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