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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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