samplers
Source: John W. Hoch website
Rotary Samplers
Rotating ribbon sampler
FLB samplerSource: AMCA Vol25 page 476
Quantification of Deposition
Water/Oil soluble tracer dyes mixed in tank
Samples washed with suitable solvent
Concentration of dye in wash solution quantified
Dye on sample surface determined
AI on sample surface determined using dye:AI ratio in the tank mixture
0
50
100
150
200
250
Distance from sprayer (ft)
3 25 50 80 130 215 300
Dep
ositi
on (
ng/c
m2)
0
50
100
150
200
3 ft horizontal6 ft horizontalRotating slideRotating ribbonFilter on ground
Water Based Single Pass Application
Oil Based Single Pass Application
Collection by Samplers
AMCA Vol25 page 521-524
Sampler Collection Efficiency
Collection Efficiency (%) at Wind Speed, mph Droplet Size1
1 5 10
FLB Small 74.1 21.2 24.6 3.8 17.0 4.6 Large 88.5 20.9 28.9 4.6 23.3 3.7
Rotating Slide Small 75.3 15.0 22.1 9.1 18.9 9.9 Large 123.2 57.3 47.6 36.1 67.4 32.9
Rotating Ribbon Small 1461.3 447.6 182.8 15.9 123.9 32.1 Large 1028.6 407.3 238.4 9.9 194.7 32.9
Modified Rotating Ribbon Small 365.5 103.3 72.9 7.8 65.1 1.3 Large 330.1 165.0 67.6 30.7 73.5 11.3
Stationary Ribbon Small 25.1 2.8 98.6 12.2 147.5 29.0 Large 36.1 6.3 224.7 19.0 257.6 73.6 1. Small droplet size 15 m VMD and large droplet size 30 m VMD
Questions?
DOD Pest Management Equipment Help Desk http://www.afpmb.org/pubs/equipment/equipmentdesk.htm