Tesla Compressor

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fastnova
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Re: Tesla Compressor

Post by fastnova » Mon Mar 09, 2009 9:03 pm

Here is my latest progress, I haven’t had much time over the last two weeks so its not really much, but I have reached a milestone so thought it best to post my progress.
The turbine section is now complete! I managed to mill the slots in the casing ends; drill the end cap mounting holes and make a new shaft, which I’m still not happy with.
Initial tests by spinning it with an airline showed that it flowed quite an impressive amount of air, but at what pressure is anyone’s guess. Also the gyroscopic effect was quite impressive, I could do some fun balancing tricks while it was at high revs.

I am now toying with the idea of getting it all anodised a nice electric blue, I will leave the disks alone as I am going to mirror polish them. But I can’t decide on if it would look best with a nice machine finish or more professional anodised and brightened. They both quite appeal to me. Does anyone here have any preferences?

Anyways, below are some pics of the finished and assembled turbine.

Jonathan
Attachments
09032009513.jpg
09032009512.jpg
I don’t see problems, only opportunities.

larry cottrill
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Re: Tesla Compressor

Post by larry cottrill » Tue Mar 10, 2009 12:19 pm

Absolutely beautiful, as expected. But, one question: Why does the interior contour of the outlet port seem to be oriented radially rather than splayed off at a tangent?

This brings to mind another (very basic, I'm sure) question: Obviously, the intent of the compressor isn't to be a "centrifugal fan", but still the flow must be from hub to edge and then beyond. In other words, you can't eliminate the centrifugal effect, even though the output flow thrust is meant to be tangential. So, how can you be sure that the housing shouldn't be a "volute", i.e. an expanding wedge of flow space around the edge of the disks, leading to a fully tangential outlet? I realize that a Tesla turbine isn't enclosed that way -- but that is a quite different situation (inward flow as energy is transferred from gas to disks).

Looking at what I've just written, it seems to have a certain mud-like clarity, and may even seem adversarial toward your design (though it is not meant to be).

L Cottrill

Mike Everman
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Re: Tesla Compressor

Post by Mike Everman » Tue Mar 10, 2009 1:48 pm

Not quite tangential... the actual angle (from a tangent line) is a vector addition of radial gas speed and the peripheral speed, which is tangential. As Larry says, that port will never be straight out radially. Huge losses will result, and this angle needs to be right within a range, because if you're using this for a turbojet, it feeds right into a diffuser to turn some of that velocity into pressure before the combustor.
Mike
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fastnova
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Re: Tesla Compressor

Post by fastnova » Tue Mar 10, 2009 7:17 pm

I fully understand what both of you are saying.
When I designed the casing my main intent was how simple can I make it? It was never meant to be as efficient as possible.
I did think about working out the gas flow angles and making the outlet to suit. But I came to a point of where do I stop, if it was to be truly efficient there would be no end of things I would change, from the bearings and shaft design to the outlet and the slots in the disks. Ultimately making the whole thing as efficient as possible would massively complicate the entire design. I was going to have to a draw a line some ware to make it practical, so I simply decided not to bother at all.
The point of this project was simply to determine the most efficient type of disk within a standard casing. I wanted it to be as simple, easy and quick to make as possible.
Designing the most efficient casing wont be to difficult to do on paper without the need for much testing, but designing the most efficient disks means getting in to some rather intense boundary layer mathematics, my solution, good old trial and error.

This aside I am working on a few other projects that will ultimately merge with this one to form (hopefully) a self-sustaining engine, these include a variable blade angle diffuser and variable disks gaps.

This is my only current project off paper. Designing a way of adjusting the disk gaps while they are spinning is proving a little compacted, anything up to five disks is easy, but I want something more like twenty disks, things here become somewhat difficult, but I will get there.
I don’t see problems, only opportunities.

vturbine
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Re: Tesla Compressor

Post by vturbine » Thu Jul 09, 2009 12:25 am

Nice work. I hope you haven't given up, since it looks like it's been awhile.

I also worked on a Tesla compressor 6 years ago, only I tried a scroll ring. This was as far as I got.

http://www.sredmond.com/disk_turbine.htm

(see pages 5.6.&7 for the compressor ring stuff)

Probably not very efficient design since there isn't a smooth turn to the axial direction out of the compressor section, but it was just a preliminary experiment back then.
Tesla_Scroll_sm.jpg
Attempt at a Tesla compressor. Front plate and inlet removed.
Of course there's been a LOT of development in small IC Turbines since I first was interested the subject -- unfortunately I didn't keep up with it -- had to build a house, and then err uhh a toddler came along. But I'm still interested in the subject and am very glad to see someone else experimenting on these lines!

My big problem was not having a means to spin the compressor up enough to get a measurable output. I think all I got up to was about 10k rpm shaft speed, at the time. I doubt something as small as mine would put out anything short of 20K rpm.

Good luck on this one -- I hope to see more!
No problem is too small or trivial if we can really do something about it.

Richard Feynman

ace_fedde
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Re: Tesla Compressor

Post by ace_fedde » Thu Jul 09, 2009 2:34 pm

Stephen,

I read in your blog:
vturbine wrote: (01/05/04 I had to put the Tesla project aside while I built a new house. I expect to resume work on the project in Feb or March of 2004).
That's 5 years ago! That house should be finished by now! Get back to work :evil:

:lol: :lol:


Fedde
Your scepticism is fuel for my brain.

fastnova
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Re: Tesla Compressor

Post by fastnova » Thu Jul 09, 2009 9:33 pm

The project is not dead and gone, not yet anyway. Things have been rather busy lately; two kids, moving house and a credit crunch have made spare time no longer spare! I still browse the forums though, even if I don’t post.

To the point,
I have been making some real progress lately, the project you see here will become the oil pump for what I am ultimately trying to achieve. And in the last month or so I have managed to get a little closer. I have done loads of design work towards a running engine, and the finished project should be very interesting (if exceptionally complex!)
I haven’t got any drawings to post yet, but they will come soon.
The engine will have two sets of about twenty bi-metal counter rotating offset disks with stators, they will also have variable gaps and be some ware around 6” diameter. This will form the compressor. It will also have variable guide vain angles.
The combustion chamber will use a vortex to (hopefully) pass the burnt gasses back threw the main combustion area to increase efficiency.
If all works as I hope the exhaust turbine disks will be made from nothing more than aluminium. Due to the nature of a tesla turbine I have found a very easy and efficient way of cooling it, which (if it works) will eliminate the need for any exotic materials. Although I will prove this from the other side of something sturdy, like a wall!

I will have the drawing ready for posing up in a few weeks.

Jonathan
I don’t see problems, only opportunities.

ace_fedde
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Re: Tesla Compressor

Post by ace_fedde » Thu Jul 09, 2009 10:08 pm

Fastnova,

You make me real curious now!! :D

Fedde
Your scepticism is fuel for my brain.

vturbine
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Re: Tesla Compressor

Post by vturbine » Fri Jul 10, 2009 3:35 am

Fedde, heh, did you build yours? :D

Man, I mixed and poured the foundation by hand, and built a bandsaw mill from scratch to mill the trees into boards, not to mention everything else. We're in the house now and have been for a 6 years, but my 2 year old now needs a bigger room. Also we need some new work on green woodchip burner construction for low cost heat. At this point the Tesla needs re-machining for ball bearings, and a suitable high speed motor for drive to test. My wife is the comptroller and for this stuff. Guess which project gets priority?

But of course I still think about what I'd like to do in off moments. Like here and now. And very glad to see others carrying the ball.

Fastnova-- bi-metallic disks? How come?

Definitely interested to see your cooling ideas.

Anybody got any suggestions for how to drive my compressor at say 20,000 -30,000 RPM to test the output? I'd thought about possibly driving it with a router motor, but I don't want to burn one out, and I wonder how I would couple them? I do have a router speed controller, so I could bring it up to speed gradually, and a laser tachometer. But any suggestions would be welcome.

ace_fedde wrote:Stephen,

I read in your blog:
vturbine wrote: (01/05/04 I had to put the Tesla project aside while I built a new house. I expect to resume work on the project in Feb or March of 2004).
That's 5 years ago! That house should be finished by now! Get back to work :evil:

:lol: :lol:


Fedde
No problem is too small or trivial if we can really do something about it.

Richard Feynman

ace_fedde
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Re: Tesla Compressor

Post by ace_fedde » Fri Jul 10, 2009 8:36 pm

vturbine wrote:Fedde, heh, did you build yours? :D
Uhh :oops: :oops:
Your scepticism is fuel for my brain.

fastnova
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Re: Tesla Compressor

Post by fastnova » Fri Jul 10, 2009 9:12 pm

Bi-metal is probably the wrong term as it is a little misleading, what I mean the centre of the disks will be 303 stainless and the outer part will be aluminium (about half and half going by diameter) this allows me to utilise the strength of stainless where the disks are weakest and the low weight of aluminium where the centrifugal forces are at there highest.
This was basically the only way I could find that would be strong enough under the forces I need them to work under.

As for spinning up your disks vturbine, how about the motor from a good shop vacuum, that’s what I got planned for my test rig and oil pump.
I don’t see problems, only opportunities.

vturbine
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Re: Tesla Compressor

Post by vturbine » Sat Jul 11, 2009 1:42 am

fastnova, how will you couple the shaft of the shop vacuum motor to the Tesla compressor shaft? I'm mainly worried about vibration from shaft misalignment at that high an RPM.

I might still use the router, which ought to be powerful enough to do the job, I think. I had considered welding up a stand that bolts both router and compressor down solid, and possibly turning down the end of the compressor shaft to fit the collet of the router. But alignment would have to be perfect.

I suppose with a speed control, I could increase speed gradually and watch for vibration. I didn't have the speed controller back when I first built the Tesla turbine, and never had the confidence to power it that way and just switch on to 25,000 RPM, cold turkey.

Hmmmm, maybe I will try to find a little time to this little experiment ....wife and toddler are off to Cape Cod for 4 days next week......starting Wednesday. Hmmmm,

It always bothered me that I didn't get to see output from the compressor mode, as opposed to the turbine mode of the Tesla.

It might redeem itself if this works.

Other thoughts:

If I were to do it over again, I'd go with only two disks, and make the diameter much larger. For the same compressor output volume, this would lower the necessary RPM, making it easier to drive with an ordinary electric motor, for tests. Likewise in turbine mode, it would have higher torque and lower rpm for the same mass flow into the turbine. You could taper the disks on the outside to increase hub strength. Nozzle design would be greatly simplified with only one gap to focus on.

re. SS/Al disks:
How would you add aluminum to the outer portion of a stainless hub disk, press it? If so, I think the disk will be weaker than an all-aluminum disk. Wouldn't it essentially act like an aluminum disk with a very large center hole? And with press stress as well? The larger the hole the worse the stresses in a spun disk, I believe. But I'd be happy to learn otherwise, if this is wrong!
No problem is too small or trivial if we can really do something about it.

Richard Feynman

fastnova
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Re: Tesla Compressor

Post by fastnova » Sat Jul 11, 2009 11:00 am

I’m using a small belt drive to hook up the motor, also lets you fiddle around with gearing in a way. Alignment is also a lot easier. I don’t know about where you live but here in the UK there is a company called RS, they sell small belt drive parts in all different shapes and sizes, cheep to as they only supply to business.

As for the disks, you need to think outside the box a little, they wont be like a normal flat disk with some holes in it, in fact there wont be any holes at all, the stainless centre will clamp the aluminium outer in place, once assembled they will be machined again to ensure the taper and alignment is correct, very important if the disks are going to overlap correctly. The air supply will come from the centre with a large hollow shaft. Although that’s not set in stone yet, still need to decide what would be better.
I don’t see problems, only opportunities.

vturbine
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Re: Tesla Compressor

Post by vturbine » Sun Jul 12, 2009 1:14 am

Hi fastnova are those belts good for 30,000 rpm on say a 3/4" pulley with 1 hp? Are they toothed belts or round?

re. disks I didn't mean the disk ports when I mentioned holes. I meant the place where aluminum stops and stainless steel begins. If you remove the aluminum piece, it has a hole in it where the stainless steel used to be doesn't it?

Maybe I'm not picturing what you are talking about.
No problem is too small or trivial if we can really do something about it.

Richard Feynman

salvapatria
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Re: Tesla Compressor

Post by salvapatria » Sun Jan 17, 2010 5:12 pm

great work, i'm looking for a very low weight air compressor, less than 1kg, for a uav prototype...

I need something lighter than a scroll compressor, and also, simpler, no loads to compensate vibration, and a contra rot engine to eliminate the momentun...

im looking for a better way to compress air, with less weight, do you think you can work on such project, do you handle solidworks, do you have time, we can talk about it, about funding and goals

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