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Burner flame goes out, help please


apache1649

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Hi, I recently built my first burner, it's a linear venturi style. I have two problems. Firstly, the flame is very billowy, not a sharp cone. Second, if my fuel pressure goes too high, the flame jumps away from the tip and goes out quite rapidly. I'm using a 20psi regulator, no gauge but I'd guess I make it to maybe 12psi before the flame goes out. I'm not sure how to solve either of these problems. The nozzle is centered and straight. I'm at work now but will post pictures when I get home. Any help is much appreciated.

 

Edit: it's naturally aspirated propane

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25 minutes ago, Frosty said:

Billowy yellow indicates it isn't drawing enough if any combustion air, so of course it blows out if you turn the propane psi up. 

What size is the mixing tube and jet?

Frosty The Lucky.

Mixing tube is 8"×.75", jet is about 2mm, set inside the tube maybe a quarter inch. Venturi is a 1.5" to .75" reducer with four .25" holes drilled in it, tip is a 1" to .75"

Edited by apache1649
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What you are describing appears to be lack of proper air induction (as Frosty mentioned).

Jet size and location are critical for most naturally aspirated burners.  Were you following a certain design or just winging it from photos or a video?  If you got the design from someone I recommend you ask them about tuning.  If you are on your own, you might consider replacing the existing orifice with a MIG gun tip.  At least these come in discrete sizes so you will be sure what you have.  Most likely a .030 or .035 tip is what you want (note that 2 mm is 0.08", while the actual ID of a .030 MIG tip is 0.038").  Your orifice is most likely too large, if your measurement is correct.  You may even need to go down to a .023 tip...

Then you need to vary the position of the tip fore and aft in your inducer section so it brings in the correct amount of air at the firing rate you are looking for.  Not sure the holes in the inducer section are helping you at all.

Good luck.

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You need to read something about the hows and whys of burner design, or else strictly follow the instructions for a proven burner design. It would be endless to go into how much is wrong with that burner. But just for starters, a millimeter is about thirty-nine thousandths of an inch. So, your gas orifice would serve better on a King size burner :rolleyes:

How big? Start with 2'' pipe nipple, about two feet long as your mixing tube.

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Apache: Mi Imigo, do NOT buy more stuff until you have some idea what's needed. Have you even decided the volume and shape of the forge? Without knowing that, it's like building a high performance engine without knowing what you're putting it in. 

Once you've done more reading and decided what you need and want it's time to make a list and go shopping.

Let us check out your plans and list before you spend money though, you won't regret it. Honest you won't. ;)

Your evaluation of what improved your current burner's performance is inaccurate. The 0.023 jets improved the air: fuel ratio. Moving them closer to the mixing tube reversed some of the improvement. If you keep buying and building mistakes you are going to slow your building of a working forge. Too many guys give up in frustration by rushing. 

Frosty The Lucky.

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So, with some more reading, a few measurements, and some modifications (I have a TON of stuff in my garage, so I dont have to buy much at this point) I've shortened my nozzle, allowing me to use the largest fitting to sit in the set screws for some more adjustability, and moved it back quite a bit. I also cut some slots more forward in my venturi, as my fitting was taking up a lot of space. Burns MUCH better now. Thanks all for helping, will post new pictures when resized as well as my plans for the forge.

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What are you reading?:wacko: It's certainly not from one of the people who understand NA burners. Like moving the jet deeper into the burner, cutting slots ANYWHERE is inhibiting several useful necessary: 1, It's raising the pressure in the mixing tube lowering air induction, 2, they're disrupting both laminar flow and the vortex further reducing induction. 

Frosty The Lucky. 

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Please listen to Frosty; he's one of those guys who knows what he's doing :D

If you deliberately start with the MIG tip too far away from the reducer's small exit hole, then carefully observe, as you move it forward toward that exit, you will be able to see the flame improve steadily. BUT, once the gas orifice at the end of the MIG tip moves past the "sweet spot," you will find the flame changing, unexpectedly,. There for, move the gas tube forward as far as the sweet spot; then, look for further advantage by changing something else.

Also, you need a double role of screws in the reducer fitting, so that you can keep the gas tube centered and PARALLEL to the burner's axis.

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I recommend you read it through a couple times and get back, details have changed Mr. Porter has learned some new tricks but the basics remain the same. 

Stick around and be patient the things aren't that difficult to understand or make but it's a serious PITA figuring them out from scratch and worse having to sift through bad info too.

Frosty The Lucky.

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15 hours ago, apache1649 said:

Just found a reference to the book Gas Burners for Forges, Furnaces, and Kilns, going to start reading that presently.

You realize you've been speaking to the author of that book and he has been telling you to please listen to the person you are ignoring.

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  • 4 weeks later...

Just finished my half inch burner from mikey's book, had to take a break from it for a while due to a broken sewer line, flooded basement, and some car troubles. Still playing around with tuning, but I thought I'd check in here and say thanks for everyone's advice, and see about any updates to the design as I'm planning to build another that's a bit cleaner, and I know someone said that there have been some changes made to the designs found in the book. 

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On 3/17/2020 at 7:12 PM, apache1649 said:

Mixing tube is 8"×.75", jet is about 2mm, set inside the tube maybe a quarter inch. Venturi is a 1.5" to .75" reducer with four .25" holes drilled in it, tip is a 1" to .75"

Your most critical problem is a gas orifice diameter that is way to large; an orifice size of around  .031" from a 1-3/4" MIG contact tip (Metal Inert Gas) from a wire feed welder will do the job.

Next, the reducer fitting should be a minimum of 2" to 3/4" (bigger would be better, but 2" is the minimum).

Finally, a reducer fitting used as a flame nozzle has a fifty/fifty chance of working acceptably, and a zero chance of working properly.

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