Different kinds of sprayers used in agricultural UAVs

I notice that there are two kinds of sprayers used in agricultural pesticide spraying system. Yamaha uses jet sprayer (figure1). Besides that, centrifugal sprayers are also used (widely?) in some agriculture UAVs (figure2 and 3) spraying systems.


I’m wondering what are the comparisons between these two kinds of sprayers.


Jetting sprayer v.s. Centrifugal sprayer. Advantages and disadvantages?


centrifugal sprayer1.png

centrifugal sprayer2.png

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  • Pierre not sure if you got this publication or not but it does provide some good background reading.


    Please note the copyright on the first page which is pretty liberal for use.


    • That would be a good one to get you started on spraying, no matter the continent you are on! Great suggestion Ed, I've never seen that one before. Thanks!
  • Pierre,
    We never heard back from you. Did any of this help you in your choice? If you can be more specific in where you are, the products you will be applying, and the crops you will be applying them on, I could be more specific if that helps.
    • Thank you very much for your careful answers, George. I just get back from my busy airfoil optimization task and will start to look at the spraying system. I will start to ask questions here.

  • Here is an application advisory off of the Fyfanon malathion label.
    This is a type of application that current UAS systems could potentially be productive at being that it has a ULV label and the maximum rate per acre is 3 ounces, thus at 4 gallons of product could cover 170 acres. The ship would be then limited by flight time. If the average swath width could be doubled to around 20' due to the light rate per acre that would make the ship need to cover 70 miles in order to get to 170 acres. At 12 mph that would be nearly a six hour flight. I use the 12 mph number because that is what the Yamaha is advertised at.
    Notice the minimum application statements, the opposite of the last label which had a maximum height statement. Also notice the statement about permanently spotting car paint if droplet sizes are larger than 60 microns when applied ULV.

    Before making the first application in a season, it is advisable to consult with the state or tribal agency with primary responsibility for pesticide regulation to determine if other regulatory requirements exist.
    • Do not apply more than 0.23 lb/ai/A/day.
    • Only treat when mosquitoes are swarming or biting. Do not re-treat a site more than 3 times in any one week. However, more frequent treatments may be made to prevent or control a threat to public
    and/or animal health determined by a state, tribal or local health or vector control agency on the basis of documented evidence of disease causing agents in vector mosquitoes or the occurrence of
    mosquito-borne diseases in animal or human populations, or if specifically approved by the state or tribe during a natural disaster effort.
    • Apply when wind speed is greater than or equal to 1 mph.
    • Do not apply by fixed wing aircraft at height less than 100 feet, or by helicopter at a height less than 75 feet unless specifically approved by the state or tribe based on public health needs.
    • IMPORTANT:lNAREASWHEREAUTOMOBILES,TRAILERS,TRUCKSANDPLEASUREBOATSAREPRESENT,undilutedspraydropletsofFyfanonULVMosquitowillpermanentlydamagevehiclepaintfinishes unless the aircraft used for the ultra low volume application meets all of the specifications listed under AERIAL APPLICATION.
    Adult Mosquitoes on Rangeland, Pasture, and Other Uncultivated Non-Agricultural Areas (Wastelands, Roadsides)
    Spray equipment must be adjusted so that the volume median diameter produced is less than 60 microns (Dv 0.5 < 60 um) and that 90% of the spray is contained in droplets smaller than 100 microns (Dv 0.9 < 100 um). The effects of flight speed and, for non-rotary nozzles, nozzle angle on the droplet size spectrum must be considered. Directions from the equipment manufacturer or vendor, pesticide registrant or a test facility using a wind tunnel and laser-based measurement instrument must be used to adjust equipment to produce acceptable droplet size spectra. Application equipment must be tested at least annually to confirm that pressure at the nozzle and nozzle flow rate(s) are properly calibrated. Adult mosquito control over cities, towns, and other areas where automobiles, trailers, trucks, and pleasure boats are present: Apply 2.6 to 3.0 fluid ounces of Fyfanon ULV Mosquito per acre. Apply only when weather conditions are favorable. Wind and rising air currents may cause undesirable spray drift and reduce insect control. See Precautions and Restrictions for additional instructions.
  • I copied an actual aerial drift reduction advisory off of a Lorsban label for you so you can see what I am talking about.

    Aerial Application
    • The boom width must not exceed 75% of the wingspan or 90% of the rotor blade.
    • Nozzles must always point backward, parallel with the air stream, and never be pointed downward more than 45 degrees.
    • Nozzles must produce a medium or coarser droplet size
    (255 to 340 microns volume median diameter) per ASABE
    Standard 572.1 under application conditions. Airspeed, pressure,
    and nozzle angle can all effect droplet size. See manufacturer’s catalog or USDA/NAAA Applicator’s Guide for spray size quality ratings.
    • Do not make applications at a height greater than 10 feet above the top of the target plants unless a greater height is required for aircraft safety. Making applications at the lowest height that is safe reduces exposure of droplets to evaporation and wind.
    • Use upwind swath displacement and apply only when wind speed is 3 to 10 mph as measured by an anemometer. Do not apply product when wind speed exceeds 10 mph.
    • If application includes a no-spray zone, do not release spray at a height greater than 10 feet above the ground or crop canopy.

    As well, here is the minimum volume statement from the same label.

    Aerial Application
    Use a minimum spray volume of 2 gpa. Mark swaths by mechanical flagging, permanent markers or use of GPS equipment.
    • I'm curious about the suggestion of not flying more than 10 feet above the plants is mainly for the concern of the droplet drift or the droplet evaporation?


      At a zero wind day, what about I let the machine fly even higher than that?

    • You're spot on with both thoughts. Droplet drift distance for sure and primarily, but certainly droplet evaporation as well for high temp/low humidity situations especially for droplet spectrums below 250 microns.

      If you fly higher than that and it is stated on the label, then you are off label and in violation.
      I don't know yet due to my lack of UAV experience, but it would appear from my observations of videos that you may get some swath pattern inconsistencies if you fly too high anyway. We do in full sized equipment. Especially if you are running those jet sprayer nozzle producing 150 micron and smaller droplets at extremely low volumes per acre.
    • Do not apply the product when the wind speed exceeds 10mph.

      I doubt do the users follow this advice or not. At most of the regions, the wind wind speed will usually exceed that value and users have to spray pesticide on time. Will the droplet really drift a lot because of only 10mph wind speed?

    • To take the wind thought one step further Pierre, those of us that have the choice, maybe 60 to 70% of applicators in the US, fill the windy time by switching to dry and slinging a little fertilizer or seed for a few hours. There is no wind limit on fertilizer and seed.
      Which is another point of interest with smaller equipment. Dry work is very load intensive and requires cubes, lots of cubes.
      Yamaha has designed a dry material dispersal system, which is the only I have seen so far, but the thought of it actually performing any real fertilizer or seed job of size is overwhelming at best.
      Here is a little video of seeding rice in Northern California. Each airplane can fly as many as 100 loads or more per day, carrying just over a ton of seed per load. They try to take less than a minute per load on the ground.
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