Paul, I think for Al's 3 rotor you would need to use something
like
360
cubic inches and 9? cylinders.
Ed Andeson
Not true. Statements like this indicate a lack of fundamental
understanding of how the rotary really works. This is also
why you are confused on the intake manifold.
A three rotor is a three cylinder 2 cycle
or a six cylinder four cycle. Forget the three faces on the
rotors.
The ONLY thing that counts is the intake, firing and exhaust
events
per revolution of the e-shaft. Think of it as a mysterious black
box with air pulses going in and exhaust gas pulses and HP pulses
coming out.
Ok, Paul, given your statement above that a 3 rotor is characterized
by
212
CID and six cylinder four cycle, then I would be interested in how a
2
rotor
is characterized? as a 2 cylinder 2 cycle or 3 cylinder four cycle?
Ed Anderson
"or 3 cylinder four cycle?"??????????
Where did that come from? I never said that. If I did it was a typo.
Don't you mean "or 4 cylinder four cycle?"?
Yes it is equivalent to a 2 cylinder two cycle or a 4 cylinder four
cycle.
They both fire twice per rev with two intake and two exhaust events
per
rev.
All racing organization around the world equate the 13B to a 2.6 liter
(160 cubic inches) four cycle engine.
One reason it generally generates more power than a 2.6L 4 cycle 4
cylinder
engine is the fact that the volumetric efficiency is much higher than
a
piston
engine. It averages 120% over a wide RPM range. This is a direct
outgrowth
of the slow rotor RPM keeping the ports open longer than would be the
case
with a 2 cycle piston engine. This high volumetric efficiency also
tends
to
insidiously convince people that the wankel is some how a larger
engine
than 2.6L.
Another reason is the intrinsic high RPM capability.
The wankel is a very subtle and shrewdly designed engine.
In order to design an effective intake manifold one must thoroughly
understand exactly how the wankel works.
Paul Lamar
Vance W Jaqua wrote:
If you are designing a tuned tube, the Physics of the action could care
less
what the
rotational speed of some mechanical part of the engine. It will be
looking
at port
(or valve) open duration. and the flow during that period, and then the
time
till
the next flow event. If you look at the relative durations, the actions
exactly
correspond to a 3 cylinder four stroke cycle 0perating at two thirds
eccentric
rpm or more meaningfully twice rotor speed because one turn of the rotor
takes
all three chambers through the four "strokes" of an Otto cycle. I
believe
that
inlet resonance likes the longer off times between pulses, which is why
they
generally do not pair up ports on piston engine resonance systems. In
resonant systems
the "Q" that we use for dynamic pressure is now a measure of efficiency
of
the
resonant system, and you would like that high- However the higher the
peak,
the narower the frequency range. The Wankel tunning is hampered by this
equivalent
pairing, but since there are no "Y"s in the system, it is less damaging
than pairing
in piston engines, and it also shortens the pipes for easier packaging.
For aircraft use a two point system would be good for fixed props -
static
and full power, I doubt that there would be any real gain at cruise in
sfc.
Vance
Hey if the open duration is only a little over 180 degrees of the e-shaft
rotation
what then must be the closed duration? Think of the rotor as some sort of
trick
valve. Forget that it has three faces. The rotor is moving very slowly.
Start at 180 degrees shaft angle in this series of pictures. Note that the
intake port is
just starting to open on chamber (C). 180 degrees later it is just closing
at shaft angle
360 degrees. The next chamber (B) in line does not start to open until
180 degrees later at shaft angle 540 degrees. Just like a two cycle.
Tuning this is no problem. The port stays closed plenty long enough.
You are confused. The engine is equivalent to a two cylinder two cycle and
a
four cylinder four cycle that has a trick valve system that stays open for
180 degrees of crank rotation rather than only a few degrees in the case
of
the two cycle and and a little over 90 degrees in the case of a four
cycle.
Simple as that. That is why it breaths so well and generates so much power
for its displacement.
Paul Lamar
I respectfuly tend to differ. I am not the one that is confused by the tax
evading logic espoused
by Wankel and Mazda. I think that you are too fixated on the rotation of the
e shaft which
does no bear a one to one relationship with the cycle that is producing the
power. For those
who may be interested in this dissenting conclusion, I refer you to the
"Wankel" link
at my web site www.geocities.com/vjaqua I have added the diagrams of the
"piston
eqivalent" Wankel for added clarification.
Vance
The entire world relates to the output shaft RPM. Gear ratios and
torque are spoke of in reference to the output shaft RPM.
There is no longer any controversy in the governments of the
world or in the racing organization of the world as to the displacement.
It is rated at 160 c.i. (2.6L) PERIOD.
Also the engine pumps roughly as much air as a 80 cubic inch two
cycle or a 160 cubic inch (2.6L) 4 cycle. It does not pump three times as much
as you claim it does. In that case the engine would be 240 cubic inches
per rotor or 480 cubic inches for a 2 rotor. All three equivalent
engines fire twice per e-shaft rev. Furthermore with equal volumetric
efficiency and equal RPM the rotary will generate almost exactly the
same power as a 2.6L four cycle piston engine. There are plenty of
racing engine examples out there to prove this. Despite the rotaries
compression ratio handicap.
You can claim the displacement is anything you feel like but as far
as the intake characteristics it is just like a piston engine.
The rotary intake port stays open for about 180 degrees and
closes for about 180 degrees. The piston engine intake port stays
open for about 90 degrees and closes for about 270 degrees.
Therein lies the rotaries ability to generate extraordinary mounts of
power at high RPM with no popit valves to get in the way of the
airflow.
This means the three rotor chambers you speak of operate
sequentially and not in parallel as you imply on your web site.
The rotary is merely changing out its "piston" tops one after
the other. There are two requirements to ingest air for a normally
aspirated engine. The chamber must suck and the port must be open.
If these chambers were working in parallel the intake port
would have to stay open 100% of the time and the chambers would
have to suck (increase their volume) 100% of the time and that
is not the case.
In the case of a peripheral port the intake ports do stay open
nearly 100% of the time but the rotor chamber is only sucking air
half of that time.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/
Copyright 1998-2003 All world wide rights reserved.