Modulação de largura de pulso no espectro e na velocidade de gotas de pontas de pulverização

Abstract

Pulse-width modulation (PWM) allows real-time flow rate adjustment of spray nozzles without changing system pressure, proving to be a promising technology for improving the quality of pesticide applications. However, its effect on the droplet formation process is not yet fully understood. This study evaluated the effect of the PWM system on the droplet spectrum and velocity generated by different flat-fan hydraulic spray nozzles. The experiment was conducted using a spray simulator to test the impact of PWM technology under various operational conditions and nozzle types (standard flat-fan, pre-orifice, and air-induction). With the aid of a real-time particle analyzer based on 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 PWM valve duty cycles and simulated operating speeds of 1.11, 1.67, 2.78, and 3.89 m s⁻¹ were considered. The PWM system altered droplet size, generally reducing the VMD, with variations depending on the duty cycle and nozzle model. Relative span was not influenced by the PWM system’s duty cycle, although system activation increased droplet size heterogeneity in some nozzle types. Droplet velocity was generally reduced with PWM, but longer valve opening times increased this parameter. Overall, the results of this study suggest that spray patterns were altered by PWM activation, and the analysis of this behavior depended on the spray nozzle model. Keywords: spray nozzles; PWM; droplet size; application technology.