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

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Introduction

FuelsWhy are nearly all vehicles and engines powered by gasoline?extremely high energy densitycheap (relative to other sources)easy and safe to move around

FuelsWhy not use other fuels?Size of engines needed to utilize these fuels is impractical for automobiles lawnmowers etc.Convenienceit takes 15 seconds to pump a gallon of gas vs. several hours to recharge batteries (i.e. electric cars)

FuelsWhat are other types of fuels that can be used?Wood- steam enginesCoal- steam enginesOilElectricity

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 cycleAlmost 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 cycleThe four stroke combustion cycle consists of:1. Intake2. Compression3. Combustion4. Exhaust

The four-stroke cycleThe 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 strokeThe piston then moves up to compress the air/gasoline mixture. This makes the explosion more powerful.

The four-stroke cycleWhen 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 engineCylinder- 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 enginePiston- 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 sumpprevent oil from entering the combustion chamber

Parts of an engineCombustion 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 motionSump- (oil pan) contains and collects oil for lubrication

Parts of an engine

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