> > > 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?
-- Paul Lamar ...No rotor no motor.

The Allison/GM now Rolls Royce T-63/250 uses a starter/generator, this
dates to the 60s and is still in production. 25K plus have been
produced. Lots of early problems on the Hughes OH-6A, I know because I
was there. Some cruise missiles use starter/generators.

The new GE GenX engines for the 787 will have two 250
KW starter/generators.

Control and power management for these applications is not a trivial
subject and is not OTS.

Steve Reed


The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.