Gas (Tesla) Turbine started

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Kakeman
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re: Gas (Tesla) Turbine started

Post by Kakeman » Mon Dec 04, 2006 1:24 pm

how about number of inlets?

i think that one would be best :/

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Re: re: Gas (Tesla) Turbine started

Post by Nick » Thu Dec 07, 2006 2:00 pm

Kakeman wrote:how about number of inlets?

i think that one would be best :/
currently ive only ever seen of one inlet but maybe on a gas turbine two or more would be a good idea?, perhaps two "hot" inlets from the combustion chamber and two from the compressor to aid cooling of the discs?

Nick

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Re: re: Gas (Tesla) Turbine started

Post by Bruno Ogorelec » Sat Dec 09, 2006 6:05 am

Nick wrote:
Kakeman wrote:how about number of inlets?

i think that one would be best :/
currently ive only ever seen of one inlet but maybe on a gas turbine two or more would be a good idea?, perhaps two "hot" inlets from the combustion chamber and two from the compressor to aid cooling of the discs?

Nick
Nick, wouldn't cool air lower the impedance and thus the efficiency of the energy transfer from the driving gas to the discs?

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re: Gas (Tesla) Turbine started

Post by Nick » Sat Dec 09, 2006 10:29 am

Hi Bruno,

i honestly dont know, but its fairly std practice to have bypass air in ordinary gas turbines?. Perhaps it should be added as bypass air ? or maybe directed straight to the centre of the disc at the back to cool the bearings?

I hope to try this out next year when ive got time.


Cheers

Nick

PS i got to within about 4 hours drive of your place in Sept by the way (or so someone told me anyway) Kaprun/Zeelum See/ Salzburg ? :-)

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re: Gas (Tesla) Turbine started

Post by Kakeman » Sun Dec 10, 2006 12:22 pm

in big jet turbine there is oil nozzles witch flows oil to bearings and oil is collected back in many sucktion stages.

Those sucking things are in labyrint seals
Between last seals there is added compressed air so there doesnt come preasure differ so it doesnt suck air from outside, i think, i dont really know why there is added copressed air between seals 8)

i got it, that isn because air could get in, that is because oil shouldnt get out :D

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Re: re: Gas (Tesla) Turbine started

Post by Nick » Sun Dec 10, 2006 5:28 pm

Kakeman wrote:in big jet turbine there is oil nozzles witch flows oil to bearings and oil is collected back in many sucktion stages.

Those sucking things are in labyrint seals
Between last seals there is added compressed air so there doesnt come preasure differ so it doesnt suck air from outside, i think, i dont really know why there is added copressed air between seals 8)

i got it, that isn because air could get in, that is because oil shouldnt get out :D
In small turbines the norm is a total loss sytem, either fuel/lube mix or straight oil delivered in small quanties at the bearings, sometimes merely by a pressurised tank kept at pressure by a bleed from the compressor but thats not the same as a cooling air blast at the turbine bearing.;

Nick

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Re: re: Gas (Tesla) Turbine started

Post by Bruno Ogorelec » Sun Dec 10, 2006 8:43 pm

Nick wrote:Hi Bruno,

i honestly dont know, but its fairly std practice to have bypass air in ordinary gas turbines?. Perhaps it should be added as bypass air ? or maybe directed straight to the centre of the disc at the back to cool the bearings?

I hope to try this out next year when ive got time.


Cheers

Nick

PS i got to within about 4 hours drive of your place in Sept by the way (or so someone told me anyway) Kaprun/Zeelum See/ Salzburg ? :-)
I think the reason is to lower the turbine inlet temperature so that the turbine wheel can take it. In a Tesla turbine, you are probably not going to run into problems of this kind and can afford to have the gas as hot as you can make it.

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Re: re: Gas (Tesla) Turbine started

Post by Nick » Tue Dec 12, 2006 8:28 pm

[/quote]
I think the reason is to lower the turbine inlet temperature so that the turbine wheel can take it. In a Tesla turbine, you are probably not going to run into problems of this kind and can afford to have the gas as hot as you can make it.[/quote]

er Ok, but Why not? or why do you think a Tesla can take higher temps?
:-)

Nick

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Re: re: Gas (Tesla) Turbine started

Post by Bruno Ogorelec » Wed Dec 13, 2006 3:08 pm

Nick wrote:Ok, but Why not? or why do you think a Tesla can take higher temps?
:-)

Nick
Well, shouldn't its disks be exposed to lesser mechanical loads? The solid Tesla disks are exposed only to major centrifugal loads (stretch). Surely this is easier to handle than the simultaneous centrifugal and perpendicular (shear) loads endured by the 'normal' turbine wheel blades. For all I know, the blades may also be exposed to torsion.

Also, the load distribution is broader on the Tesla disk than on the high-aspect-ratio turbine blade. Less stress concentration.

Lesser mechanical loading means the wheel can take greater heat without breaking apart, given the same material.

Of course, the problem is much more complex than that, but this should nevertheless roughly hold true. Unless I am badly wrong in some detail.

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re: Gas (Tesla) Turbine started

Post by Nick » Wed Dec 13, 2006 6:40 pm

good points, well made mate :D

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Re: re: Gas (Tesla) Turbine started

Post by marksteamnz » Wed Dec 13, 2006 8:24 pm

The mechanical stress ins't the problem. The one GT Tesla I've seen suffered from heat distortion. Big flat disk heat just a little bit unevenly and Opps! it's a potato crisp.
Bruno Ogorelec wrote:
Nick wrote:Ok, but Why not? or why do you think a Tesla can take higher temps?
:-)

Nick
Well, shouldn't its disks be exposed to lesser mechanical loads? The solid Tesla disks are exposed only to major centrifugal loads (stretch). Surely this is easier to handle than the simultaneous centrifugal and perpendicular (shear) loads endured by the 'normal' turbine wheel blades. For all I know, the blades may also be exposed to torsion.

Also, the load distribution is broader on the Tesla disk than on the high-aspect-ratio turbine blade. Less stress concentration.

Lesser mechanical loading means the wheel can take greater heat without breaking apart, given the same material.

Of course, the problem is much more complex than that, but this should nevertheless roughly hold true. Unless I am badly wrong in some detail.
Cheers
Mark Stacey
www.cncprototyping.co.nz

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Re: re: Gas (Tesla) Turbine started

Post by Bruno Ogorelec » Wed Dec 13, 2006 11:33 pm

marksteamnz wrote:The mechanical stress ins't the problem. The one GT Tesla I've seen suffered from heat distortion. Big flat disk heat just a little bit unevenly and Opps! it's a potato crisp.
Ah, so it has to be made dimnsionally stable. I was under the (apparently wrong) impression that the centrifugal loads might help keep it flat.

So, you have to provide expansion slots etc. Which gets you back to the same problems conventional turbine wheels have. There ain't no such thing as a free lunch, I guess.

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re: Gas (Tesla) Turbine started

Post by Kakeman » Thu Dec 14, 2006 4:19 pm

keyword is titanium :P

And some fuels burn colder

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re: Gas (Tesla) Turbine started

Post by Nick » Wed Dec 20, 2006 12:23 pm

mark do you know what material the GT Tesla discs were made from?
i plam to make them from either 316 or 304 stainless which are reasonably dimensionally stable under heat/load.
In any case if this is an issue and it must be to a greater or lessor extent, then it brings me back to my earlier comment about dilution air to cool the gasses prior to the turbine.
:idea: Just musing here but what we actually want from the combuster is a greater volume of air coming out than goes in, bearing this in mind if the air is very hot coming out then thats wasted energy really.
before i get shot down in flames i realise there's a world of difference between desirable theory and practical build.
I'll carry on and build with an eye on trying to make that theory closer to reality, of course the Tesla has a greater pressure generating ability than a conventional vaned compressor but lower volume size for size. This might mean a smaller combustor is possible and perhaps lower exhuast temps? anyone care to speculate? :?:

Merry Xmas All by the way :D

Nick

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re: Gas (Tesla) Turbine started

Post by racketmotorman » Wed Dec 20, 2006 8:25 pm

Hi Nick
Thermodynamics will dictate a certain minimum temperature rise in the combustor simply to "overcome" inefficiencies of comp and turb , and allow the machine to operate even without any excess shaft power being made available .
If you want excess shaft horsepower , then higher temps and generally greater waste energy is the norm :-((
Cheers
John

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