Burners 101

[Ted Ewert]

15 hours ago, Frosty said:

Ted:  You've figured out a working ribbon burner, I don't see how it's easier nor better than the method I used but that's okay, it works.

I'm not saying it's better, just easier to make. Using investment casting is much more time consuming and labor intensive than simply drilling holes or using removable rods. Acrylic,  as a nonstick framing material, is also easier than painting and screwing together wood. The end result is pretty much the same, although I also taper the holes once they are drilled (or formed).

 

15 hours ago, Frosty said:

YOU have introduced a vortex in the fuel air mix. You want it because you believe it accelerates the fuel air mix. Why you want this I don't know, I think you'll figure out high velocity fuel air and fame are actually bad things. The vortex on the other hand is a G-O-O-D thing as it will develop a more thoroughly mixed fuel air supply in the chamber.

I use velocity as a means to increase pressure. I have a bunch of long 1/4" holes I have to push air through, and the more pressure I can generate the more air I can get through those holes. Nevertheless, this is still secondary to the mixing properties of a vortex.

Another property of a vortex, which you may not be aware of, is that it allows more air to be blown through a given size pipe than a linear flow would. This is because a vortex creates coaxial laminations which have friction free boundary zones between them. This allows the inner laminations to slide past the outermost layer at whatever rate the pressure dictates. There is a patented device which uses this principal to pump highly viscous oil through long distances of pipe. 

If this all seems contrary to standard aerodynamics, it is. If you still need more convincing, study how a Hilsch- Rankine Vortex tube works.

 

Cheers,

 

Ted

[Mikey98118]

3 hours ago, AnotherCurtis said:

For now, only one train of burner questions.  Sort of burner questions.  Idle valves.  Are they worth the effort?  Does the forge chamber maintain a high enough temperature to not have to wait upon return?  Does it cause thermal cycling of the wall materials in a way which they won't like?  Does it require a choke which should to be adjusted when set to idle?  I would guess several of the questions will be answered with: it depends on the burner.

Welcome tp the forum, Curtis 

We call them idle circuits, and yes, they need both a ball  valve and a needle valve, so that the circuit can be used with the forge's burner(s) running at various gas pressures. They can contribute quite a bit of efficiency to fuel use. The only kind of burner I doubt the efficacy of their use with, would be a commercial fan-blown ribbon burner; but I could be wrong about that.

[Frosty]

4 minutes ago, Ted Ewert said:

I'm not saying it's better, just easier to make. Using investment casting is much more time consuming and labor intensive than simply drilling holes or using removable rods. Acrylic,  as a nonstick framing material, is also easier than painting and screwing together wood. The end result is pretty much the same, although I also taper the holes once they are drilled (or formed).

Uh huh. You use a clamp together form and I use a couple sections that simply screw down. How is clamping a form together any easier than power driving two screws? You had to  measure, cut and fit the sections you use for a form, how is that different than cutting one 2" x 6" and 3 cuts in a 2" x 2"?  so I sanded and sprayed them with Krylon? that took maybe 10 minutes once. I thought about using plastic but using common framing lumber gave me a lot more flexibility. Without doing anything but deciding what I want, I can adjust the length from zero to 12" for no more effort than measuring and screwing the form down. The other side of the 2" x 6" x 16" base is sanded and painted on both sides, that's why it took me 10 minutes to sand and seal.

I'll cede the hassle of wiping the form with vegetable grease as a release agent but I'll find something else if I make many more.

I tried drilling but set Kastolite 30 just eats bits and masonry bits chatter too much, making sloppy outlets. If I want tapered outlets, (I tried and discarded that idea before starting the NARB thread) using larger Dia. crayons and tapering them by rolling on a warmed surface with different thickness kiss blocks is really easy. I've already tried that as well as making a tapered reamer but tapered outlets made no significant difference.

Those are just observations from my experiments in spite of the commonly available commercially available multiple outlet burners utter lack of tapered outlets. multiple outlet burners have been around since (as far as my limited research showed) around the American Civil war but probably since the availability of Brown gas, before gas lamps even. Patents W/ drawings are easily found once you get past the adds. Not one patented multiple outlet burner shows tapered outlets. I'll cede here than I didn't look at all of them, I only wanted to learn enough about multiple outlet burners to make ones.

I have different goals than Mike or Ron Reil for my burner plans, design is a little too presumptuous for my taste, I developed my burners to be efficient and effective but requiring minimal shop skills and equipment. Had I gone the way of developing the MOST efficient NA burners I'd be spinning them from Inconel with full length tapered tubes and selling them for a couple hundred a pop. I grew up in a metal spinning shop and not only have a good handle on machine shop operations I can design and turn a split die and relearn to spin. Been there done that and took a different path for those folks who just want something that works and doesn't need anything more sophisticated than access to a drill press and a few hand tools.

Yeah, I have a handle on Bernoulli's principles where it applies to a fluid moving over a curved surface, inside, outside or along, boundary layers and. . .  I even know the difference between Bernoulli's principles of fluidics and Venturii's.

Efforts to impress me by dropping names is as tiresome as listing the texts I own and have read, web & library research, yada yada yada, I've done. These things only seem counter intuitive if you're just discovering them. Most are just restatements of and patents using centuries old knowledge. For example of having a good handle on fluidics and just discovering it. Your increase in velocity is the result of a reduction in pressure. Any real increase in pressure disrupts a vortex. 

I'll back away from your desire to figure it all out yourself though. Enjoy your journey.

Frosty The Lucky.

[Mikey98118]

To call ourselves burner inventors might be presumptuous (although legally acurate), but I'm comfortable calling myself and others  burner designers 

[Frosty]

I'll cop to designer . . .  on a technicality.

Frosty The Lucky.

[Mikey98118]

Ball valve only idler assemblies

instead of an idler circuit consisting of both ball and needle valves and various pipe or tube parts, a much simpler idler assembly can be made with a ball valve mounted on a metal plate with two "U" bolts. A typical ball valve goes from open to close in a quarter turn; this permits it to be used for gas flow, instead of only an open/closed valve.

The supposed downside of this use is friction damage to the valve. There are three reasons for this objection being underwhelming: First is that the flow is gas--not liquid; secondly that gas is held down to 30 PSI with a regulator; thirdly, these valves are cheap and easily replaced if the where and tear ever becomes noticeable. Not only is this assembly cheaper and smaller than an idler circuit, but it only needs an input and exit point to keep gas tight.

Full open position is provided by the valve, with partially open provided by a movable slide within a slot in the mounting plate for those who like things complicated, or by a bolt in a series of threaded holes for those who like to keep things simple.

I have built this device (page 84 of Gas burners); it works and is a whole lot easier than an idler circuit to build; so why not talk about it before now? I prefer the precise working of a needle valve. In other words, it offends me 

Still, I would rather people builds this idler assembly, than to skip building an idler circuit.

 

[Mikey98118]

Dang, Frosty!

I gave in to the KISS formula all over the place; You should at least say "aha!" or something 

[Ted Ewert]

I set up a test today to see how the ribbon burner worked in my little forge. When I first fired it up I had a lot of sputtering in the flame. Even though I had the spinner on it, I had two 90s in the line and that messed things up evidently. I took out one of the 90s which helped a lot. 

I got to thinking about this mixing problem. There has to be an easier way. I tried a twisted piece of sheet metal to induce spin. This fits right inside a 2" pipe:

It helped a little if I put it before the gas inlet. The flame still sputtered a bit though.

The next thing I tried has probably been used before since it's fairly simple. I machined a piece of 5/8" round stock by drilling a hole almost all the way through it. Then I drilled a bunch of smaller holes as outlets:

This fits snugly into the 1/2" nipple I have going into the 2" pipe. It sticks out into the airstream and distributes the gas much more evenly.

I glued it into the nipple and assembled it into the valve train.

This thing works great! I immediately had to turn down both the gas and the air to get the same flame I was getting before. The flame was nice and steady too. (I'm keeping my needle valve no matter what you say Mikey )

I had the blower wide open before this and had to turn it down to this point to get a good mix

Here's the flame

I can only conclude that this mixing tube has significantly increased the efficiency of the burner. I just picked a random drill bit and number of holes, so I'm sure some improvement can be made. I would highly recommend this to anyone who has a blown burner. 

 

Ted

[Frosty]

On 7/11/2018 at 11:15 AM, Mikey98118 said:

Dang, Frosty!

I gave in to the KISS formula all over the place; You should at least say "aha!" or something 

Aha? 

I've never bothered with an idle circuit, I usually leave it running. If I was doing something that took long enough I wanted to save fuel I'd shut it down and let residual heat re-light it a minute or so before I needed it again. 

However if a person needs to idle the burner throttling the fuel valve makes a LOT more sense than a dedicated circuit. KISS rules. 

Frosty The Lucky.

[Another FrankenBurner]

Back on page 35, G-son gave a cone making tutorial.  I had written a small program a while back that will layout the template.  It can output a dxf file which can be used for scale printing or cnc cutting or give the numbers for manual layout.  It takes the top and bottom radius/diameter and either a height or angle to output.  I originally wrote it to produce the frustum for a cyclone separation system but it would work equally well to produce cones for burner purposes.  I have found that a frustum in light stainless can be rolled with some round stock of the right size, my own thigh, and a little sweat.

Here is a shot of the program and it's output file:

 

I have also written a less refined but very functional square to round transition producer.  This was for some HVAC work but might be useful to someone here.  Here are a couple of images of it's outputs, one flat layout, one 3d model:

 

Both programs are a little over 50 KB each but zipped are under 12 KB each.  Less then the images I uploaded here.  They are legacy VB6 applications but still work properly with Windows 10.  If anyone is interested, let me know and I can upload one or both.

 

 

[Mikey98118]

 

thank you Curtis.

[Mikey98118]

The central problem today isn't deliberate lying;

its a total disregard for the difference between what sounds convenient and what is so.

No; I'm not talking about public opinion on who did what and why. What I'm describing is a total disconnect with facts and sound judgement. When we start practicing double-think, we lose the ability to ferret out actual facts. Just getting close to the truth about anything is hard. When we spend most of our time spinning opinion instead of winnowing wheat from chaff, how do we expect to solve complex technical problems that combustion engineers have been working on for the last century?

Twenty years ago I started looking hard for answers on fuel-air heating; I'm still looking hard; mostly what I've learned is how to learn... 

[stevomiller]

Dang Mikey, that last line says it all in most pursuits one dedicates themselves to deeply, and is a great reminder for all of us in life.

I’m at this same point in my engineering career.

The young ones under me come in hungry to learn but a little over confident, and I start wit high hopes for them.

Then they get a few years under their belt and they know everything but what they don’t know, and make themselves as the end all and spend as much time selling themselves to management as actually working on issues. I’m not enlightened yet, but I’ve tripped on my myself and eaten enough self baked humble pie, to realize I have not even scratched the surface of my profession.

[stevomiller]

Mikey, back to your injector burner from your book.

Have you ever used the slotted air induction with a flared mixer tube, such as the industrial inline burners use?

Can it add anything to the performance, or is it ill advised and going backwards? I’m still trying to fully grasp all the interactions and physics of the different designs.

I ask because I have access to some taper flared stainless and cast iron tubes for reasonable cost I might experiment with as a side project.

If I do, should I use the narrowest part of the throat and pick an initial gas orifice used in a straight iron pipe mixer tube of the same ID?

Or somewhat larger due to less frictional losses and back pressure (my assumption not claiming this as factual)?

Asking more for a nudge in what might be the correct direction, and not trying to suck your well dry.

I’m happy to experiment and develop on my own, but am so new at this I don’t want to pursue a fools errand unwittingly.

[Frosty]

Steve: What you and Mike are referring to in your last comments about new folk knowing everything but what they don't know is an expression of the Dunning Kruger articles. To be blunt a person doesn't know enough to know how little they know. They noted that the less people knew about a subject the more confident they were they could master it and the more a person knew the less confident they were.

A few years ago commercial burners were tapered the full length from throat to outlet at less than a 1:12 ratio. More than 1:12 causes bad "roiling" turbulence and inhibits induction. Linear induction devices can be sighted through lengthways like a telescope and the air intake is properly a trumpet shape to do two significant things: First, fluid flowing over a curved surface creates a boundary layer that reduces friction lowers pressure and accelerates the flow (more air). Secondly the trumpet flare induces a vortex to the flow increasing Bernoulli effect as just described.

There are two flows, the primary and the secondary, think of them as master and slave if that helps. When the primary flow leaves the jet it expands in a smooth cone but maintains velocity, lowering pressure inducing flow from the only available direction the air intake. When the secondary flow passes the throat it begins expanding into the mixing tube as it expands pressure falls further and it induces intake air flow. 

If the mixing tube is straight then the rate of expansion is limited so induction is likewise limited. In a tapered tube the flow expands as it travels down the tube increasing induction. 

Jet ejectors weren't used for burners their prime strength is developing vacuum. The induction ratio is roughly 27:1 meaning for every cubic inch, foot, cubit, whatever through the primary 27x that volume exits the outlet end. 72:1 is well outside the flammable range of propane so it's easy to detune one to produce a decent flame in a home made burner. A linear inducer tweaked to excellent is a 17:1 inducer so you need to do a better job to get anything near full performance.

That's the short story.

Frosty The Lucky.

[stevomiller]

Frosty thanks for the distillation of information, your sharing is much appreciated.

So it would appear then that the tapered tube would improve flow and increase the entrained air to fuel ratio on a jet ejector burner, but since they can already provide excess air to feed the combustion it’s not needed. 

Would I guess then that a tapered tube with a throat equivalent to 1/2” pipe would use a gas orifice the size midway between that used in a 1/2”and a 3/4” cylindrical tubed burner, as a starting point? Or do I have to start with the 1/2” size, evaluate the flame, and work up in size stopping before I reach a rich flame, so that I can then tune with the sliding choke? If this is an unknown that’s ok, I know I’m asking a ton of question that aren’t relevant to any of the common “build yourself burners”.

Is it possible it might provide better air/fuel mixing than the parallel walled tubes? It would definitely slow the velocity of the burning flame, which could be better or worse depending on the exact application.

And have you or Mikey played with fuel nozzle orifices designed to provide shaped discharge? In the past at work I’ve used precision nozzles that made 10* to 60* cones, both solid cone or just circular ring/empty core spray. It might be a method to either optimize the volume of entrained air or help with homogenizing the air/fuel mixture.

Best

Steve

[Frosty]

I can't say what the jet sizes should be in a tapered tube burner but they can operate at lower psi for the same effect. Jet dia. changes are pretty much the same as mixing tube dia. in pipe burners, 2x tube dia = 2x jet dia. it's not an exactly true match but close enough to tune.

You can winkle out the jet size you like as you describe, it's how I did it. AND because I'm lazy I drilled and tapped a fitting to take mig contact tips rather than drilling jet holes and mounting all that junk every time I tried a different size jet. I still have a plastic jewelry part index box with the mig contact tips I used experimenting on my first T burner, I had it in my hands today looking for a fitting.  Funny you should ask eh?

The flow in a tapered tube moves at a lower velocity and significantly lower psi so yes the propane and air mix more readily.  The lower the flame velocity at the burner nozzle the better, the fire stays IN the forge chamber longer so transfers more energy to the liner. This is one of the really attractive features of the NARB the flame velocity is really low so the forge is hotter for less fuel. 

Back when, I fantasized about fuel nozzles like you describe. I'd love to know how they'd effect burner performance. I get kind of shivery just thinking about a ring patterned propane jet with a cavitation inducer centered in the stream.  If it works like I think it would it'd mix the air fuel as completely as maybe possible. 

Hmmmmm.

Frosty The Lucky.

[Mikey98118]

1 hour ago, stevomiller said:

If this is an unknown that’s ok, I know I’m asking a ton of question that aren’t relevant to any of the common “build yourself burners”.

Both of you have brought up so many good points that we need to slow down and go over them one at a time. Alas, I'm going to start out by adding more generalities to them:

Generally speaking, jet-ejector burners are stronger running than linear burners. On the other hand, old style Ron Riel burners with my MIG tip modification ran  almost as hot as the Mikey burner design. Why this fact has never stirred public notice in the last twenty years is a mystery to me; especially as linear burners are much easier for newbies to tune.

No matter how high the gas and air inputs into burners are, the flame can only remain on a burner,s flame retention nozzle until it overcomes the differences in ambient air pressure (or the somewhat higher differences in a forge's burning chamber pressure), and the partial vacuum created by the flame retention nozzle. 

The harder your burner's air swirls--whether jet-ejector or linear style-- the lower mixture pressure in the flame retention nozzle is going to be. Therefore, the burner with the greatest potential will inevitably be a linear burners with a built-in vortex generating fan.

 

this is why I keep coming back to Vortex burners. on the other hand, multi-flame burner heads (ex. ribbon burners) have the greatest potential to work efficiently in most heating equipment, for entirely unrelated reasons. Either path has great potential for success. And so I also recommend them.

It became apparent to me that there must be ten guys who want to design their own burners for every guy who just want to get on with building his forge, and so these pages have been filled with the information those guys need to "wing it."

to be truthful, I never held out much hope for them, and most have crashed and burned, learning good lessons along the way to recovery, which most of them also saw. BUT THERE HAVE ALSO BEEN DRAW JOPPING EXCEPTIONS who broke half my little rules and still made the magic flame. After I wiped the egg off my face, they herd my applause--loud and long! After all, the successful designers started out just like them, even if it's hard to think we were ever that young 

[Frosty]

Those -

14 hours ago, Mikey98118 said:

DRAW JOPPING

 

- exceptions really set my head to spinning too MIke. 

Nothing makes my day like a good typo unless maybe it's a good straight line too. 

Frosty The Lucky.

[John in Oly, WA]

I'm back from my adventures with vortex burners...

Fun with Vortex Burners

I’ll preface this with saying I’m not a videographer or video maker of any kind, well maybe the most novice kind. So, the sound is bad, the focus of the video is sometimes out of frame, wobble, etc. etc. The first video, it was raining so hard, it just sounds like static in the background. Also, I'm no expert at building or designing propane burners. Just following Mikey's instructions (mostly) and then going off on tangents.

For what it’s worth, here are my builds and my odd experimenting.

Right off the bat, I started this process on the wrong foot. My simple calculation regarding the ratio between the fan opening in the funnel and the mixing tube diameter of 3:1 didn’t take into account the large hub in the middle of the fan blocking a good portion of the opening. So, the first two burners I made, one using the stainless steel plumbing reducer and the other, the sausage stuffer tube didn’t work so well. If I'd have listened to the 70mm part...

And the fact that I couldn’t find a reducer with a larger diameter, something close to 70mm, at the big end, pretty much ruled that out as a build method. Same with the sausage stuffer tube. Couldn’t find one with a large diameter at the big end that didn’t require several layers of 1/2” thick aluminum plate and tapered holes through each one to get to the 70mm fan diameter. I gave up on that method before I arrived at a finished burner.

So, the wine funnel method may be the way to go. Although, I didn’t try that method. I jumped to my 3D printer and printed a funnel. First of a size for a 60mm fan, because I was still stuck on that path. And then a 70mm 3D printed funnel. To me, that was the easiest build method. The printing took between 22 and 26 hours on my printer, but that was the printer working, not me.

The first video is my results with the stainless steel plumbing reducer and the 60mm 3D printed funnel. Not successful at all, so I didn’t bother to show the build process.

The second video is the 70mm printed funnel. Works a little better, but I didn’t spend any time tuning the burner - changing mig tips might have helped. I didn’t think at this point to show the flame from the front. In the first video, I went back and relit the stainless steel reducer burner and videoed the front of the flame.

The third video, I took a left turn because I wanted more air in the mix (and more power arr, arr, arr- one of those guy things) and I like the gas input tube to go straight down the middle from the back, rather than coming in from the side - easier to adjust. I drew up a vortex generator for the 70mm funnel to fit a squirrel cage fan and 3d printed that. My CAD skills are lacking, so it looks terrible (and took 36 hours to print), but the inside is generally the shape I wanted - not knowing anything about angles and air flow. And the swirl looking back into the front of the flame is beautiful, I could watch that for hours.

The fourth and fifth videos are of a burner with a passive vortex generator. I wanted to get away from the dependence on electricity. The simple is better theory. The fourth video, the vortex generator is very short with a heavy twist to it (my lacking ability in CAD). The fifth, I managed to figure out how to stretch the spiral vanes in the CAD program without them changing into odd shapes. The last segment of the fifth video, with the longer vortex generator, is using a .023 mig tip. All the other burner variations in all the videos used a .030 mig tip.

View at your own risk. LOL

Vortex burner part 1

Vortex burner part 2

Vortex burner part 3

Vortex burner part 4

Vortex burner part 5

[Mikey98118]

2 hours ago, John in Oly, WA said:

My simple calculation regarding the ratio between the fan opening in the funnel and the mixing tube diameter of 3:1 didn’t take into account the large hub in the middle of the fan blocking a good portion of the opening.

Nor is that central area of fan hub relevant. These fans are set up with impeller blades, which fling incoming air primarily outward; not primarily forward like regular axial fans; so the "big central hub" does nothing to interfere with vortex formation, because that big central area is a weak vacuum.

And thus the gas tube is placed just beyond that fan, where it creates the least interference with air flow, rather than further forward where it will do a huge amount of damage to air flow; greatly disrupting the vortex.

[Ted Ewert]

Interesting experiments, thanks for posting them. As far as fans go, I think the blower (squirrel cage) works the best for burners in general. 

Did you find any significant advantage to using a vortex over a linear flow? It's interesting how the heat will always migrate to the outside of a vortex. A vortex (when spinning quickly) will separate the flow to hot around the outside and cold in the middle. Centrifugal being the hot component and centripetal being the cold component. You can observe this same phenomenon in weather systems. 

[John in Oly, WA]

Mikey, while the fan's hub doesn't appear to interfere with vortex formation, it does just generally block airflow - makes the opening smaller - which to my untrained eye made the flame look much richer (a lot of secondary flame). So I should have listened to your statement of using a 70mm fan. But I'd already purchased the parts for the 60mm fan, so I went down that road for a bit. Then switched horses mid stream.

Ted, I liked the flame of the squirrel cage burner more than the others, but I only put one of them to use one time. I put the squirrel cage burner into a large foundry and melted a crucible (maybe B20 or 30, about 8-9" top diameter) of aluminum - that took 40 minutes from cold foundry to pouring aluminum. But it was a big foundry. Mikey, do you know what size crucible is in Bill's foundry?

Mostly this was just a run through of preliminary tests. Other than the last one - the long passive vortex - I didn't try changing mig tips or tuning any other aspect. I also didn't build in any adjustable speed control on the fans, or chokes on the air supply. So it was like riding a one speed bicycle - no way to change the flame from rich to lean. And the squirrel cage version probably falls into the blown burner category, rather than the NA, so that was a bit of a departure from the parameters of the experimenting.

The thing I most liked was the change in flame shape when the fan was turned on. It looked like the flame was thrown to the outside of the stream changing it from a cone to more of a crown and looked like it slowed down a bit, or maybe the speed stayed the same, but the air flow changed from straight line to rotational.

Next I need to set up some adjustability and put them in a forge.

[Frosty]

I'm getting a little lost here guys.

Mike first. Is your vortex burner: Naturally Aspirated, a Gun or some sort of combination?

John: I'm not wading through all your videos, I took your suggestion and looked at #4&5 but there's nothing to see of the construction, just a round plastic thing blocked view and a shot of an okay flame.

Ted: Without knowing if we're talking NA or Gun burner I don't know if a Squirrel cage or impeller fan blower actually makes a significant difference. 

Frosty The Lucky.

 

[Another FrankenBurner]

Frosty:  Back on page 40, John in Oly,WA posted a image which demonstrates the concept of the vortex burner.  It is a linear burner with an impeller axial fan at the air inlet reducer.  The purpose of the fan being to increase vortex down the mix tube more so then to provide air force.  Mikey said they can be run without power to the fan as just the vanes are enough to promote swirl of the induced air but the main purpose is to run the fan to increase the output capabilities of the burner based on the vortex.  In John's number 4 and 5 videos, the burners are skipping the fan all together and the white plastic things are just vane devices to cause the induction air to swirl.