The Rotary (Wankel) Engine

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
  70s
• 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 90s

4
History
This graph demonstrates the rise and decline of
the rotary engines popularity through the mid to
late 90s
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
• 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
• 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