Burners 101

[Trevor84]

Ok thanks that explains it I think.

I kept using varying lengths and combos of the 1" black pipe and the 1 1/4" black pipe and kept fixating on needing to use standard pipe nipples and not other combinations. 

Now I'm going to see if I can get some schd 80 1 1/4" it, in theory it should only take a bit if grinding to get a tight fit. 

 

[Mikey98118]

Familiarize yourself with a pipe size chart outside and inside diameters. Then look for alternates in tubing online.

[Frosty]

Trevor: Please try to use the common terms for burners, to avoid confusion. This last question had me confused, I'd just told you how to make the jet adjustable and stable and here you were asking almost the exact same question.

A couple posts later I discover you aren't talking about the T at all, you're talking about the burner nozzle an entirely DIFFERENT component of a burner, the opposite end in fact.

This is exactly like using fuel injection names and terms to ask about the tail pipe.

Frosty The Lucky.

[Trevor84]

Hey Frosty, I'm not sure how I confused things I was talking about two different things...... 

Yes using a jam nut will lock the jet in position whether it's in a T like the last pic or through a threaded bushing in another design. 

I then was asking about the step nozzle and which sizes of pipe were used 

So I was asking about the carb then the exaust. 

When I was talking further about adjusting, I can't really describe what I was/am thinking about and in the end it's not necesary. 

[Trevor84]

I was thinking of being able to lock the burner in the forge so doesn't rotate. Now say the threaded 1/8" fuel jet accelerator stays stationary, like it can't turn. 

Now the piece I am envisioning would be like a nut that can turn on a flange that would welded to the outside of the T. 

This way you can adjust the nut and move the accelerator in and out without removing the burner from the forge. Obviously this is frivolous, it's just something rolling around in my head.

Please if that is still confusing just disregard this. I am having a hard time putting it into words. 

Haha I found it, a swivel flange nut . Weld the flang to the end of whatever style of burner and then just turn the nut in and out for micro adjustments of the jet. 

[Mikey98118]

If there is any play between nut and washer, this arangement won't work well. To weld or braze a nut onto the burner body, and then use a second nut to tighten it in position would be a more sure fire move.

[Trevor84]

I guess I could see that flange being a bit sloppy...... Twas just an image that popped in my head. 

Anyway yes the locking nut seems the best idea. 

I found a pipe chart so I'm heading to the plumbing store tomorrow to gather a few more bits. 

Thanks guys for your patience  I'll update if I have success 

Edited May 17, 2020 by Mod30
Double paragraph.

[Mikey98118]

   Turbulent Gas Flames

 

If you look up "flame" or "flame  envelope," chances are that you will see a photograph of a candle flame, along with an explanation of how it operates to produce a flame envelope. However, even the  simplest example of a gas flame springs from an orifice hole (ex. stove flame)  or tube end (ex. Bunsen burner); furthermore, both of these examples are only laminar flames, If you're looking for powerful heat, laminar flames are so far back in your rear view mirror that they're less than a dot in the distance. Your beginning point is "turbulent flames."

A turbulent gas flame is essentially a controlled explosion; it creates a weak outward force. But the push of a gas flame isn’t equal in all directions. The gas/air mixture is being flung forward, so there is a little more shove away from the burner’s end, than in any other direction. All things being equal, the harder the flame is tuned the faster the gas/air mixture will rush forward, and the greater that imbalance grows. At some point, the out flung mixture will force the flame far enough from the ignition source to snuff it.

    Atmospheric pressure is a constant force all around the flame envelope.  But,  create a low pressure area at the burner’s exit (by use of a flame retention nozzle), and atmospheric pressure will press the flame harder against that nozzle, than in all other directions; the difference isn’t much, but it is enough to allow much harder flames to be maintained, because the kinetic force of the out rushing air and gas molecules is also minimal.

Why doesn't the candle flame have more than one flame envelope to discuss? Because is a sim[e laminar flame; that is the point, to keep that discussion simple.     

[Mikey98118]

Continuing on: There are a few high velocity combustible gases, two of which have long been used in oxy-fuel torches' they are acetylene and hydrogen. Note please, that there are even hotter gases, but they aren't used as fuels, because they are so dangerous as to make acetylene and hydrogen look tame in comparison.. Anyway, the main thing to remember about high speed fuel gases is that their flame speeds can't be improved to any appreciable degree by further changes in equipment. LPG fuels, on the other hand, make low velocity gas flames (comparably); their flames can be manipulated to increase speed to a considerable degree. Those who need scientific formulas are welcome to input "turbulent flames," and jump down the rabbit hole

[Mikey98118]

miniature burners

Why construct miniature burners at all? There aren’t a lot of people desiring a miniature forge or casting furnace. But, there are plenty of people who want to get more heat from air-fuel torches than is to be found in commercial models; in the face of rising energy prices, many more are looking to maximize equipment efficiency as much as possible.

    Naturally aspirated burners have large turn-down ranges. So, it would seem that a wide selection of burner sizes isn’t needed to accommodate heating equipment; and so far as it goes, that’s true. But, efficiency is about more than how well fuel burns.

    There is another factor to get control of, and that’s the burner’s exhaust path. It’s easy to see what goes wrong when there is too much or too little exhaust capacity available. It is harder to understand what goes right when you get superb control of the equipment’s exhaust velocity. That's because doing so involves balancing two disparate combustion issues; they are flame and exhaust speeds. Fast flames are good, but fast exhaust is bad.

    The reason burners are aimed on a tangent in some heating equipment is to cause their combustion gasses to swirl around its interior, creating a longer distance from flame to exit. A longer exhaust path increases the amount of "hang time.” That seems quite obvious doesn't it? What isn't so obvious is that most of that increased time isn't made by the gases running a little farther at a given velocity; it’s provided through a considerable drop in velocity over that distance. A bunch of little flames will decelerate much faster than a single large flame.

    The smaller flames of a pair of 1/2" burners will drop velocity faster than a single 3/4" burner on a five-gallon forge, increasing efficiency; because they can be turned up hotter without creating a tongue of fire out of the exhaust port. But, what about the guy who wants to build a two gallon knife maker's forge? He is going to need two 3/8" burners to do the same trick. The guy how wants to forge hand tools in a one-gallon forge is going to need two 1/4" burners to run it with maximum proficiency.

 

[Panik]

1 hour ago, Mikey98118 said:

    The reason burners are aimed on a tangent in some heating equipment is to cause their combustion gasses to swirl around its interior, creating a longer distance from flame to exit. A longer exhaust path increases the amount of "hang time.”

I may be taking what you are saying out of context or otherwise misunderstanding the concept, please forgive me if I am. In taking into consideration balancing back pressure with exhaust exit speed, I was wondering if there would ever be any benefit to be gained by hobbyists in using a simple baffle in front of ports in order to slow down exhaust gas and increase its "hang time" in a forge?

Put another way, I think I am contemplating whether there would be a situation where a baffled exhaust port would function better than just employing a smaller exhaust vent.

[Frosty]

Yes. It's not so much to increase hang time in the forge though that is an effect. Baffles are more effective than doors because they ALLOW an unrestricted  flow of exhaust while providing another wall to absorb energy from the flame and re-radiate the IR back into the chamber. Baffles also absorb IR radiated from the rest of the interior walls and radiate it back.

Adding dedicated exhaust ports to out level propane furnace is redundant and reduces the flame's hang time so reduces the forge's efficiency. 

However, if you REALLY want to get into hang time and scavanging as much energy as possible from the flame we can start talking about "recuperative WALL" furnaces. Literally more than double the hang time by channeling the flame from the furnace interior to a space behind the inner liner and a second refractory liner backed by an insulating refractory. This way the flame exits the work chamber and circulates behind the liner to heat it from both sides. 

This is pretty common in large furnaces but I'm not aware of recuperative walls in small furnaces let alone small forges. By small, if you can't load it with a rail car it's a small forge. 

I've still been kicking the idea around I just haven't figured out how to make the clear annulus between refractory liner walls.

Frosty The Lucky.

[Panik]

That makes a great deal of sense and answers my question. I was thinking of a baffle in the sense of a permanent obstruction in the path of exhaust rather than a moveable object used for reducing heat loss by re-radiating heat (i.e a temporary wall) Lol, I'm learning slowly... at least I can better recognize my shallow understanding 

22 minutes ago, Frosty said:

I've still been kicking the idea around I just haven't figured out how to make the clear annulus between refractory liner walls.

 

I can see the simple (as in I am missing fine detail) steps necessary to separately ram cast two cylindrical, nesting forms, with the necessary porting for exhaust to flow into a clear annulus. I can also see how someone could use a 3D printer to create the accurately dimensioned shapes necessary to press into the casts of the front and back wall; creating negative impressions that will support each end of both cylinders. (I am unfortunately behind the tech curve in that I don't have a 3D printer... and still cursing the fact that we almost bought one at work before quarantine)

Where I get hung up is how to create accurately aligned ports to accommodate the tube required to both hold and isolate the burner from the annulus.

[Frosty]

Don't sell yourself short, you catch on quickly. I took the last question as one for clarification, we have to have a mental image of new stuff.

I'm not as interested in cylindrical forges as rectangular or perhaps a vault. Even then I'm pretty sure I'll be thinking about the next one before I finish the one coming up. 

Originally I'd considered firing the burner through the annulus as a means of drawing the flame into the annulus from distant ports. I'm not sure how it'll effect the forge atmosphere though.

Frosty The Lucky.

 

[Panik]

6 hours ago, Frosty said:

Originally I'd considered firing the burner through the annulus as a means of drawing the flame into the annulus from distant ports. I'm not sure how it'll effect the forge atmosphere though.

Honest thanks for blowing my mind this morning! The concept of using the low pressure created by the passage of the flame to induce exhaust to flow into the the annulus is a beautifully elegant concept. Given the idea of "path of of shortest or least resistance", its the only way I can imagine inducing a significant amount of exhaust to flow through the annulus without having to almost completely occlude the port for the work piece. I'm not even going to attempt to claim I can fully visualize that. However, I did have a question for my understanding if you don't mind?

Assuming an eventual and ideal end state (forging temperature) inside the forge, would I be wrong to think that there might be a period of system wide gas+exhaust chaotic flow to over come while the annulus and forge interior come up to an equilibrium operating temperature?

[Panik]

Missed the timeframe for editing my last post so please excuse the 2nd consecutive post......

I think my follow up question would be: 

If you painted the outermost wall of the annulus space with Plistex or similar material, would the double wall + annular induction exhaust arrangement be a potentially efficient enough insulator and re-radiator that, at a hobbyist scale, someone could potentially get away without skinning the whole forge in Kaowool?

(I think I am correct in understanding the answer is in part determined by individual goals in terms of refractory wall thickness, operational time and patience in the forge coming up to temperature) 

* Please feel free to tell me to leave off if appropriate.... as stuff like this can occupy my mind and get it spinning in neat directions - as a diversion from day to day stress.... kinda like doing crossword puzzles) 

[Frosty]

11 hours ago, Panik said:

Assuming an eventual and ideal end state (forging temperature) inside the forge, would I be wrong to think that there might be a period of system wide gas+exhaust chaotic flow to over come while the annulus and forge interior come up to an equilibrium operating temperature?

I don't understand the question, can you put it in lay terms please?

Every example of recuperative wall furnace I remember had an insulating outer wall, usually light brick. If there isn't insulation outside the annulus a greater % of heat will be drawn outwards rather than inwards. Heat conducts fastest towards the greatest differential. I'd put at least one layer of ceramic blanket but I don't think it'd need to be 8lb, lower temp rating should be fine.

Frosty The Lucky.

[Panik]

Frosty – my apologies and thank you for having patience… sometimes when I get excited about an idea my mind runs faster than the man at the gate in front my mouth can check to make sure what I am saying makes sense. I was diagnosed with written language disorder as a child and while I have worked at compensate it still trips me up occasionally.

Not a complaint or an excuse, rather an explanation. Usually, I am able to express myself in writing pretty well, but it also frequently takes me longer the others to figure out how to arrange my thoughts into writing. When I rush because I am excited about a concept and also haven’t had my morning coffee things tend to come out in a jumbled mush.

I was thinking about how changes in temperature, as a regenerative forge comes up to operating temp, might impact the flow of gases in the forge and through the annulus.

I can’t exactly conceptualize in order explain to fully explain my thought process, but there is part of me that wonders if the flow of gas from the forge interior through the annulus might be more turbulent while the forge is cold or coming up to temperature, as opposed to when it is running at its operating temperature. I was hoping you might be able to help me verify or correct my thinking.

[Frosty]

No need to apologize, thinking faster than we can organize our thoughts but needing to get them down before they're gone isn't unusual. Unless I'm mistaken it's called "compression" needing to speak or write fast to get your thoughts out before they're gone. I do that frequently and it's worse now, the TBI  makes it hard for me to follow a line of thought. I rarely post without having re-read and edited several times. If it's a tricky thought I'm trying to describe I edit until I can re-read it a couple times without refining or correcting it. 

NOBODY can know what you think, ONLY what you say. Don't worry about making folk know what you are thinking, just get us close, we'll figure it out or make something up that fits our image. All normal human stuff. I'm sure whoever painted the moose on the cave wall at Lascaux was actually painting a dear. 

To answer your question. I have no idea, nor do I know if it matters. My concern for flow patterns is mostly over when the flame leaves the burner nozzle and only of limited concern in the forge chamber. 

I can imagine the recuperative wall forge with a NA burner might run into a back pressure problem in the annulus until it warms up. I don't know and don't know how I'd test it. If it doesn't work well until warms up then that's how it works. I'd  tinker with a next build to see what happens but I do that anyway. 

I was never satisfied enough I could induce the flames to flow into the annulus to do more than make sketches and think about. I never got to experimenting. 

Frosty The Lucky.

[Panik]

2 hours ago, Frosty said:

I can imagine the recuperative wall forge with a NA burner might run into a back pressure problem in the annulus until it warms up. I don't know and don't know how I'd test it. If it doesn't work well until warms up then that's how it works. I'd  tinker with a next build to see what happens but I do that anyway. 

I was never satisfied enough I could induce the flames to flow into the annulus to do more than make sketches and think about. I never got to experimenting. 

Frosty The Lucky.

Thank you for understanding and thank you indulging my theoretical question! I have had a mental image of the burner stuttering until things get up to operating temp for some reason. It's nice to know I might just not be completely off base in my thinking. Your input has also helped me to better be able to formulate my thoughts....... something the about colder denser air inside the annulus creating increased back pressure and impeding a smooth flow of exhaust gases through the entire forge as things come up to temp tickles my mind. Even if does not have actual bearing on the how a forge functions at temperature, for me it is fun to think about.

My first attempt at forge is up and running. With some small changes and a bit of tuning I think it will work okay for a small heat treat and experimental forge. However, I'm already thinking of something a little larger and more solidly built. Broad stoke, I've been kicking around the idea of using Cast-o-Lite to cast the inner and outer shell and a front and back wall as separate pieces. Specifically, I would love to make forms so that the front and back wall have negative impressions; serving as a register to support the two shells. It doesn't help that yesterday my coworker threw away a large amount of heavy picture mounting stock that, along with wax paper and framing, would making great backing for building forms.

I am still thinking through the burner port and its alignment for casting, but were I to use thread-all and angle iron to hold all four pieces together with gentle pressure, I could then easily disassemble it. The ability to take it apart implies that I could, potentially, have the ability to play with using the clear annulus as a means to increase the distance exhaust has to travel before leaving the forge body, while still leaving open the ability to insulate that space.

Do I have any idea of how judge the annulus volume or the port sizing necessary to create an effective recuperative forge? Not in the slightest, and it would be wildly egotistical for me to claim otherwise.... especially since I am still learning how to tune a burner. Heck, if I attempt something like the above I could easily fail wildly in just casting the forge walls. On the other hand and with no experience, I built a very functional, gravity fed 5ga sand filter for work using plexiglass and spare parts a couple weeks ago. In and of itself, stuff like this is captivating for me and a fun puzzle to think about as a distraction from everything else going on in the world these days.

[Frosty]

I'd had the recuperative wall forge planted in my brain before I made a working burner and forge, join the club. 

One last thing. "Never underestimate the value of failure."

Brainstorm on my skyballing buddy.

Frosty The Lucky.

[Mikey98118]

Recuperative burners have never proven practical. Anyone who has an inch to...has all my admiration. Better you going down that  rabbit hole

Recuperative forges are a different story, since the whole point of these structures is to maintain heat as much as possible.

[Frosty]

Yeah, guys we are NOT talking about recuperative BURNERS, they have serious problems for little or no gain. 

Recuperative wall forges are an entirely different kettle of sushi even if they both scavenge heat from the forge's exhaust gasses. 

Thanks for bringing it up Mike it could've led to more confusion than is already being generated.

Frosty The Lucky.

[Mikey98118]

Recuperative forges are already confusing enough; the difference is that they pay more dividends for the headaches

So, jumping right back into the swamp...

Double wall recuperative forges will earn there keep best with oil fired burners, or at least kerosene burners. Why? Because heavier petroleum products need a loooong flame path, with a lot of ignition surface, to finish combustion.

[Frosty]

Things have come a long way or are very different between large furnaces and household. The oil boiler in our basement completes combustion in about 8" after leaving the burner. Talking with the guys who service our boiler they say if the flame comes into contact with the liner it will burn the 3,000f split hard brick out quickly and the IFB behind it doesn't stand a chance. The flame exits the burner with a strong spin and spreads more sideways than lengthwise across the chamber. All that touches the walls or boiler tubes is super heated exhaust gasses. They tune to neutral exhaust atmosphere, either lean or rich damages or at a minimum inhibits performance. It's neat to watch through the site glass. A couple times anyway, the flame is pretty but doesn't do anything entertaining. It burns as cleanly as natural gas. 

It's a different thing entirely but unless I'm missing something a neutral burn especially with fuel oils produces the most heat per gal. 

Regardless of the efficiency or effectiveness of the burner, a recuperative wall does one thing. It transfers as much heat from the flame as possible to the flame face. It does this largely by heating it from both sides. Which as Panik surmises reduces the need for insulation. 

Still it's not possible to heat only one wall of the annulus. I dislike that as a term for the discussion it only describes a space, and the "space" under discussion is another component of a machine. Anyway, the outside flame face of the annulus absorbs energy but I'd REALLY like it better if it didn't. Reflecting it back at the outside of the inner flame face would be oh so much better. 

Ever check the price for Inconel sheet? Ever try working it? It'd do though, staying shiny at 2,000f is well within it's range. Monel might do as well but it's in the same range for price and workability. One of my  jobs  in Dad's shop was holding torch on some of the exotic alloys he spun, usually jet and rocket engine parts but occasionally reentry vehicles, Mars and Venus probes to be specific. They spun at high orange and got me yelled at if I grazed yellow. Not because it'd mess up the part but it caused problems spinning. Anyway, once it was cool you could wipe them off with a rag and they were like a mirror with spinning tool marks. The dark gray was from burned lubricant, not discoloration of the Monel / Inconel. 

The sphere on the top of the Washington State, capitol building is 20 gauge Monel Dad spun in the 40s. I think it was the 40s, he may have been working for Boeing at the time. Anyway, if you're close take a look at it through binoculars or a spotting scope, it's as shiny as the day it was installed. Well, was the last time I was there in the 90s.

It may make the sweetest most effective forge going but talk about adding at least one zero to the price and a whole drawer of skills to your mental tool box. WhoOo EE!

Making the annulus is easy enough if I cast the liners and use melt or burn out cores. Kastolite is sticky enough preplacing spacers will connect and support the two making it a almost a space frame structure. Then wrap the outside in Kaowool, rigidized like a stone and a final shell. 

My main issue in this mental image design is controlling flame flow in the annulus. It WILL want to take the most direct path NOT circulate around the whole liner. What I really want hot is the floor and dome, HOT walls are nice but it's the floor and dome that are really my target radiators.

I'm pretty settled on corrugating the floor in a tight spiral to maximize surface area for heat absorption and re-radiation. It will allow flame to flow under stock and help maintain the forge floor's temp for maximum heat transfer to the work. I want the flame faces of the dome and walls as smooth as possible and largely zirconia. Smooth to radiate IR in as uniform a manner as possible. 

I mentioned using the burner flame as an induction engine to draw flame into the annulus. I don't know how well NARBs will work as primary jets in an induction device. They're low velocity but can effect darned large intake area. That's going to take some sperimentin and I need to come up with a test method.

Circulating under the floor is an interesting problem. The NARB outlets will be angled to induce a cyclonic action. (Avoided saying vortex nicely don't you think?) This puts the higher pressure zone at the circular walls so slotting the floor just inside the walls should put positive pressure at the intakes and HOPEFULLY induce horizontal circulation in the annulus. 

Putting the final outlet in the dome puts it right AT the NARB driven flame recirculation inducer so that's out. 

I'd LOVE to put the exhaust port in the center of the forge floor but it'd need either a complicated fan assist or a really in the way vertical stack high enough to overcome all the other actions I want working. 

The best and most workable "solution"  I can think of is just let it flow out the doorways. 

Hmmmm?

Frosty The Lucky.