Jump to content
I Forge Iron

Burners 101


Mikey98118

Recommended Posts

  • Replies 3.6k
  • Created
  • Last Reply

Top Posters In This Topic

You won't find the kind of general burner or forge discussions you're looking for in that text; it was a how-to book.that is one of the reasons I discuss these thing here on IFI. The first thing you might try is to deliberately use an over sized MIG tip, like an .035" just to see how it affects the problem. It may be that you will be okay with that fix, or you may have to put up with less than ideal performance from the forge. Of course, you can pull the burner and check its performance outside of the forge; if it runs okay that way, and if you can't get satisfactory performance within the forge by a tip size adjustment, the next possible fix is to use a softer burner design, like a "T", or use a smaller Mikey burner; say a 1/2" size. I have found the common reason for burners snuffing out in forges is too large or too many burners for a given space.

Link to comment
Share on other sites

  • 2 weeks later...

A balance of swirl and friction

In conversation about the importance (and amount) of spin" in burner designs I wrote back to Another Curtis

"Yes; too much spin will make a short bushy flame. Too much spin can be caused in the design, and/or be caused be too little mixing tube length to allow the spin to be sufficiently slowed do to friction in the tube." We were writing of flame swirl.

This may sound strange at first glance, since the usual result of an over short mixing tube is a weak flame do to insufficient mixing of fuel gas and air. But a hot burner design always features enough--or far more than enough--swirl to insure sufficient fuel/air mixing.

A pattern of three rectangular air openings, with proper beveling; a combination of side air openings with a down stream constriction from a funnel shape; or a funnel shape air opening with an impeller fan, can all need added mixing tube length to provide enough friction to slow down the swirl of its incoming fuel/air mixture.

As with all things involving burners, balance is needed.

Link to comment
Share on other sites

Why linear?

I have stated that linear burners are more forgiving than jet-ejectors, and that this should allow them to go on being stable at much smaller sizes than burners with side air entrances. So, why are smaller burners less inherently stable than larger burners? They're not; A 1/2" burner of any given design should be just as stable as a 1-1/4" size; However a 3/8" jet-ejector burner won't be, unless every part is machined by a professional. When hand built from available materials, a 3/8" jet-ejector burner becomes something of a trial to construct, while a 1/4" burner turns into a nightmare.

So why should a linear burner be different? Simply because linear burners are built with easier parts to get right; long before the industrial revolution craftsmen built wonderful clocks; they did so with a lot of knowledge and mountains of care; not to mention special tools; anyone can apply that same formula to miniature burners today; a more forgiving design is the practical path. If you wanna go small; go linear.

Link to comment
Share on other sites

7 hours ago, Mikey98118 said:

Grinder,

How did your problem turn out?

Hey: Thanks for the interest. I just bought two new gas shut off valves, and hoe that will help. Apparently, i was using regular water ball valves. Not sure if it will make a difference. Hope to get it back together this weekend. I've been reading a number of post regarding burners and it seems there is a lot more to this than I originally thought. Tri tri again. Will repost with my results. soon. 

Link to comment
Share on other sites

In writing back off-group to one of the guys about his latest burner I wrote the following:

"Okay, there may be just a hint of secondary flame; with that background I can't be sure whether there is only a hint or very little; either way that is a great flame to put in a forge. Please do me a favor and show that flame in the Burners 101 thread. It's a great flame, which I would be proud to produce. Forget perfect flames with perfect shapes. A great flame is all you want in a forge; or in a hand torch for that matter. You may quote me on this. While you are trying to refine your ability to judge flames, note another thing that the photograph shows; the flame retention nozzle is glowing orange; that is also a sign of a very hot flame with mere propane for fuel."

I didn't mention that the faint streaks of orange in his flame could also be another sign of a really hot flame, because that is very dependent on what material the flame retention nozzles is made of, the presents of burrs, debris, or even oil in the nozzle. Whether or not he shares his photo there, the conversation brings up some points:

Frosty is fond of noting that perfection is the enemy of the practical, to which I could reply that the practical is the enemy of perfection. Who is right? Obviously we both are. And bother views can also be quite irrelevant. Perhaps it is best to keep them in balance, and decide for yourself how much of either goal you want. Not that his view hasn't modified mine considerably. How nice a flame do we need? A perfect flame is attainable, but only for seconds at a time. A near perfect flame is sustainable, but is it needed? No; once you have a hot and clean enough burning flame to run your forge up to welding heat with no gas left not combusted leaving the exhaust, you have arrived. Can you do matter with a perfect flame? Yes of course you can. But improving the flame, like improving the forge is an endless task. Once you reach good enough, remember the law of diminishing returns, and go do something else :)

Link to comment
Share on other sites

Here is the flame Mikey is referring to:flame2.thumb.jpg.a6b1e2ccf4eb2a95e716166af6482e8e.jpg

 

I have been experimenting with burners air inlet shapes to learn.  This is a 1/2 inch burner with an 0.025 mig tip for the jet.  The nozzle is a temporary nozzle as there was some excitement to see it lit, so the flame is not concentric.  You can barely make out the vice grips holding the tabs on the stainless sheet metal nozzle in the lower right.

I will be adding a better nozzle, playing with mix tube length and changing the jet size to further experiment.  I will try to get better images without the back drop clutter.  I was so focused on getting an imagine which had the color I was witnessing that I didn't think of back drop.  

This particular burner was an attempt to force the induced air to spin down the mix tube to see what it does to the flame.  At low pressures ( < 5 PSI), the spin is very obviously noticed in the flame but at higher pressures ( > 10 PSI) the flame moves fast and straight.  I believe I remember reading Frosty talking about toroidal flow down the mix tube so I am not sure if the spin helps or possibly gets in the way of toroidal flow.  It seems to burn very well.  I took it up to 20 PSI which burned stable and angry.  

In my current forge, I have a modified side arm burner.  It's flame is much shorter, slower and bushier.  The forge gets hot enough to weld and the burner does not produce a flame like in the image.  This experimental burner flame is very straight and longer.  I am not sure if that is good or bad as far as forge use.  I also have not experimented with the mix tube length to see how it changes the characteristics.

 

 

Link to comment
Share on other sites

Man that IS a pretty flame, I LIKE it!

I have nothing against striving for perfection, just nothing this side of the reaper is going to achieve it.

I tend to draw the line when effort starts creeping too far down the slope of diminishing returns. The T burner is just what it's supposed to be an effective burner that requires entry level shop equipment and skills. 

Seeing as I'll have proper wiring in the shop in a bit it'll be worth dragging the lathe, tooling and instrumentation out and setting it up. Then I could measure and reproduce the golden bullet T burner. Unfortunately the T isn't really designed with the machine shop and the journeyman machinist in mind.

It's just right as she is, a difinitive example of, "good enough."

If I'm going to shoot for as close to perfection as I can hit, I'll be setting up a spinning lathe, cut split tooling and be using Bernoulli's calculations and it'll be high temp stainless steel. Well, I'll have a buddy who can do the math do the calcs. It will NOT be an entry level, minimal shop skills device. ;) Heck I might even polish it. You might just need those tinted safety glasses. Ooooo SHINY!B)

Frosty The Lucky.

Link to comment
Share on other sites

Could you explain what would be the Bernoulli calculated burner?  Would I be correct in guessing that you are speaking of a linear burner with a trumpet shape inlet and a long precise tapered outlet from the restriction point?

Speaking of those tinted safety glasses, when would anyone advise they are required?  I remember reading something Mikey said about UV danger only being with flame temperatures above several thousand degrees.  I took this to mean I am not in danger of blinding myself so I prefer clear safety glasses and I don't tend to stare into the forge but mostly just so I don't cook my face.  My forge runs in the upper orange to yellow range.  I forge welded and  noticed that my cheeks got a light burn to them but was not sure if this was a UV thing or an IR thing but it made me want to ask the safety questions.  I dealt with some health stuff that now requires I be mindful of my sun exposure and so I cover bare skin when welding.  I wasn't sure if I should be concerned with the forge or if my cheeks were just from being too close to the fire as I tried to watch the flux on the metal.

I do like the experimental burner.  I have read every word I can find on reading the flame so that I can experiment with burners and have a clue what I am looking at.  I originally sent the image to Mikey to see what his read of it was and learn from that read.   

Link to comment
Share on other sites

Bernoulli wrote and explained about fluid dynamics very well. His principles and formula are often used to design anything that has liquids or gasses moving over, under around or through. Were I to design a linear then yes I'd certainly use Bernoulli's formulae to calculate the optimum foil designs. If I can figure out how to apply them I'll use them whatever I build. I just have to find someone that can do the math, I can't

Do not let Mike and I talking smack at each other send you off on wild goose chases. 

No tinted eye wear unless you're dealing with arcs or direct sunlight, no UV coming from what we do. I referred to tinted shades because I was threatening to polish the burner so bright it'd be blinding. Friendly smack talk. Yes? 

Frosty The Lucky.

Link to comment
Share on other sites

To be honest, I haven't found any that I like and none of the welding suppliers in my area carry IR glasses in stock. The recommendation made to me was shade 2 or 3 and I have a pair of welding glasses for O/A welding in shade 3 but they are too dark and totally mess with the color of the steel. I try hard not to stare into the fire when forging with either coal or propane but it's hard not to.

Link to comment
Share on other sites

I have developed the routine of standing back from the forge to not cook my face.  Does anyone happen to know if distance is enough protection from IR and if so, how much distance?  If not, does anyone have a recommendation on shades?  I am not happy with the green O/A shades either and would like an alternative.  If I have to, I don't have to like it but safety first and all that.

Link to comment
Share on other sites

As it'll be fairly broad spectrum infratred lightbeing generated in the forge, it's a matter of what part of the IR youre looking to block.  Polycarbonate (standard safety glasses) already block the farther end of the spectrum since they absorb in that band.  Regular glasses reflect in the mid to long IR as well.  Just by wearing something over your eyes you're already significantly cutting the amount of energy going into your eyeballs.  The near to short IR range is invisible to us,  but corresponds to over three times the visible spectrum.  So if we make some (inaccurate) assumptions you're getting 3x the radiated energy you can see.  

All of the above isn't considering the spectral absorption bands of the materials in question or the gases present in the atmosphere.  I would have to go back and check some references to say what the situation really is.

Also, energy from a POINT source is a 1/r^2 term.  Meaning energy drops of pretty fast the further you are away.   A couple feet difference from the mouth of a forge will reduce it some, but may require looking longer than if you can be closer and see more quickly.  

Unless you're doing this for many hours every day,  you'll be fine wearing standard safety glasses... just don't stare into the fire.  

Link to comment
Share on other sites

 

After a lot of study for another book (which a hacker ruined), I can tell you that color filters are the key to infrared protection. Think laser glasses as one way. But there are  special clear Schott safety glasses ($$$) that don't distort color. Confused yet?

My favorite answer to technical and safety problems is "just don't go there," any time I can get it. The best way to keep IR from the forge out of your eyes and off of your face is to reflect it back into the forge, where it can do some good. Can you say "baffle wall"?

Curtis,

Thank you for posting that photo. I look forward to seeing many more flame photos from your burner experiments.

Frosty,

Well actually I am contemplating  an update of the old wasp-waist burner design since I saw trumpet shapes can be purchased at reasonable prices; this brings them into the category of practical for my money. So what do I think they can provide? Cheap and aesy control of flame speed. How? The forward end of the venturi shape can be cut longer or shorter to vary flow speed. By cutting that forward end back in small stages the most desirable speed can be seen, and a short tube for the flame retention nozzle can be attached. This simple method could greatly reduce the cost of experimentation. Your thoughts?

Link to comment
Share on other sites

I use "Uvex® Genesis® S32 IR Safety Glasses", with the low IR lenses(they can also be purchased with shade 2 or shade 3 lenses), and I find that they make a big difference. I generally don't look into the forge but there is a noticeable difference with them compared to with out.

Link to comment
Share on other sites

My thoughts are, do NOT stare into the fire!

My thoughts about burners haven't changed since the last one that made low velocity more important. There is a proper term for "wasp wasted" burners but it works as a descriptive term and I don't remember the right one. My intent is the same as it's always been, to deliver as much flammable fuel air mix (FAM) to the forge chamber per second as possible without blowing it right through the forge. Lower velocity changes the how of that one of course.

The intake being curved allows smoother flow for less friction and turbulence so more air is induced into the device to the throat. I don't know if throat is the proper industry term, I saw it being used in discussions rather than the drawings, papers, etc. I came into. Now I see it being called the "constriction" Changing terms now would leave me with a constriction confliction. <shudder>

The output taper's purpose and benefits are pretty clear, it reduces pressure increasing induction. With the reduced pressure the velocity drops in proportion. 

At one time I had access to a commercially made wasp wasted burner with a 1/2" throat and it was far more effective than my best 3/4" burner. It induced more air at a lower velocity, the jet was IIRC 0.037" AND it had a choke plate almost closed because it'd induce too much air. My thinking was it needed a larger jet. The jet position was right on the choke plate as far back as fit in the burner and it made a LOT of heat on 4-5 psi.

It was several times as good a burner.

Frosty The Lucky. 

 

Link to comment
Share on other sites

5 hours ago, Frosty said:

My thoughts are, do NOT stare into the fire!

The only time I look into my forge is when I need to grab my stock with tongs, if I need to check the colour of the stock I'll usually pull it out quickly. My shop is fairly dark and other than on the weekends I only have time to forge in the evenings, and in the winter (if it ever gets warm enough) its pitch black at 4:30pm so I wear the ir/uv protective glasses as to not blind my self! That will become somewhat irrelevant in the spring when I move to my new shop which has a better electrical layout and more lights, instead of one measly 50 watt.

Link to comment
Share on other sites

Actually "wasp wasted" is a burner description I picked up from a sales catalog, Through the years I have had a love/hate relationship with industrial terms, which I started out thinking of as "holy writ," but gradually came to realize were merely the survivors of culture wars between various sales and engineering types. The last couple of decades whatever best conveys an idea to the reader is what I consider the winner; all others can go to the back of the line :rolleyes:

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...