> All this talk of over spinning turbos keeps me coming back to high speed
> alternators.
> > Monty & I discussed the topic at the Rotary Fly-in a couple years ago.
> My impression was that there were off-the-shelf high-speed alternators
> available that could be used in a turbo compound fashion. (Monty,
> please feel free to correct me if I'm off base here ...)
> > If the exhaust side of the turbo is driving an alternator, it would be
> relatively easy to control turbo RPM by varying alternator loads.
> > The load might even be a high-efficiency motor (rare-earth magnet
type)
> driving the e-shaft. That certainly would eliminate many turbo compound
> coupling issues, like fluid couplings, gear lash, linear gear tooth
> speed limitations, etc.
> > Paul's argument was that there would be too many losses in the system.
> There would be some to be sure, as with any system - mechanical or
> electrical. Also, unless the alternator/motor combination used high(er)
> voltages, there would be some heavy cable requirements to transmit the
> power. Assuming 20 HP to be recovered and no losses:
> 1 HP = 746 W
> 20 HP = 14,920 W
> 14,920 W = 124 Amps @ 120V
> 14,920 W = 62 Amps @ 240V
> 14,920 W = 31 Amps @ 480V
> FYI: Convert Horse Power to AMPS:
> HORSEPOWER= (V x A x EFF)÷746
> EFFICIENCY= (746 x HP)÷(V x A)
> > The questions of this thread should center around:
> > - Are high speed (50-80K RPM) alternators available OTS?
> - Can they be safely coupled to the turbo? Possibly replacing the
> compressor section? (U-joints are out!)
> - Are high efficiency electric motors available OTS that can be bolted
> to the e-shaft?
> - Can this be done to recover some exhaust energy, or is this a waste of
> time?
> > Point of interest:
> I like the turbo as a muffler. If I can extract energy too, that would
> be a bonus. Otherwise I'll probably stick with the low-tech
> muffler. :)
> > -- > Vince Orton
> > > Sounds expensive :)
> > -- > Paul Lamar ...No rotor no motor.
>
Vince
I was probably part of that living room sofa conversation. As someone who
was very interested in this seemingly elegant approach I have not been able
to find the elusive high speed generators yet on the market. Mazda Inc.
makes one but it is only on their R&D model.. Catapillar Inc. has been
playing with them as well. BMW also. As I understand it cooling is a major
challenge. Permanent rare earth magnets lose their power when they exceed
high temperatures. The other end of the equation is motors which are
available and you can see some of them by opening up the hoods of Honda and
Prius hybrids. They are pricey, and heavy and need large power conditioning
units. Bill Dube can probably point you to a few other specialty companies
that make smaller units for electric race cars.
I agree with you though it does seem too wonderful.. Perhaps if electric
car
get more efficient and a substitute is found for the now 97% China
controlled neodyn magnets, motors will get smaller. For now mass production
is stuck with the resistance and weight of copper wire and steel plates.
For now the only airplanes that can benefit from electrical motors are
lightweight especially designed planes with limited cargo carrying
abilities. This mean U.A.V.s or sailplanes that only need a motor for short
duration of climb.
The last time I looked into this about 7 hp was a do able number to shoot
for with a reasonable small size motor and off the shelves controllers.
Weight issues favor a mechanical device however which in my case with the
additional bell housing, traction drive and belt CVT, will add less than 20
lbs to the engine weight and could in theory deliver over 30Hp back to the
e-shaft. Paul's system coupling from the compressor and going into the
front
of the engine could conceivably be lighter.
Doug Fir
Paul and I discussed this awhile back, a very expensive development!
See:
http://www.microturbine.com/prodsol/techtour/downloads/datasheets.asp
The turbine and generator technology is there, but air bearings are
required. Capstone started as Rosen Motors with a lot of funding. The
intention was hybrid vehicle power using flywheels for peak loads. They
are now a fixed cogeneration utility product.
Steve Reed
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