> > I have been monitoring this group for three months now and
> look
> forward to
> > each day's postings. I am an active pilot (P210) and a
> long-time
> > subscriber
> > to Kitplanes, so your discussions surrounding the
> perfection of
> the rotary
> > aviation engine really intrigue me. A 337 running two
> rotaries
> would be
> > one
> > heck of an airplane!
> >
> > I apologize to the aviation purists that my posting is not
> aviation
> > related,
> > but it is rotary related. I own a small manufacturing
> company in
> North
> > Central Montana which has twenty years experience building
> portable
> > natural
> > gas compressors. Our units feature rotary screw compressors
> driven by
> > piston engines (natural gas powered).
> >
> > I would like to investigate the possibility of utilizing the
> rotary engine
> > as a "valve-less" compressor. I am hoping that through this
> group
> I can
> > find individuals who would be willing to provide engineering
> services for
> > this concept.
> >
> > Ideally, I would like to see the driver and the compressor
> integrated into
> > the same rotary engine block--one rotor driving another.
> >
> > My major concern is that the stock rotary has too much
> inherent
> overlap
> > between the intake and discharge ports to work properly as a
> compressor
> > without the installation of intake and discharge valves. Is
> there
> a way
> > to
> > re-configure the ports to eliminate overlap?
> >
> > Cole T. Chandler
> >
> > Sure you put the output p-port just about where the spark
> plugs
> > are.
> >
> > Wankel rotaries have been widely used as compressors.
> >
> > Paul Lamar ...No rotor no motor.
>
> Isn't the overlap eliminated in the Renesis, or is it just
> minimized ?
>
> John
>
> Yes it is (sort of) but that has nothing to do with a compressor
> configuration. The compressor config needs an air outlet
> port near the combustion chamber. If it is anywhere else
> the engine compresses the air and then lets it expand again
> and THEN merely escape through the existing exhaust with no
> pressure change. The difference is there is no fuel and spark
> to expand the air.
>
> Just bore a p-port hole where the lower spark plug hole is
> and you have a mighty fine, perfectly balanced, 10,000 RPM
> air compressor capable of horrendous air flow.
> You don't even have to do that if you want lower flow.
> Just screw a hose fitting in the spark plug hole.
> Block the top spark plug hole with a stock
> spark plug. You will get at least 150 psi.
> If you fill the depression in the rotors you will
> probably get close to 200 psi or more.
>
>
> Paul Lamar ...No rotor no motor.
>
>
> As I understand your suggestion, there would be only one
> compression
> cycle
> per rotor revolution? The normal "exhaust" stroke of engine
> would
> not have
> any function and not be utilized? Would this "dead stroke"
> create wasted
> horsepower?
>
> Cole
>
> Yes but if you vented it to the atmosphere it would consume
> very little power. That part of the cycle could be a used as
> a vacuum pump with the p-port exhaust as the exhaust port.
> You would need another intake port below the pressure
> port on the spark plug side. The pressure output port
> will need a one way valve. So too the vacuum input
> port. One problem might be apex seal lube but try
> self lubricating Rulon apex seals. A mixture of Teflon
> and Kevlar. What you wind up with is both a vacuum pump
> and a compressor in the same stroke and in one revolution
> of the e-shaft.
> --
> Paul Lamar ...No rotor no motor.
>
> There are in fact rotary compressors and have been for a long
> time.
> Most large industrial plants if there is a requirement use
> rotary
> compressors. Many air conditioning units use rotary compressors
> even in
> autos.
> R Matt Doody
>
>
> Paul,
>
> Is it viable to use one rotor as a supercharger for the other
> rotors
> in the engine?
>
> If this is feasible, it might make sense In a turbocompund
> engine
> where you have an exhaust turbine connected to the engine shaft
> anyway, so the power to drive the compressor rotor would be
> deducted
> from whatever your turbine is putting in.
>
> This might have packaging advantages. You could just put your
> turbine right behind the engine with a gearbox. The output
> from the
> compressor rotor would be fed to the remaining rotors.
>
> The question is how much power it would take to run that
> rotor and
> what would its thermal efficiency be? Also it is pretty heavy.
>
> Perhaps use a small single-rotor engine like the Aixro go-cart
> engine and use that as the compressor?
>
> I'm thinking here about a ducted fan turbo compound application
> where
> you want the engine to be as cylindrical as possible. This way
> everything would just go axially on the back of the engine --
> the
> compressor, the gearbox and the turbine. The turbine outlet
> would be
> facing straight back from the middle of the engine, so you
> could put
> a nozzle on it and get thrust at high speed...
>
>
> Regards,
>
> Gordon.
>
> For some strange reason the engine runs rough on only
> one rotor. I know not why.
>
> Paul Lamar
>
>
> So here's an idea -- get a 20b & a custom e-shaft. Configure the
> e-shaft such that the configuration of the lobes for 2 of the rotors
> matches the lobes on a 13b (180 degree opposed). Send gas to the 2
> opposed rotors. Use the 3rd rotor (the middle one I would guess
so the
> thermal effects on the engine are balanced front to back) as a
> compressor and feed that into the other 2 rotors. Voila - a
> supercharged engine that should run nice & smooth.
>
> Mark Supinski
This won't work, guys, because the "free air" volume displaced by the
compressor section must be larger than the displacement of the engine
section. The supercharger must squeeze a larger volume of air into a
smaller volume to increase the engine charge.\
I know we are off the original subject of making a compressor from a
rotary engine. But, Gordon's comments about the Aixro go-cart engine
and cylindrical geometry leads me to this idea: use an Aixro engine
to drive a Rotrex supercharger to pump intake air to a 13b. Boost
pressure would be easy to control using a model airplane servo on the
Aixro throttle. The Aixro/Rotrex system could be remotely located,
thereby simplifying the design of an inter cooler system and giving more
control over weight/balance issues. Bleed air would be available from
the Rotrex compressor for cabin heat.
Would this scheme be legal at Reno?
Aubrey
Sure. Here are some pictures of a White Lightening
with something similar. Used a Rotax 2 cycle to drive the
compressor. The Germans had bombers in WW II that did
this.
--
Paul Lamar ...No rotor no motor.
That's a neat idea, Aubrey.
The ability to easily control boost makes this something to think
about. You could just dial in any manifold pressure you want,
anytime you want it.
I would guess that the aixro engine making 40 hp could easily run
the biggest compressor in the Rotrex lineup. Probably enough boost
there for a 4-rotor...
Here's a picture of an RC model rotary -- I think it's just good for
a couple of hp so it would have to be a very small compressor. What
we need is something in between this and the aixro for a 2-rotor engine.
Regards,
Gordon.
Paul,
While on the supercharger subject: a fellow on a Yahoo list is
experimenting with a 1/2 turbocharger. He removed the broken exhaust
side, and added a cog belt drive -stepup 1:10 ratio- in it`s place. He
only wants 2-5 psi, so the compressor speed is adequate.
A really cheap supercharger.
Do you think such a concept will be (remotely) efficient and workable?
-
Erik Snyman
Messina
South Africa.
You pay a fuel penalty with all super chargers as opposed
to turbo chargers. All the HP to drive the supercharger
comes from the net mechanical HP of the engine. In other words
if your super charged engine is generating 200 HP net at the
e-shaft the engine is burning 220 HP worth of fuel.
The BSFC does not change. At a BSFC of .5 the fuel burn
is 110 pounds an hour or 18.33 GPH.
If your turbo charged engine is making the same net 200 HP
at the shaft the engine is burning only 205 HP worth of
fuel or 102.5 pounds or 17.08 GPH. The supercharger is
costing you over 1.3 GPH in this case. The reason is the
turbo charger is extracting otherwise waste
HP from the exhaust. A step towards turbo compounding.
It gets even better at altitude for the turbo charger.
Note the efficiency of just the compressor is the same
in both cases because he is using the same compressor.
Centrifugal compressor efficiencies are the highest in
the compressor industry. Also the mechanical drive for the
super charger is not 100% efficient. If the compressor is 80%
efficient and the drive 98% efficient the overall super charger
is only .98 times .8 or 78.4 % efficient.
Paul Lamar ...No rotor no motor.
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