Another FrankenBurner

3D printed plastic burner experiments (photo heavy)

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We did some pours today.  Several failures and lots of learning.  We are excited for the next attempt.  We had one burner turn out.  It is our best so far.  

We broke our iron ingot for some more learning.  We also drilled a hole in it, tapped the hole, threaded in a bolt, and hammered the bolt.  It is tough stuff.

ingot.jpg.cc245e49b5af5b990a1689368aaeaed7.jpg

The cast on the left is a piece of the material used to pour the ingot on the right.  When you are used to aluminum ingots, iron is heavy.  

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Continued experiments on printed injectors.  As I played with the designs, I found that the larger the opening the better it seemed to work.  Is the wasp waist even worthwhile?  So I ran a series of tests with the burners I had to see if I was going in the right direction - from no injector to a couple of my best.

Here's an overview of my thinking so far: there are 3 areas that area variables in the injector.

A)  I'll call this the intake.  This correlates to the bowl shaped part of the pipe reducer in the Reil Burner or other plumbing made burners.  The intake can be made in one of several shapes.  Either concave sides like a plumbing reducer, flat like the 1920 article pic below, or convex like in my burner.  

a sample of my burner: 43718228_WaspBurnerDiagram.png.1fb687bfbb4e81d12e3d28ebee7947ab.png  Pics from a 1920 article:2090239882_Untitled2.jpg.51c49fd682488503d0af986c1f580598.jpg

b) The size of the opening, and C) the waist.  The waist can either be nonexistent (in which case the opening will terminate on the end of the pipe) or can taper like in a burner nozzle (or see both pics above).  A smaller opening then the size of the pipe will be required to allow the waist to taper.  It is a trade off.  If you want a lot of taper, or a long waist, you need to make the opening much smaller then the pipe. The idea of the waist is to create the bornouli effect and increase the speed of the gas, decrease the pressure in the opening and pull in more gas and hopefully mix the gas.

Here's the problem in real life, as I was playing with different sizes in the variables, I found that in order to make a waist or much of a taper, I had to make a smaller opening. All of the permutations had very good flames, but as the opening increased, more air was pulled in and I had to move up to larger and larger mig tip sizes, from .030 with a .5" opening, to a .048 jet with a .75 opening.  It appeared that the larger openings were more efficient.

I began to wonder if a waist was necessary at all.  So I tried a series starting with no injector at all and adding the variables one by one (if possible).  All were at 5 lbs psi on the gauge with the same jet size, I tried to position the jet around the same distance from the injector.  All the injectors work well from nearly 0 psi to 15 psi on the gauge.   I don't know what the yellow flames were.  Something burning or being blown through the burner.

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1-No injector at all.  Just a jet in front of a pipe.  Actually a rather decent flame, considering.  Primary flame is feathery but a bit unstable.  

IMG_7975.JPG.bc60f7fde04b7c178361334ebfcd1f8f.JPGIMG_7977.JPG.5fb46e31b65747afa7d6a8df94b58d23.JPG

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2-I added my choke plate.  It didn't make much difference, but it did allow me vary the fuel mixture if I wanted by moving the jet forward or back.

IMG_7978.JPG.a1fe430016f9c03236c8c157ec5a9c54.JPGIMG_7980.JPG.32242ce6515d4a93af2529a0cfe472a6.JPG

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3- This injector is an early one.  It has no waist, and a .84" opening (the ID of the 3/4" pipe) and convex sides (much like my picture above).  The .75" marking refers to the length of the intake.  If you compare it to pic #1 you can see it created a larger and much more stable flame.

IMG_7981.JPG.7a4749860ea69a96dc4a1b6a98b353d9.JPGIMG_7984.JPG.f759e4b40d9d5f1eb5cdb7a7f4d8740e.JPG

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4-Here I added the choke.  This produced an even bigger and smoother flame.  I seems the combination of the two focuses the air even better then the intake alone.  The flame went a bit lean here, so a larger jet size would be possible.  Maybe .048".

IMG_7985.JPG.a3f7992c4586674f32501cc71e289692.JPGIMG_7987.JPG.44eedf049352cf7b8bbe51f7c24c5b09.JPG

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5- in this test I used the best of my wasp injectors.  The flame is a bit smaller, and a bit rich, but the opening is only .69".  This burner works best with a .042 jet rather then the .046 jet I have on it.  The smaller flame is due to the smaller opening.   

IMG_7988.JPG.95c6f566e5a1bec635eb797366e95bb7.JPGIMG_7990.JPG.38c08c995c247c97055750702cd23d86.JPG 

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6- Not a good comparison, but this is similar to the burner above, but with a spiral intake, .5" opening and 1" long waist.  Because of the smaller opening (and the spirals which also restrict air intake), this burner uses a .030 jet size.  I found the spiral intake produced a fine flame, but not at low pressures where the spiral motion of the gas down the pipe caused the flame wobble and to be more unstable.  It would probably work fine inside a forge.

IMG_7950.JPG.a9b3f240f3d8979670da4dceb37d5092.JPGIMG_7954.JPG.c223f4d0822858279f9d2fac832e3075.JPG

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CONCLUSIONS:

1: To my relief, the injectors are increasing the intake of air significantly.  The shape of the intake may be important (the next variable to play with).

2: The choke also added to efficiency a surprising amount and is a fortuitous discovery.  I don't know why, but this is good since I really like to be able to reduce the mixture of the gas.  The concave sides of the choke pretty much mirror the convex sides of the intake creating a kind of funnel for the air.

3: A waist, because it requires a smaller opening, decreases the volume of air being pulled in, thus creating a smaller flame.  The characteristic of the flame is, never the less, very good.  But the flame is not better then a similar injector with no waist and is thus, less efficient.

4: The spirals around the intake restrict air flow (I tried a few exact same burners with and without spirals and the ones with spirals required smaller jets) and cause instability at low pressures (under 1 lb PSI).  This is contrary to Another Frankenburners experiments, but my spirals may be different than his - I copied them from his pictures.  Further, I have a moveable choke while he doesn't.

***A burner like the one pictured in pic #4 had the largest flame at the same psi and jet size.  It would also be very easy to sand cast (which is one of my requirements for this experiment).  The larger the opening, the more air the burner can pull in, the larger the jet size required, the more efficient the burner.  Thus a burner with the largest opening is ideal.

***The moveable choke/jet design allows both for adjustment of the mixture and for ease in casting.  The burner and choke can be cast in two pieces.  This would have worked even with the spiral style of burner, but I don't think I'll be moving in that direction.  

DanR

 

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Have you considered ditching the straight mixing tube, and follow the 1920s design more? The expanding cone seems to BE the mixing tube in that design. A shallower angle may be in order to keep the flame from going back in there at low pressures, but that means a standard pipe mixing tube may be useable, a slight angle could be cut in it with a lathe.

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7 hours ago, G-son said:

Have you considered ditching the straight mixing tube, and follow the 1920s design more?

I would, but one of the primary parameters is that the end result be easy to sand cast.  I have a CNC mill, but no lathe. There is also a limit to the length that I can print on my 3D printer.  I could fabricate a sheet metal cone to try it, but it would not be an easy build to replicate.  That was the idea in what I call the "Wasp" burners...those with a waist.  Some of the 1920 designs are shorter and my longest ones replicate these.  According to the 1920 stats on them, they are almost as efficient as their best ones which are longer.

DanR

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Good evening all.

Been lurking for a while, so my first comment is - Frosty and Mikey, I already have. =D

Reading AFB's and DRottBlatt's discussion on the trumpet/bell reminded me of some older YouTube videos put out by a turbine engine repair mechanic. He explains why they install a bell mouth on the static test stand.

https://www.youtube.com/watch?v=3DQdcvzf9RM starts at 6:00

https://www.youtube.com/watch?v=eB3f_Idkiow starts at 7:45

 

Good luck gents,

Brinton

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Thanks Brijasher!  Inlet air depression...got it!  Interesting explanation, Thanks!

DanR

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I've been bad at reporting lately but we are still doing stuff over here.  

stuff.thumb.jpg.266269d0e8849fe5cf3fb8f4da5c3f20.jpg

I've been playing with nozzle shapes and thanks to jwmelvin and Dan, I've been tinkering with inlet reduction shape again.  

3D printed split patterns and core molds were used to create this mold.

cast.jpg.2b998473eefc278dfc4d0a999514566f.jpg

 

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What refractory are you using for your flame retention nozzles these days?

What substance for your core molds?

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I still use Kast o lite for the nozzles.  Several of the nozzles in the picture are just plaster for inexpensive testing.  I will be experimenting with zircopax/bentonite when I get around to it.

The core molds are sand and sodium silicate.  The other sand in the mold is petrobond.

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On 7/18/2019 at 6:18 AM, Another FrankenBurner said:

The core molds are sand and sodium silicate.  The other sand in the mold is petrobond.

You're beating me to it! :)  Exactly what I'll be doing when I get home from Spain.  Petrobond, Sand and sodium silicate cores, etc. When cast should be only one hole to drill and tap.  I'll post the design, but it will be one like #4 above with the choke and an integral clamp to hold the jet in place and centered.  I'm thinking of casting right onto a 3/4" pipe to avoid having to mill/drill the connection (don't have a lathe).  Really hard to get it perfectly straight since the casting is never perfect, but not hard to cast it in place straight! I've got it on paper and in my head....should work great, but the best laid plans and all :unsure:.  

 

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I look forward to seeing what you come up with.  After your results, I began playing with inlet shape again.  Like you found, I am finding much more aggressive reductions than I originally played with are doing very well.  Standard ventui's use an included 30° inlet and 5° outlet to reduce turbulence and pressure loss.  I kept this in the back of my mind and never deviated from this little box.  It's kind of apples and oranges because we are playing with curves but I am playing with near 70° with much flatter curves.  I have managed to induce a lot more air but I am now trying to balance the induction curve again.  It is way off.  I don't like having to adjust chokes when adjusting pressure.  I only want to adjust the choke if I want a reducing flame.  

My father finished building a sand muller.  Now we are starting to prefer a diy greensand over the petrobond.  It's inexpensive and it is not oily.  

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On 7/23/2019 at 3:21 AM, Another FrankenBurner said:

I am playing with near 70° with much flatter curves.  I have managed to induce a lot more air but I am now trying to balance the induction curve again.

I’d have to see a picture of the 70degree you are referring to. I assume you’re taking an arc or spline off a 70 degree line for the inlet profile???  Heck, we should swap some .step files (or whatever works). I’m using Autocad Inventor. If interested pm me  I’ll be back from my trip early August.

Haven’t noticed flame showing much mixture change over .25-15 lbs. range on any of my tests, but I’ll keep a closer eye - I may just have missed it. I agree about not futzing with a choke every time you change pressure. 

On 7/23/2019 at 3:21 AM, Another FrankenBurner said:

My father finished building a sand muller.  Now we are starting to prefer a diy greensand over the petrobond.

You’re dad is awesome!  I did make a sand fluffer (as we called it) to recondition the petrobond when I taught foundry, but always wanted a muller to make my own.  Used greensand a couple of times, nice not to deal with the smoke. 

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The 70° is what you think it is.  It is referring to the rough angle of the inlet profile.  The inlets are curved and I do not use this angle to set the curves.  I draw a flat line after the fact to get a rough approximation of what I am tinkering with.  Recently I have been playing with much wider angles and much flatter(larger radius) arcs.

angle.jpg.8d7a50361b00b55610dccba8c971acc1.jpg

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It seems to me that the concave configuration of the inside wall of your first burner series proved successful because it provided a low pressure area that helped incoming are to stay within of the spiraled ribs in the burner's air inlet area. How well a trumpet shape will do as the outer wall of an air inlet, may be good, or not.

That should read "... that helped incoming air to..."

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I am not following Mike.  I think I am misunderstanding what you mean.  

I have been able to induce more air in my recent experiments but v46 still remains the most stable running across the widest range of weird configurations I can put them in.  It has a longer, slower trumpet inlet. 

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Good deal. I didn't say the trumpet shape wasn't any good; just that I didn't think it would work the same way. If you're happy with it, then me too :)

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Mike: No, I meant I wasn't following what you were saying about the concave inside walls of my first series.  By concave, you mean something like a plumbing reducer?  I haven't played much with that shape.  

After running the v46 in two different forges for many hours, I am very happy with their performance.  We have forging heat at 3 psi in the 175 in³ forge.  The 20 lb propane tanks feel like they last forever compared to my old modified sidearm burner.  

That said, I have no convictions in any of this.  I just like to tinker and if something turns out to be better(or interesting), I'll follow that trail.  

Dan: Here is a shot of the muller.

muller.thumb.jpg.138cd0cee2293cb009ddbbde9645d99e.jpg

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10 hours ago, Another FrankenBurner said:

No, I meant I wasn't following what you were saying about the concave inside walls of my first series.  By concave, you mean something like a plumbing reducer?  I haven't played much with that shape.  

A  curved solid wall, like an optical lens, is easily described as either concave or convex. When describing a curve surface (wall) on a hollow structure, whether it is concave or convex depends on which side of the wall is being described. In this case whether the inside or outside surface of a trumpet shaped air entrance is effecting air flow. In your latest burner intake, air is flowing down a concave surface. In your earlier burners air was flowing past convex ribs, but also past a concave trumpet shape within those ribs.

I surmised that the concave wall of the inner funnel was helping to keep the incoming air flowing past the outer ribs from being flung out between the ribs by centrifugal force. How the trumpet shaped air intake operates--for good or ill--would be completely different than that, as other forces would be in play; that is all.

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On 7/29/2019 at 6:37 AM, Another FrankenBurner said:

Dan: Here is a shot of the muller.

I love it!  Looks hand powered or is there a motor under there?  Roller mashes the sand down, arm scrapes it up and off the sides.  Simplicity itself!  Well thought out and executed.

DanR

Back from Spain tomorrow, lovin' the trip, but want to get back in the shop and play!

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On 7/29/2019 at 7:17 AM, Mikey98118 said:

I surmised that the concave wall of the inner funnel was helping to keep the incoming air flowing past the outer ribs from being flung out between the ribs by centrifugal force.

It couldn't work like that Mike. A vortex is always drawn towards the low pressure center of the spin on a tighter, faster, curved path.

I don't know how the convex cone around the jet effects the intake air flow. I'd be playing with it and smoke a lot, probably more than using the burner. I'd LOVE to know what's going on.

Frosty The Lucky.

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25 minutes ago, D.Rotblatt said:

Looks hand powered or is there a motor under there?

There is a motor and gearbox under there.  Runs 23 RPM.  You got it, weighted wheel smashes the stuff, scrapers fluff it and push it back into the wheel path.  We now break the molds into the muller to be run after every pour.

I am still tinkering with the inlet convergent profile.  When I am done with that, I can play with the profile of the cone for the jet some more.

Not much fire play for us lately.  Summer heat makes for busy hvac guys.   I am looking forward to autumn.  

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18 hours ago, Frosty said:

A vortex is always drawn towards the low pressure center of the spin on a tighter, faster, curved path.

Normally, a vortex is confined--one way or another--within a funnel shape. I am just musing about whether or not the curve is contributing to that confinement in this case.

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On 6/25/2019 at 6:59 PM, Mikey98118 said:

For some reason, none of the guys complaining that their castings were way too hard to build equipment from were ever willing to try making ductile cast iron.

The addition of magnesium towards the end of the melt is... exciting. I have wondered whether calcium silicide or mischmetal would be less so, but I have never used those.  Not such a big deal with the proper equipment and ppe, but I doubt many back-yarders are set up for doing it safely. You would still want to heat treat it after casting for best properties. 

Malleable iron, by contrast, just takes a long (and therefore expensive) heat treatment. Again, I think it is just a resource constraint. 

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