Lesson 08 - Diesel.ppt

7/28/2019 Lesson 08 - Diesel.ppt

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Internal Combustion Engines

The Diesel


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Objectives

Uses for internal combustion engines

Thermodynamic principles involved

Components and purposes of each Operation of systems

Two stroke engines

Four stroke engines


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The Diesel is a Hacker


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Engine 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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Thermodynamic Principles

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 Components

Cylinder Block

Part of engine framethat contains

cylinders in whichpiston moves

Supports liners &head


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Structural 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 thecrankshaft

Oil sump

Reservoir for collecting and holding lube oil


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Moving Components

Three Groups according to motion

Reciprocating only (pistons and valves) Reciprocation & rotary (connecting rods)

Rotary only (crankshafts and camshafts)


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Moving Components Piston

Acted on by combustion gases Lightweight but strong/durable

Piston Rings Transfer heat from piston to

cylinder Seal cylinder & distribute lube oil

Piston Pin Pivot point connecting piston to

connecting rod

Connecting Rod Connects piston & crankshaft

reciprocating rotating motion


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Moving Components

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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Moving Components

Valves

Intake: open to admit air tocylinder (with fuel in Otto

cycle) Exhaust: open to allow gases to

be rejected

Camshaft & Cams

Used to time the addition ofintake and exhaust valves

Operates valves via pushrods &rocker arms


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Operation

Increased pressure of combustion gases actson 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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Operation Engine stroke

A stroke is a single traverse of the cylinder bythe piston (from TDC to BDC)

1 revolution of crankshaft = 2 strokes of piston


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Four-Stroke Diesel Engine

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


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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


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Strokes

Intake

Compression

Power

Exhaust


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Two-Stroke Diesel Engine

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

Uses pressurized air to simultaneously

supply new air and expel combustion gases Scavenging

Exhaust valve open, inlet port exposed

Pressurized air enters, expels combustion gases Piston near BDC


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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


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Strokes Compression

Power

(Intake/Exhaust)


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Two vs. Four-Stroke Engines

Two-stroke advantages

Higher power to weight ratio

Less complicated valve train Four-stroke advantages

More efficient burning process

As size increases, power-to-weight ratioimproves


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Gasoline vs. Diesel Engine


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Supporting 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 (more efficient)


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Supporting 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 Precautions

Noise

Fuel Flammability

Maintenance Water Issues


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Lesson 08 - Diesel.ppt

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