1. Engine Fundamentals
TRF 210

2. Engine Types
External-combustion
Internal-combustion

4. The Combustion Process
HC + O = H2O + CO2 + Heat
Fuel and air compressed
Spark
Combustion
Incomplete combustion results in Carbon Monoxide and some unburned gasoline

5. Effect of Heat Purpose of the combustion process is to produce heat
Heat to do work
Heat will cause most substances to expand
Heat will cause air to expand

6. Increase in Pressure
Pressure measured in PSI or Pounds per square inch
Air pressure will increase when heated if it is in a enclosed area (air 32 degrees will be degrees)
Air pressure will increase if it is compressed (1/6 to 1/8 original volume in gasoline engines)

7. Increase in Temperature
Air pressure and temperature increased when compressed
Gasoline engine temperature is raised several hundred degrees
Diesel temperature increase is even greater (more compression)

8. Terms Thermometer measures temperature by the expansion of metals
Thermostat different metals expand at different rates. This difference is used in thermostats by wielding two different metals together
Gravity attractive force between all objects gives objects there weight

9. Terms cont.
Atmospheric Pressure air has weight 1 cubic foot of air weighs 0.08 lbs The blanket of air that surrounds the earth amounts to many cubic feet of air. This combined weight amounts to about 15 psi at sea level
Vacuum the absence of air of any other substance

10. Producing a Vacuum
Engines produce a partial vacuum in the cylinder by the action of the piston (this allows the air fuel mixture to be drawn into the cylinder by the force of atmospheric pressure)

11. Piston Engine Operation
Imagine a large can with one end cut out
Inside that can is a slightly smaller can that fits snuggly
Now push the smaller can into the larger can trapping air between the two this compresses the air
If the air contains some fuel and a spark is supplied combustion can take place

12. Piston Engine Operation cont.
Heat from the combustion causes the air to expand pushing the smaller can back
To make the engine run this process must be repeated (reciprocate)

13. Engine Cylinder A round hole in a block of metal
No set number of cylinders ( , etc)

14. Piston and Piston Rings
Power depends on pressure in the cylinder that pressure created by the piston
Too tight clearance too loose clearance problems will occur
Piston rings allow for a good seal between the cylinder wall and the piston
2-cycle engines 1 or 2 rings
4-cycle engines have 3 to 4 rings

16. The Crank Reciprocating motion up and down movement of the piston
This motion must be changed into rotary motion before it can be used
Rotary motion is required to make shafts and wheels turn
Connecting rod connects the piston to the crank
The crank is an offset part of a shaft
Piston up and down motion causes crank shaft to turn

18. Engine Crankshaft Crank is off set section of crankshaft
As the piston goes up and down it rotates the crank shaft in a full circle
Crank shaft is assembled with flywheels (inertia) and counter weights
That help balance the weight of the crank pin and the piston-and-connecting rod assembly
This allows for the engine to run smoothly

20. Engine Bearings
Any where there is rotary motion in a engine bearings are used to support the moving parts
The purpose of a bearing is to reduce friction and allow parts to move easily
Two types of bearing used in engines sliding and rolling

21. Sliding Bearing Plain bushing or sleeve bearing Split sleeve bearings
Forms the shape of a sleeve and fits around the rotating shaft
Made of relatively soft metal so the bearing will wear

22. Rolling Bearings
Uses balls or cylinders between the stationary support and the rotating shaft

23. Making the Engine Run Gas/air mixture enters the cylinder
Mixture is compressed by the upward movement of the piston
A spark is then introduced and combustion takes place
The combustion heats and expands the air forcing the piston down ( this produces the power to turn the crank shaft)
Burned gasses must be removed and a fresh charge of air and fuel brought into the cylinder
This process must continue along as the engine is running

24. The Piston Stroke
The movement of the piston from one limiting position to another
The upper limited position of the piston is Top Dead Center TDC
The lower limited position of the piston is Bottom Dead Center BDC