ppt 4 rotary engine

7/28/2019 PPT 4 Rotary Engine

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The Rotary (Wankel) Engine

Ben Larson

Peter ShrefflerScott Steinmetz


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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


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History

This graph demonstrates the rise and decline of the rotary engines

popularity through the mid to late 90s


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Automotive Success with Rotaries

In 1991, the Mazda787B won the 24-hourLe Mans endurancerace Rotary engines were

then banned from the C2circuit

The RX-8 is able to

produce 238 hp from its1.3L engine and withgood gas mileage andfavorable emissions


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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


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Compression

Begins after intake

Volume of chamber

decreases

Fuel/Air mixturecompressed

Chamber compresses

to its minimum size


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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.


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Exhaust

Chamber decreases in

size

Forces combustion bi-

products out theexhaust port

Continues until next

apex passes exhaust

port. Entire cycle repeats


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The Cycle

Rotor mounted

eccentrically on shaft

One rotation of rotor

provides three rotationsof shaft

Spark plugs fire 3 times

per rotor revolution

One rotation of shaft foreach firing of spark plugs


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Port Timing

Intake ports shape and size can be altered tochange engine timing

Limited by oil and coolant track

Overlap is when intake port opens before exhaustport 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


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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


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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 rotaryengine has caused their production and maintenance

costs generally to be more


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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


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Challenges of Hydrogen

Storage

Requires Large Tank

Combustion

High Temperatures

Pre-ignition causes backfiring, excessive wear

NOx formation

Injection Components Low temp rubber seals


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Rotary Hydrogen Solutions

Low Operating Temperature

No Backfiring

Very Low Levels of NOx

Separate Intake & Combustion Chambers

Rubber Injector Seals Exposed Only to Intake


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Hydrogen Rotary Timeline

1991HR-X

1993HR-X2

1997Demio FC-EV

2001

Premacy FC-EV

2004

RX-8 RE

2006

Mazda5 RE


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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


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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

ppt 4 rotary engine

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