Internal Combustion Engines

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Internal Combustion Engines

• Introduction
• Fuels
• Four Stroke Engine
• Parts of a four stroke engine

Written by Marshall Brian
GA Ag Ed Curriculum Office To accompany Georgia
Agriculture Education Curriculum Office July 2002
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About this Lesson

• This lesson contains hypertext links to
  www.howstuffworks.com.
• If you are connected to the internet, click on
  the link icon and scroll to the animation at the
  sight.

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Introduction
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Fuels

• Why are nearly all vehicles and engines powered
  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 these fuels is
  impractical for automobiles lawnmowers etc.
• Convenience
• it takes 15 seconds to pump a gallon of gas vs.
  several hours to recharge batteries (i.e.
  electric cars)

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Fuels

• What are other types of fuels that can be used?
• 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 create
  movement of cars and other gas powered machines.
  This is where we get internal combustion engines.

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Internal Combustion

• A cannon uses the basic principles of internal
  combustion engines. If you take a small amount
  of high energy fuel (like gasoline) in a small,
  enclosed space and ignite it, an incredible
  amount of energy is released in the form of
  expanding gas.

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The four-stroke cycle

• Almost all engines use a four-stroke combustion
  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 a cannon
  several steps further.

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The four-stroke cycle

• The four stroke combustion cycle consists of
• 1. Intake
• 2. Compression
• 3. Combustion
• 4. Exhaust

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The four-stroke cycle

• The piston starts at the top, the intake valve
  opens and the piston moves down to let the engine
  take in a full cylinder of air and gasoline
  during the intake stroke

• The piston then moves up to compress the
  air/gasoline mixture. This makes the explosion
  more powerful.

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The four-stroke cycle

• When the piston reaches the top, the spark plug
  emits a spark to ignite the gasoline/air mixture.
  
• The gasoline/air mixture explodes driving the
  piston down.

• The the piston reaches the bottom of its stroke
  the exhaust valve opens and the exhaust leaves
  out of the tailpipe.
• The engine is ready for another cycle.

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Parts of an engine

• Cylinder- where the piston moves up and down.
  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 the compression
  stroke.

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Parts of an engine

• Piston- cylindrical piece of metal that moves up
  and down the cylinder.
• Piston rings- rings provide a sliding seal
  between the piston and cylinder.
• Rings serve two purposes
• prevent fuel/air from leaking into the sump
• prevent oil from entering the combustion chamber

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Parts of an engine

• Combustion chamber- area where combustion and
  compression takes place.
• Connecting rod- connects the piston to the
  crankshaft.
• Crankshaft- the crankshaft turns the up and down
  motion of the piston into circular motion
• Sump- (oil pan) contains and collects oil for
  lubrication

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Parts of an engine
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Source

• www.howstuffworks.com