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A pneumatic droplet-on-demand generator

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Abstract

The design of a pneumatic droplet generator to produce small (~0.2 mm diameter) water droplets on demand is described. It consists of a cylindrical, liquid-filled chamber with a small nozzle set into its bottom surface, connected to a gas cylinder through a solenoid valve. Rapidly opening and closing the valve sends a pressure pulse to the liquid, ejecting a single droplet through the nozzle. Gas in the chamber escapes through a vent hole so that the pressure drops rapidly and more droplets do not emerge. We photographed droplets as they emerged from the nozzle, and recorded pressure fluctuations in the chamber. We determined the duration of the pressure pulse required to generate a single drop; longer pulses produced satellite drops. The length of the water jet when its tip detached and the diameter of the droplet that formed could be predicted using results from linear stability analysis. The peak pressure in the cavity could be increased by raising the supply pressure, increasing the width of the pressure pulse, or by reducing the size of the pressure relief vent.

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Acknowledgements

Materials and Manufacturing Ontario (MMO) and Teck Cominco Product Technology Centre of Mississauga, Ontario, Canada offered financial support for this research. Their assistance is gratefully acknowledged.

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Authors and Affiliations

  1. Centre for Advanced Coating Technologies, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, M5S 3G8, Canada

    S. Cheng & S. Chandra

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  1. S. Cheng
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  2. S. Chandra
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Correspondence to S. Chandra.

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Cheng, S., Chandra, S. A pneumatic droplet-on-demand generator. Exp Fluids 34, 755–762 (2003). https://doi.org/10.1007/s00348-003-0629-6

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  • DOI: https://doi.org/10.1007/s00348-003-0629-6

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