Dear Sir / Paul Lamar,

I am fascinated by your articles on turbo compounding.

Having no technical backrgound however makes it hard for me to grasp some
of
the basic enegy converting processes that take place.
I hope you are willing to explain this to me (preferrably is in simple
language).

If I am correct there are three energy components in exhaust gasses that
potentially can be changed into kinetic energy (ie of a shaft)
a) high temperature of exhause gasses vs low outside temperature

b) high pressure and speed of the exhaust gasses vs normal pressure of the
surrounding air

c) unburnt fuel in the exhaust gasses

b) is obviously used by making turbine blades rotate. I can see that

But you also state that kinetic energy is the result from lowering the
temperature of the exhaust gasses.
I understand that a temeperature drop means that the energy has gone
somewhere else, But how does this process of converting thermal energy into
kinetic energy take place in the turbine?

Also you state there is potential energy to be recovered by burning the
remainder fuel in exhaust gasses.

Burning gasses in a turbine is a commonly used technology.
One wonders what would be the benefit of starting off with an internal
combustion engine and ending with a turbine engine.
The combination always seem to lead to a heavier and thus unvavorable
solution.

Erik Kappelle

"you also state that kinetic energy is the result from lowering the
temperature of the exhaust gasses."

I don't recall saying that. The opposite is true. I wrote several articles
and gave several video presentations. In which article did that appear?
It may be a typo.

"Also you state there is potential energy to be recovered by burning the
remainder fuel in exhaust gasses."

Merely running the engine lean, up to a point, will increase the exhaust
gas
temperature as unburned fuel will be burned that will increase both kinetic
and thermal energy in the exhaust. If that does not do the trick pumping
fresh
air into the exhaust ahead of the turbine will take care of the residual.
That was widely used in early rotary engine to reduced unburned hydro
carbons.

This increases the kinetic energy available for recovery.

Weight is not everything. If that were the case nobody would use anything
other than a turbine. BSFC is important. BSFC is short for Brake Specific
Fuel Consumption which is a number that specifies the pounds of fuel burned
per HP generated for one hour.

Small turbo prop engines have a typical BSFC  of .65. The turbo compound
rotary will be nearly half of that or around .35. Cost is also important.
A turbo compound rotary would also be close to half the cost of a small
turbo
prop engine.


Paul Lamar


High All, Craig here.

Here is another approach to compounding.

http://www.moller.com/files/Breakthrough.pdf

It's just a press release, but you'll get the idea.  Moller doesn't have
much on the site other than a picture of the experimental engine and some
numbers about specific fuel consumption.

They use a second rotor on the engine shaft to act as an air precompressor
and exhaust gas expander.  Same concept as turbo-compounding but with a much
simpler way of coupling the recovered energy to the output shaft.
 Obviously the second rotor won't supply as much energy as the primary
(fuel burning) rotor, but the cost of adding the second rotor without all of
the fuel and ignition accessories shouldn't be terribly high.  Also, since
it should be able to  act as a supercharger at high engine loads, it could
allow the engine to be smaller for the same maximum power output.  That
might "pay for" the added cost and weight of the additional rotor.

  Could it be added as another (identical) rotor on an Mazda 13B Wankel
without too much fuss?  What is the phasing of the new rotor on the shaft?
 What is the volume and expansion ratio of the rotor they used?  Unknown to
me.

Craig Taylor


Anything Moller says has to be taken with a grain of salt. He is in the
business
of selling worthless stock and consider this an advertisement. In 30 years
he has
never manufactured and sold any hardware to my knowledge.

Rolls Royce built something like this but nothing ever came from it.

Paul Lamar


Paul, Moller is once again smoke and mirrors. To have supercharging the
supercharger must intake a greater volume of air than the engine being
supercharged. The RR engine used in intermediate weight lorries actually did
this using a much larger rotor to supercharge the smaller rotor. As I recall
this was done to increase rotor compression and thereby raise temperature to
the flash over temperature of the diesel fuel which was difficult to achieve
by merely reducig the depression in the rotor face.The RR rotors ran timed
to transfer the air to the upper rotor and were at a 1 to 1 ratio. For
Moller to supercharge with a rotor of the same size as the working rotor it
would need to run much faster, doable with a planetary gear at exactly 2 to
1 or 3 to one (necessary for transfer to the working rotor), however,
deriving power from the exhaust through the exhaust cycle of a rotor turning
twice as fast doesn't appear likely. It would lower exhaust temperature
significantly and exhaust noise from the lower pressure but the power
production would be unlikely and certainly less than the turbine compound
arangement. At the point where the engine rotors exhaust port opens there is
virtually no where for the exhaust gasses to go if it is to expand  and push
the secondary rotor. If it is introduced later in the rotation much of the
expansion has already occurred and again power gain is minimal.
         I would like to point out however that the RR diesel appears to be
built with alloy end housings and center housings. I was wondering if any
details of construction or alloy specification are available for the RR
rotary.

george grimes