Time-resolved transient spray characterization using high speed digital inline holography*

Transient spray dynamics play a crucial role in various industrial processes, including spacecraft propulsion, agricultural irrigation, and pharmaceutical production. This study investigates a transient planar spray modulated temporally by varying the frequencies and duty cycles of electromagnetic valve operations. High-speed imaging is utilized to visualize the temporal evolution of lamella formation and breakup, while time-resolved digital inline holography quantifies the resulting droplet size distribution. The results indicate that the transient spray angle evolves over time, with the range of angle variation increasing with flow rate and decreasing with frequency. Increasing the duty cycle reduces the range of spray angle variation and delays the time to reach the maximum angle. For all cases, the maximum angle reaches a continuous spray angle of 104°. The droplet size and number in modulated sprays fluctuate over time with phase opposition. The transient spray duty cycle and frequency plays an important role in determining the mean droplet size as well as the temporal size fluctuation levels. These findings underscore the importance of modulating parameters to optimize spray systems for enhanced performance and efficiency.