3D printed plastic burner experiments (photo heavy)

[Mikey98118]

Maybe silicon bronze would do the same job with a lot less hassle for burner parts?

[D.Rotblatt]

Well, I'm back and have had a bit of time to play.  Finally cast by first burner.  Here's a pictorial.  I'm hoping the pictures will explain why I did certain things:

1-This is the 3D printed mold for the core and the exterior mold (with the gray background).  The core mold is clamped together, and the brass rod inserted.  The blue tape around the rod will allow me to insert it in the pipe and make sure the jet is straight.  The brass rod is 7/16" from the hardware store...it's the hobbyist stuff.  A 1/8" schedule 80 pipe (for the jet assembly) fits inside perfectly.

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2-Just the sodium silica and a cup with the sand. 1.5% sodium silicate by weight, but I just pour a little in with the sand.  I used to measure, but I have a feel for it now, and it's not too critical, just shouldn't have too little or the sand will not hold together.  The sand is a very fine mesh sand I got at a foundry.  One bag has lasted over a decade...and it's only about 1/3 empty.

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3-The sand is tamped down a layer at a time.  If you put too much in at first, the bottom will not be packed enough.  Maybe 3/4" layer at a time.  The sand packs down a lot.

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4-Here I'm injecting the sand with carbon dioxide.  I run it at about 15 lbs on the regulator.  The injector is just a 1/8" brass tube with several 1/16" holes in the sides of the end and the end mostly pressed closed.  I don't know it it reads in the pic, but in my hand is just an air blower handle that I attached tubing to.  

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5-Here I'm taking the core apart.  The sand is almost immediately hardened.  It's a quick process.  The holes from the injector are not where bronze will be anyway, or I would fill them with either petrobond or some sodium silicate sand.  Here you can see the brass tube passing through the core.  It's filled with core sand as well and I will be casting over part of it.  Brass melts at a few hundred degrees lower, but I've done this before and it doesn't melt.  I filled it with core sand anyway to prevent it from distorting.

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6-Here the mold is placed in the mold.  The burner pipe is in place, and the blue tape on the brass tube centers the brass rod.

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7-It turned out the burner didn't leave much sand thickness in my box, so I clamped a board on top of the flask to prevent it from breaking due to hydrostatic pressure.  I also made a quick cup to pour in to increase the pressure.

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8-Worked the first time!  I was truly surprised, castings this complicated usually don't and need some futzing. I was really careful to make all thicknesses the same at .25".  And yes Mikey, I did use silicon bronze.  I as going to, but was considering aluminum and your comment supported my initial feeling...thanks!  It's what I usually cast in since I usually do sculptural castings and have hundreds of lbs in stock.  It also make a beautiful cast.  

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Here's the cast with the core broken out a bit.

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In my excitement to cast something, I forgot to cast the choke with it...so here's the choke.

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Here's the burner with mig tip drilled out to .046.  With the choke wide open, it's a good neutral flame.  Stable down to about 1lb on the gauge (or almost not reading), and I took it up to 20lbs on the test (I never go over 15 anyway).

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Closeup of the flame at 5 lbs.

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Problem is, I put it on my ribbon burner in the forge and it ran really rich.  I switched down to a .040 mig tip and voila, it worked great.  Seems that the back pressure was too much for it, or for this burner I need a ribbon burner with more holes.  Unfortunately, that is the same size jet as my ancient Reil Burner.  It may end up that all I have built a really nice looking, chokeable burner.  

To test, I'll run this for 30 minutes in the forge at 5 lbs, and the Reil burner at 5 lbs and see if there is a temperature difference.

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That's it for now!  Cheers,

DanR

 

 

[Mikey98118]

It is a very nice looking burner--BUT-- I totally disagree with you about its potential. It seems to me that you're likely stopping six feet short of the gold. That burner design is quite sound. You need to change the choke; not the rest of the burner. Design a choke with built in fins on a flat plate, or a three way opening; anything to actively promote swirl in the incoming air. That tiny additional emphases is all that is needed to get the most out of your reducer opening; try it, you'll like it

[D.Rotblatt]

5 hours ago, Mikey98118 said:

anything to actively promote swirl in the incoming air.

 I tried some with fins, (copied what I could see of Frankenburner's) but found little difference in the flame.  The flame showed it was swirling, but it wasn't more powerful then the same without fins.  Now, I might not have got it right, since it seems that Frankenburner is getting really good results.   Tried a few with fins around the nozzle but it did not promote the swirl.  Seems the fins have to go around the edge of the intake vortex. It also prevented this easy way of choking, though there are many ways to choke.

The main difference in my experiments that I found was; first, simply the size of the orifice to the burner tube and, second, the shape of the intake orifice (mainly to stability).  I was trying some that necked in and then opened up (what I called the 'Wasp' shape), but they restricted the size of the orifice and mainly just reduced the flame size (and jet size).  I also tried an intake that was shaped like a plumbing reducer (but without the threads, etc) vs. one with flat sides (just a conical intake) vs. one with convex sides (like I am using).  The plumbing reducer shaped intake (I'll call that concave sides) was just less stable at low pressures but produced a good flame, while the closer i got to convex sides decreased the pressure that a induced a stable flame.

I don't know how a swirling inducer (fins) would induce more air into the mix unless it's decreasing turbulence in some way.  I do see how that would mix the gas/air an allow for a shorter burner tube and possibly a more stable flame.  I seem to be getting really good mixing with this.  It's also very very stable.  For example, without the choke on, I can move the jet from 1" inside the tube to 1.5" outside and the only difference in the flame is that it induces more air the further out I put the jet.

Not to say I won't try a few more with fins...if only to make sure it's working.  The problem with fins is that it makes it a really hard cast, since I'm doing a sand cast.  Not impossible, but really hard.  I think I'd have to make a multi part core.  3D printing makes this much more doable.  Actually...it sounds like a nice casting challenge...

First I'll try a temperature test comparing this to the Reil Burner (an old gold standard).  

DanR

[D.Rotblatt]

9 hours ago, D.Rotblatt said:

First I'll try a temperature test comparing this to the Reil Burner (an old gold standard).  

It's a sad day for tinkerers here at the Old Canyon Forge.  I tested my new burner against a Reil Burner with Bourdeaux modification.  I ran them through my modified ribbon burner at 5 lbs pressure (I have a quick release on my propane, so it was the exact same pressure), and ran them until the temperature stabilized.  The thermocouple was not moved either. i.e. the only variable was the burner and the jet on the burner.  I tweeked the mixture on the bronze burner until I got the highest temperature.  The Reil burner has a .036 hole drilled in the  pipe.  I tried the Bronze cast burner with .036 and .039 (and others, but they came out lower temps).  both the .036 and .039 came were the same temp.

Reil Burner: 2198 F

Bronze Burner: 2130 F

The Reil burner is much louder then the new burner, sounds like it is sucking more air or the gas is exiting much faster.  It is possible that the .036 hole in the pipe allows more gas to flow then the longer mig tip, thus my burner could be more efficient and have to be turned up a few pounds pressure to get the same result.  The only way to tell now is to run them at the same temperature for a time and weigh the gas tanks.  Which sounds like a pain.  Especially in 100 degree weather....

The other variable is that this burner may not work well with the ribbon burner nozzle.  It may need a different number of holes since it seems more powerful outside the forge.  I made the ribbon burner head with the Reil burner, so it is "tuned" to it.

Well, I'm trying some finned samples as Mikey suggested.  Took a careful gander at Frankenburners v40 and made some mods to allow for an internal choke.  Not sure if its castable though.

Sigh, back to the drawing board....

DanR

[Goods]

Would casting some spiral ribs into the face of the choke induce the vortex mixing without much lose of induction. One small casting to try?

I have been really enjoying watching the progress here...

Thanks for sharing it!

David

 

[Mikey98118]

Dan,

Sometimes a minor change in balance makes for a major change in the flame. I think that is where you're at. I predict that even a flat disc for a choke plate would provide better performance than you are getting right now.

[Another FrankenBurner]

That is a good looking burner Dan.  Looks a lot like several of the commercial burners I have worked with.  Casting and 3D printing go well together.

What is the large ID of the inlet reducer?  Looks to be 1 3/8" maybe?  What is the ID of the reducer in your Reil Burner?

With the Bordeaux modification, you have got some straight pipe before the convergent section.  I wonder if this is helpful to the Reil burner performance.

[D.Rotblatt]

7 hours ago, Goods said:

Would casting some spiral ribs into the face of the choke induce the vortex mixing without much lose of induction. One small casting to try?

Ive tried that, both shallow and tall ones.  Doesn't seem to make any difference.  Most of the air is pulled in around the nozzle or choke in my case.

7 hours ago, Mikey98118 said:

Sometimes a minor change in balance makes for a major change in the flame. I think that is where you're at. I predict that even a flat disc for a choke plate would provide better performance than you are getting right now.

Thanks Mikey.  I'm definitely going to try some mods - thought I had a good one, but should have tested inside the forge.  

I don't know why a flat choke disc would work better then a conical.  I'd love to know what your thinking is on that.  It seems that the conical choke would focus the stream of air better.

6 hours ago, Another FrankenBurner said:

Casting and 3D printing go well together.

Yes they do.  I'm starting to go a little wonky trying to figure out negative/positive/negative spaces.  I found a command on my CAD program tonight that allows me to create negative spaces of any object I make.  You just merge two objects and subtract one.  Now I have to figure out how to make a multiple piece core (kind of like one of those wood chinese puzzles) in case I want to cast one with fins.

6 hours ago, Another FrankenBurner said:

What is the large ID of the inlet reducer?  Looks to be 1 3/8" maybe?  What is the ID of the reducer in your Reil Burner?

The Riel burner has a 1.75 reducer, and is actually 1.75 ID inside.  The OD of my burner is 2.25 (remember, I'm working with a 3/4" burner tube not 1/2"), but since it is a trumpet shape rather then a bowl, there is no real ID.  The trumpet is .75" deep tapering to the width of the ID of the pipe (.84 I think, but if I rub my finger in there there is no lip).  I believe the radius on the trumpet is 1.75".

6 hours ago, Another FrankenBurner said:

With the Bordeaux modification, you have got some straight pipe before the convergent section.

I was thinking the same thing today when I pulled apart the Reil burner to see what the jet size actually was.  It's certainly food for thought.

I just copied your v40 burner as best I could from the pics (80 degree fin, etc - looking at it I might have made the ring too close to the trumpet...we'll see tomorrow).  Same trumpet as the bronze burner, so the variable is the fins.  I left space in the center for a smaller choke that will plug that hole in the disc and be able to be moved in and out like the bronze one.  We'll see if it pulls more air.

    

 

And for those physics folks, and an interesting factoid (and before one chimes in) - I was taught back in college that there is no 'pulling' in physics only pushing.  The jet is creating a low pressure area, and the pressure of the air around it is pushed into that area. 

DanR

[G-son]

I'm thinking that the two supports going from the "funnel" to the gas assembly could be shaped to help the air start moving around, rather than being more or less square. I don't think it should be a huge difference to cast a different shape there?

[Another FrankenBurner]

I look forward to your results on the new finned burner.  It is looking pretty familiar.  

I am very happy with my burners performance but I have never put them against other 1/2" burner styles for direct comparison.  I may have it all wrong but it is better than my 3/4" modified side arm in my current forge.  I should build 1/2" Mikey, Reil, and Frosty T burners for some fun trials.  Each burner will have it's strong points and better applications.  Balance of forge and burner also being a big factor, I think.

I think you have an apples and oranges kind of thing going on.  Your bronze burner is in the linear category and the finned burner more jet ejector.  As far as I can tell, air inlets on the side is jet ejector, not sure.  I don't understand the science behind it but the guys say jet ejectors have a higher induction ratio than do linear. 

You are also plumbing into a ribbon burner which changes the game.  With such a violent changing of direction and expansion in volume, energy has to be lost.  I don't know if a loss in through put has to be accepted or if a balanced ribbon block makes some of the difference.

As to the fins causing more air to be induced, I don't know that they are.  In mine, there are 3 vortices behind the jet which join into one at the jet which may be causing a lower pressure zone in the eye.  I don't know.  I was playing with the inlet shape quite a bit and without fins, got to bigger mig tips and produced flames which were oxidizing but the secondary flame envelope was larger and fluffier.  Frosty mentioned packets of unmixed fuel and packets of unmixed oxygen in Burners 101.  I suspect that might be what I was seeing.  I wonder if the fins are causing a reduction in total air induced but also a thorough mixing.  Burning all the fuel being more important than having more FAM.  Maybe?  

I do know that if I close the choke a third, the forge runs a little quieter and the flame still looks pretty good but the temperature drops substantially.  

This stuff is fun.  I know more about burners than when I started but the amount of questions has multiplied.  

[D.Rotblatt]

5 hours ago, G-son said:

I don't think it should be a huge difference to cast a different shape there?

You're right about the casting.  I could make them much wider with ease.  It seems 3 openings trump 2, but I'm sure two would make some difference.  In my experiments I did find that it took a lot to get that swirl though.  It would be worth a try, easy to do one on the printer.

1 hour ago, Another FrankenBurner said:

I look forward to your results on the new finned burner.  It is looking pretty familiar.

It should, it's a unabashed copy, and thank you!!!  

There are so many variables here it is mind boggling.  I don't even know if my burner is worse then the Reil.  Both have .036 openings, but the Reil's is about 3/32 deep (thickness of the brass 1/8" pipe) while the other is a mig tip.  The mig tip may restrict the flow due to it's length, and thus the burner may be more efficient, but need to be turned up to a higher pressure. Certainly the dragons breath out of the forge was much greater with the Reil.  I may have to do a several hour run where I am measuring the gas consumed the same temperature rather then pressure, that's a real test of efficiency.  

Most of the DIY burner crowd is going on non-scientific observation.  One person says something is fantastic because it worked for them, so others try it, it works and many people copy it.  But we don't really have a back to back comparison.  I've always had great experience with Reil burners, I tried some sidearms years ago and they just didn't work for me, much poorer heat then my Reil. Wayne Coe used crayons in his first ribbon burner, so everybody followed. I tried 1/8" sprue wax, and it's far superior stability at low pressures to the one I used crayons in (even that is an apples and oranges since my 1/8" is NA and the other is a gun).  Even my Mikey burners don't seem too much different then the Reil when I stick them in my forge, though they work much better outside the forge.  Once more, it may be a pressure/efficiency thing or the Reil may work really well with back pressure.

You are also right that I am using this as an injector for a ribbon burner which is a different application then a straight burner.  Both my forges are set up for ribbon burners right now, though my small one is easily convertible (3 nuts) - I just haven't made the regular burner assembly since my ribbon burner works so well.  I just realized I do have a furnace set up for a regular burner...I'll try them in that today and see if there is a difference.

1 hour ago, Another FrankenBurner said:

This stuff is fun.  I know more about burners than when I started but the amount of questions has multiplied.  

It is!  But it's like the hydra, cut off one head, and it grows two more.  At least it's a fun cuddly hydra to play with!

 I'm loving the 3D printer for making castings.  I've been thinking about it for years, but I've had no practical application.  Models of knife/sword guards and pommels are just easier/quicker to do freehand then on the CAD/3D printer.  And since the model is reusable in sand casting there is no need for multiples.

Cheers!

DanR

[Frosty]

3 hours ago, Another FrankenBurner said:

As far as I can tell, air inlets on the side is jet ejector, not sure.  I don't understand the science behind it but the guys say jet ejectors have a higher induction ratio than do linear. 

A jet ejector's air inlets are at 90* to the jet. The difference between an ejector and a linear's air intake being 90* is the ejector's intakes are in one or two discrete positions where a linear is 360* around the jet's axis.

Jet ejectors are used to create high volumes of LOW pressure, vacuum pumps. The hangars NASA uses to vacuum test probes and space craft are evacuated with jet ejectors the size of semi tankers. 

Linear inducers are used to mix flammable gas and air and I don't know what else.

As I've said I don't know how many times since I started messing with NA burners I don't know why ejectors and linears are so different but they are so I just live with it. 

While tinkering for max performance it might help to remember effective for a burner is in how much flammable mix it can deliver per second. 

If Ron's burner is making a hotter flame it doesn't mean it's making MORE heat. BTUs and Temperature are different things. Air fuel ratio is probably a little leaner if the forge is Hotter but the BTUs delivered may be lower. Ron was using lab grade meters to determine propane flow and it nearly drove him nuts as his forges were still scaling steel while the CO monitors were reading higher than they should. (ON PAPER) That issue was a matter of propane NOT liking to mix with air and the mix wasn't thoroughly mixed so it was burning in packets, some lean some rich.

He was trying to apply exact measurements and calculations to something that wasn't behaving by exact rules. The high efficiency burners being developed every day have been attempting to get propane and air to mix for a long long time. I tend to pump the furnace guys and the guys at the HVAC shop when they have a spare minute. 

Anyway, the point of that last paragraph of rambles is splitting performance hairs. Propane burners seem to have an endless list of the pesky variables to wade through. I just don't think it's practical to try and get the stuff to mix with air completely, if the big makers are still trying I think it's off our radar.

You should see the schematics of an All States oxy propane torch. Lyle when he was alive sent me the prints. I don't know why,  maybe he expected me to become his Alaska Sales rep. Anyway, their torch is designed from the regulators to the nozzles in the tips to MIX propane, not burn it, MIX it. They're crazy internally, swirl strips, grids, deliberate turns, on and on. The propane is metered at crazy low psi. The volume of propane is determined by the volume of oxygen, the meter is in the handle, not the gauges. The jets in the handle that introduce the two together are at angles to each other. Just crazy but it works.

There was an outfit in I think Europe with a really high efficiency propane burner but it required electricity to super heat the propane then a heat exchanger to cool it enough it didn't spontaneously ignite on contact with air. They were almost passing it through an arc, almost causing dissolution into carbon and hydrogen gasses. Weirdness but it worked.

Not suggesting anybody stop tinkering but this is a seemingly endless quest. Then again most tinkerers I've known, myself included are more into the journey than the destination.

I've been staying out of this simply because you guys have progressed WAY out of my wheelhouse. I'm following but don't have much to contribute to the actual tinkering.

Frosty The Lucky.

[Mikey98118]

8 hours ago, D.Rotblatt said:

I don't know why a flat choke disc would work better then a conical.  I'd love to know what your thinking is on that.  It seems that the conical choke would focus the stream of air better.

All I'm basing my guess from is observations of other burners of this type. I've noted that  these burners run hotter at a sweet spot where the choke plate is about 1" away from the reducer opening--hotter than they do at a larger distance. The only reason I can imagine for such an effect is that the plate is causing incoming air to swirl more. Of course I could be wrong, but that is my thinking.

[D.Rotblatt]

9 hours ago, Mikey98118 said:

Of course I could be wrong, but that is my thinking.

Your thinking seems sound to me - and your guess is always an educated one I respect!  This choke also is sweeter between about 3/4 to 1" out also.  Further and I can smell a touch of propane around the burner, it seems to me the jet of gas is widening so it's not all focused into the tube.  

Still thinking and pondering the results...

DanR

[Frosty]

I've observed this about chokes on factory burners as well. I hadn't thought about the position enhancing the vortex but now you mention it . . . Of COURSE! The vortex is caused by conservation of angular momentum, the Coriolis effect from Earth's rotation determines the direction. The choke plate close to the trumpet bell intake acts as a nozzle so air enters at a higher velocity. Higher velocity, more momentum to be conserved = faster stronger vortex.

Plausible?

Frosty The Lucky.

[D.Rotblatt]

10 hours ago, Frosty said:

Plausible?

Yup!  Works for me!

[Mikey98118]

Well, that is a bad sign. If you already see that effect, we have to look for a solution somewhere else. Next choice to try is to reduce the size of the mixing tube, sense you can't increase the size of the reducer. Cut the tube into a short sleeve, and insert the next larger pipe or tube within it. Don't forget to bevel its end, and use a smaller MIG tip.

[Another FrankenBurner]

22 hours ago, D.Rotblatt said:

The mig tip may restrict the flow due to it's length, and thus the burner may be more efficient, but need to be turned up to a higher pressure.

The technical papers which were shared by jwmelvin go into their findings on orifices from pages 11 through 28.  They would call the mig tip a channel orifice vs a sharp edge orifice which has no length of channel.  Pages 16 through 20 have a bit of information about this.  Specifically they speak of gas rates per length of channel vs pressure.  Here is a quote from page 16:

Quote

A study of this figure, the values of which were plotted from Table i, shows that as the length of channel is increased, beginning with a sharp edge, the gas rate rapidly increases and reaches a maximum at a certain length of channel and then gradually decreases.  It should be noted, however, that with the higher pressure the gas rate increases more rapidly than it does at the lower pressure, 

What I found more interesting was their talk of orifice velocity vs fuel pressure and what that does for air induction.  Here is a quote from page 20:

Quote

 This shows that the air injected by the channel orifice is always less than by the sharpedge type, with the same pressure and gas flow. This is because the maximum velocity of the gas, and therefore its momentum, is greater with the sharp-edge orifice than with the channel orifice, and hence its air-entraining power is greater.

Nothing being for free I guess.  They do not go into the possible benefits of the channel type orifice though.  When mig tips were first put into Reil burners, people were saying they made a more powerful burner.  This was in comparison to the hand drilled cross tube which could be roughly drilled and also demands that the fuel change direction right at the shorter length orifice.  I haven't read many people diy making shorter length orifices and the few I have read about had their burner perform better after they followed Frosty/Mikey advice to ditch the home made orifice for a mig tip.  This may be due to a crude rough orifice.  The more laminar jet coming out of the mig tip, punching down the center of the mix tube may be doing such great things that it is worth the loss in jet velocity.  Frosty's shortening of the mig tip to tune his burners may be something worth trying on our burners.  

On 8/31/2019 at 12:24 PM, Frosty said:

The difference between an ejector and a linear's air intake being 90* is the ejector's intakes are in one or two discrete positions where a linear is 360* around the jet's axis.

I think I understand.  With jet ejectors, the jet is surrounded by a low pressure chamber which has specific intakes.

[D.Rotblatt]

Wow....too much info at once!  My brain is exploding!!!  

On 8/31/2019 at 11:24 AM, Frosty said:

Not suggesting anybody stop tinkering but this is a seemingly endless quest.

Yes it is.  And you have much to offer. Love to hear stories about Ron Reil and you guys developing the early DIY burners.  

On 8/31/2019 at 11:24 AM, Frosty said:

If Ron's burner is making a hotter flame it doesn't mean it's making MORE heat.

If I get you right, the hotter flame may be leaner and less efficient (less BTU's) but heat the forge hotter.  One thing I did notice was that the dragons breath on the Riel burner is much larger for the same pressure.  I tried to tune the burners to be the same mixture (neutral for this test), so the flame should be the same temperature.

 

On 8/31/2019 at 11:24 AM, Frosty said:

You should see the schematics of an All States oxy propane torch.

The difference between seat of the pants tinkering and application of science with the backing of a multi-million dollar company....

 

On 9/1/2019 at 9:20 PM, Another FrankenBurner said:

This was in comparison to the hand drilled cross tube which could be roughly drilled and also demands that the fuel change direction right at the shorter length orifice. 

Thanks for the references.  I'll have to read them again.  

 

On 9/1/2019 at 9:20 PM, Another FrankenBurner said:

This was in comparison to the hand drilled cross tube which could be roughly drilled and also demands that the fuel change direction right at the shorter length orifice. 

I don't know if the gas is actually changing direction on the Reil burner.  It's a hole in the center of a 1/8" capped tube rather then a bent tube.  Imagine the gas backing up in a .25 x 3" chamber under pressure (the capped tube), in the side is a hole.  The static gas is pushed straight out the hole rather then turning a corner.  Either way, it seems there might be a large difference between the channel and sharp edge type of orifice.  I'll try shortening the Mig tip, and maybe I'll fabricate a sharp edge tip as well.

I'm also thinking about the lip on the reducer you mentioned.  A little tape and cardboard could add that to my bronze burner.  I'll give that a try as well.  

BURNER TEST UPDATE:

I did try the yellow A.Frankenburner type of injector.  The flame was similar to the one on my burner, but visibly smaller.  Reacted the same when connected to the ribbon burner.  Obviously restriction of the intake due to the fins.  I'd take a break on this and let it stew a bit, but with the heat out here (around 100F) I'm not doing any forging.

DanR

[Mikey98118]

On 8/31/2019 at 3:30 AM, G-son said:

I'm thinking that the two supports going from the "funnel" to the gas assembly could be shaped to help the air start moving around, rather than being more or less square. I don't think it should be a huge difference to cast a different shape there?

You have the right of things.

[Another FrankenBurner]

9 hours ago, D.Rotblatt said:

If I get you right, the hotter flame may be leaner and less efficient (less BTU's) but heat the forge hotter.

I think of flame temperature as energy density.  Whereas BTU's is energy volume.  A perfectly running super hot 3/8" burner puts out less total energy volume than a "colder" poorly running 3/4" burner.  The 3/8" burner may be liberating more of the fuel's possible energy than the 3/4" burner but the 3/4" burner is being given more fuel so it is liberating more total energy.

If the BTU output of two flames is the same but one is higher temperature, it's flame will be smaller/shorter.  More heat per unit of flame area is being output.  

Provided similar mixing, the more air we induce, the hotter the flame.  If we induce too much air, we can increase orifice diameter to increase the fuel in the air-fuel ratio which increases our btu output so long as we don't push the flame so rich that it is liberating less of the possible fuel energy.  

Something I am curious about, in perfect land, if you take two same forges, run them with two different burners outputting the same btu's, one being more efficient and running a higher flame temperature, it will consume less fuel but will the forge also be hotter?  

I ran a modified sidearm 3/4" burner in one of my forges, then I switched to my 1/2" burner, the forge uses less fuel and it also runs hotter.  I don't know if this is because the 3/4" burner was running so poorly that it was outputting less btu's than the 1/2" or if the higher temperature of the 1/2" causes the forge to attain the higher temperatures.  Maybe a little of both?

Hopefully that all makes sense, it does in my head.  After all of my treatments, I think I still have all my marbles but they are a lot more difficult to herd some days.

[Mikey98118]

7 hours ago, Another FrankenBurner said:

I think of flame temperature as energy density.  Whereas BTU's is energy volume.

Yes, yes, yes!!!

[Buzzkill]

On 8/31/2019 at 3:18 PM, Mikey98118 said:

All I'm basing my guess from is observations of other burners of this type. I've noted that  these burners run hotter at a sweet spot where the choke plate is about 1" away from the reducer opening--hotter than they do at a larger distance. The only reason I can imagine for such an effect is that the plate is causing incoming air to swirl more. Of course I could be wrong, but that is my thinking. 

The following may have no relevance whatsoever due to the number of variables involved, but I'll throw it out there anyway.

Several decades ago we had a drainage problem in a field.  The water had to exit down a vertical tube into a tile system.  What we found is that the natural vortex actually decreased the amount of water that could drain in a certain amount of time.  The solution was we built a flat circular plate that was installed a few inches above the vertical tube entrance.  This cut down on the swirling effect and increased the rate at which water drained from the field.

Again, I have no idea if that would apply here or even why it worked, but I can tell you that it did work.  Perhaps it's another balancing issue - maximum vortex for mixing may decrease the maximum amount of air that can be drawn in.

[Mikey98118]

That is likely to remain a mystery. Twenty-five years ago I had to re plumb nearly the entire house, and found out that plumbing has its own set of hard and fast rules. Water is, for all practical purposes, not compressible. But, when designing burners, I treat air as though it isn't compressible either. But gravity isn't a factor in burner design, but it is a very potent factor in plumbing; all this to say "I'm not jumping down that rabbit hole"