1. The Rotary (Wankel) Engine
Ben Larson
Peter Shreffler
Scott Steinmetz

2. History Ideas have existed since the 16th century
German scientist Felix Wankel was the first to put the idea into a working design
Funded by the German Aviation Ministry during WWII
Germany believed that the rotary engine would propel their industry into eventual greatness
Wankel perfected his design and sold the rights for the design to several car companies
Mazda produced its first rotary power car in 1961 and created their Rotary Engine Division in 1963

3. History
Popularity for the rotary powered vehicles increased rapidly until the gas crisis in the mid 70’s
Rotary engines were not very fuel efficient compared to piston engines
Strict emissions standards could not be met with current rotary technology
These two factors severely hurt the sale and development of rotary engines
Mazda was the only car company that continued to produce cars with rotary engines through the 90’s

4. History
This graph demonstrates the rise and decline of the rotary engine’s popularity through the mid to late 90’s

5. Automotive Success with Rotaries
In 1991, the Mazda 787B won the 24-hour Le Mans endurance race
Rotary engines were then banned from the C2 circuit
The RX-8 is able to produce 238 hp from its 1.3L engine and with good gas mileage and favorable emissions

6. Intake Begins when apex passes intake port Increase in chamber volume
Creates low pressure zone
Pulls in Fuel/Air mixture
Completes when next apex passes intake port

7. Compression Begins after intake Volume of chamber decreases
Fuel/Air mixture compressed
Chamber compresses to its minimum size

8. Combustion Spark plugs ignite mixture
Two spark plugs to maximize amount of fuel ignited
Causes rapid chamber expansion
Turns rotor which produces work output on shaft
Power stroke continues until apex passes exhaust port.

9. Exhaust Chamber decreases in size
Forces combustion bi-products out the exhaust port
Continues until next apex passes exhaust port.
Entire cycle repeats

10. The Cycle Rotor mounted eccentrically on shaft
One rotation of rotor provides three rotations of shaft
Spark plugs fire 3 times per rotor revolution
One rotation of shaft for each firing of spark plugs

11. Port Timing
Intake ports shape and size can be altered to change engine timing
Limited by oil and coolant track
Overlap is when intake port opens before exhaust port closes
Support at least 50% of apex seal
Street ports
Moved up to delay intake closing
Moved out to open intake earlier
Limited overlap and with reasonable limits of oil tracks
Racing ports
Very close to oil tracks
Reduced engine life
Sometimes large overlap
Increased power at high RPM
Decreased power at low RPM

12. Advantages Vibration Power/Weight Simplicity
No unbalanced reciprocating masses
Power/Weight
For similar displacements, rotaries are generally 30% lighter and produce twice as much power
Simplicity
Contain half as many moving parts
Have no connecting rods, crankshaft, or valve trains

13. Disadvantages Fuel Efficiency and Emission Cost
The shape of the combustion chamber, which is long instead of small and concentrated, makes the combustion travel longer than a piston engine
Due to the longer combustion chamber, the amount of unburned fuel is higher which is released into the environment
Cost
The lack of infrastructure and development for the rotary engine has caused their production and maintenance costs generally to be more

14. Future Trends: Hydrogen
Highly Flammable
Production Energy from
Crude Oil, Coal, Natural Gas, and Nuclear
Combustion Results in Water and NOx
Energy Density
High Per Unit Mass
Low Per Unit Volume

15. Challenges of Hydrogen
Storage
Requires Large Tank
Combustion
High Temperatures
Pre-ignition causes backfiring, excessive wear
NOx formation
Injection Components
Low temp rubber seals

16. Rotary Hydrogen Solutions
Low Operating Temperature
No Backfiring
Very Low Levels of NOx
Separate Intake & Combustion Chambers
Rubber Injector Seals Exposed Only to Intake

17. Hydrogen Rotary Timeline
1991
HR-X
1993
HR-X2
1997
Demio FC-EV
2001
Premacy FC-EV
2004
RX-8 RE
2006
Mazda5 RE

18. RENESIS Hydrogen Rotary
Dual Fuel
Switches from Hydrogen to Gasoline
Direct Injection
Electronically Controlled
Extended Seal Life
Twin Injectors
Increased Injection Volume
Control Valve
Adjusts pressure of injected hydrogen

19. Hydrogen Conclusion Cleaner Burning
Water, Minimum NOx
Rotary Engine Solves Combustion Issues
Low Temperature
Separate Induction and Combustion Chambers
Dual Fuel Mazda5 RE
Practical For Gas-Hydrogen Transition