snips....

"So theoretically it should be a wash between the engine driven
compressor and the turbocharger since it takes the same amount of energy
to drive the compressor."

As far as net HP output is concerned this is probably true.
Given that this is true, and all the mechanical power to drive the
compressor comes from the core engine, each additional core engine
mechanical HP generated requires  4 HP worth of fuel burned as the core
engine is only 25% or so efficient. On the other hand if all the power to drive
the compressor is extracted from the waste heat in the exhaust the
overall efficiency will be higher. I think they used the stock
2 speed mechanical driven compressor because it was there in the
original B29 version of the R3350.


Gordon I forgot to explain  one thing here. Since the compressor and the turbine
are on the same shaft, and are geared to the e-shaft on the test configuration
using the stock turbo charger, in effect it is both a supercharger and a
turbo charger. If the torque from the engine is greater than the torque
from the turbine the compressor will be partly powered by the
engine. This configuration may accelerate the engine RPM faster than the
plain turbo charger. That does not concern us in the aircraft configuration.

(BTW Due to increased rotational inertia it won't accelerate as fast as if
the engine was powering just the compressor as in a pure supercharger. On
the other hand the engine is sucking out its own exhaust gas.)

As engine RPM builds up and hopefully excess turbine power rises more of the
torque required by the compressor will come from the turbine and less
from the e-shaft. If there is any turbine torque left over it will be applied
to to the e-shaft.

Adjustments to this system  can be made in several ways.

1)The turbine can be made larger or smaller (A/R changed).

2)The compressor can be made larger or smaller.

3) The gear ratio between turbo charger and e-shaft can be changed.

4) An over running clutch can be added so the engine never drives
the turbocharger.

I suspect that a fixed gear ratio can be found that will work as
is because I suspect the turbine is more powerful than necessary
to merely compress the combustion air at a steady engine RPM.

If this can be made to work the advantage is less heat lost to the
second turbine and its additional hot plumbing required. Not to the
mention the simplicity and lighter weight.

Paul Lamar ...No rotor no motor.

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