ERuttan wrote:
I have a basic question as I am not entirely comfortable with the rotary.
I noticed some pictures of rotors in the rotary have a "dish" out of the
surface. If so that means to me that the "bent in" parts of the rotary
housing (please, what is the correct or common name?) do not seal
against the surface of the rotors but only that apex seals seal the
chamber. Is this true?
Are there any formulas commonly available to describe the shape and
motion of the rotor in the housing? Does there exist a software tool
that would allow one to change parameters to see the effect on the
cylinder shape and movement of the rotor?
Thank you for your time
The outer housing is called the rotor housing. Yes the seals are located at the three
corners of the rotor. Hence they are called the apex seals. The dish out of the face of the
rotor forms the combustion chamber. The depth of the dish controls the compression
ratio. The rotor orbits around the center of the eccentric output shaft. The time
of the orbit is the same as the eccentric shaft takes to make one revolution.
As the rotor is orbiting around the center of the e-shaft is is revolving only
1/3 as fast as the e-shaft. The combustion chamber actually moves around inside
the rotor housing. For these reasons the engines is sometimes called a rotary
combustion engine or a planetary engine.
Yes there are lots of formula. The formulas are available in several books.
I don't have the formulas scanned in but if you can't find any of these books
let me know and I will scan them in for you.
* The definitive book on the rotary is simply called "ROTARY ENGINE"
by Kenichi Yamamoto published by Toyo Kogyo Co. Ltd. (Mazda) in
1969. This is a highly technical book chronicling the development of
the wankel by Mazda. Kenichi is an engineer and has risen to CEO of
Mazda.
* This book on the rotary is also called "ROTARY ENGINE"
by Kenichi Yamamoto published by Sankaido Co. Ltd.
Second edition published in 1981. This is an updated version of
the first "ROTARY ENGINE" book. Confusing eh what? This book
has a much greater emphasis on emmisions.
* Another technical book on the Wankle rotary engine is; "The Wankel
RC Engine Design and Performance" by R.F.Ansdale Published by A.S.
Barnes & Company Lib of Cong 69-18692
* The Wankel engine Design Development Application by Jan P. Norbye.
Chilton Book Company. ISBN 0-8019-5591-2 Published in 1971. A little
history and results of the Wankel engine development by NSU,
Mercedes, Mazda and others and some results of work by
Curtiss-Wright. Also some history on all rotary engines. Not as
technical as I would like but not bad.
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.
How the Wankel Works
by Paul Lamar
The wankel rotary consists of a three sided rotor moving in a modified oval
chamber or rotor housing. There are at least two holes in the walls of one
side of the rotor housing. In the other side of the rotor housing there is
at least one spark plug. One hole is used as an intake port and the other as
an exhaust port. Just like a one cylinder two cycle piston engine. The rotor
rotates around the center of the output shaft while at the same time
rotating around its own axis. This is very similar to the way the earth
rotates around the sun while rotating around its own axis. The rotor rotates
one third as fast about its own axis as it does around the center of the
output shaft. Actually what is happening is the center or CG of the rotor is
moving in a circle around the center of the output shaft while the output
shaft rotates. Very very clever on the part of Felix Wankel to invent and
engine that uses this motion.
As this motion is taking place the tips of the triangular shaped rotor are
passing the ports in the housing. As one tip, call it tip A, passes the
intake port in the rotor housing the face behind tip A starts to draw in the
fuel air mixture. Call it face or chamber number 1. When the next tip call
it tip B passes the intake port the mixture is captured and starts to
compress. As the chamber continues around the housing it encounters the
spark plug and the mixture inside it is fully compressed. The spark plug
fires and the chamber starts to expand imparting the pressure energy in the
burning mixture to the output shaft. As the rotor continues on around tip A
passes the exhaust port and the burnt mixture starts to leave chamber 1.
This completes the four cycles for chamber one. In the mean time chamber two
and chamber three are completing various cycles of this same sequence
simultaneously.
This three chamber simultaneous action is the reason the wankel engine is
so light and compact for the power it is able to generate. Furthermore the
forces in each chamber due to the pressure in each chamber are completely
contained in the one piece cast iron rotor. In a four cycle piston engine
this is not the case. The compression force must pass down a connecting rod,
into the crankshaft and up another connecting rod into another chamber that
is expanding and extracting power from the burning mixture. This makes
piston engine force paths and consequent stresses far far more complicated
than the wankel engine.
Although the wankle has similarities with a two cycle engine, particularly
in regard with the way the porting mechanism works, it is in no way a two
cycle engine. All four cycles are continuously taking place simultaneously
and those are intake, compression expansion and exhaust.
