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Author(s)
First Name
Middle Name
Surname
Role
Email
Robert
E.
Wolf
Researcher
rewolf@ksu.edu
Affiliation
Organization
Address
Country
Kansas State University
229 Seaton Hall
USA
Manhattan, KS 55506
Author(s)
First Name
Middle Name
Surname
Role
Danial
D.
Frohberg
Student
Email
Publication Information
Pub ID
Pub Date
021101
2002 ASAECIGR Annual
Meeting Paper
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily
reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not
constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review
process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should
state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2002. Title of Presentation. ASAE-CIGR
Meeting Paper No. 02xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical
presentation, please contact ASAE at hq@asae.org or 616-429-0300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Paper Number: 021101
An ASAE Meeting Presentation
Comparison of Drift for Four Drift-Reducing Flat-fan
Nozzle Types Measured in a Wind Tunnel and
Evaluated using DropletScan Software
Robert E. Wolf, Assistant Professor
Bio and Agricultural Engineering Department, Kansas State University, 229 Seaton Hall
Manhattan, KS 66506, email: rewolf@ksu.edu
Danial D. Frohberg, Undergraduate BAE Student
BAE Department, KSU, Manhattan, KS 66506
Written for presentation at the
2002 ASAE Annual International Meeting / CIGR XVth World Congress
Sponsored by ASAE and CIGR
Hyatt Regency Chicago
Chicago, Illinois, USA
July 28-July 31, 2002
Abstract. Four drift-reducing flat-fan nozzles were evaluated in a wind tunnel to compare drift.
Each tip was compared at 47 and 94 L/ha, parallel to a 4.6 m/s wind speed, and at the common
recommended field operating psi for each. Drift was collected on water-sensitive cards positioned 2,
3, and 4 m downwind from the nozzle. Cards were scanned and DropletScan software was used
to measure percent area coverage for each card. Percent area coverage was used to represent drift.
The extended range (XR) flat-fan nozzle created significantly more drift than nozzle types designed
to reduce drift, i.e. turbo flat-fan (TT), Combo-Jet flat-fan (DR), and venturi flat-fan (AI). The TT flatfan was significantly better for reducing drift than the XR flat-fan at 47 L/ha, but not at 94 L/ha. The
DR and AI flat-fans were not significantly different from each other, but did significantly produce less
drift than both the XR and TT flat-fans. For the XR flat-fan, increasing the application volume from
47 to 94 L/ha significantly reduced the amount of drift. This finding did not hold true for the TT, DR,
and AI flat-fans. The use of drift reducing nozzle designs significantly reduces drift.
Keywords. Spray drift, Spray tips, DropletScan, Droplet size, Wind tunnel, water sensitive paper
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily
reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not
constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review
process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should
state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2002. Title of Presentation. ASAE Meeting
Paper No. 02xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical
presentation, please contact ASAE at hq@asae.org or 616-429-0300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Introduction
Controlling or minimizing the off-target movement of sprayed crop protection products is critical.
Researchers have conducted numerous studies over time to better understand spray drift
problems. Particularly, a recent group of studies conducted by the industries Spray Drift Task
Force (SDTF, 1997) generated numerous reports to support an Environmental Protection
Agency (EPA) spray drift data requirement for product reregistration and future label guidance
statements on drift minimization.
Even though a better understanding of the variables associated with spray drift exists, it is still a
challenging and complex research topic. Environmental variables, equipment design issues,
many other application parameters, and all their interactions make it difficult to completely
understand drift related issues (Smith, et al., 2000). Droplet size and spectrum has been
identified as the one variable that most affects drift (SDTF, 1997). Many forces impinge on
droplet size, but it is still the drop size that must be manipulated to optimize performance and
eliminate associated undesirable results (Williams, et al., 1999). Drift is associated with the
development of high amount of fine droplets (Gobel and Pearson, 1993). Wolf, et al., (1999,
2000, 2001, 2001) in field studies, found that commonly used flat spray nozzle types exhibited
significantly different potential to drift.
Over the last several years there has been an increased interest by nozzle manufactures to
design nozzles that will effectively reduce the volume of driftable fines found in spray droplet
spectrums. This is being successfully accomplished with the use of a preorifice and also with
turbulation chambers (R. Wolf, 2000). A recent trend with spray nozzle design is to incorporate
a ‘venturi’ that includes the spray droplet in air to lessen the drift potential while still maintaining
adequate efficacy. Several nozzle manufacturers are including this new design as a part of a
marketing campaign for drift control. Early research would indicate that the venturi nozzle is
producing larger spray droplets (Womac, et al., 1997; Ozkan and Derksen, 1998; R. Wolf, et al.,
1999, 2001, 2001).
Spray drift data collection in the field is very complicated, expensive, and time consuming.
Efforts and techniques to use wind tunnels to measure spray drift from various boom sprayer
nozzle types are being developed (Phillips and Miller, 1999). Wind tunnel studies with simple
nozzle mounting structures can provide valuable nozzle performance data independent of a
sprayer and tractor while reducing much of the variability experienced in the field measurement
process (Miller, 1993). Phillips and Miller (1999) determined that wind tunnel experiments are
adequate to simulate the results of field measurements for spray drift.
Application of postemergence herbicides is becoming an ever-increasing complex phase of crop
production. More information about how to use the latest nozzle technologies to apply herbicides
for postemergence control of grasses and broadleaves is paramount for achieving optimum control
of the undesired pests. The complexity of the postemergence application process is exemplified as
recent nozzle technology is placing an increased emphasis on keeping the drift potential at a
minimum. However, while minimizing the drift potential is important, efficacy of the targeted pest is
2
still a goal. Detailed droplet information will be important to equipment manufactures, chemical
company representatives, university research and extension personnel, crop consultants, and
private and commercial applicators.
New standards for application will specify application specific droplet sizes to match the
environmental conditions at the time of application with a major emphasis on reducing damage
to sensitive areas. All the variables that can lead to spray drift problems increase the risk
associated with applying crop protection products. Minimizing spray drift is an important
parameter relating to the safe and efficient application for the environment and the operator.
Objective
The objective of this study was to compare, in a wind tunnel, the amount of drift from venturi,
Combo-Jet, extended range, and turbo flat-fan nozzles at the recommended operating pressure
for each. Water sensitive paper, a flatbed scanner, a computer, and DropletScan software
were used to collect, measure, and analyze the droplet information.
Procedure
This study was designed to measure in a wind tunnel the amount of drift from venturi, (AI);
extended range, (XR); turbo, (TT); and Combo-Jet, (DR) flat-fan spray tips. The AI, XR, and TT
are Spraying Systems/TeeJet tips and the DR tip is from Wilger. The four tips were compared
at 47 and 94 L/ha. The spray pressures used were 173 kPa for the extended range flat-fan, 242
kPa for the turbo and Combo-Jet flat-fans, and 345 kPa for the venturi flat-fan. The nozzle angle
and orifice sizes used were 110015 and 11003 for the XR and TT flat-fans, 110015 and 110025
for the AI flat-fans, and 80015 and 8003 for the Combo-Jet DR flat-fans. The 015 and 025/03
orifice sizes respectively determined the 47 and 94 L/ha application volumes. Applications
using water with a single nozzle boom configured for use in a wind tunnel were made. A
constant wind speed of 4.6 m/s was maintained throughout the experiment. Each nozzle
treatment was positioned parallel to the wind and located from 45.7 to 50.8 cm above the target.
A canopy, 25 cm high, was placed on the wind tunnel floor to simulate field conditions for a
postemergence spray application. Water sensitive cards were placed downwind from the spray
boom to collect the off-target droplet data. Three cards located at 2, 3, and 4 meters downwind
over four replications per nozzle and volume treatment were analyzed representing 24 cards for
all treatments with a total of 96 cards. DropletScan software was used to analyze the cards
and determine percent area coverage (Wolf, 1999). Tests for equality of means were performed
using ANOVA.
A boom was designed to position one nozzle in the wind tunnel 14.3 meters downwind from the
beginning of the working section in the wind tunnel. A TeeJet QJC364 nozzle body with a
CAPSTAN Pulse Width Modulation (PWM) valve attached to the diaphragm check valve was
used for connecting and controlling each nozzle (Wolf, 2000). Nozzles were placed in position
for each treatment by the researcher. The PWM valve was connected to a timer and used to
control the length of spray cycle. The PWM valve allowed the system to be preset to the
treatment pressure for instant and accurate spray volume control. To achieve adequate
coverage on the water sensitive paper, a two-second-spray interval was used in this study. All
3
controls were actuated from a control room outside the wind tunnel. The wall was equipped
with a viewing window to verify the equipment functioned properly.
The wind tunnel used in this study had a working section 17.68 m long, 1.52 m wide, and 1.93
m high. A recirculating push-type fan (tip to tip blade measurement, 2.0 m) driven by a 125 HP
General Electric DC motor was used to develop the air stream. A diffuser the size of the wind
tunnel cross-section was placed at the start of the working end of the tunnel. The diffuser was
made from steel pipe (5.1 cm in circumference by 30.5 cm long) welded to form a honeycomb
design. Spires, designed to increase both the depth and turbulence level of the wind tunnel
boundary layer, were placed at the base of the diffuser. A crop canopy simulation was created
using plastic broadleaf plants with the tops placed at 25 cm above the floor of the tunnel. The
plants were placed randomly through the entire length and width of the tunnel. Artificial grass
was placed on the floor of the tunnel under the boom to minimize spray droplet bounce. The
spray boom was placed in the tunnel 14.3 meters from the diffuser and ranging from 45.7 cm to
50.8 cm above the canopy top. The boom was designed to minimize wind turbulence in the
nozzle area. The nozzle, located in the center of the wind tunnel, was placed upwind 2 m from
the first collector with additional collectors placed at 3 and 4 m downwind. The collector was
designed for removal from the wind tunnel after each treatment to facilitate drifted card removal
and replacement with dry, clean cards for the next treatment.
Temperature and humidity were measured using a Campbell Scientific CR10X probe system
with data logger. The probes were positioned at boom height. A KURZ Model 1440M air
velocity meter positioned above and near the center of the boom was used to continually
monitor wind velocity. Adjusting the amperage to the fan motor controlled wind speed velocity.
Results and Discussion
A statistic measured by DropletScan software is percent area coverage. Spray droplets
collected on water sensitive paper are a good indicator of spray drift when measuring the
amount of coverage obtained on the cards (Wolf, 1999). Since the cards are placed outside
and downwind from each treatments target area, differences in the amount of area covered on
the card will reflect the amount of drift. The drift (percent area coverage) means for each nozzle
and volume treatment for cards in both position one and two (2 and 3 meters downwind) were
compared and are presented in table 1. The card in position 3 was not reported due to the lack
of consistency in coverage for all the treatments. DropletScan software was programmed to
measure an area on the card equal to 40 percent of the card.
The mean for drift on the card in position 1 for the XR flat-fan at 47 L/ha reflects a significantly
greater drift amount than for the TT, DR and AI flat-fan tips (28.78, 8.85, 1.28, 1.45). There was
also a significant difference in the amount of drift for the TT flat-fan compared to the DR and AI
flat-fans. No significance was found between the DR and AI flat-fans.
4
Table 1. Drift (Percent Area Coverage*). ANOVA Mean Estimate**
Card Position 1(2 m downwind)
Treatment
47 L/ha
c
94 L/ha
c
Card Position 2 (3 m downwind)
Nozzle Mean
1.49
c
47 L/ha
94 L/ha
c
c
.33 c
.28
.38
Nozzle Mean
AI
*1.45
1.53
DR
1.28 c
2.03 c
1.65 c
.28 c
.38 c
.33 c
TT
8.85b
8.85 b
8.85 b
2.45 b
2.90 b
2.68 b
XR
28.78a
13.72 b
20.96 a
9.15 a
3.55 b
6.35 a
Volumes Mean
10.09 a
6.39 b
3.04 a
1.80 b
* Percentage represents a 40% scanned area for each 2.54 X 6.45 cm water sensitive card.
** Tests for equality of means were performed using ANOVA. Values with different letters in
each column indicate significant differences. Similar letters indicate no differences (5%
confidence level). The volumes mean difference is listed horizontally in the last row.
At 94 L/ha the amount of drift created from the XR flat-fan was more than the TT flat-fan, but
was not significantly different (13.2, 8.85). Both of these tips did develop significantly more drift
that the DR and AI flat-fans (2.03, 1.53). Again, the DR and AI flat-fans were not significantly
different in the amount of drift created.
Similar results were measured on each of the cards located at position 2 for each treatment. As
expected with the cards located at 3 meters downwind, the quantity of drift was less for each
treatment than on the card located in position 1 closer to the nozzle.
At both card locations, a summary for each tip across both application volumes shows similar
trends for creating drift as reported for each application volume separately. The XR flat-fan tip
created the most drift, which was significantly more than the TT, DR, and AI. Again, the TT
created significantly more drift than the DR and AI, and the DR and AI were not significantly
different in the amount of drift created.
For the XR flat-fan tip at both card locations, increasing the application volume from 47 to 94
L/ha significantly reduced the amount of drift created. For all the other nozzle treatments, no
significance was found as the application volumes increased. Summed across all tips and
cards, there was a significant reduction in drift as the application volume was increased.
However, the data would reflect that the XR flat-fan was responsible for the difference.
Conclusions
Comparisons of four nozzles types widely used to apply crop protection products were
performed. Each nozzle type was compared at its commonly recommended operating
5
pressure. Two application volumes were compared for each nozzle treatment. Results showed
significant differences between treatments.
As expected, even with a lower operating psi, the XR flat-fan nozzle created significantly more
drift than the nozzle types with drift reducing designs operating at a higher psi. The TT flat-fan
was significantly better for reducing drift than the XR flat-fan at 47 L/ha, but not at 94 L/ha. The
DR and AI flat-fans were not significantly different from each other, but did dramatically produce
less drift than the XR and TT flat-fans.
The data in this study supports a previously recommended drift reduction strategy for
conventional flat-fan nozzle designs such as the XR flat-fan. The common recommendation for
reducing drift has been to increase the application volume (a larger nozzle orifice produces
larger droplets resulting in less drift). This trend is not shown with the newer drift reductions
nozzle designs used in this study (TT, DR, AI). Thus, it may not be appropriate or necessary to
consider increasing the application volume with these drift reducing nozzle designs.
As evidenced in this study, even when used at the recommended pressure, the four nozzles
compared produced significantly different amounts of drift. The newer nozzle designs do not
show drift reductions when increasing the application volume. Based on the research reported
in this study, using nozzles specifically designed for reducing drift will significantly reduce the
creation of drift when compared to conventional XR flat-fans.
Additional research is needed to support this finding.
Acknowledgements
I would like to acknowledge the Manhattan, KS USDA-ARS Wind Erosion Research Unit staff
for their support and use of the wind tunnel to complete this study. A special thanks is offered
to Jonathan Zimmerman and Andrea Peterson, undergraduate ATM students in the Biological
and Agricultural Engineering Department at K-State, for their assistance in conducting the
research and analyzing the data for this study. An additional thank you goes to Cathy Minihan,
graduate student in Agronomy, for her assistance in running the statistical analysis on this data.
I would also like to thank Syngetna for there continued financial support of my spray program.
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