Transcript PPT 5 Rotary Engines

Rotary Engines
The Detroit Piston
Jason DeVoe
Bijal Patel
Tom Place
How It Works
• Triangular Rotors used in lieu of
pistons
• Rotors follow a translational
path in addition to rotating about
the crankshaft
• Intake/exhaust ports are located
in the side walls of the housing
instead of using valves
• Torque is transmitted via the
ring gears inside each rotor
The Cycle
Intake
• Fresh Air/Fuel is
drawn in while intake
port is uncovered
Compression
• Air/Fuel mixture is
compressed by rotor
The Cycle
Ignition
• Spark plug ignites
mixture at maximum
compression
Exhaust
• Burned fuel is
released through
exhaust port
Parts
•
•
•
•
•
Rotor
Rotor Housing
Side Housing
Eccentric Shaft
Stationary Gear
Rotor
• Triangular shape
• Convex surfaces
• Recess increases
displacement
• Maintains constant
contact on all three
points
• Rotates around
stationary gear
Rotor Housing
• Epitrochoid shape
• Forms outer envelope
of working chamber
• Contains Exhaust
Port and Spark Plugs
• Must withstand wear
from rotor apex seals
Side Housing
• Contains all seals
• Keeps rotor from
moving front to back
• Contains Intake Port
• Passages for
lubrications and
cooling
Output Shaft
• Offset lobes
• Each rotor fits over
one lobe
• Force of rotor on the
lobes creates torque
Stationary Gear
• Meshes with rotor
internal gear
• Contains main
bearings for output
shaft
• Delivers lubrication
and cooling to output
shaft and bearings
Comparison to Piston Engine
Rotary Advantages:
-
-
-
-
Much more compact, can be
placed lower and farther back
to change weight balance
Continuous rotating motion is
much smoother with higher-rev
capability
One power stroke per full
crankshaft revolution reacts
more like a two-stroke power
cycle while maintaining fourstroke operation
60% fewer moving parts and
very little vibration
Piston
VS.
Rotor
Comparison to Piston Engine
Rotary Disadvantages:
-
Slower combustion
characteristics
Poor fuel economy
Durability/reliability problems
due to seal fatigue
High emissions and unburnt
hydrocarbons
Powerband typically
reminiscent of a turbocharged
piston engine, linearly
increasing instead of a flatter
torque curve
Comparison to Piston Engine
Since the displacement of a rotary
is fired twice as often in two
revolutions as in a piston
engine, the power output and
fuel economy resembles that
of an engine twice its noted
size. The resulting powerband
looks more like what you
would see from a two-stroke
engine.
For example, the RX-8 rotary is
listed as 1.3L, 238hp, and
17mpg. Those performance
numbers reflect that of a 2.6L
engine, not a 1.3L. Most highperformance, naturally
aspirated IC engines can
produce ~100hp/L and other
cars of similar weight and
power output can obtain fuel
economy closer to 25mpg.
The listed displacement is
more a judge of physical size
than of comparable efficiency.
History
• 1926 – Dr. Felix Wankel begins to investigate
rotary engines
• 1956 – Wankel develops working prototype of a
single rotor engine
• 1958 – Curtis-Wright Corp. (now John Deere)
buys the North American rights
• 1965 – 1st rotary-powered vehicle, the NSU
Spider is produced
Mazda and the Rotary
• 1967 – 1st rotary powered vehicle is released,
the Cosmo
• 1978 – RX-7, the most well known rotary
powered vehicle is released
• 2002 – Mazda stops production of the RX-7
• 2003 – RX-8 is released with new generation
Renesis rotary engine
Websites
• http://auto.howstuffworks.com/rotaryengine.htm
• http://www.rotaryengineillustrated.com/ind
ex.html
• http://www.rotarynews.com/
• http://www.keveney.com/Wankel.html
• http://www.mywiseowl.com/articles/Wankel
_rotary_engine