Oxidizing/nonoxidizing Information

[natenaaron]

Several months ago I read, on this site, somewhere, I think, a description of oxidizing and nonoxidizing flames and how to identify which is which.  There were pictures and everything.  Now I can't find it.  Anyone know where it is?

[Frosty]

What kind of fire?

Frosty The Lucky.

[Judson Yaggy]

All the old pics here are gone, gone, gone...

[Mikey98118]

So, starting again from scratch: Neutral gas flames can either be all primary combustion in a single wave front, or more commonly show both primary and secondary wave fronts; also called flame envelopes; The primary wave front should be light to medium blue (depending on which liquid petroleum fuel gas is combusted), WITH NO SLIGHTEST TINGE OF GREEN in it. Even a hint of green means that you have a reducing flame; the more green the more reducing (fuel rich) the flame is.

As a blue flame darkens in color it becomes more and more oxidizing; this is described as a "lean" or oxygen rich flame. The color can deepen all the way into purple, and then to reddish-purple as the flame becomes leaner and leaner. Most flames will blow out before they hit reddish-purple; I have only ever built one burner that could make a flame that lean.

[natenaaron]

17 hours ago, Frosty said:

What kind of fire?

Frosty The Lucky.

LP using your T-burner design. 

 

Mikey98118

I am familiar with the parts of the flame as the outer envelope, intermediate cone and inner cone (I learned this in high school chemistry class and it stuck with me).  Are the wave fronts the outer envelope and the intermediate cone?

 

Everyone

What type of flame do I need for general smithing (scrolls, flowers, gates, etc.).  What would be the draw back to using one type of flame over another?

What type of flame does one want for bladesmithing?

[Mikey98118]

Flame envelopes, cones, and wave fronts are different descriptions of coherent flame configurations. I got into the habit of using the term wave front, because I was reading a lot of material written by combustion engineers who were concerned with "designing" better flame configuration, for better combustion in industrial equipment. Torch experts usually speak of flame envelopes (inner and outer). I suppose flame cones would be a description more likely to be found in gas stove and hot water heater maintenance manuals. Regardless, it's all just different lingo for flame patterns.

I simply say secondary combustion for what you call an outer flame envelope because my burners are designed to dispense with secondary combustion altogether at best and leave only a wisp of secondary combustion at worst; nothing that could meaningfully be described as a flame envelope, what you call the intermediate cone is my primary wave front, while a white inner flame cone doesn't exist on any decent forge burner. Instead, a clear cone shaped area should only denote the back side of a primary combustion wave (flame "envelope").

You're simply asking the wrong question about flame "types" for different smithing tasks. Unlike torch work, the last thing you want is to aim the flame directly at a work-piece being heated in a forge, where the flame should be used to heat the forge interior, which then heats the part indirectly. Always remember, that a flame is an ongoing chemical process creating heat as a byproduct. Inside that chemical process exists free super-heated molecules of oxygen, which cause scale to rapidly form on heating steel. Burners that produce secondary flames shoot super-heated oxygen molecules quite a long way. You will commonly see burners aimed at forge floors, but only to avoid direct flame impingement of  insulated walls, where it would do much more damage than causing scale to form on part surfaces. However, there are ways around this problem. The short hard multiple flames created by a ribbon burner burn further away from the work than longer single flames from other burner types. And if you are willing to install refractory rings over insulated walls to protect them from direct flame impingement, your burner(s) can then be located on the forge bottom, facing upward; this gives a flame three times the travel distance before encountering parts then down facing burners.

The correct question is what forge design does one want for blade smithing. Think of the burner as just one more part interacting with the rest of your forge, and you'll do much better. So, what size forge is best for the blade smithing you plan to do? will you make pocket folders or Bowie knives, swords, and axes? After you answer that we can deal reasonably with the question of what kind of burner design you need.

[Frosty]

I gotta get with you more in depth Mike I want to see how you overcome the nature of propane to achieve a clean neutral burn. I dealt with the negative effects rather than trying to solve the problem. Solving the problem is much more complex than just running it a little reducing.

Nate: I'm still getting a handle on Mike's terms for flame structure but we're talking about the same beast. I associate a burner flame with an oxy acet torch flame as that's so commonly familiar. Almost everybody has seen a cutting torch or can find pics of a brazing torch. The light colored opaque cone at the tip is the "primary", the darker more transparent shell surrounding it is the "secondary" and the last rather bushy more poorly defined is the "tertiary." I'm not taking issue with Mike's terminology these are just what I use and why.

Post a couple pics of yours in operation and I'll make some suggestions.

What you need is completely up to you and what you're doing. One, well tuned, 3/4" NA burner will bring 300-350 cu/in to welding temperature provided it's reasonably mono-dimensional. Meaning all 3 dimensions are close to the same. Long and narrow needs more burners to have an even heat so you may end up with several 1/2" burners rather than a single 3/4" one.

We've been talking about refractories, insulation and kiln washes in another thread, the whys, hows and how comes of them. You might want to skim or join in.

Frosty The Lucky.

 

[Mikey98118]

Frosty,

I do make up some terms to describe  equipment built, and you have every right to be suspicious of them, and ask for their justifications; "Cage" is the term I used for the outer structure which holds my Multi-hole glass furnace in chapter  10, in order to distinguish it from "A" frames (the most common way to suspend a tilting furnace), and square frames used to make the forge cart and its 6" thick insulated table top. Making up terms for things that aren't easily described correctly with usual terms is an inventor's privilege; one that should never be used without necessity, and which is quite often ignored or even overturned by the public. My fifth generation high speed tube burners are now called Mikey burners; a completely unintended consequence of my own actions, and a good joke on me

However wave fronts is a term invented by combustion engineers; perhaps to reflect the nature of flames as semi-controlled explosions. Also an explosion's wave front within a gas filled tube (of an extended length; usually nine feet) is the phenomena which is electronically timed, to determine a given fuel's flame speed. Flame speed is one of the factors used to determine adiabatic flame temperature; the maximum (and utterly theoretical), flame temperature of a given fuel.

According to combustion engineers a flame burns from its outside envelope (the boundary between mixed gas and oxidizer with ambient air) inward from all directions, but because a gas flame proceeds out of an orifice at speed it also has a very strong tendency to burn from its front backwards; thus, I suspect began the term "wave front." Wave front is also a more useful descriptive term for my purposes than envelope, because all my burner designs are deliberately made to speed up mixture feed, and then to ignite it well inside the flame nozzle in order to modify the natural tendency of a gas flame to burn from front to back with a constant source of ignition from back to front; this is how a burner can achieve complete combustion of propane (and all other LP fuel gases) in a single primary "envelope."

One of the things that's so handy about this group are the constant reminders that being "right" is only as valuable as the ability to communicate that "right" answer to others; when there is such a thing as one right answer...and when you challenge mine, you sharpen me. Thank you.

[Mikey98118]

Frosty,

BTW, It is no surprise that you have difficulty with the idea of complete single primary wave combustion; everybody does to begin with; that included me. Back in 2002 Ron Riel requested that I teach Rex Price all about my burners, because Rex wanted to make burners for sale, and Ron had wanted someone to offer g-o-o-d gas burners for sale for some time; this is how the three of us came together and Hybrid burners were born. After about two months of emailing back and forth, Price sent me his version of my burner for evaluation; it was hilarious...and awesome.

The hilarious part was that he built it two feet long! The awesome part was that by exchanging my rows of holes for slot shaped air openings he had completely changed the nature of the flame it put out; there was no secondary flame present at all! Anyone who has run oxy-fuel torches will immediately understand how mind blowing that is to see in an air-fuel flame. I cut down the various parts of the burner to the minimum length it could work at, and sent it back to him. In following months I sent him models for all but his smallest burner, and let him build finished versions of them. We discussed the technical details of my 3/8" "pocket rocket," which he shortened to "Rocket" burner, but I never sent him that model, as we had a falling out about then. Anyone can see total primary flame combustion, by going to the Hybridburners.com web site.

What you don't get there is the feeling of magic that only comes from seeing that flame exit a burner that you built with your own hands.

I went Price one better, after doing research on why an air slot performed better than a row of holes, by making rectangular openings, which were beveled for and aft for laminar flow; this final improvement sped up mixture flow so much that the burners no longer needed a built in funnel shape, allowing me to cut air openings into a single tube structure; it also allowed tapered flares to be replaced with the more effective tube and spacer ring found on my burners. Most importantly, it enables the burner to put out a neutral single primary combustion wave. Hybrid burners put out lightly oxidizing flames, which is why they are dark blue, instead of light or medium blue.

Price is not one of my favorite people; I took a lot of abuse over the first few years from morons who assumed that I stole his burner design, and then made a few "insignificant" changes to it. But no one can take this away from him: Rex Price made the first all primary combustion flame come out of a fuel-air burner; one look at that flame completely changed my thinking about burners, and the rest is history.

[Frosty]

No problem survives a good explanation, I'll need to think about the wave front description but I get the flame. The pics on Rex's front page about the middle of the page show a 2 part flame, mostly primary that's a little bushy and a bit of tertiary, showing minor orange rich characteristics. Hmmm.

The effect is obvious and it only takes a little thought to see the benefit. Is Rex still machining his burners from billet? I've never talked with him that I know of but there was chatter when he was getting known. I was frankly shocked when it was said he was machining them from billet (heavy tube maybe?) on a lathe. Doing it that way beyond prototype and test units never crossed my mind, ever and I grew up in a machine shop. . . Metal spinning and machine shop that is. Even with CNC machines the time and material waste is staggering.

Okay, I need you to explain why the intake slots are superior to rows of holes. I've never liked rows of holes for intakes, even in some of my other experiments but I want to know the why of it. I can visualize differences in how the air interacts as it enters the tube but my minds eye and reality aren't necessarily very closely related.

Slots: Even number, odd? Radially opposing, alternating? Intake area vs. tube x sectional area? You know the basics. Ever test them with smoke to the intakes? I mean actually watched the action? The sugar mist they use to test respirator masks behaves similar to propane. I wonder if I can color it to keep track of mixing by port? Hmmmmm.

I know how you felt when Rex showed you HIS first interpretation of your burner. Years ago, when Ron and I were winkling the things out, about the time we took our different paths. We  never had a falling out we just went our way and we still talk occasionally.  Anyway, I was just getting decent results from the "T", I got tired of all the stuff it took to get a linear burner to work. I think I'd just gotten my second mig contact tip jet working and performing in a forge.

Deb and I were building the house, I'd moved a basic kit out but not my propane forge, I didn't have enough secure storage and we weren't really living here yet. Deb and I'd mostly moved in when an Artmetal list friend drove the Alcan in his camper and spent a week visiting. Robert and I took a little tour of Turnagain Arm in my Eagle Talon and we talked burners down and back. I learned a REALLY important lesson as a result too. Robert was intrigued by my "T" burner concept and was kind of excited when I told him how I got one tuned. He'd built several of Ron's linear burners and Robert said to get them to do the job he had to build them just way too big.

Well, we had a great visit, his wife and Deb did some of their own touring, we shared food, drink, laughed and lied good stories. After a too short week we parted ways, happy folk.

About 3 months later Robert sent me an Email with an attached picture!! ! Being able to attach to email was just getting started on my level. What was the picture? Robert's version of the "T" burner with a beautiful 3 section flame. It was, the primary was a clean graceful cone, the secondary was a close tight sheath and the tertiary was but a feathery reminder of one HOT MOMMA propane flame. Imagine (IF you can ) my shock and dismay to see he'd built it WRONG!

He'd rotated the T fitting 90* and plumbed the jet fittings on one side of the run opposite the tube and was using the chase as the air intake! My fingers fairly FLEW on the keyboard explaining what he'd gotten wrong and how to do it correctly. HAPPILY I reviewed his message and noted a couple details I'd forgotten when I saw the picture. This was a 1 1/4" burner that Robert used in his iron melter and it'd melt 30lbs of iron in about 30 minutes. I was still wrapping my head around that tid bit when I refocused on the picture of the absolutely perfect flame.

Sooo, I deleted my embarrassingly wrong reply and congratulated him on a beautiful burner.

Robert Grommon(sp?) had built the SideArm out of a misunderstanding from talking to me about the T burner. THAT was my lesson of the time, I never NEVER go anywhere without a pad of graph paper and pencils. Of course if I'd had any paper with me the Side Arm might not have gotten introduced to folk when it did.

I'd better sign off for now. I have a lot to think about. Thank you MIke it feels good to stretch the brain.

Frosty The Lucky.

 

[natenaaron]

Whoa.  Lots to digest here.  I appreciate it but it will take a bit for me to understand what you wrote.

 

[Mikey98118]

Frosty asked "Is Rex still machining his burners from billet?"

I haven't communicated with him in nearly  fourteen years, and have no interest in his problems.

 

You know those little curled arrow symbols at the back end of airplane wings in drawings of what happens to air flow over one of them? Imagine for a minute that if you can get that much drag from what, for all practical purposes is a knife edge, with the air running past it in parallel on the bottom side, and at a very close angle on the top side, how much more drag you get with air running past an edge at close to right angles. How much drag is in direct proportion to how fast the air flow is, but naturally aspirated burners only use tiny forces to induce air flow, so a little bit of drag goes a loooooong way in interfering with burner operation.

Round edges produce more drag than straight edges, and a row of holes has a whole lot of round edges. So, you would naturally assume that reducing those round edges down from many to just two in a slot shaped opening would get rid of all that drag, yes? NO; it gets rid of a lot of drag, but one of those round edges is right at the mixing tube entrance and just forward of the gas jet; the amount of drag a round edge creates there is a REAL BIG DEAL! Even at the back of the air opening you can see a definite performance difference between straight edge and curved. So, I cut out rectangular air openings, but didn't get as big of a performance leap as expected...until I went the extra mile and beveled the forward and rear faces of those rectangles to knife edges. it was like driving down the road, and finally remembering to release the safety brake; big difference.

Orange and red streaks are not uncommon in high speed flames coming out of a stainless steel nozzle. I had occasionally noticed them in one of my burners, but paid them no mind, until a couple of glass artists posted a question about it on one of the casting groups; I invited them to send me their burners (with return postage prepaid). The burners were correctly built and worked beautifully, but their flames made a lot of red and orange streaks. The flame nozzles were also highly reflective. They had used #304 stainless. On a hunch, I replaced the nozzles with #316, and presto; no more streaks.

I will have to visit the Hybridburners.com site and look at the flames; that's what I get for throwing in an out of date memory...suppose we need to refresh them every decade or so

It is fine that you're interested in burner mechanics, but just remember that your burner has probably been built by more blacksmiths than all of mine. It takes about eight hours and a lot more money to build a high speed tube burner, or over $200 to buy one; that can be discouraging for people just starting out. I'd much rather they built an easy to construct burner and come play in the pool. I get to lure more people down to the deep end that way 

[ede]

10 hours ago, natenaaron said:

Whoa.  Lots to digest here.  I appreciate it but it will take a bit for me to understand what you wrote.

 

Funniest comment on iforge that I've read in a long time!   Just sit back and enjoy the show. 

[Mikey98118]

Frosty,
You also asked about air opening position and size.

I made my slots about 40% larger (when the area of all of them was added together) than the area of the flame nozzle; this turned out to be unnecessary, which became obvious when the burners were tuned As the choke was opened on these burners it would reach a point of maximum efficiency before coming even with the front of the air openings. I was being very conservative in my construction methods, because I wanted "some of everything to spare" when readers built my burners, which brings us to your other question...

All air openings were laid out in odd numbers (3, 5, so that they were never positioned opposite of one another. so as to insure that each entering air stream was less likely to interfere with another stream; I thought that necessarry becuase spin was imparted to the air streams. I also used more openings than needed, to ensure smooth operation (longer  thenner openings tone down the performance a bit more than shorter wider openings do). Of course the optimal number of openings on any jet-ejector burner is three, but I was a lot less concerned with maximum performance than in ensuring maximum stability in an entirely new burner design. After years of retrospection, I would not recommend more than three air openings on these burners; but that is now; not then.

The difference between what we picture in the mind's eye and what happens is the reason for experiment, but looking back on it all, I am still "taking some of my mental pictures" on faith; I did enough experiments to design good burners, but not enough to prove everything I 'know' on the subject. After two years the publisher wanted a finished book. I probably will run smoke test, etc. on the Vortex burners, though.

 

[Frosty]

Okay I got it. Slots to minimize trailing edge or "slipstream" turbulence. What are you making your tubes with? Experimented with exhaust or light wall tubing? The thinner the air foil the less slipstream is generated. That's the point of high aspect wings, long narrow and thin for a better lift to turbulence ratio. The "lift" relating directly to induction vacuum necessary to draw intake air.

What's the intake port to tube area ratio in your current builds? Are you using a slide or rotating choke?

On possibly a different subject, how are you generating the vortex?

A person needs to take little mind journeys before they start building things or they're depending on luck to get things right. Shotgunning ideas isn't the most efficient method. Shotgunning is not to be confused with brainstorming. Brainstorming is to generate departure points. Shotgunning as a panic mode depending almost exclusively on luck for results. Shotgunning as a valid method IF logical progression isn't working.

Frosty The Lucky.

[Mikey98118]

Frosty,

I just wrote out a full  page reply to your questions, and this site not only won't accept them, but won't even let me submit them one or two paragraphs at a time.

My URL is michael.a.porter at comcast.net mail me yours and I can at least mail your answers to you at home, since I'm being muzzled on this group; something I won't tolerate much longer.

 

[Mikey98118]

Frosty,

There are no chokes on vortex burners, since the air stream can be "tuned" via fan  speed, to match perfectly with increases and decreases in gas feed and flame nozzle diameters. All my tube burners have sliding chokes; I tried revolving chokes, but they are problematic.

[Frosty]

Vortex burners are guns, got it. Oil burners rely on a strong vortex to keep from burning the liners out of furnaces and boilers on household scale units.

I was thinking of using a rotating choke to induce a vortex in the intake air Never got to playing with the idea though.

We'll see if my email gets through, I'm not finding a URL though.

Frosty The Lucky.

[Mikey98118]

Neither is there any point in trying to install a point of one of the Vortex burners in order to seal it against chimney effects, since the plastic fan could not withstand the temperature increases that can happen with all metal burners are expected to, once the forge is shut down anyway; this means that either the burner must be removed every time the forge is shut off, or the burner(s) need to be installed upward facing.

Those who have questions need to ask them. Remember that "the only stupid question is the one you don't ask."

Revolving chokes are problematic because when they are partially closed over slots or holes they completely change air opening shapes, creating so much more turbulence that the burner can be destabilized; they cause trouble even on rectangular openings, because they change the shape of the opening too much, creating unexpected performance changes, which don't happen with a sliding choke; such changes can be accounted for, but they increase the learning curve for tuning a burner. Why would anyone go there, without a comelling reason to?

[Mikey98118]

That would be "compelling; more coffee needed :-)

[Frosty]

That makes sense, shortening the intakes maintains the slot width and slip stream characteristics. Adjustability and consistency are so nice together.

So install a centrifugal valve in your vortex burner so it shuts as soon as the fan does. Or perhaps an iris on a recoil spring so it opens when the fan is driven and snaps shut when the power's off.  Hmmmm?

Frosty The Lucky.

[Mikey98118]

The computer fans are delicate and easily overheated (also easily and cheaply replaced, but what fun is that?). I prefer to advise people to set the burners up to be easily removable at shut down, or else to aim them upward. On the other hand, people will go and do what they want, and that's fine too :-) You have to remember that I can play around with ideas as just another member of this group, but anything I write in a for-profit book becomes lawyer bait.