Landspeed bike with DIY gas turbine

[Johansson]

Sept 11, 2013 14:17:16 GMT -5 ripp said:

Hallo John,
You are right. Under load, a Turbine can also glow.
Anders Turbine run too hot because the nozzle was too small.
I'm sorry, I have read too late the text

rip

google Translation

Hi Rip,

The camera is very IR sensitive so to the naked eye the jet pipe didn´t glow at all like it looks in the video, I read a TOT in the region of 730°C at 3.7PR during one of the latest runs and that is not bad. Might need to open up the exit area a tiny bit if I want to push it towards 4PR.

Cheers!
/Anders

[ripp]

Hi Anders,
Just wanted to make you point out, your turbine has a problem with the heat dissipation on the shaft bearing I think. The exhaust turbine with the shaft, and also the NGV have much heat in the material after a run, the oil film is small and coked very quickly
Turbochargers are so constructed as they are built.
So I think the next wave damage is inevitable, sorry.

rip

google Translation

[Johansson]

Hi Rip,

I agree that heat soak after a run will be inevitable with a big heavy turbine wheel and NGV, and I should probably keep a fan nearby to cool the engine down after shutdown.

I use bleed air through the NGV wall to cool the turbine hub, there is a heat pattern on the shaft up to where the rear bearing is but no further than that. That might very well be caused by some of the early hot runs, I´ll remove the heat pattern before I assemble it so I can see the next time I take it apart if it keeps coming back.

I am not sure that I understand what you are suggesting, I haven´t seen any signs of cooked oil inside the shaft tunnel or on the bearings and some heat shield or rebuilt shaft tunnel won´t keep the heat from creaping down the shaft from the turbine wheel once the engine is stopped.

Perhaps I should keep the oil circulating for a minute until the engine has cooled down somewhat, with a fan blowing into the intake it should cool down pretty quickly. That wouldn´t hurt.

Cheers!
/Anders

[Johansson]

By the way, a turbocharger in a car is often tortured with sudden shutoffs while the entire exhaust section is glowing and they seem to last quite a while without any post-cooling or circulating oil.

Not saying that you aren´t correct, just that the rest of the bike will probably have worn itself down way before the bearings coke up.

[ripp]

Hi Anders,


Hi Rip,

The camera is very IR sensitive so to the naked eye the jet pipe didn´t glow at all like it looks in the video, I read a TOT in the region of 730°C at 3.7PR during one of the latest runs and that is not bad. Might need to open up the exit area a tiny bit if I want to push it towards 4PR.

Cheers!
/Anders


I am interest the exhaust gas temperature without nozzle.
should be 550 ° - 650 ° C, so you have a reserve for the power turbine.

rip

google Translation

[ripp]

Perhaps I should keep the oil circulating for a minute until the engine has cooled down somewhat, with a fan blowing into the intake it should cool down pretty quickly. That wouldn´t hurt.

Cheers!
/Anders[/quote]


Hi Anders,
Then the bearing are safe

rip

google Translation

[turbochris]

the nimbus in the van doesn't glow when viewed w the naked eye

[Johansson]

Sept 11, 2013 16:08:44 GMT -5 ripp said:

Hi Anders,
I am interest the exhaust gas temperature without nozzle.
should be 550 ° - 650 ° C, so you have a reserve for the power turbine.

rip

google Translation

Unfortunately I haven´t run the engine without the jet nozzle so I don´t know the exhaust temp without it.

[ripp]

Hi Anders,
You need neither the heat shield in front of the combustion chamber or a ceramic coating.
A heat color is normal on the combustion chamber.
importance is a clean burning in a combustion chamberand and no hot spots


www.frankturbine.com/tag/brennkammer/

www.rconline.net/magazin-2000/turbine/12_turbine_funktion_2.htm

ut160.de.tl/Galerie/pic-1000609.htm

rip

google Translation

[racket]

Hi Rip

If you checkout my 10/98 build Thread jetandturbineowners.proboards.com/thread/19/10-98-engine and the video Links you'll notice my temperatures were lower by >100 deg C even though we both used a similar jet nozzle diameter, the main difference between our engines is the NGV throat area , Anders has used a throat area ~11% greater , this could possibly be allowing a slightly greater mass flow but his temperatures are still well within the original design parameters for his engine .

Assuming a 3.7 Pressure Ratio at 70% effic , that'll produce an ~185 deg C temp rise requiring an ~150 deg C drop through the turbine at the temperatures Anders is using , with a TOT of 730 deg C that equates to a T I T of ~880 deg C , our Inconel turb wheels can cope with 1050 deg C T I Ts , the engine was designed for TITs a bit below that .......but not a lot less ;-)

Cheers
John

[Johansson]

Since I made my gas producer NGV back plate out of cheramic coated mild steel I will probably have to replace the NGV sooner or later with an all stainless one, then I will tighten up the throat area a bit to see how it affects the TOT.

I ordered two bearing sets today, good to have some spares just in case.

[gidge348]

Just a quick question, the Nimbus engine uses the central bearing shaft as the fuel supply spray. So centrifugal force is used to help disperse the fuel and fuel is used to help cool the shaft.

Could a system like this be used on one these type of engines?

Is there any benefit/disadvantage to a system like this?

Ian...

[Johansson]

Sept 12, 2013 8:41:40 GMT -5 gidge348 said:

Just a quick question, the Nimbus engine uses the central bearing shaft as the fuel supply spray. So centrifugal force is used to help disperse the fuel and fuel is used to help cool the shaft.

Could a system like this be used on one these type of engines?

Is there any benefit/disadvantage to a system like this?

Ian...

Hi Ian,

I think size is our biggest enemy, with our small engines and narrow turbine shafts there won´t be much centrifugal force to build fuel pressure before the spray nozzles.

Another thing is the journal bearings, to get fuel into the shaft you would need a swivel of some sort and for that to work I think the shaft needs to be secured by ball bearings so it doesn´t move radially.

You would still need a throttle arrangement and a fuel pump to meter the fuel going into the shaft, so it would only add unneeded complexity to a DIY engine.

I know a Williams jet engine used for drones and cruse missiles used this system, but I guess that is mostly to save weight and cost since the engine is disposable.

Cheers!
/Anders

[ripp]

Hi John,
fantastic work!
All parameters are calculated correctly I think

rip

google Translation

[Johansson]

Hi Rip,

You´ve got us all wondering now, who are you? Where are you from and how have you come by your knowledge of gas turbines?

Anyway, welcome to the forum in case I forgot to say it earlier!

Cheers!
/Anders