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Discussion Starter · #1 ·
Does anyone have any slight knowlidge of "dynamics of flow"? :rolleyes:



This device has come up thanks to the experimentation of Charles T. McCullogh, described at www.steamup.info It's a "killer replacement" for chimneyfans, in my view. Even this initial crude design, provides more than double the suction provided by traditional chimneyfans. It will easily hold a 4x4 inch paperclipping. 



All parts are standard plumbing, and a beachtoy inflator. The inflator moves a lot of air, with only moderate pressure.



The air-inlet pipe must end in between the downward column (to the chimney), and the air outlet. It can even just go into the narrower outlet, as long as a small portion around it connects to the air behind and around the air-inlet blowing pipe.

The air-outlet can not be larger in diameter than the inlet blow-pipe - hence the reduction for the outlet, that make them exactly equal. I don't know what would happen, if the inlet blow-pipe was smaller than the outlet ;-)



I bought all the parts ready made yesterday, and was running the T&inflator suction device in 10 minutes! Some standard plumbing-parts, a snippet of hose, and the rechargeable inflator, everything just off the shelves. Total cost (in Sweden) about USD 30!


I would be grateful for any suggestions for further experimentation, because I know nothing about "dynamics of flow", so I have absolutely no idea in what direction to look / go :confused:
 

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RE: Help! Dynamics of flow & new killer suction device!

Pauli,

Excellent work! By the way, this device is an excellent example of Bernoulli's Principle. The pressure of the stream of air inside the blowpipe is lower than the pressure inside the loco's chimney. Therefore there's a pressure differential at the outlet end of the blowpipe, and this causes a flow of air from the chimney to the stream of air from the blowpipe. The air outlet is small to increase the air velocity at that point which lowers the pressure of the stream of air even more.

At least that's how I understand it.

Steve
 

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RE: Help! Dynamics of flow & new killer suction device!

Wait a minute! I got the part about the restriction at the outlet backwards. Had the wrong image in my head. Now I've got to think about this some more.

Maybe the restriction is controlling the volume of chimney air that can get pulled into the blowpipe air stream from the pump, and this prevents "killing" the pressure differential between the two air flows that would be caused by allowing a large volume of higher pressure chimney air into the air stream?
 

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Discussion Starter · #5 ·
RE: Help! Dynamics of flow & new killer suction device!

Yes Henner, that seems to be the case! :) Only, my injected airstream is in the center, not around the circumference. The inside of "my" T reminds a lot of a steam water injector.

Having spent the day thinking, I think I'll try with a smaller inlet blow-pipe. That ought to increase the pressure in the inlet jet-stream (and probably reduce it's velocity). That should increase the difference in pressure between the "chimney" air, and the through-put airjet = increasing suction.
- But what is the importance of the smaller outlet? Maybe, thefull size fitting was so big in diameter (and short length?), that it went over a critical maximum, killing the vacuum alltogether. Proportions maybe have to be within reason / limits?

According to Henners link, a 1:25 ratio of airflow amplification is possible. In that case I don't I'm achieving more than 1/50 of the effect I ought possibly achieve! /DesktopModules/NTForums/themes/mls/emoticons/wow.gif
 

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Discussion Starter · #6 ·
I finalized the design yesterday. Inlet is now 4mm diameter, compared to outlet 10mm. It does not go far into the "T", and placement is not that critical. The 4:10 diameter ratio is probably due to the characteristics of a beachtoy inflator = low pressure, lots of air. With a compressor = higher pressure = I would guess the inlet should be considerably smaller. The "T" is iabout 20mm diameter (inside threaded to fit a 1/2" pipe)

The whole thing actually works as an auxilliary locomotive chimney! Anyway, it seems to work great. :D



Unfortunately, Aster has made my chimney 9,8mm inside, so I had to turn and drill a fitting pipe! /DesktopModules/NTForums/themes/mls/emoticons/crazy.gif


I really did experiment with all sorts of modifications. Extensions, airstream as circumference, all sizes of pipes and... :rolleyes:
 

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RE: Help! Dynamics of flow & new killer suction device!

I've seen a similar one made by David Outteridge of Colorado. I suspect it's an old design, and it seems to work quite well.
 
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