On a lighter note, what is your thoughts on coupling
a exhaust turbine to the crankshaft, via cog belt or micro v belts? My
thoughts are to stop the vibrations of the crankshafts getting thru to
the turbine, while extracting the energy from the exhaust.
I also have not been able to locate the suppliers of
alloy end bits for the rotary engines.
Thanks
John Burey.
Paul, we have an interest in a similar setup replacing the gearbox with a
starter/generator and deleting the compressor.
milo
Will the generator run at 100,000 RPM?
Paul Lamar
High speed microturbine electric generators are common state of
the art in low power (50 to 200 kW) cogeneration sets.
The 80,000+ RPM, 2 poles or homopolar generators are reliable
industrial machines... for still ground based installation,
not for flying machines with angular velocity and accelerations.
As a minimum requirement for aircraft use, I would place the
turbogenerator axis parallel to the roll axis of the airplane,
axis of maximum rotational speed, and, of course, avoid aerobatics.
Philippe Dejean
What is the efficiency of the generator alone Philippe?
Paul Lamar
-
On high RPM and/or high frequency generators, the losses
increase in the stator core material,
Up to 1000 to 1500 Hz, laminated steel is still the best
material as far as induction remains in the linear range
(<1.6 or 1.7 Tesla anywhere).
For much higher RPM/Frequency ferrite is to be used, but
induction cannot be more than 0,4 Tesla.
On a 30 to 60 kW 80,000+ RPM two poles permanent magnet
generator, the overall power efficiency of the generator alone
should be around 90%, including the 1,5 to 2% of losses in the
power electronics to make industrial frequency (50 or 60 Hz)
I think you could have more information by contacting CAPSTONE,
the american leader on that market, based in California.
Here is some data found on their site :
(See attached file: c30electrical.pdf)(See attached file:
capstone_specs.pdf)(See attached file: diesel.pdf)
Applied to Wankel turbo compounding, the generator electronics
should not produce 50 or 60 Hz, but the frequency
required by the starter-generator placed on the Wankel shaft to
work as a motor...
Philippe dejean
I have heard of them before and I am rather surprised the 25%
overall efficiency is as high as it is. They are not saying what the
turbine eff. or generator eff. is. Just the overall 25%.
Not so hot. I think a turbo compound Wankel would do better.
The problem with any gen set is prime mover eff X gen eff.
For example if the turbine is 80% and the gen is 80% the combination
eff. is 8 x 8 or 64%. This is giving it a huge benefit of the doubt.
Obviously the turbine eff is more like x times 80 = 25 or
turbine eff = .31. That is a very high number for a small turbine.
Most diesels are .35, Gasoline engines .3 and a turbocompound
Wankel could be .35 or higher.
A bottoming cycle full size power plant can be as high as 50% overall
by using the waste heat from a turbo-shaft engine exhaust to make steam.
Another form of turbo compounding.
Paul Lamar
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