Let’s hold off on using a lot of words. Going forward, please take it that any air-assisted sprayer used for trellised and free-standing perennial trees, vines, cane, and bush crops is meant to be referred to when we write “sprayer.” This indicates a considerable degree of morphological and structural variability and as a result, producers appear to have created an alternative sprayer (occasionally multiple) for every particular crop. There is no one explanation for the optimal way to operate a sprayer due to the variability in sprayer design.
But despite their variations, all sprayers have three basic mechanical systems. Together, these systems can generate and meter droplets of a liquid solution air to carry such droplets to a destination.
Explaining the Geometry of Sprays
It took us about three months into writing this edition for us to realize that we were referring to spray geometry with different terms. We had to take a step back and create a common language for the flex sprayer. As you read the book, you’ll come across these terms, so spend some time getting familiar with them.
• Spray
The mist produced by the sprayer consists of air and droplets.
• Air wash
The spray plume’s width at the canopy’s contact. is usually inherent in the design of the sprayer and dependent on the distance between the sprayer and the target.
• Spray Height
The height of the spray was measured from the ground. influenced by the sprayer’s design, the resistance of the intervening canopy, the travel speed, and the surroundings.
• Swath
To compute product rates, a swath is a theoretical application width. Usually, it is from row center to row center (one row) or from row center to the target canopy’s midpoint (half row).
• Throw
The actual distance that the spray travels, whereas swath is the theoretical intent.
The environment, travel speed, sprayer design, and the resistance of the intervening canopy all have an impact.
• Penetration
How far (or how deep) a spray can penetrate a canopy.
Air Sprayer Behavior
The most crucial and poorly understood mechanical system on a sprayer is air handling.
Small droplets don’t have much kinetic energy because they have a very small mass about their surface area. A small droplet’s propulsion is only slightly increased by increasing hydraulic pressure. The majority of droplets would never travel in the direction or speed we want them to if air weren’t present. Air also causes a canopy to open and move, revealing surfaces that would otherwise be hidden from the droplets it is carrying.
Characteristics of Air Behavior
One or more fans produce air, which is then directed, deflected, or otherwise aimed to carry spray droplets to the intended target. It is impossible to discuss air handling systems without first taking the characteristics of the air into account. The four elements of air behavior are turbulence, angle, volume, and velocity.
• Velocity
Air velocity is its speed.
• Volume
The amount of air that the sprayer is releasing.
• Angle
The direction of the net airflow.
• Turbulence
This is the mixing and dispersion of air.
It is possible to modify the spray’s volume, velocity, and angle to increase coverage and lower the risk of off-target drift. Typically, turbulence is a built-in feature of sprayer designs. Whether your sprayer is adjustable or not, knowing these things will make it easier for you to use it.
Air Handling System
Air handling systems can be either generalists or specialists; some are made to be very good at one thing, while others are more flexible but less accurate. The kind of fan a sprayer has a big impact on its capabilities. Although a fan’s natural traits may fit them better in some situations, there can be a lot of capability crossover. The type of fan matters, but what happens to the air at the outlets matters more.
The operator has control over the configuration and operation of the larger, engineered air handling system that houses the fans. The fan is merely a means to an end, which is why it is crucial to think about how the air leaves the sprayer. However, we do need to quickly talk about fan types.
Atomization System
The liquid is atomized or turned into droplets. A sprayer’s hydraulic nozzle, or point of atomization, is where the liquid handling and air handling systems converge.
Three atomization systems can be distinguished based on the relative contributions of mechanical, liquid, and/or air energy. Breathe in, and let’s dive right into the discussion of atomizers and droplet size.
Different Rules for a Different Sprayer
The size of the droplets that a nozzle produces is referred to as spray quality. Given that droplet size is the primary factor influencing droplet behavior, we can infer some information about nozzle performance from it. The majority of spray quality recommendations deal with the use of herbicides in broad-acre crops like beans and grains. The necessity to create a level area and stop drift is what drives this. When droplet momentum and gravity are the main factors to be taken into account, coarse droplets make sense. For air-assist sprayers, the regulations are different, though. The most important thing is coverage. In our universe, the majority of sprayed products are not systemic.
Conclusion
Finer droplets are therefore preferred because they deliver a more consistent dose to all target surfaces, provided that they arrive intact. Compared to finer droplets, coarser droplets move more quickly and consistently. However, we don’t usually depend on the kinetic energy of the droplet. The main instrument we use to mitigate drift and provide coverage is the air configuration of the target canopy.
It is more difficult to work with coarser droplets. Compared to finer droplets, they have greater intrinsic energy (momentum) and are less sensitive to air energy.
Compared to most field crops, our three-dimensional canopies are frequently denser, deeper, and farther from the nozzles. More air-assisted droplets penetrate and deposit material overall more effectively.
