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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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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

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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

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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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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

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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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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

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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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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

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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

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Engines – Cams

Power Plants – Engines

• Cam – lobe that forces open valves

• Camshaft – cylindrical rod that runs length of cylinder bank

• Explain valve operation:

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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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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

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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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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

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Engine Oil

Power Plants – Engines

Filler Cap

Oil PanDrain Bolt

Images: www.installuniversity.com