[TheForge] On the table monday.

[Kathy]

Frosty,
That was probably just because the smoke from the burning blocks obscured your
vision and generally distracted you; Get a gas mask and try again. Onward, ever
onward for science! :-)))

One of the things I like about the external baffle is that exhaust gases help
turn the baffle into an IR generator, rather than merely an IR mirror. The main
reason I'm giving a second look to gun burners is their ability to use natural
gas (low pressure methane). Methane, hydrogen, and butane are the three fuels
which benefit most from oxygen enrichment. However hydrogen is costly,
dangerous, and requires expensive handling equipment. Hydrogen regulators either
cost a fortune or leak like sieves, and the safety equipment mandated for any
area where hydrogen is used indoors is also a nightmare. Inexpensive butane in
DOT cylinders is not available in the Northern USA. I was quoted $250 by my
local welding supply dealer for a standard five gallon DOT cylinder shipped to
Seattle ( the #%!#$%*!). So, at last we arrive back at inexpensive humble old
methane. The difference between the price of propane and methane can be used to
purchase oxygen for a 20% enrichment, which will boost the flame temperature of
natural gas 1000 degrees. Preheating the fuel and oxidizer boost your numbers
about six or seven hundred more, allowing you to cut back on the enrichment to
zero percent and still beat out a propane flame for heat.

I can't see a recuperative wall doing much good with a gas fired forge; after
all, the gas must be displaced by the incoming flame, or the burner idled back
to accommodate such extreme hang time. Now, on an oil fired forge it would be
another story; there you  have an excess of complex hydrocarbons to combust, and
the partial doubling of the internal chamber would give the added benefit of
superheating the combusting oil vapors. There was a double chambered oil fired
furnace that was discussed at length on Castinghobby, when oil burners made
their first thread on the group (spring or summer of 2003). Apparently such a
design has been used with great success in the past.

As to burner aim, I have noticed that vertical down works nicely in small forges
with burners running at minimal pressure, but aiming at a tangent is the way to
go if you want to produce hi heat at moderate expense; it should also match up
well with a recuperative air scheme. Probably, I would employ a ceramic burner
ring with tiny gas holes drilled at a tangent, and incoming heated air openings
piped through it, and aimed in parallel to them. Both fuel and air would be
preheated, but unable to combust until they mixed in the firing chamber. Even
oxygen enrichment can easily AND SAFELY be employed by adding a line into the
air heating chamber; what more could you ask? Of course, oxygen enrichment
probably sends caution flags up immediately about scaling, but you must remember
that I'm always thinking multiple use (forge/furnace). When my forge is rotated
from the horizontal to the vertical position, a different baffle will be swung
into place over it, serving as an adjustable sized opening, an IR generator, and
a drying rack for materials to be added to the charge.

So, why didn't that old fart Frankenburner go for this setup in the first place?
All that natural gas pipe really slows you down when trying to reach an off site
location :-) It is also not cheap to build, nor very flexible in use (you aren't
going to remove the gun burner for use as a hand torch), and finally, such a
piece of equipment can't simply be tucked away under the bench by novices just
starting out in their garages.
Mikey


-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net]
On Behalf Of Jerry Frost
Sent: Friday, April 27, 2007 5:26 PM
To: Sponsored by ABANA
Subject: Re: [TheForge] On the table monday.

I'd been thinking about, sketching and playing with Leggo blocks for some time
trying to come up with a baffle system to do what you describe. Or at least I
think it was what you're talking about. I didn't get a Leggo model to actually
work very well though.

I don't recall who on this list suggested the air curtain but it pretty much
ended my playing with the baffles. Of course it requires a gun burner forge but
I'm a lot less concerned with combustion by products in the portable. The shop
forge on the other hand is going to be a relatively permanent indoor
installation.

The air passage between the inner and outer walls of a recuperative forge can be
offset by reducing the overall thickness of the insulating outer layer, because
the heat exchange aspect of a recuperative forge or furnace should result in a
good reduction in heat loss through the outer shell anyway? Just a thought. I
had considered using parts from sagers in order to reduce the thickness of the
inner wall; also, an IR reflector on the hot face side of the outer wall would
do a lot to reduce heat loss by re-radiating IR back to the cold face side of
the inner wall. Also, the fact that only heating air is passed by the reflector
coating, would keep it from losing efficiency through attrition.

My experiments with baffles were not only incomplete but blowing smoke into a
Leggo model probably isn't such a good model. It did model a recuperative
(double) wall pretty well though so maybe they were working better than I
thought but I don't know. What I did determine about the recuperative wall forge
is it better be a shop forge as it's going to be pretty big. 
The total thickness of the forge walls is a much larger percentage of the over
all forge size. Just adding a 1/2" annulus adds about 1 1/2" to the wall
thickness or 3" to the OD of the forge. anyway, the bigger the furnace, the more
practical a recuperative wall becomes.

Being able to close the doors on a forge for better heat and reduced fuel
consumption are also excellent arguments for gun burners. With the doors closed
even partially the baffle system in my Leggo models worked well. Of course if I
closed the door all the way it didn't need baffles at all.

I've always thought the burner nozzles should be aimed to keep the fire in the
forge as long as possible.

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

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Kathy" <keporter at comcast.net>


> Frosty,
> I had not even considered an air curtain. I am planning on combining 
> an internal shoulder (ring of refractory to compress the flame path's 
> spiral) with a two (upper and lower) part external baffle. The lower 
> half is affixed to the forge and uses a half ring to prevent exhaust 
> from escaping any way but upward, .while still allowing the baffle to 
> be placed at a 1 1/2"
> distance beyond the forge
> opening. The upper half is movable and has a small opening at its base 
> for stock to be slid through it; to insert or remove scroll ends, the 
> upper baffle slides up and down.  Escaping IR is bounced back into the 
> forge, and exhaust gases are forced upward and away from the operator. 
> The back end of the forge has a small hinged door, allowing stock to 
> protrude from both of the forge's ends, but remaining closed most of 
> the time. Running the forge with a single opening most of the time 
> allows the burner or burners to be aimed at a backwards facing 
> tangent, increasing hang time for the spiraling gases.
> Mikey
>
> 

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