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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 generation Droplet Characterization Dispersion Flux Transport Deposition Deposition Measurement Deposition Measurement Droplet Size Measurement Intrusive Collection Direct Non Intrusive Photographic Indirect Optical 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 Intrusive Methods Water Sensitive paper Oil Sensitive paper Coated Films Glossy Paper Leaf Surfaces Liquid Media Cascade Impactors Air sampled Droplets segregated by inertial separation Amount on each stage related to droplet size Air speed increases and droplet size decreases Intrusive Methods Source:www.envcoglobal.com 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 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 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 Frozen Image Photomicrography Rathburn & Miserocchi, JEE, Feb. 1967 Laser Imaging Source: www.oxfordlasers.com Source: www.oxfordlasers.com Image Analysis for Size and Velocity 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 Velocity Number density Mass Flux Size-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 image 100 ns time between images Source: www.LaVision.de Digital Image Correlation Source: www.LaVision.de Systems Developed Particle 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 Holography The image can be reproduced with laser to measure droplets Optical Array Spectrometers Principle Number of obscured diodes related to droplet size Source: CAB International, 1993 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 Laser Diffraction Technique 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 Doppler Droplet Sizing Principle Measurement /probe volume Laser Beam splitter Detector 1 Measurement volume Detector 3 Detector 2 Laser Doppler Droplet Sizing Principle • Filtered signal Doppler Signal • Frequency of the signal related to droplet velocity • Phase shift related to droplet size 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 20 Vel oc i ty (m /s ec ) 15 10 5 0 -5 0 20 40 Diameter (um) 60 80 100 Data Extraction Dia (mm) V (m/s) Dia (mm) V (m/s) 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 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 Summary Data 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 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 generation Droplet Characterization Dispersion Flux Transport Deposition Deposition Measurement Deposition Measurement 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 Deposition Measurement Sampling Quantification may include extraction Amount of material extracted Deposition Collection area of sampler Samplers Indicating Samplers Plant species for herbicides Sensitive Paper Water sensitive Oil sensitive 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 Samplers Active samplers Air Samplers Rotating 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 sampler Source: 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 Collection by Samplers 250 Water Based Single Pass Application 3 ft horizontal 6 ft horizontal Rotating slide Rotating ribbon Filter on ground 200 150 Deposition (ng/cm 2) 100 50 0 Oil Based Single Pass Application 200 150 100 50 AMCA Vol25 page 521-524 0 3 25 50 80 130 Distance from sprayer (ft) 215 300 Sampler Collection Efficiency Droplet Size1 Small Large Small Large Small Large Collection Efficiency (%) at Wind Speed, mph 1 5 10 74.1 21.2 88.5 20.9 75.3 15.0 123.2 57.3 1461.3 447.6 1028.6 407.3 FLB 24.6 3.8 28.9 4.6 Rotating Slide 22.1 9.1 47.6 36.1 Rotating Ribbon 182.8 15.9 238.4 9.9 Modified Rotating Ribbon Small Large 365.5 103.3 330.1 165.0 72.9 7.8 67.6 30.7 Stationary Ribbon 17.0 4.6 23.3 3.7 18.9 9.9 67.4 32.9 123.9 32.1 194.7 32.9 65.1 1.3 73.5 11.3 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 mm VMD and large droplet size 30 mm VMD Questions? DOD Pest Management Equipment Help Desk http://www.afpmb.org/pubs/equipment/equipmentdesk.htm