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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
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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 four-stroke 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
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 high-performance, 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. Comparison to Piston Engine
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/rotary-engine.htm • http://www.rotaryengineillustrated.com/index.html • http://www.rotarynews.com/ • http://www.keveney.com/Wankel.html • http://www.mywiseowl.com/articles/Wankel_rotary_engine