Development and Evaluation of a Monodisperse Droplet-Generation System for Precision Herbicide Application

Traditional methods of weed control during field management often result in herbicide waste. Precision herbicide application is crucial in agricultural production. This study presents a monodisperse droplet-generation system designed for precision herbicide application, capable of generating monodisperse droplets induced by an electric field. Droplet-generation experiments were conducted to investigate the effects of capillary tube outlet shape, liquid flow rate, and capillary tube size on the generation of charged droplets. A droplet diameter prediction model was established based on the system parameters. Experimental results indicated that as the applied voltage increased, the droplet diameter decreased, and the droplet-generation patterns transitioned sequentially from dripping, micro-dripping, to unstable dripping modes. In a weak electric field, capillaries with beveled outlets produced smaller droplets with more stable diameter distributions compared to those with blunt outlets. In a strong electric field, the smallest droplet diameter from blunt capillaries was 138.2 μm, whereas from beveled capillaries it was 198.7 μm. Within the design parameter range, droplet diameter was basically positively correlated with liquid flow rate and capillary tube size. By controlling the applied voltage, liquid flow rate, and capillary tube size, stable droplet generation could be achieved within a diameter range of 198.7–2520.8 μm, and the coefficient of variation of droplet diameter under the same working conditions was generally less than 6%. The monodisperse droplet-generation system developed in this study can effectively reduce herbicide usage and improve application efficiency.