[TheForge] propane forge

[Jerry Frost]

The efficiency difference I'm refering to has nothing to do with the burn
efficiency, I'll get to that next. <grin>

A jet ejector is a better inducer than a linear by around 30%.

Feed a linear inducer/amplifier 1 cfm of primary pressure and the output
will be up to around 20 cfm. a 1:19 ratio.

Feed a jet ejector inducer/amplifier 1 cfm. primary pressure and it's output
will be around 30 cfm. a 1:29 ratio.

As to why a jet ejector will produce a more efficient flame, I have a
hypothesis or three.

First, it's much easier to tune as it's output is so much more than you need
for a neutral flame. You just plain have wider tolerences to work within.

Second, having the air intakes at 90* does increase turbulence and aid
mixing, I agree.

Lastly (for my limited imagination anyway) has to do with a jet ejector's
higher amplification rate. A jet ejector, even a home made one delivers much
more air than desirable for a neutral flame so we run it choked. Whether we
add a choke device or just build it with smaller intake ports for a proper
air/fuel ratio doesn't matter, the device is choked and running under a
vaccuum. A respectably strong vaccuum in fact, these things are used in
industry not as burners but to produce large quantities of strong vaccuum.
We all know liquids evaporate (vaporize) faster in a vaccuum so does
propane. This really aids mixing.

Outside of the basic characteristics of jet ejector and linear inducers
there is something else I do to aid mixing. I do not try for the jet that
will allow me to operate it at low pressure, I use a smaller jet diameter at
higher pressure. From my experimenting a higher pressure jet produces a lot
more turbulence, a stronger vaccuum and much better air/prop mixing.

In reply to Marc's post regarding the Robert Grauman's Side Arm
configuration, I do it differently. (of course<grin>) The jet ejector I'm
running right now is also made from a pipe "T" but the tube's mounted in the
side position, not on one arm. I run it as a "T", not a single side port.

Industrially, single side port jet ejectors are most commonly used to
produce vaccuum. As Ron Reil discovered experimenting the output is an
asymmetrical flame, it leans against the far side of the tube from the
intake. In Robert's foundry furnaces this isn't much of a problem in the
confined space and strong vortex environment. Though I haven't tried the
experiment, Ron wasn't very satisfied with the way it heated his forge.

I run a 1" burner tube in my forge with a 1 1/4" "T" and a 0.040" mig tip
jet. I assembled the tube and "T" then chucked it up in my lathe and drilled
the "T" to tap for 1/8" pipe.  As Marc points out, lamp parts have very
similar threads to 1/8" pipe. Pipe thread being tapered and lamp thread
being straight means you need lock nuts to keep it tight.

Anyway, I spent about $10.00 not counting the regulator, hose, gage, etc.
and about half an hour putting it together. It doesn't have a choke and runs
just a little rich producing a couple inches of pinkish orange flame from
the front of the forge at heat. Zero scale formation in the forge.

Frosty
------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.


----- Original Message -----
From: "Shannell Sugrue" <sjs@ihug.com.au>
To: <theforge@mailman.qth.net>
Sent: Friday, September 06, 2002 9:05 PM
Subject: Re: [TheForge] propane forge


> I think its about the way the air and propane mix better with the air
> entering at such an angle, apparantly its actually quite hard to get the 2
> gasses to mix well.
>