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I am making a small (desktop) wind tunnel for educational purposes, I want to have 10 fairly thick smoke-streams about 3cm apart. I have experimented with incense but the stream is not thick enough and barely visible.

I was thinking of using a pipe with holes drilled in it to get the 10 smoke-streams, the low pressure of the airflow drawing the smoke out through the pipe from a container with the burning substance.

What can I burn that will produce a nice thick white smoke and is non-toxic?

Is there a different/better way to get non-toxic 'smoke' without burning anything?

Is the pipe a good way to distribute the smoke or are there any other/better techniques to getting the multiple streams?

Air
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jhabbott
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6 Answers6

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The testing of ventilation systems and of building air-tightness is done using smoke sticks or similar - non-toxic smoke generators that produce no ash residue. One of these may be suitable for your needs.

Smoke generators typically use mixes of two or more of:

  • alcohol
  • glycol
  • glycerol
  • water

I suppose strictly speaking they're fog generators rather than smoke generators.

There are a wide variety of parameters to chose from. There are fast-dispersing mixes, and lingering ones. There are generators that run off batteries, and some that run off mains power. Some generate high flows, some low flows. Some start generating within seconds of being switched on, others take a few minutes before they start producing the fog (smoke).


(Drager Flow Check - source as above)

410 gone
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6

In automotive testing we use baby oil. When heated it produces a thick white smoke that is non toxic in low volumes and doesn't stick to surfaces.

I built my own smoke tester using a metal pressure fed wax-oil/underseal sprayer, I drilled a hole and inserted an automotive glow plug to heat the oil. You can then experiment with a pressure that works best for you.

I have successfully filled car interiors with smoke under pressure and it hasn't left any residue.

Newbie Noob
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3

I made my own wind tunnel,but it was NASA's visualization one. Incense did not work as a smoke source for me, but you might have better luck. What I ended up using for smoke was dry ice and hot water. One drawback to this is that the fluid density is higher than air, so the condensed air drops in a horizontal wind tunnel. The solution to this for me was to have the wind tunnel vertical.

Dan Powers
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I am making one right now. These posts are all old and the problem is usually the same. I am using a camping pump, some tubes, and a vaporizer. I use no nicotine juice that I make myself just using glycerin diluted with a little bit of distilled water. The pipe is plugged at the end and as several holes to watch the airflow at different heights. Works great, but I only get smoke for 10 seconds at a time or it will burn out the coil. Wait 3 seconds and then fire it up again.

Kenn Loewen
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I'm thinking of using dry ice fog in water, or by heat up kerosene until smoking. Dry ice produced fog when put in water, and kerosene will get gasification when heated.

RainerJ
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Depending on the Mach numbers and Reynolds numbers, the size of the seeding rakes have different effects on the flow over the test object. Here is a commercial manufacturer of smoke machines for wind tunnel testing. Check out their Q&A section for some great information about different types of seeding.

Here is another consultant group that talk about issues when developing seeding systems.

Lilibete
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