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

3. About this Lesson zThis lesson contains hypertext links to www.howstuffworks.com. zIf you are connected to the internet, click on the link icon and scroll to the animation at the sight.

4. Introduction

5. Fuels zWhy are nearly all vehicles and engines powered by gasoline? yextremely high energy density ycheap (relative to other sources) yeasy and safe to move around

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

7. Fuels zWhat are other types of fuels that can be used? yWood- steam engines yCoal- steam engines yOil yElectricity

8. Internal Combustion zWhere do we get internal combustion? yThe 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.

9. Internal Combustion z 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.

10. The four-stroke cycle zAlmost all engines use a four-stroke combustion cycle to convert gasoline into motion. yThis is also known as the Otto cycle in honor of Nikolaus Otto who invented it in 1867. yThis process takes the basic example of a cannon several steps further.

11. The four-stroke cycle zThe four stroke combustion cycle consists of: y1. Intake y2. Compression y3. Combustion y4. Exhaust

12. The four-stroke cycle zThe 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 z The piston then moves up to compress the air/gasoline mixture. This makes the explosion more powerful.

13. The four-stroke cycle zWhen the piston reaches the top, the spark plug emits a spark to ignite the gasoline/air mixture. zThe gasoline/air mixture explodes driving the piston down. z The the piston reaches the bottom of its stroke the exhaust valve opens and the exhaust leaves out of the tailpipe. z The engine is ready for another cycle.

14. Parts of an engine zCylinder- where the piston moves up and down. Most lawnmowers are 1 cylinder while automobiles are 4,6,8, and 10. zSpark plug- supplies spark for the fuel/air mixture. zValves- let air in and exhaust out. Note: both valves are closed during the compression stroke.

15. Parts of an engine zPiston- cylindrical piece of metal that moves up and down the cylinder. zPiston rings- rings provide a sliding seal between the piston and cylinder. zRings serve two purposes: yprevent fuel/air from leaking into the sump yprevent oil from entering the combustion chamber

16. Parts of an engine zCombustion chamber- area where combustion and compression takes place. zConnecting rod- connects the piston to the crankshaft. zCrankshaft- the crankshaft turns the up and down motion of the piston into circular motion zSump- (oil pan) contains and collects oil for lubrication

17. Parts of an engine

18. Source www.howstuffworks.com