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IOT
POLY ENGINEERING3-6
1. Energy Sources – Fuels and Power Plants2. Trigonometry and Vectors3. Classical Mechanics:
Force, Work, Energy, and Power4. Impacts of Current Generation and Use
UNIT 3 – ENERGY AND POWER
Topics Covered
IOT
POLY ENGINEERING3-6
Power Plants
1. The engine, motor, and related parts a. Supplies the motive power of a self-propelled objectb. Produces a kinetic energy output from a fuel source
input2. Electricity generating station
a. Typically what is referred to by “power plant”b. Mechanical, heat, chemical, solar sources
Types of Power Plants
IOT
POLY ENGINEERING3-6
Power Plants
1. Insight into the fundamental operation of most engineered technologies
2. Application of scientific and mathematical principles in real-world problem-solving situations
Why Study Power Plants?
IOT
POLY ENGINEERING3-6
Power Plants – EnginesTypes of Engines
Reciprocating Engines:• Reciprocate: to move forward and backward
alternately• Pistons move linearly, forward and backward, in
reciprocating engines.• A crank converts linear motion into rotational
motion.
IOT
POLY ENGINEERING3-6
Power Plants – Engines
Types of Engines and Uses1. External Combustion (EC) Engines:
• Steam – steam locomotives; turbines in electricity stations2. Internal Combustion (IC) Engines:
1) Four-stroke: cars, trucks, motorcycles, construction machinery, airplanes
2) Two-stroke: moped, dirt bike, chainsaw, trimmer, motor boat, lawnmowers, go-karts
3) Diesel: 50% new cars in europe, submarines, ships, locomotives, large trucks/machinery
3. Gas Turbine Engines:• Power plants and airplanes
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POLY ENGINEERING3-6
Power Plants – Engines
2. Spark Ignition – FOUR STROKE
Otto Engine / Otto Cyclea. Nicolaus Otto first to develop
functioning 4-stroke engine – 1877
b. Uses spark plugs to ignite fuel/air mixture
Types of Engines – IC
IOT
POLY ENGINEERING3-6
Power Plants – Engines
2. Spark Ignition – FOUR STROKECycle begins at Top Dead Center (TDC)
3. Intake – fuel and air enter cylinder4. Compression – fuel mixture under pressure5. Combustion – causes expansion against piston6. Exhaust – cooled combustion products exhausted
Cylinders fire once every other revolution
Types of Engines – IC
IOT
POLY ENGINEERING3-6
Power Plants – Engines
2. Spark Ignition I.C.E. – FOUR STROKEIdentify the following components:
1) Piston2) Connecting rod3) Crankshaft4) Valves5) Spark plug6) Cams7) Cam shaft8) Cylinder Block 9) Crank Case10)Oil Galleries
1
2
3
4 4
5
6 67
8
9
10
Types of Engines – IC
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POLY ENGINEERING3-6
Power Plants – Engines
3. Spark Ignition – TWO STROKE
a. Does not have valves – simplifies construction and lowers weight
b. Fire once every revolution, instead of every other (4-stroke) – power boost
c. Work in any physical orientation (4-stroke limited due to oil flow)
Types of Engines – IC
IOT
POLY ENGINEERING3-6
Power Plants – Engines
3. Spark Ignition – TWO STROKE1) Expansion/Transfer/Exhaust
a. Spark ignitionb. Intake port exposedc. Exhaust forced out
2) Compression/Charginga. Compression of air/fuel/oil
mixtureb. Fuel pulled into crankcase by
vacuum – “charging”
Types of Engines – IC
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POLY ENGINEERING3-6
Power Plants – Engines
3. Spark Ignition – TWO STROKEa. Can you identify the strokes?b. Notice in this animation the “return positive pressure”c. What purpose does it fulfill? Returns unused fuel to
cylinder, and charges cylinder
Types of Engines – IC
IOT
POLY ENGINEERING3-6
Power Plants – Engines
Types of Engines – IC
4. Diesel Ignition Compression Ignition – not spark ignition
a. Spark ignition – 1) Piston compresses air/fuel mixture, spark ignites
combustion.2) Amount of pressure is limited (early combustion bad)
b. Compression ignition – 1) Piston compresses air (fuel is not mixed)2) Fuel injected into hot compressed air – initiates
combustion
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POLY ENGINEERING3-6
Power Plants – Engines
4. Diesel Ignition (cont.) d. Early gasoline engines very inefficiente. Greater power and efficiency available at higher pressuresf. Rudolf Diesel – patented engine by 1892
Student of Polytechnic High School of Germanyg. Fuel has higher energy density than gasolineh. Fuel emits fewer greenhouse gasesi. Fuel emits greater N-gases and soot
Types of Engines – IC
IOT
POLY ENGINEERING3-6
Power Plants – Engines
4. Diesel Enginea. No spark plugb. 4-stroke engine
1) Air intake2) Compression 3) Fuel injection / Combustion4) Exhaust
Types of Engines – IC
Engines – Cylinders
Power Plants – Engines
1. Typically, the larger the number of cylinders, the more powerful the engine.
2. Engine power is determined by volumetric displacement
a. The combined volume of all cylinders
b. Example: 5 Liters, 308 Cubic Inches, 250 cc’s, etc.
W / “3-bank”
Straight/inline 4 V6 Flat 4
IOT
POLY ENGINEERING
Engines – Cams
Power Plants – Engines
• Cam – lobe that forces open valves
• Camshaft – cylindrical rod that runs length of cylinder bank
• Explain valve operation:
IOT
POLY ENGINEERING3-6
Gasoline• Petroleum-derived liquid mixture, primarily fuel in
internal combustion engines
(not external combustion or gas turbine engines)
• Enhanced with additives to tune performance and reduce emissions
• Enhanced with isooctane to prevent engine “knocking”
“same” 8 hydrocarbon
Power Plants – Engines
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POLY ENGINEERING3-6
Gasoline – Octane Rating
1. Engine Knocking – when combustion occurs in the cylinder at the wrong time
2. Not due to spark plug igniting incorrectly
3. Due to pressure exploding fuel before plug ignites
4. Octane Rating – the higher the rating, the less knocking
5. High performance cars operate at higher pressures – require higher octane.
6. Standard performance cars – higher octane is a waste of $
Power Plants – Engines
IOT
POLY ENGINEERING3-6
Engine Oil
1. Lubricates moving parts
• Creates separating film between surfaces
• Minimizes direct contact between parts
• Decreases friction, wear, excess heat
• Prevents the waste of useful power and the degradation of the engine, and increases efficiency
2. Cleans and inhibits corrosion – metallic parts and sludge carried out of engine to oil filter
Power Plants – Engines
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POLY ENGINEERING3-6
Engine Oil
3. Improves sealing – keeps fuel and combustion in the right place
4. Cools the engine – carries heat away from moving parts
5. Oil Galleries:
• Small passages in cylinder block
• Allow oil to flow to moving parts
Power Plants – Engines
1. Oil starts in the sump/pan
2. Pump sends oil through filter
3. Oil enters galleries
4. Oil lubricates main bearings and camshaft bearings
5. Lubricates crankshaft and rods
6. Seals piston rings