Burners 101

[KENR2600]

I was thinking of a wide bowl type floor raised up. I wasn't sure the best way to support the floor. I figure to invest in a kiln shelf floor - and saw a recommendation to use some segments as wall sides out at an angle. Then using other material to make a curved floor up.  The perlite lift, some rigidized blanket, and a shelf floor? Would shelf posts work under that to keep it lifted, while it sets on the blanket/perlite? Or will they not like the environment - or conduct heat through...??? I was thinking to bring the floor up to the bottom of the door area, about 3" up. I like the idea of a fairly wide floor for odd objects...or multiple pieces... or...... Plus, I thought a wide pan with rounded up sides would really help promote some good flame swirl in the forge and armor up the sides a bit too. I had considered just bracketing in a steel floor, and then just do the blanketing and such over that. But that will create an empty air space underneath.  I don't know what that would do to the overall environment inside.

 

[Mikey98118]

 

Ron Reil used kiln posts to support his floor; I went a different way because I didn't like the potential heat loss through them, but they will work.

[Mikey98118]

For a wide bowl of a forge floor you should look at slumping dishes; these are used for warm-glass artists, so they won't be found in just any old pottery supplies store, but you can always buy online...

[Mikey98118]

An improved cast flame nozzle from your hardware store

A page or two back, The Legend posted a photo of his first (?) burner attempt; and it is worth a second look-see, because, instead of screwing the pipe fitting that he used for a flame retention nozzle directly onto the burner's mixing tube, he screwed it into a short section of the next larger pipe than the mixing tube. In return for this extra step, his burner gained the ability to be tuned somewhat by moving the nozzle back and forth along the mixing tube; creating still another type of slide-over flame nozzle.

While not my first choice for flame retention nozzles, cast iron pipe fittings serve many of the functions of nozzles, which are deliberately constructed for the purpose, including the ability to last longer than mild steel; they are cheaper and simple to buy, when picking up the other pipe parts at your local hardware store.

Legand's additional step brings them much closer to being a practical choice.

[Mikey98118]

The why behind air entrance design

It is all but impossible for your burner to establish a stable flame without swirling the air and fuel gas into a somewhat homogeneous mixture, as they travel through the burner’s mixing tube.  Any burner providing a stream of gaseous fuel before the entrance to a cylindrical opening (the mixing tube) will induce air entertainment (via Bernoulli’s principle), a funnel shape behind the gas stream will also provide swirl to the air entering the mixing tube. All linear burners need some type of constricting form mounted at the air entrance, to create air swirl for sufficient mingling of air and fuel gas. Jet-ejector burners create air swirl with the geometry of their side air entrance or entrances. A single entrance will weakly swirl incoming air. Dual entrances strengthen swirl, and triple entrances maximize it.

 

[Mikey98118]

Burners are tools used to maintain balance in a combustion process

EXO313 writes "I'm specifically trying to sort out the 'how it works' of naturally aspirated burners."

"I understand that you need fuel and air, and the two need to mix. The more homogenous the mix, the better, correct?"

Correct; this applies to all burners, whether fan-blown or naturally aspirated. But the matter doesn't end there, or you will have created a fuel/air bomb! A nicely homogeneous fuel/air mixture must continuously flow into a low-pressure combustion area, such as a flame retention nozzle, and be eliminated (cook-off) by controlled combustion (a flame) before it goes BOOM! Once mixed it is the nature of a fuel/air mixture to ignite with the slightest encouragement. The only difference between a flame and an explosion is the amount of control you build into your heating equipment. Also, you can have too little swirl, but there is no such thing as too much swirl of a naturally aspirated burner.

"This is where it breaks down for me. Fuel mixing seems to be a complicated relationship between air intake design and ratio, fuel orifice size, and mixing tube length and diameter."

Yes and no; the process gets a lot more complex than that; fortunately, you only have to come up with a solution (in the form of the correct part) for each complication at a time. You build a wall one brick at a time. Furthermore, the complication is only a matter of understanding the process that each part effects. Once you understand the why of things the how of things become straightforward.

"The length: diameter of the mixing tube, if I'm recalling right, is 9:1?"

Sometimes; what you are referring to is the so-called nine diameters rule of thumb; which has grown to have so many exceptions that we are best off in regarding it as a beginning point. If you want maximum performance on linear burners, providing nine times the inside diameter of your burner's mixing tube is generally considered a safe move. Once you have built your burner and played with it for a few months you may decide to reduce mixing tube length to eight diameters, or lengthen it to ten diameters to maximizes a particular desired performance ( a shorter tube for shorter flames in a forge, or longher tube for a smoother flame when using the burner as a hand torch). Some jet-ejector burners, such as the Frosty "T" use eaght diameters for best performance. My Vortex burners need forteen diameters to steady their flames.

"I think I saw an intake ratio of tube D+40% mentioned somewhere..."

One hudred and forty percent the area of the mixing tube is a THEORATICAL minimum amount of intake air area needed for proper combustion on a burner. You never want to supply the minimum amount of anything on a burner design; you want to go for the maximum possible, and provide a means for reducing it to where you want it at any given task.

"Uncertain as to how gas orifice sizes work out in relation to all of this."

The smaller the gas orifest the high the gas pressure can be turned up on a given burner; the higher the gas pressure the more air is induced into the burner, BUT there is a given orifice size that gives the best results for every mixing tube's inside diameter; furthermore those sizes change somewhat between burner desighns due to differences of mixture flow dynamics.

"Then we come to nozzles, which, as I understand, help to soften the flame and therefore keep it inside the forge longer."

No; flame retention nozzles Provide a low pressure area behind the flame; the difference between that low pressure area and the the higher pressure of ambient air beyound the flame is used to offset the thrust produced by the flame, wiich otherwise would blow the flame off of the burner's end, snuffing it out. This is a balancing process; therefore slide-over nozzles (which are adjustable) can be used to harden or soften flames as desired.

"I guess what I'm asking is, what are the fundamentals of burner design? Also, please help correct my misunderstandings as you come across them, both above and in the discussion."

[Frosty]

I'm going to stop trying to answer questions like this except in this, hopefully, last case.

The reason you don't understand burners is pretty basic. You've been reading posts, watching videos, etc. of WAY too many folks, most of which don't know what they're talking about or doing.  Asking a list of questions which have a lot less to do with burner design than you've confused yourself into thinking on a forum that covers 150 countries around the world and the last I heard has 4,7500 subscribed members is worse than coming at this cold. 

Pick ONE set of established plans and follow them. Do NOT try mixing and matching plans and stop "researching" burners, there's just too much junk opinion to sort through untill you have some experience. 

That's it. Frosty out.

[Mikey98118]

I believe he has previously read Burners 101 and had complained that it bounces around too much. I see his point and also the limitations of the best run thread. Threads aren't textbooks. On the other hand, such books are a huge amount of work to write and publish; therefore they aren't free or easy to find.

We is danged if we do and danged if we don't, so we slogs on through the mud and the rains

[Frosty]

Even our individual posts tend to jump around don't they. Okay, let's take the pick one set of plans and follow IT a logical step farther. 

Read ONE person's opinions and descriptions of a subject. Think of it like picking one professor's class in college, there may be several English lit classes but taking more than one is only going to be confusing.

Frosty The Lucky.

[Mikey98118]

When it comes to building a burner or a forge you are right; following a proven design, step by step is the wise move. However, the whole point of this thread is to scratch the itch of those who want to know the why of things, whatever we may think of their reasons for wanting to know. As with all knowledge, what purposes people put it to will vary, but it is hard for bright and creative people to "listen and do what they're told" without knowing why; after all you and I didn't, now did we?  

[Frosty]

If a person actually wants to know the how and why of NA devices they should study Bernouli, not us. When you and I get to yakking about burners we don't say things we expect the other to know or derive. One or the other of us explaining or wool gathering on the subject might be confusing but it's only one confusing old fart. Two of us confusing folk isn't 2x as confusing, these things aren't additive, they're geometric.

Meaning of course, together we're confusion squared! 

Frosty The Lucky.

[Mikey98118]

I only bring up Bernouli'sPrincible when someone asks how a gas jet can induce air entrainment; I figure that if he can't simply accept that it does, he deserves to waste the time to look it up, and then wrap his brain around it, just like I did 

[Frosty]

I didn't mention Bernouli except to point out where you have to go to "understand" NA burners rather than a blacksmithing forum. Heck even then Bernouli just has the best description of what he could observe, I don't think we can actually UNDERSTAND things like we like to think.

I know I had to unwrap my brain from what I "knew" so I could re-wrap it around what I think I learned. My first shock was when I discovered Venturi had nothing to do with the things, it was all Bernouli.

I just describe what's going on rather than explain what's actually causing it to do that. It makes my head spin.

Frosty The Lucky.

 

[Exo313]

 Frosty, Mike,

You guys are fantastic. Thank you for not only these answers, and past answers, but also the necessary gatekeeping you do to hopefully keep people from exploding themselves or burning their homes to the ground. 

As far as how vs. why: Absolutely, there are multiple designs out there ranging from the workable to the very good. Any of them can be copied, and I come away with a new appreciation for the how. Copy all of them exactly and compare the differences, and I might even start scraping away at the "why". 

The brilliant thing about having experts at hand is that it reduces the entry cost (in both time and money) for -both- the how people who want a proven design to copy, - and- the why people who want to not only copy a design, but understand the purpose of all the parts. 

This is an incredible thing for the craft, on both accounts. It means an increase in participation, and an increase in innovation. Which is a huge gift of blood, sweat, burns, and tears that you've both given to smithing. 

Thank you. 

 

[Mikey98118]

The desire to move hot iron and stell is good for art, which I consider as needed for a healthy society as food, drink, and greenery. But the practical bonus is that it draws people to learn a lot about general steelwork tools, in an age when people increasingly are encouraged to specialize.; that is good for the pocketbook but very bad for the mind.

On a lighter note, I have spent about three years looking for the answer to why the flame would help induce intake air. Since I first heard that view proposed, I've been of two minds; on the one hand, it seemed likely; on the other hand, I was less than certain it was correct. I finally realized that the flame strongly induces air through the burner port, so why not through the burner itself? This isn't conclusive but does constitute a strong indication. I would prefer a resolution, one way or the other 

"...stell"? Let's try "steel".

[ThomasPowers]

I was thinking "Stella!!!!!"

[Mikey98118]

Good; it's time for a little humor

[ThomasPowers]

Well you wouldn't be wanting to work with Stellite---it's a pain!

[Frosty]

Uh . . . A flame doesn't have anything to do with induction, except to increase back pressure and inhibit it. Both linear and induction inducers are to  move material and were easy to adapt for mixing and supplying a flame. 

Back in my search for how, why and when, the earliest reference I cam across for an induction device was the deliberate channeling of water into mine shafts to force in breathing air and vent gasses out.  I don't have a cite Thomas, sorry but it was cited in the article I read. 

Linear inducers seem to be THE fuel air mixing devices used in modern gas appliances, range tops, water heaters, etc. Boilers use gun burners because they're required to burn a LOT of fuel concentrated in a small volume.

Jet ejector types are generally used to draw towards a vacuum. Ships needing to clear the bilges fast use a jet ejector type induction device that is basically a large side arm and uses steam as the primary pressure. If you've ever seen pics or videos of a ship on the rocks or after a collision with jets of water shooting out the sides 30'-40'-?' you're seeing jet ejectors doing what they were designed for. 

Trying to figure out all the whys of the things is fun but not really necessary for a functioning tool. Sure you need a working handle on the things if you have something special in mind for instance. I actually drew on some of my how and why to start thinking of the ribbon burner and why using a high pressure blower is unnecessary to make them work. Before saying anything  online I decided I'd better do some experiments first. My foot doesn't taste so good.

Have I run any of Bernouli's calculations? Are you KIDDING!? Not just no but HECK NO! I tinkered till it worked and kept notes.  

On the tinkerer note. Have you done any smoke tests to determine if a conical intake really induces a vortex or just reduces friction? (Venturi effect)

Frosty The Lucky.

[Irondragon Forge ClayWorks]

On 4/20/2018 at 9:10 AM, Mikey98118 said:

people increasingly are encouraged to specialize

Definition of an expert/specialist.

Someone who studies more and more about less and less, until they know everything about nothing.

[Mikey98118]

On 4/20/2018 at 9:09 AM, Frosty said:

On the tinkerer note. Have you done any smoke tests to determine if a conical intake really induces a vortex or just reduces friction? (Venturi effect)

Any reducer can be employed to induce a vortex. I only use conically shaped funnels to reduce back pressure as much as possible at the fan interface.'

I was getting ready to make clear plastic burner sections, not for seeing if a powered vortex works, but to include photos of them in the vortex burners text to answer that question in readers minds. After two strokes, I have enough give-a-darn left to converse here; authoring more books? Maby yes, probably no.

[Frosty]

2 minutes ago, Mikey98118 said:

Any reducer can be employed to induce a vortex. I only use conically shaped funnels to reduce back pressure as much as possible at the fan interface.'

I was getting ready to make clear plastic burner sections, not for seeing if a powered vortex works, but to include photos of them in the vortex burners text to answer that question in readers minds. After two strokes, I have enough give-a-darn left to converse here; authoring more books? Maby yes, probably no.

I misunderstood you then. I thought you were telling folks a tapered intake on a linear burner induced a vortex and improved mixing.

Frosty The Lucky.

[Mikey98118]

You did not misunderstand me; I am telling people just that. We can 'swirl' air down a mixing tube to mix fuel gas and air, but the swirl of air down a reducer IS a weak vortex. Mounting a computer fan with impeller blades only strengthens that vortex. 

 

On 4/20/2018 at 12:09 PM, Frosty said:

A flame doesn't have anything to do with induction, except to increase back pressure and inhibit it. Both linear and induction inducers are to  move material and were easy to adapt for mixing and supplying a flame. 

I am not about to agree with that statement. On the other hand, I'm not inclined to disagree with the viewpoint behind it, which would put me in the camp of those who definitely feel that the flame does induce airflow at the other end of the burner; a place I'm not ready to occupy. So, I will only repeat the observation of burner flames causing ambient air to be induced through burner parts, leading me to wonder if there is any reason it might not also be induced within the burner; a reasonable question.

You state that "A flame doesn't have anything to do with induction, except to increase back pressure and inhibit it." That would seem logical at first view, but once again I feel indecisive about it; remembering that the forward velocity of flames are inclined to blow them right off of the burner's end; thus requiring the use of flame retention nozzles and/or the increased internal pressure of a forge. Am I disagreeing with you? No; I'm stating that I'm undecided--so far.

Indecision is not something I enjoy. The only thing worse is "getting it wrong."

 

This question is well worth a decision, but hardly worth arguing about

[Frosty]

Once outside the burner the flow can't effect anything behind it without lowering the ambient pressure. It does this in the tube because it is in a tube and moving. The energy input into the system is the primary, propane from the jet. The propane is cold, freeze your fingers in seconds cold and induces roughly 17.5 times the volume of ambient temperature air. The bit of chill from the propane causes the air to condense slightly.

So, what happens when you cause a, call it 72 f., air/fuel mixture to ignite and turn into say, 2,700 f. mix of combustion byproducts? Takes up a LOT more space doesn't it? More volume in a limited space can't do anything but raise pressure. No?

The flame of any gas torch or burner I've seen can be made to jump off the nozzle by over pressuring it. Doesn't mean the flame is increasing induction. The flared nozzle does improve induction because the larger diameter means a larger volume and the same volume of fuel/air filling it so the pressure MUST drop, in the tube. It's moving forward at velocity which is reduced but regardless the pressure drop is behind it closer to the air intake. Nature abhors a vacuum so draws more air through the closest source the intake ports. Force always takes the shortest least energy path.

A burner tuned for max performance in a forge, removed to open air won't hold the flame. The air/fuel is moving faster than its rate of propagation so it blows out.  The inducer however continues to move the same volume of air/fuel. This last statement is a deduction I didn't test it by inflating or deflating something large enough to measure with a stop watch. I have used my fingers to estimate the flow at the intakes and didn't notice a difference. It's been a long time too.

Air is induced through the burner ports by the same mechanism as the burner operates, though in this case the burner IS the jet. The energy expended inducing air through the burner ports causes the burner output to lose velocity, there is NO free energy, it's a zero sum solution. Giant flames are caused by combustion and the expansion of really HOT gasses.

These are the conclusions I'm drawn to make by my observations and reading. I speak in statements without many qualifiers because I believe my conclusions to be pretty close to what's going on. Won't surprise me if I'm wrong though, I have a LOT of practice being wrong.

Make sense?

Frosty The Lucky.

 

[Mikey98118]

We don't have to agree to disagree. I simply remain undecided and will feel that way until I don't; not that I don't appreciate your input; I'm simply slow to masticate new thoughts. When I finally arrive at a settled view, I will say so. In the meantime, I will keep looking over your view