Measuring Spray Droplet Size from Agricultural Nozzles Using Laser Diffraction

Abstract

When making an application of any crop protection material such as an herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e., plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describes methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter-and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. Successful adaption of this method can provide a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected.

Analysis of the Influence of Different Parameters on Droplet Characteristics and Droplet Size Classification Categories for Air Induction Nozzle

“…The volumetric droplet diameters and proportion of spray volume contained in droplets with a diameter below 150 µm (% < 150 µm) for the different BFS nozzles under different spray pressures and air velocities are shown in Figures 2-4. Figure 2a shows that the results obtained in this study were similar to those in previous reports [29][30][31], which showed the droplet diameter size decreased with increasing spray pressure. More details were observed in this study as follows: (1) When spray pressure increased from 200 kPa to 300 kPa, Dv0.1, Dv0.5 and Dv0.9 decreased 16.1%, 15.8% and 14.4%, respectively; (2) when spray pressure increased from 300 kPa to 400 kPa, Dv0.1, Dv0.5 and Dv0.9 decreased 14.0%, 15.4% and 13.3%, respectively; (3) when spray pressure increased from 400 kPa to 500 kPa, Dv0.1, Dv0.5 and Dv0.9 decreased 8.6%, 11.2% and 10.4%, respectively; (4) when spray pressure increased from 500 kPa to 600 kPa, Dv0.1, Dv0.5 and Dv0.9 decreased 6.0%, 7.9% and 7.7%, respectively; (5) when spray pressure increased from 600 kPa to 700 kPa, Dv0.1, Dv0.5 and Dv0.9 decreased 2.5%, 3.0% and 2.3%, respectively.…”

Evaluation of Droplet Spectra of the Spray Tip Ad 11002 Using Different Techniques

“…In the Spraytec equipment, the entire jet crosses the laser beam transversely during the reading. In image-based equipment, if there is no tip or equipment movement structure, there is a focus region that limits the analyzed area (Fritz & Hoffmann, 2016). Thus, in spray tips with a variation of droplet size along the sprayed jet, such as flat fan spray tips, there may be a greater discrepancy between the analyzed spectra.…”

Influence of Nozzle Type, Working Pressure, and Their Interaction on Droplets Quality Using Knapsack Sprayer

“…A nozzle type that produces big droplets size is usually selected to control spray drift. Whereas, the type that mainly produces fine size is utilized to increase spray deposition and spray coverage percentage on the zone treated (11,16). Selection of the correct nozzle critical type and nozzle pressure is the most important issue to reach certainly the effective spray deposition and spray coverage thereby improving pest and weed control (6).…”