Craig Martell on wed 4 dec 02
Hi:
I'm working on some hybrid compound injectors for my propane fired salt
kiln and I have a question about placement. I know that if you turn the
mixer and venturi parts of a burner 90 degrees to the inlet port and you
fire with natural gas the orifice needs to be horizontal with the nozzle or
part where the flame exits the burner or the orifice must be below the
nozzle. My question is, does this apply to propane as well. Natural gas
is lighter than air and rises but propane is heavier and will not rise so
would it be acceptable to place the orifice in a propane burner above the
nozzle???
thanx, Craig Martell Hopewell, Oregon
James Bledsoe on wed 4 dec 02
C
in short, no
the flow of fire is up
and the velocity of the air mixture
over rules gas density
see Olsen's Kiln Book
for more
j
> Hi:
>
> I'm working on some hybrid compound injectors for my propane fired salt
> kiln and I have a question about placement. I know that if you turn the
> mixer and venturi parts of a burner 90 degrees to the inlet port and you
> fire with natural gas the orifice needs to be horizontal with the nozzle
or
> part where the flame exits the burner or the orifice must be below the
> nozzle. My question is, does this apply to propane as well. Natural gas
> is lighter than air and rises but propane is heavier and will not rise so
> would it be acceptable to place the orifice in a propane burner above the
> nozzle???
>
> thanx, Craig Martell Hopewell, Oregon
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
vince pitelka on wed 4 dec 02
> in short, no, the flow of fire is up and the velocity of the air mixture
over rules
> gas density. See Olsen's Kiln Book for more
James -
Olson's kiln book is great, but it is not right on everything. It is true
that the velocity of the air mixture overrules gas density, but the flow of
the fire is not necessarily up. The fire does not occur until the burner
tip, so the flow of the fire at the burner tip goes in whatever direction
the burner tip is pointed. It doesn't make any difference whether the body
of the burner and the orifice are above or below the burner tip.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
vince pitelka on wed 4 dec 02
> My question is, does this apply to propane as well. Natural gas
> is lighter than air and rises but propane is heavier and will not rise so
> would it be acceptable to place the orifice in a propane burner above the
> nozzle???
Craig -
As far as I can see over thirty years of kiln experience, this is an old
wives' (old potter's?) tale. 90-degree natural gas and propane burners
aimed into a horizontal port both work fine whether the body of the burner
extends up or down.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
Craig Martell on wed 4 dec 02
James sez:
>in short, no
Hi James:
Whaddaya mean No!? OK, I got to thinking about things after I read your
post and I realized that I wasn't thinking about the real issue with
venturis, which is moving a lot of air. Gas is no sweat because it's under
pressure but the air needs to be taken for a ride, so to speak. With the
orifice below the nozzle, or at least in the same horizontal plane, the air
will move more efficiently.
What made me think about orifice position was looking at some pix of forced
air burners that were downfiring with the nozzle below the orifice. That's
a different ball game though. You have a blower moving the air and draft
ain't that big a deal.
thanks for the response, Craig Martell Hopewell, Oregon
Paul Taylor on mon 9 dec 02
Dear Craig.
What is a hybrid compound injector?
I agree with Vince on the positioning of the burner block in relationship
to the nozzle does not matter - but obviously the relation ship between the
positioning and size of the primary air and the burner jet does. When I
built my kiln the venturi suppliers were very insistent on what the distance
of the tube that supplied the premixed air should be (the tube between the
burner block(head) and the jet. I suppose that a corner in the system would
effect some slow down in the air gas mixture, causing a resistance in the
primary air movement, but here - as usual- would the difference be
noticeable. So much in this subject seems to lack quantifiable measurement.
there is so little firm data. Because there is no firm data any bodies
opinion is right and what makes for more right is emotional certainty as
opposed to reasoning.
However I suspect I did not follow what you were asking about. I seem
to have entered into a new 'world' with this burner business and I am not
quiet sure with the terms. I also get answers to posts where the potter
replying has not understood what I was talking about, so the chances are I
have done the same .
I am now looking for a design or any help for a closed burner system for
forced air. Bailey's have the system I am thinking of on their kilns. They
call it an Air Gage Manifold system it looks simple, yet safe, The burner
heads are internal (not placed outside the kiln); but I can not work out
from the photo (resolution for screen only) how the safety shut off probes
are placed, or if there is just a pilot venturi working. If you want to see
it its the second burner description on the page (the first is the standard
outside burner head) http/www.baileyspottery.com/kilns/gasdesignsafety.htm.
Not that I plan to exactly copy baily kilns it's just that there design
proves that it is possible to fit the burner heads internally in a forced
air system.
Form your posts I gather that you feel that with enough thought you can
build a venturi system that utilizes air efficiency enough to make it as
efficient at mixing air and gas as in forced air burner - If you crack that
I would be interested too .
As for the forced air burner I am wondering what mixes the air and gas in
the forced air burner . just because it is forced through the same tube it
does not necessarily mix, or is the turbulence in the length of tube enough
to mix the gas and air.
On my venturi burners, on the end of the pipe that takes the premixed air
and gas, I use a ceramic cup burner. The gas and air is restricted then
opens out into a cup in which the flame burns - to stop the burner blowing
off . I do not know if this also prevents the burner blowing back as well.
Is this necessary or recommended for a forced air burner? From your question
I am wondering if the cup burner also restricts the primary air . But
thinking about it - could the gas coming out of the jets at 4ppsi be of such
force that a slight restriction at the burner tip matters very little.
As you have probably worked out that I have given up on the preheated air
and probably can not afford a nozzle mix system , But I am still inclined
towards a forced air system there by cutting out the damper and secondary
air setting as a variable and just having the relationship between gas
pressure air pressure and kiln pressure to adjust in my 'test cum small
production run kiln' (16 cu foot packing).
--
Regards from Paul Taylor
Fifteen minutes of fame is all we ever need.
http://www.anu.ie/westportpottery
> From: Craig Martell
> Reply-To: No title defined
> Date: Wed, 4 Dec 2002 18:22:11 -0800
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: another burner question
>
> James sez:
>> in short, no
>
> Hi James:
>
> Whaddaya mean No!? OK, I got to thinking about things after I read your
> post and I realized that I wasn't thinking about the real issue with
> venturis, which is moving a lot of air. Gas is no sweat because it's under
> pressure but the air needs to be taken for a ride, so to speak. With the
> orifice below the nozzle, or at least in the same horizontal plane, the air
> will move more efficiently.
>
> What made me think about orifice position was looking at some pix of forced
> air burners that were downfiring with the nozzle below the orifice. That's
> a different ball game though. You have a blower moving the air and draft
> ain't that big a deal.
>
> thanks for the response, Craig Martell Hopewell, Oregon
>
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