Burners 101

[Mikey98118]

Thanks for the info. I like the brass tube idea; that could help others

[Mikey98118]

 

Control of secondary air

Now let's discuss the induction of secondary air, and unwanted cooling of the equipment. Even single combustion envelope burners can benefit from external cooling air if the burners penetrate extra thick insulating layers (more than 2") or the burners are very small 3/8" or less, because internal cooling from the cold incoming fuel gas could be overcome during long heating cycles, under these conditions.

    Most burners have at least primary and secondary flame envelopes, so some builders deliberately leave their burner ports unsealed, because secondary air induction (now powered by the flame) is needed for complete combustion of such flames. Unfortunately, this usually leads to an overabundance of a good thing, because the flame becomes an even more powerful induction "motor" than a burner's gas stream makes. It takes energy to heat air, so extra secondary air becomes a drag on performance within the equipment; leading to as much as 20% heat reduction. Fortunately, we don't have an if/or choice to make. It is just as easy to control incoming air through the burner port as incoming air through the burner, with the use of a variable choke on the burner’s mixing tube.

    Simply mount a washer brazed to a short thick tube, drilled and threaded for a thumb screw, on the burner; once the burner is installed, it can be slid up against the portal tube's end to seal the port against heating from chimney effects after shutdown, and slid closer or farther from the portal tube for secondary air control during operation.  Is this more work? Obviously, but you should expend the additional effort; especially because it is an add-on project, which need not delay getting your forge up and running.

[Jimw3326]

And here I was under the impression it needed to be somewhat sealed, go figure. I have a washer free floating on the pipe and stuff a little insulation around the tube. The washer seals it up pretty good.

[Mikey98118]

Since you already have the washer, all you need do is weld or braze on a nut for a srew or bolt to run through, and act as a break.

Perfection is the enemy of practicality, but so is an early assumption that we are doing well enough already

[Mikey98118]

Yesterday our Gig Harbor casting group met, and John from Olympia (who's interest is knife making) showed up and discussed his experimental Vortex burner; he started out following my directions on this group, but said he ran into a problem with insufficient forward pressure in his fan-induced burner; this is something new to be aware of. Anyway, he changed over to  a squirrel cage fan, to deliberately provide more push into his air/fuel mixture, and arranged to have the incoming air from the fan impinge the burner opening on a tangent, to still provide lots of swirl. He was satisfied with the result, but was intrigued to find that the flame had a lot of swirl in it.

    This can be avoided by lengthening the mixing tube enough to stabilize the flame (by allowing friction within the tube to slow the mixture’s swirl and forward velocity, before it exits into the flame retention nozzle).

Or, internal vanes near the tube’s exit can be made to slow air spin, in order to keep the mixing tube’s length shorter. A larger diameter flame retention nozzle can break the flow’s exit speed sufficiently. Thus, you would need to exchange your smaller flame retention nozzle, used at lower gas pressures and fan speeds, for a larger one, when running a fan-induced burner full-out.

It turned out he liked that flame swirl, and didn't want to lose it

Anyway, it has now become time to sweet talk John into describing his new V burner design for the mob to copy

 

If john to help people to copycat his design? Why yes. After all, it could prrrrrove to be the the cat's meow

[Frosty]

Why don't you like flame swirl Mike? I'd think it would make for more even distribution and lower linear flame velocity for longer hang time over a larger liner area. No?

John? Speak up John, curious old curmudgeons are wondering here.

Frosty The Lucky.

[Mikey98118]

2 hours ago, Frosty said:

Why don't you like flame swirl Mike? I'd think it would make for more even distribution and lower linear flame velocity for longer hang time over a larger liner area. No?

I don't dislike flame swirl; a couple of my early burners featured it. I'm simply into different goals. Again we come back to "no one shoe fits all." If you desire flame swirl, then enjoy the fit

In fact, I agree with all your points, and hope John's preference has fans; I promote variety in burner designs and equipment designs too; it just isn't my own preference. Nevertheless, "I have no dog in this race."

[Frosty]

Okay, re-reading I realize I thought you were making a case for eliminating swirl, not suggesting ways to. My bad. I've never messed with swirl other than to think and read about it as a device for mixing air and propane more thoroughly. Or as a device for potentially making a fuel oil burner practical by causing complete combustion before the flame can impinge the furnace liner. 

Then again, were I serious about a fuel oil forge / melter, etc. I'd just buy a small oil burner from the local HVAC supply. I'm thinking the one scaled for domestic water heaters would be about right in maybe a 1,000cu/in forge/melter. 

Years ago the tech repairing our boiler had it apart and showed me the guts while explaining the whats and whys of it. The air entered through vanes at a shallow pitch and the oil was introduced through a nozzle that induced an very shallow pitch at a few thousand psi. If you envision a power prop on a boat imagine a tug boat prop that converts 7,000hp to maybe 10 knots but can push a cruise liner 10 knots sideways without raising engine temp.

Anyway, he said that if the oil flame touched anything but cast iron in the boiler it would burn it right up and it wasn't good for the cast iron. I asked if it was worse than propane and he said oh yes, MUCH worse. With the emphasis.

That long ago service call intrigued me into wondering about benefits or penalties of a strong vortex propane flame.

Frosty The Lucky.

 

[Mikey98118]

42 minutes ago, Frosty said:

I've never messed with swirl other than to think and read about it as a device for mixing air and propane more thoroughly.

Neither did I, before stumbling over it, by attaching an axial computer fan over the air entrance of a laminar burner m (about eight years back). The difference was so extreme, that I had to research the what and why of the changeover to impeller blades from regular blades on these new fan designs; this led straight into research on the web about vortex flow, and the advantages it could make.

Is vortex flow the "end all and be all" of burner design? NO! It's just one more thing. For instance, I don't think it will contribute anything but problems in ribbon burners, since the plenum chamber already drops mixture pressure quite a bit. As always, everything burner is all about balance

[Frosty]

Hmmmm, a pair might do interesting things to T burner performance. 

Nah, there is no end all be all burner, humans are too inventive.

Jer

[Mikey98118]

7 hours ago, Frosty said:

Nah, there is no end all be all burner, humans are too inventive.

Yes; exactly so.

[Mikey98118]

What tool is the most useful for burner construction, might depend on what kind of burner design you choose. All those inside cuts and bevels on a high speed tube burner, make a rotary tool your best bet, but most burners only call for a few simple cuts from a chop saw, angle grinder, or from an angle grinder mounted in a fixture that allows it to be used as a small chop saw.

It is also likely to depend on what tools you already have. A 6" chop saw from Harbor Freight Tools cost about the same price as the average rotary tool, but is way faster to use in building most burners. On the other hand, if you already own and angle grinder, that money could be spent for a fixture, which allows you to make accurate right angle cuts in pipe and tubing, instead.

But, if you extend the question to involve building the forge or casting furnace it heats, the picture might change still again. For one thing, the angle grinder can be used to cut into cylinders, etc. that you'll use as equipment shells. Also, a special chuck can be mounted on the grinder, allowing you to use it as a right angle die grinder. All of these choices involve tradeoffs.

[Mikey98118]

That special chuck is called an angle grinder conversion chuck. Two things to keep in mind is that most of these chucks are meant to screw unto M10 thread, M10 spindles are found on 4" (100mm} angle grinders. 4-1/2" angle grinds have 5/8" spindles.

The other thing, is that you need to use all three holes consecutively (one, two, three, one, two, three...) to gradually tighten accessories in the chuck. You will find all manner of ignoramuses complaining about how worthless these are, rather than using the tool properly. 

[Leather Bill]

On the subject of swirl and vortex ,I wonder if there is significant difference between flame temperature of conventional air/propane torch and TurboTorch.   I used oxy/acetylene when working in refrigeration while others seemed to do fine with air/acetylene TurboTorches.  I also wonder if increased heat comes at expense of more fuel consumption. I wonder how difficult principle is to duplicate.  Lastly i wonder why voices inside old men's heads talk about such things instead of tropical beaches.

[Mikey98118]

All good questions, Bill.

Air/acetylene TurboTorches are rated at 3600 F. For decades, air/propane torches were rated, by their sellers, at between 1800 F to 2200 F. In recent years, thoe claimed heat has been rising. I think in response to what we say on sites like this one. It isn't all that far fetched, once you understand that most ads are just thought up by sellers trying to match the claims of other drop-shippers

All LPG gases are potentially capable of creating about 3600 F, burning in air. However, how hot their flames actually get, is strictly a matter of mechanical manipulation. So, why couldn't an air/acetylene flame be manipulated even higher, too? The answer is partially that much of its increased heat is do to its chemistry, which isn't effected by such manipulation. The rest of the answer is that it naturally burns at much higher velocity than LPG fuels, and raising flame velocity is how flame temperatures are already being raised in LPG fuels.

Increased heat is most easily achieved with more fuel consumption; this is only one way, and far from the best way. You used hand torches for years, so it should be instinct by now for you to get is to get the job done, whenever you can, by conserving heat; this is, after all, the whole purpose of a forge

So, lets revisit the question, from a different angle. Hotter fuels are more expensive than propane or methane. The next step up would be propylene, which burns about one-third hotter than propane, and when purchased in refillable cylinders from a welding supplies store, only cost about one-third more than propane. So, no accrued benefit right? WRONG! Most heat lost from gas equipment is right out the exhaust opening. The hotter a burner's flame the farther it can be turned down, greatly slowing heat loss through the exhaust. Naturally, someone will ask, "why bother with insulation than?" The main value of insulation is to raise surface temperatures inside a forge. As internal surfaces become incandescent they radiate heat back into the forge. The higher the incandescent range the greater the amount of heat on the work  this contributes. At yellow incandescence, more radiant heat is absorbed into the work than is conducted into it by the flame.

16 hours ago, Leather Bill said:

I wonder how difficult this principle is to duplicate.

 You haven't stated what principle, so I can't provide an answer.

16 hours ago, Leather Bill said:

Lastly i wonder why voices inside old men's heads talk about such things instead of tropical beaches.

Could it be that such old men, realize that part of the scenery is meaningless now? You know; the part in a bikini. If we're honest, that ship has sailed long ago

[Frosty]

I sunburn too badly for the voices to talk about tropical beaches, a pretty girl on the other hand .

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Most tropical beaches have been ruined by humans who act like pigs with their litter. So no sense of dreaming about them.

[Frosty]

We're talking dreams here, I don't know about you but I don't dream about trash. Beach combing is a good time and you can dream about finding the treasure map in a bottle or stubbing your toe on a treasure chest.  

Lots of good dreaming about beaches, tropical to arctic. We have a couple famous for fossil hunting, Megalodon tooth anyone? 

Frosty The Lucky.

[Mikey98118]

12V 300W Brushless 75mm (3”) Cordless Angle Grinders are sold on eBay and Amazon; they can be used as a saw, by mounting a cutoff disc; it is the safe and sane alternative to high power die or angle grinders, for grinding and surface cutting on curved equipment surfaces, but can’t be used as a rotary tool. Ads for this tool and the (earlier) Parkside version can be found on eBay and Amazon. These grinders have a maximum speed of 19,500 RPM. The mounting bolt that holds accessories on these grinders is 6mm.

    Even the strongest angle grinder will be limited by the accessories you mount on it; that is especially true with cutoff discs. Thick (3/32”) resin bonded cutoff discs are much slower cutting than the thinner Weiler, Shark, Miller, or 3M cutoff discs; thin discs are more expensive, because they must be more carefully constructed to hold up with as little as one-third the material thickness to work with.

   Better quality 3” (75mm) cutoff discs all have sheet metal washers press-fit into one face, to act as spacers. The Chinese manufactured 75mm cutoff discs, which come with their 12V angle grinders, have 0.395” metal spacers in their arbor holes. I bought a number of generic 3” cutoff discs, which were supposed to have 3/8” arbor holes; their metal spacers measured 0.375”; so, they provide a closer fit than the Chinese discs, but those were 0.053” thick, while the generic discs were 0.073” thick.

    The best discs are only 1/32” thick; that provides 0.031” of cross section, in which to sandwich two layers of fiberglass reinforcement between a v thin layer of resin bonded #80 grit abrasive. For fast cutting with 3” diameter discs, you should be looking for 1/32” (0.031”) thickness; 0.040” thickness balances speed and disc strength; you definitely don’t want thicker discs for surface cutting than 1/16” (0.0625”).

    Using 3” diamond coated cutoff discs is not a very safe cutting choice. The grinder’s smaller torque, can be combined with a homebuilt side handle, making a 12V grinder a far lesser risk than a 120V electric die grinder, but it is still not a smart move for most people. Are your wrists and hands strong enough to keep control of the tool during kickback? Remember that a steel disc won’t break during kickback, so you will have to ride out the incident without that help. If you can’t resist the advantages, be sure to surface cut, only. Don’t plunge cut, and deliberately position the steel guard as a rest to keep the disc from penetrating more than minimally beyond the kerf.

    Wear safety glasses and a face shield, when trying to peer around a steel guard.

     3” diameter grinding wheels come from 3/16” to ¼” thickness; they aren’t cheap, but cutoff discs are too thin to be safely used for grinding. Flap discs work better than grinding wheels for many tasks, but the 3/8” arbor holes on 3” flap discs are not likely to fit well on these angle grinders. Some people use 3” diameter Roloc flap discs by drilling out the center with 6mm dill bits; obviously, I can’t recommend doing that, because modifying accessories does not constitute “best practice.”

The Bauer 20v 3" cutoff tool (available from Harbor Freight Tools ) is a burlier version of the handier 12V 3” angle grinders. You trade greater handiness for extra power.

The SHENHAOXU 7.2V Mini Angle Grinder spins 2” diameter accessories at 6,000 RPM, which is slow for 2” grinder; it is a cordless tool, with brushless motor for increased torque, and a guard that can be rotated 180 degrees, sold on Amazon; they can be used as a surface saw, by mounting a cutoff disc; it’s a safe and sane, but very low power alternative to high power die or angle grinders, for grinding and surface cutting on curved equipment surfaces, but can’t be used as a rotary tool. Ads for this tool and the Herzo version can be found on Amazon. The mounting bolt that holds accessories on these grinders is 5mm. This is the second brand of this tool I have bought. My first purchase, a Herzo, was dead, right out of the box; the drop shipper who sold it, was no more help than a black hole, when it came time for them to back their product.

[Mikey98118]

Update on the 2" angle grinders.

The SHENHAOXU 7.2V Mini Angle Grinder spins 2” diameter accessories at 6,000 RPM, which is slow for a 2” grinder; this is a cordless tool, with a brushless motor for increased torque, and a guard that can be easily rotated 180 degrees, sold on Amazon; they can be used as a surface saw, by mounting a cutoff disc; it’s a safe and sane, but low power alternative to high power die or angle grinders, for delicate grinding and surface cutting on curved equipment surfaces, but can’t be used as a rotary tool. Ads for this tool and the Herzo version can be found on Amazon. The mounting bolt that holds accessories on these grinders is 5mm. This is the second version of a 2” angle grinder I have bought. My first purchase, a Herzo, was dead right out of the box; the drop-shipper who sold it, was no more help than a black hole, when it came time to back this product. I did eventually get the Herzo to work for very short periods, and found that this tool is much smoother and quieter; these are completely different models; not the same design under a different brand. As a final indignity, the Herzo’s shield won’t actually rotate through more than 90 degrees; rather than the promised 180.

[Mikey98118]

The Bauer 20v 3" cutoff tool (available from Harbor Freight Tools) is a burlier version of the handier 12V 3” angle grinders. You trade handiness on delicate task for extra power, and extra battery time can be added. This is one of the latest 3” angle grinders with close to the power to be expected from a 120V power tool. Worx and DeWalt brands also have 3” tools in this power range. Other brands will probably pop up this year.

[Mikey98118]

Homemade miniature angle grinder to rotary chuck adapter

JTO size are probably the smallest keyed drill chucks on the market; they have opening ranges from 0.3 to 4mm (0.013” 0.156”); a comfortable range for use with rotary tool accessories (Yakamoz sells their kits for $11 on Amazon.com). These chucks are small and tough enough to be run at the speeds of 3” and 2” cordless angle grinders; they are usually mounted on DC motors, and used as miniature drills. It is common to find them sold as kits, with brass JTO to 1/8” mandrels for the motor spindles to be mounted to.   

    Both 12V 3” and 7.2V 2” angle grinders employ the same 5mm threaded mounting bolts. If you are set up to enlarge the existing hole, keeping it centered and parallel to the chuck’s axis, and then run the right 5mm threads into your new hole, a bolt can be run into the chuck, and secured with Thread-locker; then the excess length is cut off.    

    Thereafter, the chuck can be secured on one of these small angle grinders, using the chuck’s key as a wrench. The slack between the bolt threads and those in the tool’s threaded mounting hole should allow the chuck to perfectly match surfaces with the grinder’s face plate. You should then be able to employ your angle grinder as a perfect little angle head rotary tool. If you’re really sharp, you should be able to do a good enough job of drilling and threading with a drill press. Otherwise, I suggest using a lathe for the work.

    You may note that this is called a rotary chuck adapter; not  a drill chuck adapter. You will find that 3” angle grinders mostly spin too fast for use as drills. 2” angle grinders run slow enough to be used as drills sometimes, depending on material and drill bit diameters.

 

[Mikey98118]

Homemade miniature angle grinder to rotary tool chuck adapter: Further thoughts.

At present you must build this attachment yourself; eventually, something like it will be marketed. Whether that happens in a couple of years or or a couple of decades, who can say? If you want to trust some OEM to market an obviously needed tool that would save you from buying two of their products, instead of just one, go right ahead. You’ll wise up…eventually. After all it took seven decades for them to market a see-through safety shield for rotary tools. Oh, wait; we had to wait for the Chinese to do that, didn't we...

[Trevor84]

Wow I gotta lot of catching up to do but I wanted to shine this magic mistake and improvement. 

I shared these 3/8" 0.4mm mini burners before but couldn't get them to overcthe pressure in the forge and ran rich. 

 

I trimmed a half inch off the back so I could get the orifice a bit deeper, then I tried clamping the tube in the vise horizontally and proceeded to cut the threads deeper buuuuuuut the side I was tapping ie backside of skiny supports and the threads locked and I twisted the intake. 

Oh the tragedy, the failer the oh, wait it twisted straight..... Seriously the overall profile of the 3/8" tube stayed straight as an arrow but with a twist. 

 

These tiny burners are hard to take pictures of but these two changes were repeated on the second burner first try (crazy maniacal laughter) 

 

These run hard, loud and hot! It looks like I have Flares on the end but they are only spacers there is no over hang the flares are shaped into the refractory. 

 

 

I have to stop plumbing my burner's together this close, I always end up with one side running a lot harder. 

 

Does my plumbing at the burners look like it could cause a kind of cavitation (?) as the gas splits at the last T? When I plumb like this there is always one burner that goes whomp, whomp, whomp so the one burner has to be choked right out until the internal temp is up. Or it's just what happens when you try to duplicate something, which is why we use the chokes eh... Yes I'm Canadian EH. 

"swirl" ummmmmm I wish I could see the effect my twisted intake had but these are so small it's hard to photo. 

 

I mean I wonder if and how much the twist changes things, I guess if I went from rich to vavoom I must be on to something. 

 

Mikey I really like the baffle concept to adjust secondary air..... 

 

 

[Mikey98118]

1 hour ago, Trevor84 said:

Does my plumbing at the burners look like it could cause a kind of cavitation (?)

When two or more burners are mounted in a forge, they will interfere with each other's performance; this is especially true of naturally aspirated burners. But this is due to back-pressure being created in the equipment's internal atmosphere, by the burner's flames. How much interference depends on how hard (intense) the flames are. The harder the flames the less back-pressure can interfere with them.

Different pressures of fuel gas to the burners, do to plumbing, can also create some problems, but these are easily adjusted by needle valves mounted directly on each burner.

So, the first thing you want to do is to increase flame intensity. How? file or power sand internal bevels in the front edges of your burner's air openings. I suggest you change your "problem" burner first; that will encourage you to change the other one, too.

Your lucky twist is likely to be copied by quite a few people, how want that effect, but don't want to cut their air openings that way, to get it

I doubt that many will have the success you did; usually twisting the ribs creates a bent burner!

Finally: Congratulations on a very hot forge, perfect burners or not

BTW, your burners are not placed to close together; they are further apart then most of us place ours.

2 hours ago, Trevor84 said:

Mikey I really like the baffle concept to adjust secondary air..... 

You also can adjust back-pressure to be more equal against the burners, with a baffle wall in front of the exhaust opening. I believe that some of your problem is due to the great difference in back-pressure that is being exerted against each burner. The rear burner is the one giving you problems, right?