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Internal Combustion Engines

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					Internal Combustion Engines
*Introduction *Fuels *Four Stroke Engine *Parts of a four stroke engine

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.

Introduction

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

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)

Fuels
What are other types of fuels that can be used?
Wood- steam engines Coal- steam engines Oil Electricity

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.

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.

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.

The four-stroke cycle
The four stroke combustion cycle consists of:
1. 2. 3. 4. Intake Compression Combustion Exhaust

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.

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.

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.

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

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

Parts of an engine


				
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