Measurement of internal circulation in droplets using laser-induced fluorescence

Area of Science:

• Fluid dynamics
• Chemical engineering
• Spectroscopy

Background:

• Internal circulation in submillimeter droplets is poorly understood.
• Hydrocarbon droplet behavior is critical in various industrial processes.
• Non-invasive diagnostic techniques are needed to study these phenomena.

Purpose of the Study:

• To develop and validate a novel diagnostic technique for investigating internal circulation in submillimeter hydrocarbon droplets.
• To determine the importance of internal circulation in decane droplets.
• To visualize fluid flow patterns within these droplets.

Main Methods:

• Utilized laser-induced fluorescence (LIF) based on oxygen quenching of naphthalene.
• Employed a 2-D CCD detector to capture fluorescence images.
• Analyzed images from initially oxygen-free decane droplets (300-500 micrometers in diameter) with and without oxygen absorption.
• Applied computer processing to interpret fluorescence intensity variations.

Main Results:

• Successfully visualized oxygen penetration into the droplet surface.
• Identified darker zones in fluorescence images corresponding to oxygen-quenched regions.
• Computer processing of image data revealed distinct internal circulation patterns.
• Demonstrated the capability of the technique in submillimeter decane droplets.

Conclusions:

• The developed laser-induced fluorescence technique is effective for visualizing internal circulation in submillimeter hydrocarbon droplets.
• Internal circulation is a significant phenomenon in decane droplets of this size.
• This method provides valuable insights into fluid dynamics within microdroplets.