Assessment of a CDA rotary atomizer for weed control
Ouled Taleb Salah S., Massinon M. and Lebeau F.
Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium
ISOFAR / MOAN Symposium Sousse, Tunisia
Assessment of a CDA rotary atomizer for weed control
Ouled Taleb Salah S., Massinon M. and Lebeau F.
Gembloux Agro-Bio Tech (University of Liege), Gembloux, Belgium
ISOFAR / MOAN Symposium Sousse, Tunisia
Introduction
Crop protection is mainly achieved by spraying pesticides using hydraulic nozzles. This can lead to environmental contaminations that can be minimized especially in the context of reduction application rates. The challenge is therefore to ensure a required level of protection in these conditions.
Controlled Droplet Application (CDA) has proved to be the most successful way of delivering pesticides at very low volume application. In the past, their use was found inefficient in arable crops essentially due to bad settings, such as inappropriate application rate, and problem of penetration of spray in cereal canopies. These spray generators may be, however, the best solution when treating small hydrophobic weeds because spray retention can be maximized and drift of smaller droplets minimized thanks to reduced droplet span.
This study deals with blackgrass control in cereals while limiting environmental losses using properly set rotary atomizers. The droplet size and velocity were measured to characterize treatment efficiency.
Results and discussions
Rotary atomizers (Fig 2a) produce narrower droplet size distributions than hydraulic nozzles (Fig 2b) as it can be highlighted by a lower span defined by (V90-V10)/V50 (Table 1). V10, V50 and V90 indicates that 10, 50 and 90% of the volume of spray is in droplet diameters smaller than this value.
Material and Methods
A high-speed camera used in double exposure mode coupled to a LED backlighting records water droplets produced by a Micromax® 120 (Micron) at various flow rates and rotating speeds. Images were analyzed with a Particle Tracking Velocimetry Sizing (PTVS) algorithm developed in Matlab®. This atomizer was benchmarked to a flat fan nozzle.
0 100 200 300 400 500 600 0 10 20 V ol um e re la tif c or rig é [% ] Diamètre [µm]
Volume corrigé en fonction du diamètre
0 100 200 300 400 500 6000 50 100 V ol um e re la tif c or rig é cu m ul é [% ] 0 100 200 300 400 500 600 0 10 20 V ol um e re la tif c or rig é [% ] Diamètre [µm]
Volume corrigé en fonction du diamètre
0 100 200 300 400 500 6000 50 100 V ol um e re la tif c or rig é cu m ul é [% ]
Conclusion and perspectives
PTVS allowed a good characterization of droplet size distributions required for application method efficiency assessment. Reaching an optimal spray retention on weed surfaces while reducing the proportion of smaller droplets to reduce drift potential is a challenge that should rely on a reduced droplet span. Retention and drift are currently under investigation as a function of flow rate and rotating speed. Débit (ml/mn) V10 (µm) V50 (µm) V90 (µm) Span (V90-V10)/V50 2000 tours/mn 560821 302 404 519 0.53 324 443 556 0.52 3500 tours/mn 560821 221 310 398 0.57 249 367 474 0.61 5000 tours/mn 560821 181196 271306 347421 0.600.73 Teejet XR 11002 560 113 208 361 1.18 Hardi Injet 015 560 177 325 514 1.03 0 100 200 300 400 500 600 0 2 4 6 8 10 V ol um e re la tif c or rig é [% ] Diamètre [µm]
Volume corrigé en fonction du diamètre
0 100 200 300 400 500 6000 20 40 60 80 100 V ol um e re la tif c or rig é cu m ul é [% ] 0 100 200 300 400 500 600 0 2 4 6 8 10 V ol um e re la tif c or rig é [% ] Diamètre [µm]
Volume corrigé en fonction du diamètre
0 100 200 300 400 500 6000 20 40 60 80 100 V ol um e re la tif c or rig é cu m ul é [% ]
Fig 3: Drop formation for a rotary atomizer
Satelite droplets were observed in the spectrum of CDA sprayer but their percentage is low compared to flat fan nozzle (Fig 3). This phenomenon is gradually reduced when rotation speed is rised.
Fig 2: Droplet size distributions: (a) Micromax (2000 rpm, 563 ml/mn), (b) Teejet (560 ml/mn; 1.4 bar)
