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Internal Combustion
Engines
*Introduction
*Fuels
*Four Stroke Engine
*Parts of a four stroke engine
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Introduction
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Classification of IC engine
Engines can be classified in manydifferent ways: By the engine cycle used,
the layout of the engine, source ofenergy, the use of the engine, or by thecooling system employed.
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Fuels
Why are nearly all vehicles and enginespowered by gasoline?
extremely high energy density
cheap (relative to other sources)
easy and safe to move around
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Fuels
Why not use other fuels?
Size of engines needed to utilize thesefuels is impractical for automobileslawnmowers etc.
Convenience
it takes 15 seconds to pump a gallon of gasvs. several hours to recharge batteries (i.e.electric cars)
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Fuels
What are other types of fuels that can beused?
Wood- steam engines
Coal- steam engines
Oil
Electricity
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Internal Combustion
Where do we get internal combustion?
The idea here is to take a fuel (gasoline for
example) and burn it in an engine to createmovement of cars and other gas poweredmachines. This is where we get internalcombustion engines.
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Internal Combustion
A cannon uses the basicprinciples of internalcombustion engines. Ifyou take a small amountof high energy fuel (likegasoline) in a small,enclosed space and ignite
it, an incredible amountof energy is released inthe form of expanding
gas.
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The four-stroke cycle
Almost all engines use a four-strokecombustion cycle to convert gasoline into
motion. This is also known as the Otto cycle in honor
of Nikolaus Otto who invented it in 1867.
This process takes the basic example of acannon several steps further.
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The four-stroke cycle
The four strokecombustion cycle
consists of: 1. Intake
2. Compression
3. Combustion
4. Exhaust
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The four-stroke cycle
The piston starts atthe top, the intake
valve opens and thepiston moves down tolet the engine take ina full cylinder of air
and gasoline duringthe intake stroke
The piston thenmoves up to
compress theair/gasoline mixture.This makes theexplosion more
powerful.
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The four-stroke cycle
When the pistonreaches the top, the
spark plug emits aspark to ignite thegasoline/air mixture.
The gasoline/air
mixture explodesdriving the pistondown.
The the pistonreaches the bottom of
its stroke the exhaustvalve opens and theexhaust leaves out ofthe tailpipe.
The engine is readyfor another cycle.
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Parts of an engine
Cylinder- where the piston moves up anddown. Most lawnmowers are 1 cylinder
while automobiles are 4,6,8, and 10. Spark plug- supplies spark for the fuel/air
mixture.
Valves- let air in and exhaust out.Note: both valves are closed during thecompression stroke.
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Parts of an engine
iston- cylindrical piece of metal that moves upand down the cylinder.
Piston rings- rings provide a sliding sealbetween the piston and cylinder.
Rings serve two purposes:
prevent fuel/air from leaking into the sump
prevent oil from entering the combustionchamber
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Parts of an engine
Combustion chamber- area where combustionand compression takes place.
Connecting rod- connects the piston to thecrankshaft.
Crankshaft- the crankshaft turns the up anddown motion of the piston into circular motion
Sump- (oil pan) contains and collects oil forlubrication
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Parts of an engine
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Applications of IC engine
Internal combustion engines are mostcommonly used for mobile propulsion in vehiclesand portable machinery
In mobile equipment, internal combustion is
advantageous since it can provide high power-to-weight ratios together with excellent fuelenergy density
Where very high power-to-weight ratios are
required, internal combustion engines appear inthe form ofgas turbines. These applicationsincludejet aircraft, helicopters, large ships andelectric generators.