Burners 101

[Mikey98118]

Wow; that takes me back. I had a two lbs. ball peen that I used so much in the ornamental iron shop, that the handle was bowed just right to match my left hand swing

My computer is playing games. Stuff dissappears, and then reappears...maybe its time for a defrag job.

[prtb]

Mikey,

 For your "Mikey Burner" Jet burner designs, can you explain how do you calculate the ideal gas jet inner diameter for a given mixing tube inner diameter?

Thought these forums, several times you quote an ideal jet orifice diameter for a particular burner diameter/design (usually the mixing tube inner diameter). 

• The 1/4" burner design has 0.370” inner diameter for mixing tube, and a recommended gas jet inner diameter  of 0.016” .
• The 3/8" burner design has 0.495” inner diameter (which happens to be closer to 1/2") for mixing tube, and a recommended gas jet inner diameter  of 0.019”.
• You have said for 1/2" burner ideal get jet  inner diameter  of 0.028” (which does not exist as a mig tip). is this 1/2" #40 pipe  book design? e.g.  nominal  #40 1/2" pipe (so google says inner diameter of 0.622"? )  
   

I'm suspecting 1:28 ideal ratio of propane:air is important in the calculation, but i can't work it out or find a reference.  I think i'm getting nominal pipe and actual ID sizes all mixed up.

Thanks,
Peter

[Frosty]

Welcome aboard Peter, glad to have you. If you'll put your general location in the header you might be surprised how many of the Iforge gang live within visiting distance.

Frosty The Lucky.

[prtb]

Location updated.  I'll likely be a flash "Flash in the pan" here.

I do think you guys are doing great work here. 

I'm looking at building a brazing hearth (wanted for another project) and i was researching refractory materials. I somehow stumbled across Mikey98118 posts on potential makeup of ITC-100. I said to myself "That guy knows his stuff". So started stalking his posts, found a book and the "Mikey Burner". 

So here I am... Researching burners.. down a researching rabbit hole.

Peter.

[Frosty]

"Flash in the pan" isn't the most desirable term to use to describe yourself when discussing propane forges you know. However if you like the web handle who am I to argue? 

I think Mike and I are well beyond ITC-100 for a kiln wash. Check out Wayne Coe's website for forge building materials in small quantities for reasonable money. Metrikote and Plistex are similar to and in some ways superior for gas forges than ITC products and better still WAY less money.

Recently Mike discovered and brought Veegum T to our attention and we're having to try really hard not to run in circles shouting wild ideas at our spouses who could care more about cracks in the sidewalks across town.

Frosty The Lucky.

[Mikey98118]

Peter,

You are correct that jet orifice diameters are tied to mixing tube inside diameters; that said, jet orifice sizes are also effected by gas/air mixture flow rates, so that a Frosty "T" burner will generally run one MIG tip size larger, than most other burner designs, including most of mine; the Vortex burner being a possible exception to the rule, as it is to everything else! Finally, the larger the burner the more that jet orifice sizes can be relaxed, but the smaller the burner the more critical they become.

You can find an early chart on page 22 of Gas Burners for Forges, Furnaces, & Kilns (available free on the web); it is eighteen years out of date, but still provides a starting point for jet sizes. In the end orifice diameters and lengths frequently boil down to personally tuning the fine points for your individual burner; not least because people decide to "just change the burner 'just a little bit" every way they feel like , and then expect it to act as advertised

What  kind of brazing hearth ? A small square of high alumina kiln shelf with two low walls of fire bricks, making a corner to bounce heat back from, or something more on the order of a classic English brazing hearth, with a burner fired chamber of ceramic chips, to keep the work close to working temperature, and an air/fuel hand torch to raise the work  up the final amount for braze welding temperatures where wanted?

[blacksmith-450]

 I did the «Oliver Upwind» but I opened the holes along the length.

I also added a sliding choke (not on the picture) but it is useless since I do not need to do any air restriction.

The only adjustment remains the flare.

Since i took the picture I filed the slots for a better look.  The jet is a no.60 hole.

I changed the flare... a simple 1inch pipe x 2 inches long.  The flame still good ! 

 

[prtb]

10 hours ago, Mikey98118 said:

What  kind of brazing hearth ? A small square of high alumina kiln shelf with two low walls of fire bricks, making a corner to bounce heat back from

Thank you. You just designed my brazing hearth.  
My plan wasn't really thought out yet, i got distracted by burners. I was thinking  insulating fire bricks base + corner with  2 or 3 additional loose firebrick to place around  as required.

 

10 hours ago, Mikey98118 said:

You are correct that jet orifice diameters are tied to mixing tube inside diameters; that said, jet orifice sizes are also effected by gas/air mixture flow rates, so that a Frosty "T" burner will generally run one MIG tip size larger, than most other burner designs, including most of mine; the Vortex burner being a possible exception to the rule, as it is to everything else! Finally, the larger the burner the more that jet orifice sizes can be relaxed, but the smaller the burner the more critical they become.

You can find an early chart on page 22 of Gas Burners for Forges, Furnaces, & Kilns (available free on the web); it is eighteen years out of date, but still provides a starting point for jet sizes. In the end orifice diameters and lengths frequently boil down to personally tuning the fine points for your individual burner; not least because people decide to "just change the burner 'just a little bit" every way they feel like , and then expect it to act as advertised

That table in the book is actually  what prompted me to ask the question. You have a "2-inch (probably)"  burner in the table. So i figured  behind the "probably" bit, there was some "magic mathematical air jet induction  theory with  formula"... or something.  Sounds like  there are too many contributing design factors to give an generic answer.

Anyway, I'm satisfied. Thank you for for responding.

I did come up with the following table by digging through you various "Mikey Burner" designs ( a few assumptions here).  

There's always patterns to be found in  these things. If the patterns scale and are even useful is different matter.

Thanks,

Peter

[Mikey98118]

2 hours ago, blacksmith-450 said:

I did the «Oliver Upwind» but I opened the holes along the length.

Thank your for sharing these photos, which show how small changes in a burner can make huge changes in the flame.

Folks the shortened club shaped neutral flame, is a fine example of  total combustion of a primary flame.

[Mikey98118]

Here's another ballpark number for you: the actual WORKING length of the flame nozzle, that is the amount of overhang of a flame nozzle beyond the end of the mixing tube, will usually turn out to be roughly equal to its inside diameter of the nozzle, plus somewhere between 1/16" to 1/8", depending on how large the nozzle is. The rest of the nozzle's length is just used to assure it stays parrallel to the burner's axis.

[Mikey98118]

On 7/12/2017 at 6:32 PM, prtb said:

I'm suspecting 1:28 ideal ratio of propane:air is important in the calculation, but i can't work it out or find a reference.  I think i'm getting nominal pipe and actual ID sizes all mixed up.

No; you may be trying trying to reduce my designs to mathematical formulae. but that won't work. In the real world burners have to be made from available parts, if possible. Even if you had the equipment and time to drill your jet orifices using wire gauge drill bits, you would find that there is no straightforward progression of sizes with them. You simply come as close as you can, and live with your results in an imperfect world.

[Mikey98118]

I am a notorious picky butt about burners. I practice this not to build a Bentley, but so that when all the things that can go wrong have done their worst, the result will end up satisfactory; that includes the equipment the burner is mounted in. The idea is to start off aiming high, so that you can live with the result.  Their have been burners of marginal design that put out marvelous flames, but I would rather not gamble on that; it is a rare exception; not a happy rule..

[Mikey98118]

Mixing tube lengths effect flame shapes

the "rule of thumb" on mixing tube lengths, whether eight times the inside diameter ("T" burners), nine diameters (most burners), or fourteen diameters (Vortex burners), are given to achieve sufficient mixing of a burner's gas and air mixture--primarily.

By considering these rules of thumb as a ballpark figures, mixing tubes can be lengthened and shotened to effect flame shape. Longer tubes will soften the flame; bringing it closer to laminar flow, which is important for brazing purposes. and as a method to help achieve stability in miniature burners.

Shortening the tube will harden the flame, which will shorten it; this can be very important to keep superheated oxygen from creating scale on the work. So, you would most often find yourself shortening the burner's mixing tube to stop scale formation in a forge with very limited space for the flame path; for instance in a short square square shaped forge, with a burner facing directly toward the work.

Just remember what the ballpark is for the burner design you are modifying, and change lengths in small increments. It should go without saying that you should not kid yourself about the results you see; if you can't do this, than stay on the beaten path, by following instructions.

This technique cannot be used to strengthen a weak flame. You get a strong flame by choosing a burner design known for producing them, and fottowing the designers instructions. You need sufficient potential in the burner's mixture flow, to have something to successfully manipulate. Kidding yourself is no substitute for being in the ballpark before choosing between a fastball and a slider.

[Mikey98118]

In a 3/4" Mikey burner, shortening the mixing tube from nine diameters to eight, will shorten, and harden, a leaf shaped flame into a club. Lengthening the mixing tube up to a maximum of 10" will soften the flame into a smoother laminar flow. How much lengthening or shortening will cause these effects changes by tube diameters. How much is too much? When you don't like the results you've gone to far. Isn't hindsight wonderful?

[(M)]

I am thinking of building the Oliver upwind burner.  Some guys have had great success--welding heats-- but i also seem to get the vibe that others say it is a piece of garbage.  does  it usually crash and burn (excuse the pun) or is it likely i can do some basic knifesmithing with it?

thanks

(M)

[MonkeyForge]

following the Oliver Upwind  thread it looks promising, depending on the time frame you want to build the burner in you could:

 

1)  wait for the detailed plans and instructions in the Oliver Upwind thread so you can replicate. ( or contact the builder directly)

2) follow another set of plans. (Frosty T burner here on the forum or Michael Porter's book)

 

NOTE: I have experience with manufacturing the T burner.

[Frosty]

Not to be a picky Butt Mike but I recommend 8x - 9x the ID with 8x being the minimum for a reliable burner and 9x about the point of diminishing returns. I tend to list 8x most often because of the number of folk in the more is better camp.

Frosty The Lucky.

[Mikey98118]

Please understand that this burner has been modified with air slots; not air holes. What other changes have been made I don't know; but that is a big one.

Frosty,

I stand corrected.

[Frosty]

[Mikey98118]

Frosty,

Just after I wrote you back, the Net go down.

[Mikey98118]

"Galvanized" pipe fittings are a YES!

Zinc coating, which is what "galvanized" usually means these days, is a good idea: unless the part is getting very hot. In that case, the coating can be stripped with a few hours in a pan of vinegar, or burned away in a charcoal grill. It is important not to say "no" to a source of threaded pipe fittings, in the face of ever shrinking sources. Furthermore, you are a lot less likely to end up with bottom-of-the-barrel fittings (with crooked threading), with a part you must pay a higher price for than in black pipe fittings.

[Square Nail]

1 hour ago, Mikey98118 said:

"Galvanized" pipe fittings are a YES!

Zinc coating, which is what "galvanized" usually means these days, is a good idea: unless the part is getting very hot. In that case, the coating can be stripped with a few hours in a pan of vinegar, or burned away in a charcoal grill. It is important not to say "no" to a source of threaded pipe fittings, in the face of ever shrinking sources. Furthermore, you are a lot less likely to end up with bottom-of-the-barrel fittings (with crooked threading), with a part you must pay a higher price for than in black pipe fittings.

Thanks Mikey! I had wondered if galvanized wold work for plumbing up to the burners!

[Mikey98118]

Zinc coated does fine, so long as you pay attention to how you use it; this holds true for any parts.

[Mikey98118]

One last thing about zinc coated pipe parts: 1" and smaller pipes tend not to quite fit inside each other; you need to file or power sand a few thousandths away from them, to get them to fit. When the zinc coating is gone from  the mixing tube and spacer ring, getting the flame nozzle to accept the spacer ring, and the ring to slide freely on the mixing tube becomes a whole lot easier; kind of helps make up for the effort of getting rid of the coating

[Donniev]

Finally diving into the gas forge side of things, and I have what is likely a dumb question. I'm planning on making a NARB, if I make a forge that after refractory is 8"*6"*14" will I need 2 t burners? I've seen that you need 1 3/4 burner for every 350 cubic inches, so I'm wondering if that holds true when making a NARB? I could scale is back smaller to say 6*6*10 so I only need to make 1, haven't decided yet.

Thanks