Burners 101

[Mikey98118]

Or, since it is likely to be a one-off burner, as experiments often are, a guy could simply heat up a strip of sheet and pound the inverted nipple shape into one side; heat if up a second time, and tap it around a pipe to roll it into a tube with the dimples inside; then braze or weld the outside of its seam to seal it.l One could even stretch thin sheet over a hardwood tapered form, and roll it into a taper, if one were inclined that way...and I think it is a good experiment to try.

But, my plate is running over already.

[Charles R. Stevens]

I wasn't even thinking about dimpling the inside of the mixing tube, but thinking out loud as to why the inside of a threaded fitting didn't cause fits, but as the same effect can be seen with the old Yonkers bomber and corigated skinned trailers maybe simply treading the inside of the fitting with a tap would be the answer...

[Frosty]

I agree with your thoughts about the thread protector's threads not interfering with the flow. In fact, back when I had my lathe hooked up and was tinkering with the things more I cleaned the threads out of a thread protector and it didn't work as well by quite a bit.

Here's a couple brainstorm ideas: Cast refractory is good, we could make a dimpled core from rubber and inflatable. It would index into the outer mold at the jet end, using a high temp high alumina water setting refractory sifted free of aggregate as the cast. Once set and cured simply let the air out of the core and mold and strip them.

Or here's another bit of brain storm, maybe brain squall. Braze ball bearings to a spring steel bic. Heat the burner tube in the forge and use a clapper on the outside while rotating it over the bic.

Last and least fun brain storm. Buy a small dia, carbide or diamond spherical burr and grind dimples into the tube.

Cutting threads in the tube would be an option worth experimenting with, depth and pitch would no doubt matter. Then there are different shape threads, "rope" threads for example. A person could also broach the tube for an interrupted screw. Picture rope thread and half round broach which may come close to being dimpled.

Frosty The Lucky.

[Charles R. Stevens]

Have you tried cutting out the threads in the "T", Jerry?

[Frosty]

Yeah, easy greasy but about the same effect as moving up 25% dia. That's exactly how I went from using a 3/4" T and 0.030" mig tip jets. up to 3/4" x 1" T and 0.035" jet.

I cut the threads out of a 3/4" T and built one, needed to increase the jet dia. to tune the flame. Then I took a pair of calipers to the Ts and tried the next one with a 3//4" x 1" and that's how I make them now.

Frosty The Lucky.

 

[Frozenforge]

I have a 1/2 Experimental T burner that I bored out the threads, cleaned and smooth it all out. I have the mig tip screwed into a threaded tube to enable easy adjustment. It has a nozzle comprised of 3/4" as the step to 1" pipe. Tried a .025 mig tip.

Best way to describe is that it has too much velocity?? so it will only run between 3 and 5 psi. Anything above 5 blows the flame out unless I choke off over half the air. Moving the mig tip in or out seem to have a limited effect on the mixture.

Sorry I don't have a picture of the flame but it is well centered and has a nice form at the lower pressures.

Have not had much time to experiment with it much more lately.

[Charles R. Stevens]

So then taking the treads out had the same effect as going up a 1/4" in pipe size, so no real gain or loss?

[Frozenforge]

Hard to say, I wouls say yes on the air side anyway. I knew I was making too many changes at once but I figured what the heck?

My thought was that if the propane velocity is high enough to really pull alot of air in with it then you could have a tighter forge and decrease the heat loss.

[Frosty]

Yes, exactly Charles it may have been a little better but not appreciably and not worth the work.

You're using too small a jet, use a 0.035" mig tip. and no need for the pointy ones, the blunt ones don't interfere with air intake as it's hitting it from the sides. The idea of making a LOT of heat in a forge is putting as much fuel air mix in the chamber as possible at the same time.

This entails a couple things but mostly you want as large a jet as possible that will induce enough intake air for clean combustion at a velocity just high enough above the mixture's rate of propagation as possible. It needs to be enough faster to cool the nozzle and prevent it from getting hot enough to pre ignite the  mix in the tube.

You're reply just showed up. It's a good thought unfortunately NA burners are pretty susceptible to back pressure and while you can use smaller jets at higher pressure to offset it some it's still blowing the heat right through the forge. You MUST exhaust the combustion gasses and even a gun burner won't work all that well into a high pressure environment.

I'm thinking of trying to use larger jets in mine see if I can slow the flame down. You've seen my shop forge haven't you? I've brought it to meetings until recently. It's shooting 6" of dragon's breath out the opening to make welding heat. Listening to Mike has me wanting to slow it down till it starts burning back then speed it up a touch.

Frosty The Lucky.

 

[Mikey98118]

Great discussion guys; love hearing all those details come out, because it gives others some clues about their own "what if" questions.

I get the strong feeling that Frosty "T" burners are good candidates for making into miniature burners like 3/8" (.019" to .022" by 1-1/4" long jet orifices) and 1/4" burners (.010" to .013" by 1/2" long jet orifices). Of course such small jets require different parts then MIG contact tips to come up with the desired  diameters. I would suggest dispenser needles; also called "blunts"; that is just in case anyone out there wants to experiment

Why the constant push for smaller burners? Are there really all that many people who want to build a bean can, or two brick, forge? No; but there are plenty of people who want to get as much efficiency as possible from their equipment, in the face of ever higher energy prices, in an ever tighter general economy.

Granted NA burners have large turn-down ranges. So, at first look it would seem that it doesn't take a wide variety of burners to accommodate a wide number of forges; and so far as it goes, that is true.

But, EFFICIENCY takes more; a hot forge is all about what goes where and how well it burns there. But, for efficiency there is another factor to get control of; exhaust. Its easy to see what goes wrong with too much or too little exhaust. But it seems harder for most folks to wrap their heads around what goes oh so very right when you get some control of exhaust velocity.

That's because we need to get a little sly; we have to sneak up on them, and separate a couple of issues; and that is flame velocity and exhaust velocity, if ever we are to find happiness (that is to say efficiency). Fast flames are good, but fast exhaust is bad.

A great example of what is needed is the ribbon burner. A load of very fast little flames both get quite hot, and still slow way down before they reach the exhaust port. The reason burners are set on a tangent is to cause their combustion gasses to swirl around the equipment's interior, creating a longer exhaust path.

A longer exhaust path increases the amount of "hang time. That's all quite obvious isn't it? What isn't so obvious is that most of that increased time isn't made by the gases running a little further at a given velocity; its because the longer the distant the greater the drop in velocity over that distance.

A bunch of little flames will drop velocity a lot faster than a single large flame; you do the math.

So too, the smaller flames of a pair of 1/2" burners can be turned up faster/higher than a single 3/4" burner on a five gallon propane cylinder forge, and increase efficiency; because they are small enough to create the higher velocity that creates high flame temperatures, without blowing a tongue of fire out the exhaust port . But, what about the guy who wants to build a knife maker's forge from a two gallon refrigerant cylinder? He is going to need two 3/8" burners to do the same trick. The guy how just wants to forge hand tools and folding blades in a coffee can is going to need two 1/4" burners to get there efficiently, isn't he?

And so we see that "bean can burners" are a practical issue after all.

[Mikey98118]

A burner discussion wouldn't be complete without a section on fuels, alas  there are a few problems when it comes to considering fuels; about half the troubles comes from greedy lies; the other half comes from folks wanting easy answers.

The favorite tool for liars is adiabatic flame temperatures; these are arrived at mathematically from sound scientific principles applied with regard to the chemical makeups of various fuels. The concept makes a handy starting point for engineers to use when putting together fresh ideas; it makes a lousy tool for jumping to conclusions from in the real world. Nearly all fuel ratings you'll find on various lists are adiabatic temperatures: they won't tell you that:

(1) Natural gas only delivers about one-half the working heat of propane.

(2) Although propylene only burns at about two-hundred degrees higher than propane in pure oxygen, it will burn between six-hundred and one-thousand degrees higher in air, depending on you burner design.

(3) Butane has such a low pressure at room temperature that that it reaches zero at about thirty degrees.

(4) Acetylene, by far the hottest available fuel gas, is only rated at 3600 degrees burning in air, so when someone states that one of the LPG fuels burns that hot in air, you can be sure they used an adiabatic flame listing right off of some chart.

(5) There is no such thing as MAPP gas; that was a registered trade mark for an MPS fuel gas that hasn't been made since 2008. The real thing was contained in yellow cylinders, similar to the yellow  cylinders used for propylene, which burns within 50 degrees of MAPP gas's claimed burning temperature. So some slick advertiser came up with the idea of calling all those yellow polypropylene canisters down at the hardware store MAPPro and similar names. But if it is about the same flame temperature than "no harm to fault" right? Well, those canisters down to the hardware store costs three-hundred percent the price of propane canisters, while propylene from your local welding supply store costs about thirty percent more than propane. I would say that is plenty of harm. But only to you; its fat profits for them.

 

[Mikey98118]

Aha! he says in one place that propylene can burn up to 1000 degrees hotter in the right burner design. Seems to me that would top out at around 3500 degrees. But is also derided the idea of adiabatic flame temperatures being so close to a much hotter burning fuel (acetylene) Get the tar and feathers boys; we got him now!

Well, no; 3600 degrees is the rated temperature of an air-acetylene flame by the manufacturer of a fuel/air brazing torch. The point of this torch is that it makes gentle laminar flames for brazing expensive gold and other high end filler alloys with, without the flames moving the materials about.

What the air-acetylene flame temperatures might reach from a high speed burner is something I'm not crazy enough to ever attempt to find out!!!

[rjs]

2 hours ago, Mikey98118 said:

 

 

What the air-acetylene flame temperatures might reach from a high speed burner is something I'm not crazy enough to ever attempt to find out!!!

wiki gives 4593 F for acetylene in air

[Frosty]

Engineering chart and converter says 4532f. I know it's not a significant difference but it's the scientific temp F for a stoichometric flame. I probably would've taken your conversion for granted had you not cited wiki.

The most I use wiki for is suggestions for search terms and I go to accredited sites for the real poop.

Frosty The Lucky.

[rjs]

8 hours ago, Frosty said:

Engineering chart and converter says 4532f. I know it's not a significant difference but it's the scientific temp F for a stoichometric flame. I probably would've taken your conversion for granted had you not cited wiki.

The most I use wiki for is suggestions for search terms and I go to accredited sites for the real poop.

Frosty The Lucky.

Thanks you inspired me to do some more reading.

Again from the dreaded wiki  (https://en.wikipedia.org/wiki/Adiabatic_flame_temperature )  I fond the following:

  "In the study of combustion, there are two types of adiabatic flame temperature depending on how the process is completed, constant volume and constant pressure, describing the temperature the combustion products theoretically reach if no energy is lost to the outside environment."

So either the they contradict themselves or the value I quoted earlier was not a constant pressure value.  In any case lets go with 4532 F for this discussion.  the point I was trying to make was the theoretical value for acetylene Is over 900 f higher than the value for propane.

  BTW any time I see a completely round number like 2500 C given I am suspicious  that it may have been rounded off.

But In the end the stuff is just too expensive to use for general blacksmithing  (at least where I live) and I am sure it would quickly destroy any refractory we pointed it at.

So if we were to build the torch that Mikey spoke of (high velocity air acetylene) it is safe to assume the the resultant temperature would be lower than 4532 F

bob   

 

 

 

 

Edited June 6, 2016 by rjs
deleted redundant quote

[Charles R. Stevens]

Carbide and water, lol

[Frosty]

The absolute temperature in the forge chamber isn't dependent on just the absolute temp of the flame. Chamber volume is the most important. If torch temp was the only factor anybody who'd lit an oxy acet torch in a building would be ionized vapor.

You can even use an oxy fuel torch in a forge if you're observant and adjust. Done that a few times for special reasons and don't recommend it for general use.

Frosty The Lucky.

[Mikey98118]

Even using the lowest temperatures given for air-acetylene flames, we find it to be too high to be practical for forges. Even propylene is likely to be just to hot in a forge, unless we are real darn careful.

Over time I've learned not to push the limits too hard with fuels, lest I end up paying out a fortune in special refractories.

[Mikey98118]

• Below is an account of  Frosty's burner history; it has valuable insight into how he want from having ideas to proving them, in stead of using wishful thinking.

"I was given a number of papers printed by companies making various induction devices all toting their advantages and explaining in detail why they were better. It was also a time when you could JUST search the US patent server without being overloaded by marketing BS. Anyway, I learned more about linear inducers like Ron's burners, then there the "ejector" type inducers like the "T", "Sidearm," MIkes, etc. but don't stop there there was a BUNCH of info about the "Amplifier" type inducer of which Mr. Dyson is finally putting into public hands. An "Air Amplifier" induces IIRC 40+ to 1 and so is pretty worthless for a burner.

Anyway, there were a bunch of us messing with the things and I went down the "Ejector" road and I aimed at a build that required NO adjustment in use. There is a reason Ron has a choke plate on is stronger inducers. It's not bad it just is.

When I started using mig tips it was literally because I was getting REALLY tired of drilling holes in pipe caps to make jets. It would've been okay if I could just drill a #58 (or whatever) and it was good to go but NO I have to adjust the air fuel mix to get a good flame. So, I just tapped the pipe nipple and started trying mig tips. Then I discovered after rereading the papers I had, I could increase the induced air by moving the orifice farther upstream. So I cut and clean mig tips to tune the burner now.

By setting up a mock up "burner" using clear plastic tubing I substituted smoke for propane and discovered what I thought was happening actually was. I'd guessed right! The smoke was maintaining a smooth uniform cone as it was blown down the burner tube. Air being induced was then forming toroid turbulence with the smoke. If the tube were too long the toroid formation started breaking up and induction fell off. The pamphlets and patent papers all said 8or9 to one diameter to length. It's an industry standard ratio.

Doing the same experiment with a piece of pipe with a hole drilled in it like Ron's basic design didn't form such a nice uniform cone, it was much more obtuse, it expanded quickly and not so smoothly. This meant he HAD to put his orifice closer to the throat and it had to be smaller in dia. to induce work.

One of my early drawings (I wish would go away!) shows a build using threaded lamp rod and locking nuts to carry the jet. while it was pretty easy to adjust the orifice setback by turning the lamp rod the lamp rod induced a LOT of bad turbulence and inhibited air induction. It worked but it was far from a good design.

You should've seen some of the gas jets I made on my lathe, I came close to commercial performance and would if I set up a metal spinning lathe so I could contour the tube and intake chamber. Unfortunately it would be pretty useless posting those plans here I doubt there are two people here who know how to spin tube on a split die. Heck know what I'm talking about even.

Yeah, my burner can be tricky to get tuned but once it's dialed in you don't have to mess with anything but the fuel pressure.

When I started experimenting with MIG tips I certainly noticed how much better the gas jet was, the MIG tip was acting as a nozzle as well as a quick change artist! Nozzle good and that's all the more I thought about it. a few years later Mike and I exchanged a few emails and he was talking about a accelerator and I was only thinking it's effective whatever it is.

We have two different approaches but we speak the same language. Mike and I trying to discuss the fine points of the hows and whys of these things here is probably more confusing than helpful. I'm not smarter than you guys I've just read about, thought about and tinkered with the things since the early '80s."

Frosty The Lucky

Note: "MIG tips" stands for  Electrical contact tips for yjr metal inert gas welding process.

[Charles R. Stevens]

I acualy think Jerry is wrong on whether your discussions are helpful. When you understand how it works, it's a lot easer to figure out what's going wrong. That's the basis of diagnostics. 

[Mikey98118]

Connections, fittings,tubing, and hose

One of the most watch thread on this forum involves "freezing" fuel cylinders; yet my perusal of it only showed me how little understanding is available on the subject. So, this section will begin where your burner does: at the fuel source.

Touching the high points only: The most common fuel tanks found are five gallon propane cylinders, which have two common problems; to begin with they are simply too small to keep available pressure from falling off in warm whether when running the average gas forge, let alone in winter; the other problem is only common in some states, and that is a builtin excess flow valve, which shuts down if more than the amount of flow it is set for is encountered. You can imagine how little flow is used in a barbecue grill, so if you buy one of these tanks, it isn't going to run a forge.

Getting back to pressure falling off disastrously in small tanks; propane, like all fuel fuel gases, has a vapor pressure (which is about 150 PSI at 70 degrees). As fuel is withdrawn from the tank the refrigeration effect causes the remaining content to cool down; when that happens tank pressure drops; without some way to replace the tanks missing warmth, its pressure would quickly drop to zero. The needed warmth is supplied by the warmth in your shop's air, through the wall of the tank--and no that isn't a very efficient transfer mechanism; it wouldn't work well enough without help from the remaining fuel, which is greedily sucking up incoming warmth from the inside of the steel cylinder wall; this creates still another problem, since only the portion of your tank that still has fuel in it is effectively warming the tank from surrounding air. Thus, the main advantage of larger tanks isn't that there is more wall space, but that the fuel amount falls more slowly!

In fact two 5 gallon tanks ganged together has much more ability to gain warmth from ambient air then one 10 gallon tank does, because of increased surface area. So, considering that the smaller the fuel to surface area ratio is the better for keeping tank pressure up, what is even better than ganged tanks? Fuel hose has vastly more ability to warm its fuel content from shop air than tanks do; as does any pressure pipes you include in your system. But the vary best warmer comes from a small coil of copper tube in some cool (never hot) water. But will it back up and over heat the fuel tank? Not hardly; you need to remember that the cross section of the tube greatly limits its ability to transfer heat the enough through incoming fuel to effect the tank, while copper will transfer heat quite effectively enough to fuel on its way to the burner. One birthday candle under a pan of water would provide enough  to meet your needs. Remember that you only want to keep the water well above freezing; not actually warm.

So, since "more is better" wouldn't a warm water pan be best? NO!!! The safety of your forge requires a burner that is still being continuously cooled down by super cold fuel. It's a balancing act.

 

[Mikey98118]

 

So, how do you get the candle heat high or low enough to work out right? By changing how far or near it is above the pan of water.

[Mikey98118]

Outlet bushings

A 1/4” male pipe thread to  9/1-18 left hand fuel thread outlet bushing is commonly used to allow fuel hose to hook up to regulator outlets (thus the name); it also allows regular fuel hose, such as are found on twin torch leads to be used with things like cylinder fittings and needle valves via pipe thread: https://www.amazon.com/Marshall-ME24C-Outlet-Bushing-Thread/dp/B00Z1WYAVC/ref=sr_1_14?ie=UTF8&qid=1467434253&sr=8-14&keywords=outlet+bushing

But, suppose you live in the UK or South Africa? Wherever you live, your local threading system is going to have the equivalent of an outlet bushing in order to hook up the local fuel hose to the local regulators...

That is 9/-18 left hand fuel thread.

Third times a charm? 9/18” left hand thread.

[Mikey98118]

 

This exchange is from a different thread, but its subject matter belongs here too.

On 7/1/2016 at 10:28 PM, Mikey98118 said:

Don't confuse the higher pressures with much smaller gas jets found on naturally aspirated burners with the much larger gas jets and lower pressures found on SOME fan burners. 4 Lbs pressure on a 3/4" burner is likely to be the bottom of its turn down range.

Andy replied

"Ah - that's interesting. It never occurred to me that there would be a minimum, but it makes sense. I guess why I was confused was that so many of the burner designs (including on Ron Reil's page) go on about how stable various burners are at low pressures (at one point IIRC Ron was talking in the oz's range) so I assumed a good/great burner would work at anywhere 0+."

My reply was:

"Thank you for bringing up this subject, Andy. The more I learn the more I forget the early lessons...

You will find one of my first burner design shown on Ron's burner pages, and I seem to remember that he was running it at the bottom of his regulator's range, but it was a design that ran at much lower mixture speeds than my later burners; it was also a much smaller burner (1/2" copper mixing tube, which would make it the equivalent of a 3/8" (water pipe size) burner if I remember). the larger the burner the nigher the bottom of its turn down range will be. Also the faster the burner is designed to run the higher the bottom of its turn-down range.

That little burner was the last one I ever made that produced a secondary flame envelope; a lack of which that is important to me, but it had a heck of a long turn-down range which was important to him. I have no idea what will end up being important to you or various other folks; this is why I try to write on how things work, so that everyone else can do a better job of making informed decisions, about how to get where they are trying to go. And if where they decide to go makes me laugh, I try to do it quietly"

[Frosty]

It's human nature to get fixed on things and take them as a challenge. We all do it and one of Ron's early experiment challenges was seeing how low a pressure at which he COULD get a stable burner flame. He seemed to have gotten fixed on it and taken it to a practical limit.

Commercial linear burners usually run well below 4psi. IIRC the one on the patch truck ran somewhere in the neighborhood of 2psi. and once I got it tuned we locked down the regulator and choke plate. The patch truck is a dump truck with a largish pan hanging from the box. The pan holds about 1-1.5 yards of "cold mix" asphalt. It has a double floor and in the space is a pipe with holes drilled in it every 6" or so. The burner feeds it air fuel mix and the flames keep the asphalt hot. Yeah, it's a ribbon burner.

If you are intent on running really low pressure all you need do is understand how they work well enough and have good shop skills so you can build such precise devices.

Mikey here got fixed on developing very high performance home built burners. Very similar to Ron but on a slightly different track. If you go far enough both desired conditions are filled by an advanced enough design. EG commercial burners and NO not what you see tacked on modern forges and glass kilns.

Frosty The Lucky.