[Diy_efi] This turbo assist stuff, suggestions

[Bernd Felsche]

On Thu, Jan 02, 2003 at 06:41:20PM -0600, Mike Schwall wrote:
> > [mailto:diy_efi-admin at diy-efi.org] On Behalf Of Bernd Felsche
> > 
> > On Wed, Jan 01, 2003 at 10:30:54PM -0600, Mike Schwall wrote:
> > > Correct, the materials are applied using plasma spray process.
> > > Though I've heard of it used in power generation turbines, not
> > > sure exactly what coating materials are used in the military
> > > and high output commercial engines.

> > See http://www.eurofighter.starstreak.net/Eurofighter/engines.html
> > and http://www.rolls-royce.com/media/prod_info/tech/threeshaft.htm

> Excellent find!

Thanks. I found them interesting. Google came up with it's usual
million hits in a second but the two shown caught my eye.

Nice thrust range on the R-R engine, eh?

I'm wondering how long the metal on the turbine blades stands up to
the direct heat if the ceramic coating does fracture and expose the
metal to the hot gases... 12 to 16 hours is a long flight (e.g.
SIN-LHR).

When you consider that some of the first axial flow turbojets
deployed into service (Jumo) had a design life of around 10 hours
(IIRC) the current generation are incredibly reliable.  Still, the
Jumo engines' turbine blades were of pressed steel with little alloy
(material shortage) but introduced internal cooling air flows.

Brings me back back on-topic - sort of... are the "ceramic turbos"
solid ceramic turbines or are they coated?

Are there any turbos with internal cooling air flows?

It'd present an engine management problem (mixture feedback) if the
cooling air was "fresh" air and it leaked into the exhaust gas
stream with sensing done downstream of the turbo. Cooled EGR doesn't
fare much better - it'd tend to dampen out fluctuations in oxygen
content and introduce unwanted due to the long EGR cooling path.

-- 
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