> > 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?
> > First, turbocharging does not increase efficiency.
> However, a carefully designed system using a
> turboalternator might increase the torque.
> > I'm not aware of OTS high speed alternators, at
> least
> just yet, for the rotaries. Custom, they can
safely
> be
> coupled to the turbo. The compressor section can
be
> replaced too.
> > High efficiency brushless electric motors are
> available.
> > Given the notorious inefficiency of the rotary
> engine,
> any heat recovery would be of great value. A
custom
> turbo alternator has been done.
> > see Barber-Nichols site
> >

http://www.barber-nichols.com/products/specialty_products/turbo_alternators/default.asp

> > To do this single design change in isolation would
> make the engine prohibitively expensive. However,
an
> estimated 20-30% could be recovered assuming a
base
> efficiency of 40%.
> > However...one design takes the rotary engine and
> eliminates the "bulkiness" of past and current
> designs
> in RX-7/8 and other rotaries.
> > Almost all rotating parts are placed on the main
> rotary shaft including a starter/alternator, a
> compressor, and a flywheel in line with the rotary
> engine! Intake and exhaust would be designed to
> assist
> in cooling/heating.
> > The result is interesting since efficiency goes up
> as
> weight goes down. With the above changes, and by
> using
> other materials, the efficiency could reach 75%
and
> the weight could drop 50%. The gross increase in
> power/pound would be a factor of 3 1/2, very
> significant for airplane use.
> > Starter/alternators are already here and gives the
> engine a bit more breathing room.
> > Instead of one turbo alternator, smaller multiple
> turboalternators might be used for redundancy
sake.
> Also, there are scalability issues to address with
> the
> larger the rotating parts.
> > David Mathes
> > "Given the notorious inefficiency of the rotary
> engine,"
> > It is not as bad as you think David. We are within
> 4% of a typical Lycoming BSFC. .47 for the rotary
as
> opposed
> to .45 for the Lyc. Sure people are claiming .38
but
> they
> have no independent data to back it up. That is
> diesel territory.
> > What more than makes up for that is the ability of
> the rotary
> to burn auto fuel. Most Lyc's now a days require
100
> LL.
> Typically there is a 50 cent a gallon saving or
> about
> $2.50 verses $3.00 or about a 17% savings in favor
> of the rotary.
> > Paul Lamar


Paul

The gasoline rotary is an advantage in time. Diesel
used to be cheaper as well as propane and natural
gas.
However, gasoline appears to be cheaper than any
other
flight fuel, and allows one to fill at their
favorite
low cost gas station.

I'm not sure a multi fuel rotary engine would be
desirable.

The rotary history has been one of lower "gas"
mileage
than comparable. i was thinking autos at the time.

With all the recent improvements, and the rise of
competitors like Rotamax, there is a lot of work
moving the custom techniques onto the production
products.

The rotary wins on weight which translates to energy
density. Lycoming has solid engines but the 2% fuel
efficiency advantage can be eaten up by the heavier
engine.

Energy density is power per mass per volume

Energy density = P /(mass*vol.)

Volume is often ignored in improvements unless there
is a radical change since lighter weight parts are
usually form, fit and function replacements. An
example would be going from Aluminum housing to
magnesium housing, or using a lighter weight
alternator.

The advantage of putting everything in line and on
shaft especially in a plane is that we can actually
combine functions. For example, the turbo alternator
properly designed can combine starter, alternator
and
turbo functions. Access may be easier; remove and
replacement may require removing the engine however.

David Mathes

A few years ago there was a lot of buzz about a
starter/
alternator. Then reality apparently set in. If it
has enough
HP to work as a starter it is too heavy as an
alternator and the
idea never took hold. Also I think cost was a
factor.
Hard to beat cost wise an established alternator and
starter
infra structure. It is probably perfect however for
a UAV.

One of the off setting factors as far as car mileage
is concerned
is if you have 250 HP with a real smooth engine you
are
likely to use it more. At 65 to 75 MPH cruise my RX8
gets 25 mpg.

The rotary is still in its infancy. We are just now
getting
another ratio of rotor width to eccentricity ratio
in the 16B.
First time in 34 years. How many zillion piston
engine bore to
stroke ratios have been tried?

Don't hold your breath on Rotomax.

Paul Lamar ...No rotor no motor.

Paul,

The automotive folks are frothing over recent
technologies which allow them to do the
starter/alternator package. I know of a couple of
companies that produce these OTS.

Expensive for now.

David

Yea there are a few out there but a couple of years ago
it looked like it would be a revolution. GM was claiming
10% better city by turning the engine off while
waiting for red lights. What happened to that?