Vince Pitelka on thu 29 mar 07
Hank Murrow wrote:
> The way flame retention tips work is that they trap a small portion
> of the gas/air mixture behind a restrictive ring inside the tip,
> which has holes drilled in it to permit a small portion of the
> mixture to pass through. When the burner is lit, this smaller mixture
> creates an annular ring of flame that is protected against blowout,
> and through which the main fuel/air mixture must pass. this annular
> ring of burning gases keeps the flame on the tip and prevents
> burnback in the tube.
Hank -
Your description is certainly accurate regarding the Sticktite and some
other finely engineered flame retention tips, but there are a broad range of
far-simpler retention tips that hold the flame at the burner tip just fine.
The ceramic venturi tubes used on the old Norman updraft kilns feature a
sudden increase in bore diameter just shy of the tip, which causes
sufficient turbulence and accelerated mixing to keep the flame at the tip.
The incredibly popular Gaco MR-750 and MR-100 burners feature a fairly
radical sudden increase in diameter and then a slight constriction right at
the tip, and flame retention is very good. And then of course there are the
Ransomes, a fine old design, that feature a radical increase in diameter at
the flame-retention tip, with a cast iron grid of openings across the face
of the tip.
I still own a set of six industrial cast iron tube burners that I used on my
car kiln in California. I bought a manifolded bank of fifteen of them for
$15 back in the early 1970s at a Humboldt State University auction. They
had been salvaged from a big heating boiler. Each burner had a series of
grooved nubs just inside the tip, and a spring-steel ring snapped into the
grooves. They retained the flame very effectively. Based on that model, I
built pilot burners for several kilns, and used rings of Nichrome wire as a
flame-retention device. Worked great. That's what Paul Herman was
describing.
You wrote:
>You can make your own by welding a large washer inside
> the tube and about 5"8" back from the mouth. Be sure to drill five or
> six 3/16" holes in the washer to form the annular ring. And be sure
> that the center hole in the washer is big enough to pass full gas/air
> mix.
I second that. I did exactly that on a homemade powerburner that I used for
preheating cast iron before welding. I used a heavy steel pipe coupling,
welded a fabricated "washer" just inside the tip, and drilled a series of
holes around the opening in the center of the "washer." It worked quite
well.
So, it's apparent that just about anything that creates turbulence at the
tip can effectively retain the flame. It seems that many designs also
incorporate a slight or radical increase in diameter in the flame-retention
tip. I like the Sticktite design - it seems to have a certain grace and
finesse, but I cannot deny the efficiency of all those other designs.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Robert Klander on thu 29 mar 07
Apologies to the list, if the lower portion of this note has already
appeared...I sent it in the day that the server was being worked on,
and didn't see that it showed up in the archives...Thought I would
include it again with today's new information...
Some further tests made today showed improvement in the quality of
the flame on these burners. New feed lines from the manifold to the
burner restricted the feed of the LP enough that the 3/32 orifice
worked better.
I read some articles in the archives from Paul Herman and Vince
Pitelka from a few years back regarding flame retention devices.
Vince explained that the function of these devices was to cause
turbulence at the tip, to better mix the LP and the air, so that
combustion could be more complete. Most important reason for these
devices was to prevent the flame from being extinguished, but at
times could also aid in the prevention of back-burning in the tube.
As I remember, it was Paul that suggested that a loop of element wire
could be inserted into the end of the tube to create this
turbulence. Tried that today, and it seemed to work quite well.
Thanks again to Mel for making those notes, drawings, and photos available.
Well, we did the assembly and first test last night on the new
burners. All-in-all a pretty painless project.
Decided to use 2 inch pipe for the burners, and 3/8 inch pipe for the
feed. From the ball valve the burner lines up like this:
1. Ball valve 3/8 Bronze approved for Gas
2. 3/8 nipple to 2 x 3/8 in. reducer
I chose to tap the other end of the reducer in order to thread
another 3/8 nipple
into it to mount the orifice. The reducer was steel, so it was a
bit tough to get
the threads started, but they ended up very clean.
3. 2 in. T -- Drilled a hole in the edge of the middle port to
accept a self tapping screw
that will hold the primary air "flap" adjuster.
4. Mixing tube 2" x 12"
5. 2" Elbow
6. 2" x 6" tube
7. 2" coupling
We had a bit of a scramble looking around for the right connection to
get the fuel hooked up to
the 3/8 valve, but we finally found it and hooked it up. Then the
moment of truth.
Nice flame, once the air mix was fine-tuned. I believe I'll change
the flapper a bit, use something lighter weight
than the junction box cover..perhaps a canning lid? and also will
attach that with a longer screw, coupled with a
spring to help hold the flap in place.
There was periodic blow back or back burn, I'm not sure I have the
term stated correctly. I'm told that some of that
will be cleared up once the burner is directed into a kiln, and not
just burning in the open air...Also, I think I will try
mounting the orifice to a longer nipple inside the T, to move it more
downline, further into the port leading to the mixing tube.
Also, I intend to try a smaller size orifice, just to see if there is
much change in the operation.
We spoke about "retention nozzle" device that could tend to lessen
the back burn as well...a donut, perhaps 1/4 inch wide
that would have a series of small holes drilled all the way
around. This would be installed perhaps a 1/4 inch back inside the
2 inch coupling that is serving as the burner tip.
It is my intention, once the kiln is built, to add pilot burners and
baso valves to each burner.
Suggestions or comments are encouraged!
Robert Klander
Hank Murrow on thu 29 mar 07
On Mar 29, 2007, at 1:22 PM, Robert Klander wrote:
> I read some articles in the archives from Paul Herman and Vince
> Pitelka from a few years back regarding flame retention devices.
> Vince explained that the function of these devices was to cause
> turbulence at the tip, to better mix the LP and the air, so that
> combustion could be more complete. Most important reason for these
> devices was to prevent the flame from being extinguished, but at
> times could also aid in the prevention of back-burning in the tube.
Dear Robert;
The way flame retention tips work is that they trap a small portion
of the gas/air mixture behind a restrictive ring inside the tip,
which has holes drilled in it to permit a small portion of the
mixture to pass through. When the burner is lit, this smaller mixture
creates an annular ring of flame that is protected against blowout,
and through which the main fuel/air mixture must pass. this annular
ring of burning gases keeps the flame on the tip and prevents
burnback in the tube.
The Eclipse Co. makes a very nice line called "Sticktite" that work
beautifully. You can make your own by welding a large washer inside
the tube and about 5"8" back from the mouth. Be sure to drill five or
six 3/16" holes in the washer to form the annular ring. And be sure
that the center hole in the washer is big enough to pass full gas/air
mix. You'd need to experiment with this.
Cheers, Hank
www.murrow.biz/hank
Hank Murrow on fri 30 mar 07
On Mar 29, 2007, at 8:25 PM, Vince Pitelka wrote:
> Hank Murrow wrote:
>> The way flame retention tips work is that they trap a small portion
>> of the gas/air mixture behind a restrictive ring inside the tip,
>> snip.......
>
> Hank -
> Your description is certainly accurate regarding the Sticktite and
> some
> other finely engineered flame retention tips, but there are a broad
> range of
> far-simpler retention tips that hold the flame at the burner tip
> just fine........snip.......
> So, it's apparent that just about anything that creates turbulence
> at the
> tip can effectively retain the flame. It seems that many designs also
> incorporate a slight or radical increase in diameter in the flame-
> retention
> tip. I like the Sticktite design - it seems to have a certain
> grace and
> finesse, but I cannot deny the efficiency of all those other designs.
Dear Vince; Thank you for amplifying my limited description of how
flame retention tips work.
My experience did not include the ones you mentioned.
Cheers, Hank
www.murrow.biz/hank
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