Lesson 08 - Diesel

8/3/2019 Lesson 08 - Diesel

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Internal CombustionInternal Combustion

Engines Engines

The DieselThe Diesel


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ObjectivesObjectives

Uses for internal combustionengines

Thermodynamic principlesinvolved

Components and purposes of each

Operation of systems Two stroke engines

Four stroke engines


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The Diesel is a HackerThe Diesel is a Hacker


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Engine UsesEngine Uses

Emergency Diesel Generators(EDG)

Propulsion Certain amphibious landing ships Mine warfare ships Patrol craft

Tug boats Small boats Outboard motors


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T ermo ynam cermo ynam cPrinciplesPrinciples

All internal combustion Open cycle, heated engine

Gasoline (Otto) engine Spark ignition Compresses air-fuel

mixture

Diesel engine Compressed ignition

Compresses air only


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Structural ComponentsStructural Components

Cylinder Block Part of engine

frame that

containscylinders inwhich pistonmoves

Supports liners &head


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Structural ComponentsStructural Components

Cylinder Head/Assembly Serves to admit, confine, and release

fuel/air

Cover to cylinder block

Supports valve train

Crankcase Engine frame section that houses the

crankshaft

Oil sump Reservoir for collecting and holding


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Moving ComponentsMoving Components

Three Groups according to

motion Reciprocating only (pistons andvalves)

Reciprocation & rotary (connecting

rods) Rotary only (crankshafts and

camshafts)


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Moving ComponentsMoving Components Piston

Acted on by combustiongases

Lightweight butstrong/durable

Piston Rings Transfer heat from piston to

cylinder Seal cylinder & distribute

lube oil Piston Pin

Pivot point connectingpiston to connecting rod

Connecting Rod


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Crankshaft Combines work done by each piston Drives camshafts, generator, pumps,

etc.

Flywheel Absorbs and releases kinetic energy of

piston strokes -> smoothes rotation of

crankshaft


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Valves Intake: open to admit air

to cylinder (with fuel in

Otto cycle) Exhaust: open to allow

gases to be rejected

Camshaft & Cams Used to time the addition

of intake and exhaustvalves

Operates valves via

pushrods & rocker arms


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OperationOperation

Increased pressure of combustiongases acts on piston -> converted

to rotary motion Can be 2 or 4 stroke engines

2-stroke: 1 power stroke per 1

crankshaft rev 4-stroke: 1 power stroke per 2

crankshaft rev


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OperationOperation Engine stroke

A stroke is a single traverse of thecylinder by the piston (from TDC toBDC)

1 revolution of crankshaft = 2 strokesof piston

F S k Di lF St k Di l


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Four-Stroke DieselFour-Stroke Diesel

EngineEngine

Intake stroke Intake valve open, exhaust valve

shut

Piston travels from TDC to BDC

Air drawn in

Compression stroke Intake and exhaust valves shut

Piston travels from BDC to TDC

Temperature and pressure of air

increase

F St D


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Four-Stro e D eseour- ro e eseEngineEngine

Power stroke Intake and exhaust valves shut Fuel injected into cylinder and ignites Piston forced from TDC to BDC

Exhaust stroke Intake valve shut, exhaust valve open

Piston moves from BDC to TDC Combustion gases expelled

F St D


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Four-Stro e D eseour- ro e eseEngineEngine

Strokes Intake

Compression

Power

Exhaust

T St D


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Two-Stro e D esewo- ro e eseEngineEngine

1 power stroke every crankshaftrevolution (vice every two w/ 4-stroke)

Uses pressurized air tosimultaneously supply new air andexpel combustion gases

Scavenging Exhaust valve open, inlet port

exposed Pressurized air enters, expels

combustion gases

T St D


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Compression Intake and exhaust valves shut Piston travels from BDC to TDC Temperature and pressure of air

increase

Power stroke

Intake and exhaust valves shut Fuel injected into cylinder and ignites Piston forced from TDC to BDC

T St D


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Strokes Compression

Power (Intake/Exhaus

t)

kT F S k


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Two vs. Four-StrokeTwo vs. Four-Stroke

EnginesEngines

Two-stroke advantages Higher power to weight ratio

Less complicated valve train Four-stroke advantages

More efficient burning process

As size increases, power-to-weightratio improves

Gaso ne vs D eseaso ne vs ese


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Gaso ne vs. D eseaso ne vs. eseEngineEngine


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Supporting SystemsSupporting Systems

Air system Supplies & removes air/gases

Air supplied at constant pressure byblower/compressor

Fuel System Carburetor: mixes air & fuel in proper

proportion (NOT on diesels)

Fuel injector: sprays fuel in (moreefficient)


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Supporting SystemsSupporting Systems

Ignition system Diesel has compression ignition Gasoline has spark plugs

Cooling system Uses fresh water and/or salt water to

cool

Lubrication system Provide lubrication and cooling

Drive Train Direct or Indirect


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Safety PrecautionsSafety Precautions

Noise

Fuel Flammability

Maintenance Water Issues


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QuestionQuestion

s?s?

Documents

Lesson 08 - Diesel