The guys at Nye Thermodynamics seem to have been pursuing
turbomachinery as a hobby/business for years (at least as of 1997-8
when I discovered their site), and in the last several years seem to
be interested in getting usable electrical or hydraulic power from
their gas generators. Specifically, they have a design for gear
reduction of an auto turbocharger turbine to be used with an electric
generator:

http://www.gas-turbines.com/nt-pu37/index.html

http://www.gas-turbines.com/t18a40/index.html

Now my question is this: what, if any, design flaws (weight aside)
prevent this very simple means of gear reduction from being used for
turbocompounding?

The potentially obvious to me would be driven gear rigidity and shaft
alignment, and of course engine overall diameter limitations in
practical applications. Do gears experience unusual stresses at high
speeds that make this a complete bust? Are there efficiency or
durability concerns that make this design impractical for some reason
I can't see?

-Chris Wood

None that I know about. Interesting work.

Paul Lamar


By comparing the diameters of the reduction gears, I would say the pinion is
designed to turn at about 36,000 RPM. This is well within the range of a lot
of industrial turbos. As Paul has described previously, for power extraction
they can not run free as per an engine intake supercharger. About 50% RPM to
get the most torque out of it. This is based on generators running at 1800
RPM. This would pose no problem for the pinion gear as well.
As a note; many gas compressor stations use gas turbine engines, Rolls Royce
being one of the more popular. They make aircraft and industrial versions. The
aircraft are a bit more expensive due to lighter materials used. They exhaust
then goes through a large axial turbine that is about 10 feet in diameter.
This supplies the torque to turn the compressor gear reduction box and the
compressor. The engines have an electric motor and over running clutch to
start them with a drive shaft that looks like it came from a semi.

Dale Davies