AKSHATH K.M1st M Tech AutomotivePES UniversityBangalore

@7urboCharger

• The Wankel engine is a type of IC engine whichuses a rotary design to convert pressure into arotating motion instead of using reciprocatingpistons.

• Felix Wankel, a German engineer, developedthe engine bearing his name in the 1950s and1960s with the help of NSU Motorenwerke AG.He first conceived the idea in 1924 beforefinally seeing the first prototype at work in1957.

• Uses a triangular shaped rotor spinning insidean oval-like housing.

• Manufactured mainly by Mazda, currently usedin Mazda RX-8.

• Extremely lightweight and small whencompared to engines with similar poweroutput.

First DKM Wankel Engine designed by FelixWankel the DKM 54 (Drehkolbenmotor), atthe Deutsches Museum in Bonn, Germany.The rotor and its housing spin.

BASIC PARTS

SO HOW DOES IT WORK?

• The Wankel engine works in the same 4-stroke cycleas the reciprocating piston engine, with the centralrotor successively executing the four processes ofintake, compression, ignition (combustion) andexhaust inside the trochoid chamber.

• Both types of engines rely on the expansionpressure created by the combustion of the fuel-airmixture, the difference between them derives fromthe way they harness it to transform it intomechanical force.

• In a rotary combustion engine, this expansionpressure is applied to the flank of the rotor. Becauseof the rotor’s triangular shape, the inside space ofthe housing will always be divided in three workingchambers. This is fundamentally different from thepiston engine, where the four processes take placewithin each cylinder.

COMPARISON OF THE 4 STROKE CYCLE IN A WANKEL ENGINE & A RECIPROCATING ENGINE

• While a four-stroke piston engine completes one combustion stroke per cylinder for every tworotations of the crankshaft (that is, one-half power stroke per crankshaft rotation per cylinder), eachcombustion chamber in the Wankel generates one combustion stroke per driveshaft rotation, i.e.one power stroke per rotor orbital revolution and three power strokes per rotor rotation.

• Thus, the power output of a Wankel engine is generally higher than that of a four-stroke pistonengine of similar engine displacement in a similar state of tune; and higher than that of a four-stroke piston engine of similar physical dimensions and weight.

• The displacement volume of the rotary engine is usually expressed by the unit chamber volume and by the number of rotors (eg. 654cc x 2). The unit chamber volume represents the difference between the maximum volume and the minimum volume of a working chamber, while the compression ratio is defined as the ratio between the maximum volume and the minimum volume.

Reciprocating Engines Rotary Engines

Uses pistons to regulate intake and exhaust of fuel and gas.

Has a spinning rotor that creates three separate chambers and regulates the inflow and outflow of gasses.

All four strokes, intake compression, combustion and exhaust occur in same cylinder.

Each chamber draws in air and fuel, is compressed, ignited and combusted then expelled creating power while at the same time forcing the other two chambers to do the same.

Pistons continually reverse direction creating more wear and tear on the engine .

Rotors move in a continuous direction making it smoother .

Bad power to weight ratio in comparison.

Only about three moving parts creating less friction, so higher RPM.

• A far higher power to weight ratio than a piston engine.

• No reciprocating parts.

• Runs with almost no vibration.

• Not prone to engine-knock.

• Far fewer parts than a piston engine.

• Cheaper to mass-produce as contains few parts.

• Superior breathing, filling the combustion charge in 270 degrees of mainshaft

rotation rather than 180 degrees in a piston engine.

• Supplies torques for about two thirds of the combustion cycle rather than one

quarter for a piston engine.

• Wider speed range gives greater adaptability.

• It can use fuel of wider octane ratings.

• It is approximately one third of the size of a piston engine of equivalent power

output.

• On some Wankel Engines the sump oil remains uncontaminated by the

combustion process requiring no oil changes.

ADVANTAGES

» Rotor sealing is still a problem as the engine housing has vastly differenttemperatures in each separate chamber section.

» The combustion is slow as the combustion chamber is big and moving.

» Less thermodynamically efficient.

» The biggest disadvantage, however, is its considerable fuel consumption.Comparison tests showed that a Mazda RX8 used up more fuel than a heavier V8engine with over four times the engine displacement, but comparableperformance figures.

» The exhaust stream is enriched with unburned mixture and carbon monoxide.

» Poor emissions. As unburnt fuel is in the exhaust stream, emissions requirementsare difficult to meet. This problem looks to be overcome by implementing directfuel injection into the combustion chamber.

MAZDA’S CONTRIBUTION TO WANKEL’S ENGINE

MAZDA WANKEL ENGINE

• Mazda introduced the world’s first twin-rotor rotary engine car in May 1967 with the CosmoSport/Mazda 110S model. It featured a 491cc x 2 Wankel engine that developed 110 hp at 7,000 rpm.

• In 1970 Mazda introduced the first automatic transmission on a Wankel-powered engine and threeyears later the world’s first pick-up truck with a rotary engine.

• Introduced six-port induction system featuring 3 intake ports per rotor chamber to achieve improvedfuel consumption by controlling them in three stages.

• Another noteworthy development was the implementation of a two-stage monolithic catalyst.

• Introduced Wankel Engines with Turbo Chargers in 1982. Building on thatachievement, Mazda would later adopt the twin-scroll turbo, minimizing the engine’sturbo lag.

20b Mazda street port turbo GT42R20B-REW (Triple`Rotor Twin Turbo)

• Introduced a 3-spark plug ignition system (Mazda 26B) to improve combustionprocess.

• Introduced 'thermal reactor’ (which is an enlarged chamber in the exhaustmanifold) in 1973 to reduce the HC emmissions and improved the fuel efficiency ofthe thermal reactor system by 40% by the time of introduction of the in 1978.

• In 2003, Mazda introduced the Renesis engine fitted in the RX-8. The Renesis enginerelocated the ports for exhaust from the periphery of the rotary housing to the sides,allowing for larger overall ports, better airflow, and further power gains.

• Mazda is still continuing development of the next generation of Wankel engines,the 16X. The company is researching engine laser ignition, eliminating spark plugs,and direct fuel injection to which the Wankel engine is suited. This leads towards agreater rotor eccentricity, equaling a longer stroke in a reciprocating engine, forbetter elasticity and low rpm torque. These innovations promise to improve fuelconsumption and emissions.

• To improve fuel efficiency further Mazda is looking at using the Wankel as a rangeextender in series-hybrid cars and announced a prototype, the Mazda2 EV

A cut-away of a Wankel engine shown at the Deutsches Museum in Munich, Germany

MAZDA WANKEL ENGINE POWERED SPORTS & RACING CARS

• In the racing world, Mazda has had substantial success with 2-rotor, 3-rotor, and 4-rotor cars.

Sigma MC74

• The Sigma MC74 powered by a Mazda 12Aengine was the first engine and only teamfrom outside Western Europe or the UnitedStates to finish the entire 24 hours of the 24Hours of Le Mans race, in 1974.

• Mazda is the only non-pistonengine ever to win Le Mans, whichthe company accomplished in 1991with their four rotor 787B (2,622 ccor 160 cu in—actual displacement,rated by FIA formula at 4,708 cc or287 cu in).

787B

• The Mazda RX-8 is the successor to the RXSeries and it is powered by a 1.3 L 2 rotor13B-MSP Renesis/3-rotor 20B-REW Wankelengine.

Mazda RX-8