1. US Navy Entomology Center of Excellence, Jacksonville, FL
CUTTING EDGE TECHNIQUES TO MEASURE DROPLET SPECTRUM AND CHEMICAL DEPOSITION OF PESTICIDE SPRAY
Muhammad Farooq
US Navy Entomology Center of Excellence, Jacksonville, FL

2. 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.

3. Spray Application

5. Intrusive Methods Coated Slides
Coated with MgO, teflon, gelatin, petroleum, resins
Impressions or stains are measured
Droplet size determined indirectly
Mainly suitable for laboratory measurements due to handling issues

6. Intrusive Methods Coated Films Glossy Paper Leaf Surfaces Liquid Media
Water Sensitive paper
Oil Sensitive paper
Coated Films
Glossy Paper
Leaf Surfaces
Liquid Media

7. Intrusive Methods Cascade Impactors Air sampled
Droplets segregated by inertial separation
Amount on each stage related to droplet size
Air speed increases and droplet size decreases
Source:

8. Intrusive Methods Fibrous Media Droplets 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

9. DCIII Portable Droplet Counter

10. 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

11. Drop Vision Slide Microscope with digital image processor
Droplet Image Analysis software
Graphing & Reporting software

12. 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

13. Reading of Collected Droplets by Photography
Source: Aalborg University, Denmark, Website

14. Non-Intrusive Methods
Photographic Measurements
Holographic
Optical Array Spectrometer
Light Scattering
Laser Doppler droplet sizing

15. Photographic Measurements
Frozen image by
Short 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

16. Frozen Image

17. Photomicrography
Rathburn & Miserocchi, JEE, Feb. 1967

18. Laser Imaging
Source:

19. Image Analysis for Size and Velocity
Source:

20. Frozen Image of fast moving object
Source:

21. Interferometric Mie Imaging
Fringe pattern produced by out of focus imaging
Number of fringes related to droplet size
Droplet size and 3-D Velocity
Number density
Mass Flux
Size-Velocity correlation
Source:

22. 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:

23. Particle Image Velocity
6-10 ns image
100 ns time between images
Source:

24. Digital Image Correlation
Source:

25. Systems Developed Particle Master Spray Master Flow Master
Size and Velocity of droplets
Spray Master
Visualization of spray
Flow Master
Study of flows
Strain master
Deformation of flows or materials under stress

26. Holography
The image can be reproduced with laser to measure droplets

27. Optical Array Spectrometers Principle
Number of obscured diodes related to droplet size
Source: CAB International, 1993

28. Light Scattering Methods
Light Intensity Technique
Forward scattering spectrometer probe (FSSP)
Laser Diffraction Technique
Malvern droplet sizing system
Sympatec droplet sizing system

29. Light Intensity Technique
Source: CAB International, 1993

30. Laser Diffraction Technique Principle
Source: CAB International, 1993

31. Laser Diffraction Technique
Location of droplet in the beam does not effect the size determination
Source:

32. Laser Diffraction Technique
Use He-Ne class 3, 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

33. Laser Doppler Droplet Sizing Principle
Beam splitter
Measurement /probe volume
Detector 1
Detector 2
Detector 3
Measurement volume

35. Laser Doppler Droplet Sizing Principle
Filtered signal
Frequency of the signal related to droplet velocity
Phase shift related to droplet size 
Doppler Signal

36. 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

37. Droplet Size-Velocity Correlation

38. Data Extraction Dia (mm) 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
3.68
7.72
0.25
6.79
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
8.03
0.50
7.42
0.10
6.51
0.35
4.18
3.66
0.12
7.00
0.37
6.94
1.87
8.42
0.38
3.55
1.93
0.13
11.85
0.39
4.19
0.52
8.65
3.60
1.47
0.54
6.18
0.14
5.24
0.41
0.55
2.57
0.16
6.02
0.43
9.41
0.56
3.67

39. Summary Data

40. Portable Particle Counters
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

41. 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.

42. Spray Application

43. Why Deposition? Fundamental part of sprayer evaluations in agriculture
Practices in public health
Bio-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

44. Deposition Measurement
Sampling
Quantification may include extraction

45. Samplers Indicating Samplers Plant species for herbicides
Sensitive Paper
Water sensitive
Oil sensitive

46. Samplers Passive Samplers Cylindrical collectors Paper Mylar Sheet
Plant Leaves
Cotton squares
Filter papers
Plastic tapes
Cotton ribbons
Useful for course high volume agricultural sprays

47. Samplers Active samplers Air Samplers
Rotating samplers
Useful for sub-micron particles and ULV space sprays

48. 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

49. Air Sampler Settings
Source: CAB International, 1993

50. Rotary Samplers
Rotorod Sampler

51. Rotating slide samplers
Rotary Samplers
Rotating slide samplers
Source: John W. Hoch website

52. Rotary Samplers Rotating ribbon sampler FLB sampler
Source: AMCA Vol25 page 476

53. 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

54. Collection by Samplers
AMCA Vol25 page

55. Sampler Collection Efficiency

56. Questions?
DOD Pest Management Equipment Help Desk