Hi Paul,

When I was a student at Sac. State a group of us made a Minto Wheel to
demonstrate its low tech, low speed but great torque characteristics. I
heard that Minto had patented and developed a closed cycle high speed
hydraulic motor also using freon but it wasn't until  recently that I found
a site showing the details of his patent.


http://www.rexresearch.com/minto/minto.htm#usp3636

For people unfamiliar with Wally Minto's work, the top of the 26 pages
shows some basics of a very simple power producing device that you can make
in your own workshop.

The information that  pertains to us pilots is at the bottom of the page.
Basically he takes a heat source of 250 C, separates the vapor from the
fluid and runs the high pressure vapor through what appears to be a helical
screw compressor run backwards.

Perhaps this is one of those half baked ideas that has no business flying,
and is easily applicable for co-gen  or solar heated applications on the
ground.

I can't help thinking however that aircraft engine power plants flying a 8K
plus altitudes have  high delta (differences) in temperature and pressures.
Minto's Carnot cycle device could be driven from the free source of exhaust
heat flowing  through what could possibly be an low resistance muffler.
Think silencer on a gun for a design approach.

Ambient air will cool the condenser.

For running a compressor on the engine it hard to beat a directly coupled
turbo/compressor in simplicity and efficiency.

At present IMHO this is how I see the choices for the turbo compound.
Note in all scenarios of turbocompounding it is assumed there is a turbo
charger attached to the exhaust, that a fixed rpm is desired and targeted.
This rpm, will depend upon using a C/S prop to absorb (change pitch) any
increase in power (rpms) that the turbo-compound idea might produce. Ideal
operations would result in an increase in the amount of miles per gallon
flown. It should be noted that all of these techniques will encourage a
certain increase in weight, complexity and cost to implement.
Please feel free to add your thoughts to the list.

1. Blow down turbine where exhaust gases (after the turbo/charger) are
channeled through a directly connected turbine.  Advantage: Good simple idea
in principle that has been used on an aircraft engine before.
Disadvantage: High temperatures immediate adjacent to the engine components.
No selection of off-the-shelf components to experiment with.

2. Another turbo downstream connected to a gearing mechanism and vibrational
dampening device.  Advantage: Its been done and is used currently in use on
large diesel engines. Large selection of parts available.
Disadvantages: Needs some sort of mechanical transmission. Input torque
matching capability and response time unknown.

3. One turbo coupled to  one gearbox with two PTOs of different rpms.
Advantages: More compact than number two and output speeds designed to
match the applications more closely.
Disadvantages: Custom gearbox and clutch  mechanism needed. Input torque
matching capability and response time unknown.

4. A closed loop freon gas driven Carnot cycle powering a hydraulic motor.
Advantages: No direct influence on the exhaust gas flow. Motor speed and
torque can be controlled  easily. Lower rpms negate the needs for gearboxes.
Hydraulic motors have  a built-in vibrational absorbing capability.
Disadvantageous: Size, reliability issues, and response time.

I'll try to do a little more background research to see what system sizes
are needed for 5,10, and 20Hp units.

Doug in Japan