Prediction Research of Ligament Fragmentation Critical Flow Rates and Droplet Characterization in Rotary Cup Atomization

Rotary cup atomization is widely used in low-volume agricultural spraying. In this study, fragmentation visualization and droplet size measurement experiments were conducted to systematically investigate fragmentation behavior and droplet characteristics in rotary cup atomization. Particular attention was given to the ligament fragmentation (LF) regime, and dimensionless correlations were established to predict the upper and lower critical flow rates defining its stable operating window (R2 > 0.97). Within the LF regime, predictive models for the droplet volume median diameter (Dv0.5) were developed using the same dimensionless framework. In addition, droplet size distributions were described using the Rosin-Rammler distribution, enabling unified prediction of both characteristic droplet size and distribution. An engineering-oriented analytical framework was established that integrates fragmentation regime delimitation with droplet characterization, providing theoretical guidance for parameter optimization and stable operation under low-volume agricultural spraying conditions.