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How do spray nozzles work? How do they convert liquid to aerosol? Is it possible to print tiny spray nozzles from metal powder?

do-the-thing-please
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Robotex
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  • Defining "tiny" might help guide more specific answers. Specifically you could provide a required scale or dimensions. Tolerances would also be helpful. Also the question is a bit broad as there are really two questions here: how do nozzles work; how to print a nozzle. The question in the title might be a good merger, but we need to know what your part design looks like first to guide the manufacturing process design or any part changes. – do-the-thing-please Nov 01 '15 at 00:02
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    Good questions require a measure more focus than what this is currently providing. Please [edit] your question to better describe the actual problem you're trying to solve and let the community know what research you've already done. –  Nov 01 '15 at 01:38
  • There's many types of spray nozzles. I suggest a (image) search for "spray nozzle" for an overview, a mechanical process engineering textbook for an explanation and coming back here with more focused questions. – mart Nov 02 '15 at 06:30

1 Answers1

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Nozzle design can be fairly complex, but basically the nozzle speeds up the velocity of the fluid to the point where inertial forces exceed surface tension forces, and the fluid breaks up into drops. The Weber number, $We = \frac{\rho u^2 l}{\sigma}$ is a convenient parameter to do a basic analysis on a nozzle flow. In this equation, $\rho$ is the fluid density, $u$ is its velocity, $l$ is a characteristic length (usually droplet diameter), and $\sigma$ is the fluid surface tension. When $We > 1$, the fluid is likely to break up into smaller droplets.

You can use the Weber number equation to calculate how fast your fluid must be traveling to break up into the target droplet diameter. This velocity, combined with the flow rate of the fluid through the nozzle, can be used to estimate the orifice area: $A = \frac{\dot V}{u}$ (area is volumetric flow rate divided by velocity). Compare the orifice diameter to the resolution of your printer; if the diameter is too small, then you might have to drill the orifice separately, after the nozzle is printed.

Carlton
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