Spray Flow Measurement Using an Event-Based Camera

This study presents quantitative spray measurements using an event-based camera. Compared to conventional high-speed frame-based cameras, event cameras are compact, cost-effective, and offer microsecond-scale temporal resolution with significantly reduced data storage demands. Accurate spray characterization is crucial across various engineering applications, including fuel injection and medical technologies such as Pressurized Intraperitoneal Aerosol Chemotherapy (PIPAC). Due to the relatively low particle density typically found in sprays, conventional particle image velocimetry is unsuitable; thus, optical flow techniques were adopted. To enhance accuracy, we developed an adaptive frame-generation method tailored to the event camera's top-to-bottom sensor readout. Adaptive accumulation times ranged from 40 to 60 µs (~16,000–25,000 fps), far exceeding frame-based camera capabilities, enabling temporally smooth, overlap-free frames for reliable optical flow estimation. We characterized the velocity field in the far-field region of a swirl atomizer spray at 0.5 mL/s. After complete atomization, measured droplet velocities ranged from 0.5 to 3.5 m/s, matching closely with high-speed camera optical flow and particle tracking velocimetry results. Additionally, we discuss the distribution of Sauter mean diameter of captured droplets comparing with the results from other methods. This study shows the potential of event-based camera as a versatile tool for measuring complex flows.