Making nozzles

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pezman
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Making nozzles

Post by pezman » Tue Dec 21, 2004 5:43 pm

I'm working on an engine design that derives from some experiments that I've done using torches. One of the things that I need to build is a nozzle that works kind of like a Bernzomatic torch head. I.e., a pin-hole nozzle in a tube that has ventillation holes around it. The high-speed jet of propane going through the nozzle entrains air and moves the gas/air mixture up through the tube for combustion. I guess that technically this is a ventiuri, although the roles of fuel and air are kind of reversed in this case.

At any rate, I managed to build a crude nozzle like this by putting a plug in a 1/4" merchant coupling (a tube that is threaded all along its interior) and then screwing in a plug that had a 1/16" hole drilled in it. The 1/4 inch tubing was selected because I'm able to thread a spark-plug into a "T" inorder to ignite the mixture.

THe hime-made nozzle works "ok", but not great. The biggest issue is that the 1/16" hole is a little too big for the flow rates that I'm interested in using. As a result, the speed of the gas exiting the hole is too low and the nozzle doesn't entrain enough air. The tube is also too large and the "aerodynamics" of the nozzle don't come close to those of an actual torch (even a cheap one).

Anyone know of a standard source of parts that could be used to build something like this? I'd need to be able to build it for well under $14 -- otherwise, I'll just get a bunch of torch heads, cut them up and thread them together.

Hank
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Re: Making nozzles

Post by Hank » Thu Dec 23, 2004 5:41 am

Hello- What I've done along the lines of what you're doing is to scrounge some old carburetors. The venturis can be drilled at their swaged ends and pushed into the throat of the carb. You can use the jets also. 1/16" is a lot of flow for something small. Can you tap a hole? Threads.
Hank

larry cottrill
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Re: Making nozzles

Post by larry cottrill » Thu Dec 23, 2004 9:41 pm

For very small engines, I would think that the spray nozzle from a mantle lantern would work. They are obviously designed for gasoline and produce a nice fine spray that comes out in a fairly broad cone at moderate pressure.

I'm sure they would be inadequate for anything very big, since camping lanterns will run a LONG time on the small amount of fuel they hold - so the flow rate can't be much. On the other hand, you'd get more by applying more pressure (than what you can pump by hand into the bottom of a lantern).

L Cottrill

pezman
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Re: Making nozzles

Post by pezman » Fri Dec 24, 2004 12:49 am

Thanks, two good tips.

I'm using propane, so the mantle nozzle might be a nice trick. My guess is that propane will exit a lot more quickly than the gasoline would.

I've studied the propane nozzle a little more closely and it turns out that my home-made nozzle was missing a few features.

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