Pulse Width Modulation on the Droplet Spectrum and Velocity of Spray Nozzles

Silviane Gomes Rodrigues, Guilherme Sousa Alves and João Paulo Arantes Rodrigues da Cunha ()
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Silviane Gomes Rodrigues: Institute of Agrarian Sciences, Federal University of Uberlândia, Uberlândia 38408-100, Brazil
Guilherme Sousa Alves: Jacto Agricultural Machineries, Pompeia 17580-018, Brazil
João Paulo Arantes Rodrigues da Cunha: Institute of Agrarian Sciences, Federal University of Uberlândia, Uberlândia 38408-100, Brazil

Agriculture, 2025, vol. 15, issue 17, 1-17

Abstract: Pulse width modulation (PWM) allows for the real-time flow rate adjustment of spray nozzles without changing system pressure, indicating that PWM is a promising technology for improving the quality of pesticide applications. However, its effect on the droplet formation process is not yet fully understood. In this study, the effects of a PWM system on the droplet spectrum and velocity generated by different flat fan hydraulic nozzles were evaluated. The experiment was conducted via a spray simulator to test the impact of PWM technology under various operational conditions and flat fan nozzle types (standard, pre-orifice, and air inclusion). With the aid of a real-time particle analyzer and high-resolution imaging, the following variables were analyzed: volume median diameter (VMD), relative span, droplet velocity, and the percentage of volume composed of droplets with a diameter smaller than 100 µm. Four simulated working speeds (1.1, 1.7, 2.8, and 3.9 m s −1 ), which were equivalent to four PWM valve duty cycles (35%, 42%, 71%, and 100%), respectively, were evaluated. The PWM system altered the droplet size, generally reducing the VMD in comparison to the conventional system. The relative span was not influenced by the PWM system’s duty cycle, although system activation increased droplet size heterogeneity in some nozzle types. The droplet velocity was generally slower using the PWM system in comparison with the conventional system, but higher duty cycles increased this parameter. Overall, the results of this study suggest that spray patterns are altered by PWM activation, and the traits of this behaviour depend on the spray nozzle type.

Keywords: droplet size; droplet velocity; duty cycle; flat fan nozzles; PWM (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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