Need a little help with burner tuning.

69_knives

69_knives

Joined
Nov 20, 2008
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I built this burner for my small HT forge and being not very experienced with burner design I thought I would ask a little help from the more experienced folks here.

The specs for the burner are 0.031" jet, 4" of 1/2" sched 40 burner tube with 1/2"-1 1/4" bell reducer and 1 1/4" close nipple to complete the burner tube I threw a chunk of 3/4" (I think) iron pipe on the end for a flare because it needed it.

I've uploaded a video of the burner working and myself holding the tube and adjust, moving it etc. It seems to have a bit of a 'jitter' effect that I wonder what needs to be done to fix it. This is at 2 PSI.

http://www.youtube.com/watch?v=iDj10djb574

I did not widen the flare, it is just a straight piece of pipe, I wonder if I should widen the flare tip a bit to fix the jittering.

Here's a pic of the burner and flare tube:

GEDC0421.JPG



Thanks for any thoughts or input.

Steve
 
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I don't have a needle valve, do I need one?

I forgot to mention that the burner was at 2PSI on the regulator in the video.

made correction in original post.
 
I think you have made the burner too complicated,have you tried it in the forge?Check out ron reils or larry zoellers sites----Regards Butch
 
It's based on the Ron Reil design, the only difference is the jet depth is made to be adjustable. I do like the 'Z' burner though, looks simple.
 
Steve:
Have you set the jet in the pipe, conect it to a hose or some water source, I put tape on the pipe and shoved the garden hose up aginst it, course it was summer but if you get a chniook in.
Anyways with water you can aim the jet exactly down the middle of the pipe. Also go over the inside of the burner pipe and anything downstream of the jet and remove any burs or rough spots which will mess up the gas/air flow, same with the jet opening, make sure it is clean of defects around the opening. This might help, also what was said the videio looks like the gas pressure is to low, try 10 psi or so. Your flair does not look flaired but you will not use it in the forge anyways. You can cut the flair with a hach saw in strips and bend the strips out to get the flair effect.
Once you get it going you can mess with the air gas mixture a little more.
I don't have a needle valve in mine just agjust the regulator.
Order up some nice global warming for me I will be in Cowtown next week.
Cheers Ron.
 
http://www.youtube.com/watch?v=J-hKs_D5Mzk

That's a video of the new burner and the new forge, first firing to burn off the chemically bonded water. It was burning just like that for around 2.5 hours after about a 2 hour warm up.

Seems to work OK but stil has the jitters, I wonder if the regulator could cause that for some reason. The flame is inside the flare tube so maybe the flare is too big??

The propane tank is a bit low and it is below freezing so I suppose that is another reason it could run funky.

Gedc0425.jpg


Gedc0432.jpg
 
2PSI is too low. Raise the pressure. If using a near empty 20# propane tank at sub-freezing temps, you are going to have pressure problems. I would try and flare the burner tube at the end a bit, but what you have should work fine with enough pressure to create the venturi. You can grind the inside of the flare with a rotary burr in a hand drill to taper it out.

The sputter is the venturi collapsing ( backflash). If it is bad enough (Gas pressure way too low) , the flame jumps completely back into the burner tube and makes a screaming noise. Obviously, that is not desirable. If it is just a little low on pressure, the flame sputters.
Stacy
 
I've had venturi forge burners act like that when fired in the open atmosphere. If you install it into the side of the forge so the end of the burner is even with the inside of the heating chamber, the stutter should stop.
 
Thanks Guys!

I'll fill up the tank today and perhaps play with the pressure and flare a bit. I really like the even heating I get from the burner entering from the end, I haven't decided yet if it will be in the front or rear but I think I like it in the rear (um, what?) :) because it's a fairly small diameter chamber and the burner would be in the way in the front.

It's a bit of a shame if I have to use more than 2 PSI for this as it seems to be just right to keep it at around 1500F or 815C for HT and with any higher pressure seems like most of it just blows out the end. Ah well, it still early and the forge isn't finished yet, I am going to do a wrap of expanded metal and fold it around the ends then another layer of insulation which will likely be refractory cement as well but lightened a LOT with perlite, this should make it cool to the touch on the outside, as it was at the end of the 2.5 hour burn a ball of spit took about a minute to evaporate off the top. I will likely use a steel pail for the outer form.
 
Make a blown burner, and run it at any temp you like. Venturi burners are hard to keep from backflashing at 1500F.
Stacy
 
I ran into the same problem when I built my burner. The venturi burner design needs a choke plate on the back end to tune the amount of incoming air. Unfortunately with that design, you will have a difficult time figuring out a choke plate that will work. If you scroll down to the bottom of this page:

http://andersonknives.ca/Digitally Controlled Forge.html

you will see the flat round choke plate on the back of my burners. They are just a piece of plate with a threaded hole in the center and can be adjusted by screwing them in or out on the threaded rod. I can run my burners at any just about any pressure and maintain a rich/neutral/oxidizing atmosphere in the forge by simply adjusting the choke plate.

Try to evenly choke some of that air off where it enters the back of the large threaded nipple and see how that works. I think you will find you will have to redesign the burner so that a choke plate can be used.

edited to add:
In case you aren't aware of it, you don't want the burner to point at your steel when its in the forge. Plan ahead to aim your burner at the roof of the forge on a tangent so when the flame exits the burner, it swirls around the roof, down the far side wall, and is dispersed by the time it rolls across the floor of the forge. This promotes even heating and will keep you from getting hot spots on the steel. Don't forget to account for the thickness of your insulation on the inside when aiming the burner. If you are using satinite on the inside, you can form your burner "flare" right in the satinite. This prevents burning the tip off your burner constantly.

Brad
www.andersonknives.ca
 
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