3D printed plastic burner experiments (photo heavy)

[Mikey98118]

On 12/15/2022 at 8:05 AM, Another FrankenBurner said:

Me too.  My definition has changed along the way. 

My definition hasn't changed, but I've learned that there are more than one or two versions of a very hot flame; there are fast, slow, multi...and probably several more to come

[Buzzkill]

If any of you guys have .stl or .obj files for these vortex burners that you'd be willing to share I'd surely appreciate it.   I received a 3d printer for Christmas, but I've never used a CAD program before.  I hate to reinvent the wheel anyway, but eventually I will teach myself to use CAD (Blender is the one I'm starting with) and I should be able to recreate what I've seen on here.  However, if someone wants to help me out with a shortcut to the process I'm happy to take advantage of the opportunity.

I understand if you guys don't want to freely distribute the results of your hard work and experiments, but if you are willing to share I'd be happy to send some money your way.  PM me if interested.

[DonB82]

I wouldn't recommend Blender for this. It's more of an organic/sculpting software. There are a lot of free trials and open-source engineering CAD software you can try. I would recommend Autodesk Fusion 360 or Onshape. Plenty of people on youtube with tutorials to get you started.

I use NX free trial at home. There is plenty of information to get you started but I think it has one of the steeper learning curves.

I did spend some more time experimenting with designs this weekend. I drilled out some 1" DIA stainless tube to an ID of .938" but have a new problem. Heat travels up the thinner wall much faster and starts melting the plastic before I get a chance to do anything with it. I did get a really dark blue to purple flame to the naked eye with a 4" long mixing tube before meltdown.

[tinkertim]

I use the free CAD tool Designspark 3D by RS.  Powerful but surprising easy to use.

I got part way through trying to make a tri-finned burner head but got a bit stuck on the profile of the blades and decided to park it until I have a bit more time to learn about "lofting".

I'll 3D print myself one one day, to experiment with smaller hand-held Rose-bud type burners, and include a handle.

[Jake18]

I wonder how it would work including a few angles find in the mixing tube. It kinda replicates a plane wing tip. It being angled creates a high and low side and as the air flows over the fin from high to low it creates a swirl. Would that create too much drag and interference? Id like to try it but I don’t have time to design anything right now 

[tinkertim]

Hi Jake,

I don't think it does replicate a wing tip, as in these vortex inducer designs, both ends of the "wing" are attached to the inducer body.

The current design has sloped vanes, and these vanes also appear to spiral inwards a little, so guiding and inducing spin to the airflow as it turns through ~90* and is accelerated down the mixing tube by the gas jet.

I believe Another FrankenBurner (AFB) tried various designs for the vanes including aeroplane wing profiles, but that it didn't make that much difference compared to the width and spiral-angle of the vanes. At least that what I recall from this many-pages thread over the years.

Maybe AFB will pop by and correct me, as it would be nice to hear from him again.

Tink!

[Buzzkill]

2 hours ago, DonB82 said:

I wouldn't recommend Blender for this. It's more of an organic/sculpting software. There are a lot of free trials and open-source engineering CAD software you can try. I would recommend Autodesk Fusion 360 or Onshape.

Thanks for the suggestions.  I won't use cloud based software on principle.  I prefer to work offline as much as possible.

  However, since I have no experience with CAD programs I will look for something different than Blender.

 

2 hours ago, tinkertim said:

I use the free CAD tool Designspark 3D by RS.  Powerful but surprising easy to use.

Thanks. I'll check it out.

[Mikey98118]

You both have good points on air flow, but I think Tinkertim is correct. The only fast flow is from the gas jet, which is parallel to the "wing" edges. The induced incoming air, which could otherwise create drag will be traveling way too slow to create vortices. AFB, may hold a different view.

[Another FrankenBurner]

I like what is happening in the thread today.  Talking ideas.

11 hours ago, tinkertim said:

Maybe AFB will pop by and correct me, as it would be nice to hear from him again.

I'm always lurking.  Been busy lately.  If only I didn't have to work.  My free time has been spent building an attachment for the lathe.  It's for burner work, to play with some ideas.  No experiments lately though, so nothing useful to contribute.

I did play with airfoil design for the vanes/ribs with several iterations.  Then I did some smoke testing and realized that I had the induction streams all wrong in my head.  The beginning of the mix tube (the throat) is a low pressure zone.  The atmosphere outside the inspirator (the thing I print) is at a higher pressure so it pushes air into the low pressure zone.  Imagine straight lines from the perimeter to the center, kind of.  Air is not being gracefully pushed along the vanes/ribs as a wing through air.  It is being pushed around the vanes from perpendicular.  The little bit of sideways movement is all that it needed to nurture a vortex.  After the head slapping realization, the rib design went pretty boring to be as streamline as possible while still providing a little sideways movement.  Anything else caused more drag than its effect was worth... for my goals.  

Hopefully that made sense.  If not, tell me I am horrible and I will take more time to attempt to articulate it more gooder.

9 hours ago, Buzzkill said:

I won't use cloud based software on principle.

Same here.  Pesky principles. 

I designed the burners in FreeCAD.  It's freeware so it may not be as intuitive, maybe a little clunky here and there.  I have not had any ideas that I could not model accurately.  The latest version is miles ahead of the version I started on.

[Mikey98118]

The only thing missing is description on the effect that the outer face of the inner cone has on incoming air.

[Another FrankenBurner]

By inner cone, are you referring to the cone of the orifice block?  (Frosty coined it the aerospike)

[Mikey98118]

I am referring to the cone that can be seen by looking between the ribs; the part that the gas jet protrudes from.

[Dr. Rusty]

That's what I think we were experiencing with our initial designs. Three wings may as well have been obstructions, as soon as the air gets past the directional surface the whole bulk volume is pulled straight in. I haven't had much time but I now try and think of ways to swirl/premix the bulk with propane prior entering the pipe.

I had a recent realization. I think a print could be internally porous. Propane could be piped into the walls of a 3d printed funnel, and holes could be made along the surface of the inner portion of the funnel so that you could have many micro leaks of propane into the bulk air for premixing. 

Now that I have my own printer I need to learn a little cad. I'd also be curious if an array of Tesla valves with a propane link from printed internal pipinh may achieve unidirectional flow with mixing.

[Jake18]

I believe i get what you are saying AFB. While i am not sure everyone understood exactly what i meant ( i probably could have explained it a little better) i see what you are saying. since the air is not traveling parallel to the pipe then any ribs or whatever would just cause drag. While i am here has anyone uploaded any cad files for designs here?

[tinkertim]

No.  No files have been posted up.  It is more a discussion so that people can get ideas and try things out themselves.

I wouldn't expect AFB to post up any CAD plans or STL files as his high-efficiency burner design would rapidly appear on Ebay and Alibaba! He has posted enough pictures of his various versions and experiments so that anyone on here could have a play with a CAD package and print something out to play with.

In the past, people have suggested that AFB make and sell his Vortex Inducer bodies for people to assemble into burners, but he wasn't looking to commercialise his design, more to experiment, learn and enjoy himself.  I'm sure if you put together your own CAD model based on his images, and tried it out, he'd be happy to give you feedback.

Tink!

[Mikey98118]

1 hour ago, tinkertim said:

I wouldn't expect AFB to post up any CAD plans or STL files as his high-efficiency burner design would rapidly appear on Ebay and Alibaba!

I don't think so. Foreign OEMs are always looking for high volume items to make. Burners just aren't. Two years after my book came out, I found rectangular air openings featured in the latest lab burner designs, but nothing else. Cast burner parts, which can be used in everything from camp stoves to turkey fryers, yes. But high velocity burners for forges...no. Burners, and gas forges are built in places like Australia, England, and the USA; not Asia.

[Jake18]

Yeah that’s what I figured. I was kinda hoping he may have even posted an early one so that I wouldn’t have to start from the very beginning. Guess I’ll just have to make the time.

[Hefty]

Jake, not sure if you have some knowledge and experience of CAD software but if you do, AFB's pictures of his different numbered versions will be enough to give you an initial design to tweak. That's what I did! 

Some things will depend on what software (if any) you have experience with. What I did was to insert one of AFB's images into a sketch, scale it to match the size of the pipe I had and trace it. Then I created a revolved 3d profile from that to get the "trumpet bell" funnel shape and the "aerospike" shape (as Frosty calls it). I then used the same method with one of his section views of the vanes onto the top view of the funnel and did a helical revolve to get the spiral shape (tools and terminologies may vary between software).

I hope that makes sense.

Cheers,

Jono.

[Another FrankenBurner]

Poor drawing alert.  I could have done worse, but I couldn't find any crayons.  

The inner cone increases induced air.  Originally, I added it thinking that the volume that it takes up was just dead air space which may have caused turbulence with incoming air.  After playing around with smoke testing, I discovered that it causes vortices in the incoming air.  Without it, the incoming air follows curved paths towards the jet and down the mix tube.

This was a major improvement in the burners.  With how much extra air it entrained, the orifice size was bumped up, a more aggressive nozzle was designed, and its output increased.  

[Jake18]

Yeah hefty that makes sense, thanks for that that’ll help me. I have fusion and autocad through A&M and have taken some classes on modeling so I do have experience but not much in designing things which alot of curves.

[DonB82]

On 2/15/2023 at 12:26 AM, Another FrankenBurner said:

Without it, the incoming air follows curved paths towards the jet and down the mix tube.

 You're drawing was very helpful to me. I was comparing your curve (the red one below) to mine. I thought opening the outlet would help with airflow, but now I can't get it to light and it does some weird fluttering when I choke it off enough to get a flame.

I wonder if those penny donation funnels you would see at a mall are a good visual of what is happening to the air flow. I think the term is angular velocity. It increases as the coin reaches the bottom of the funnel. Do you think by opening the mouth I'm hurting the amount of spin before going into the mixing tube?

[Mikey98118]

The answer is YES! Speed of angular velocity, which we just call spin or swirle around here, increases in direct proportion to the difference between input and exit diameters in a funnel shape. increase the difference to increase the spin, and visa versa. However, burner performance is a balancing act. There is definitely cases of "too much of a good thing."

[Jake18]

How much will steepness/ shallowness of the funnel arc affect the performance. I see the concept of it being like one of those coin machines they used to have at Walmart where as it gets smaller the “swirl” becomes faster. Have you tinkered with the degree of your funnel? Or will it mainly just depend on the beginning diameter vs ending diameter 

[Mikey98118]

Yes, I have. First you need to understand that my limitations and preferences don't always directly apply to yours; that's because I am experimenting on vortex burners that are built from sheet-metal products; not 3D printed, so they won't always parallel yours; when they don't, if I know they don't, that will be pointed out.

So, the closest my burners come to answering your present question is that the shorter a funnel shape is the closer its low pressure zone comes to the funnel entrance. So far, with naturally aspirated burners, this causes no problems. However, with fan induced burners, it dang sure does!!! Why? Because the addition of an axial computer fan, with impeller type blades, will further lower pressure at the burner entrance to the point that some fuel gas will back up into the fan, and cause backfiring, unless the funnel shape is long enough to avoid the problem.

I recommend no more than a 3:1 reduction in diameter, and no less than a 2:1 funnel length.

[Another FrankenBurner]

On 2/21/2023 at 7:39 AM, DonB82 said:

I wonder if those penny donation funnels you would see at a mall are a good visual of what is happening to the air flow.

20 hours ago, Jake18 said:

I see the concept of it being like one of those coin machines they used to have at Walmart where as it gets smaller the “swirl” becomes faster.

The answer to this being a good visual is no.  The concept, yes, kind of.  I had this same idea before I started playing with smoke.  I even experimented with several iterations of airfoil design based on this idea of air flow.  

The air does not enter the burner as the penny enters the funnel.  The air is pushed from the high pressure zone (outside the burner ambient air) to the low pressure zone (the throat of the burner) in a short path.  The burner is not inducing enough air to get the air outside the burner swirling.  

Here is another rough drawing to demonstrate the difference:

On the left is the penny funnel idea.  How I thought it worked until I played with smoke. 

On the right is a representation of the smoke paths I witnessed.  Smoke moving perpendicular to the ribs, some of which goes behind the ribs.  I think the canted ribs cause just a little bit of movement in some of the air but all in the same direction.  This little bit is all that is needed to nurture the vortex.  

As you can see, the ribs are in the way.  I have induced more air with small round ribs, but the burner did not perform as well.  I have compromised some air induction for better mixing with this rib style.

This is not to say that the reduction shape, specifically the trumpet, is not important or that it does not affect vortical flow. 

When I was playing with shapes, I made one of those tornado tubes that kids build with 2 liter soda bottles except I found specific shaped bottles and printed a shaped/sized orifice between the bottles.  The trumpet shape did the best, by far.  I always found the shape of the total vortex interesting.  I have wondered if part of the greatness of the trumpet shape is that it somewhat matches the shape of a vortex.  Potentially limiting dead air space which just slows the flow down.  Maybe?

On 2/21/2023 at 7:39 AM, DonB82 said:

Do you think by opening the mouth I'm hurting the amount of spin before going into the mixing tube?

It's hard to say.  You could play with some smoke.  As to the hard to light with fluttering, what if you have caused such a dramatic increase in air induction that you are now trying to coax a very lean flame?  It is a possibility.  Make sure to fully test something you already have to learn as much as possible before making changes.

20 hours ago, Jake18 said:

How much will steepness/ shallowness of the funnel arc affect the performance.

A lot.  A have spent a lot of time on this.  I still haven't figured it all out.  It can get deep, fast.

For simplicity, let's assume Mikey's above posted ratios (3:1D, 2:1L) and a simple single arc.  Both the center and radius of the arc can be played with:

Big difference in performance among just those.  We can also play with length, diameter, and multiple arcs or splines to complicate things.  

I trial and error my way through it.  I'm not educated enough to understand the why's of this one.