Creating intelligent technologies for land and water based industries
Summary
 Identifying the optimum droplet size spectrum for
each target
 Balancing efficacy and drift avoidance
 Overview of droplet size data resources, models, etc.
Droplet Size Classification
 The use of absolute size values can be confusing
because they are affected by measurement techniques
 ASABE S-572 and BCPC schemes bridge across systems
 Round-robin inter-laboratory atomisation study
underway through ISO to compare different
laboratories around the world; draft standard under
revision (convenors: Hewitt and Valcore)
ASABE S572 Reference Sprays
Example: CPAS Curves (Sympatec)
100
95
90
85
80
75
70
Cumulative distribution Q3 / %
65
60
55
50
45
40
35
30
T rt
25
20
15
15
15
15
15
15
10
5
cm
cm
cm
cm
cm
laser
laser
laser
laser
laser
to
to
to
to
to
nozzle
nozzle
nozzle
nozzle
nozzle
T ank Mix Nozzle Pressure Dv0.1
µm
Water
11001 450 kPa 58
Water
11003 300 kPa 114
Water
11006 200 kPa 181
Water
6510
200 kPa 274
Water
6515
150 kPa 364
Water
8008
250 kPa 218
VMD
µm
141
255
392
600
752
481
Dv0.9
µm
239
448
664
1175
1297
911
%V<150µm
%
54.77
17.66
6.37
1.99
0.65
4.15
%V<200µm
%
78.37
32.25
12.64
4.45
1.75
8.19
0
100
200
300
400
500
600
700
800
900
1000
1100
particle size / µm
1200
1300
1400
1500
1600
1700
1800
1900
2000
Sympatec
CPAS Sympatec, BBA PDPA and SSC Oxford Laser
1500
(Different shades of same colors for each boundary)
BBA VF/F
BBA F/M
BBA M/C
BBA C/VC
1300
BBA VC/XC
BBA XC/UC
1100
CPAS VF/F
CPAS F/M
900
CPAS M/C
CPAS C/VC
700
CPAS VC/XC
CPAS XC/UC
500
SSC VF/F
SSC F/M
SSC M/C
300
SSC C/VC
SSC VC/XC
100
SSC XC/UC
-100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Optimum Droplet Size: Efficacy
 Coverage: cubic relationship between size and number of droplets –




smaller is better for coverage (assuming effective deposition) but must
achieve correct application volume rate, especially for coarser sprays
Collection efficiency:
Soil >200 µm for sedimentation deposition (typically 300-600 µm – M-UC)
Narrow leaves on trees 40-80 µm (VF)
Broad leaves on trees and plants 80-160 µm (F/M)
Narrow leaf (e.g. grass) weeds 120-240 µm (M)
Adult mosquitoes 20-40 µm (UF)
Spreading/ sticking: air inclusions may help; adjuvants often important –
PPCnz work looking at bounce/ shatter/ retention modeling for AGDISP
Biocidal area (area of influence of droplet)
Biological effect (a.i. particle size; penetration, uptake)
Optimum Droplet Size: Drift
 Without a mechanism to reduce drift such as
shielding, shrouding, air-assistance etc, the trend is for
small (≤F) droplets to drift further than large droplets
(≥C), therefore many researchers consider droplets
<150-200 µm to be the main drift concern for
conventional applications from ground and aircraft
boom sprayers except in a canopy (e.g. forestry)
 For tree and vine crop applications, 150-200 µm would
be considered larger than optimal, and in this case the
canopy and spray targetting are more important
Narrow v Broad Size Distributions
 Where a range of targets are being sprayed (e.g. mixed
grass and broad-leaved weeds), a range of droplet sizes
may be best
 Where a specific target is being sprayed, and where
drift and other issues are important, a narrow
spectrum (e.g. few “fines” relative to the Dv0.5) may be
optimal
RS 
Dv0.9  Dv0.1
Dv0.5
Five Nozzles:
Same Dv0.5, Different Dv0.1 and RS Values
100
90
80
Cumulative Spray Volume (%)
70
60
50
40
30
Spinning disc
20
Disc-core
Cone
Deflector
10
Flat fan
0
0.0
250.0
500.0
750.0
1000.0
Upper Diameter of Droplet Size Class (µm)
1250.0
1500.0
RS (“Fines”) Reduction as a DRT
Droplet Size Resources
 Nozzle catalogues (water data, ground applications)
 Published data
 AGDISP and AgDRIFT libraries and models
 USDA-ARS models
 CPAS models – more being developed for a.i. tank mixes
in ground application scenarios (GRDC support)2011-14
Questions?