Unit III Main Engine

8/9/2019 Unit III Main Engine

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UNIT III

MACHINERY

MAIN ENGINE


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Steamengines were usedalmost

until 1900s. Laterthesteamturbineandthe

internal combustionengine

replacedsteamengines.


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Gasturbineshavebeen usedin

merchantshipsandnavy. Somesubmarines,merchantships,

andicebreakershavenuclearpower

plants.


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STEAM ENGINE

Thesteamengines convertheatenergyintomechanical

energyby usingsteam.


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Steamenginesoperatebyhaving

superheatedsteam forceapistontoreciprocateina cylinder.


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Thepistonisattachedbya

crossheadtoa crankshaftthat convertsthe

reciprocating (back-and-

forth) motionofthepistontorotarymotion forpropulsion.


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Inasteamengine,hotsteam

suppliedbyaboilerexpands under

pressure,andtheheatenergyis

convertedinto work.


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STEAM TURBINE

Inthesteamturbine,highpressure

steamisdischargedathighvelocitythroughnozzlesandthen flowsthrough

aseriesofstationaryandmoving

blades, causingarotortomoveathighspeeds.


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Steamturbinesaremore compactandusuallypermithighertemperaturesand

greaterexpansionratiosthansteam

engines.


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Theturbineis usedtogeneratelarge

quantitiesofelectric powerwithsteam.


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Nowadaysthesteamturbineis usedascargopumpdrivingsourceintankers.


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INT

ERNAL COMBUST

ION ENGINE

Aninternal combustion engine

operatesbyburningits fuelinsidetheengine.

It converts chemicalenergyofthe

burning fuelintomechanicalenergy.


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The commoninternal

combustionenginesare;

gasturbine

dieselengine


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The compressionignitedinternal

combustionenginehastwomaindesigns:

twostroke cycle

fourstroke cycle


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Thetwostrokeand fourstroke

termsrefertothemechanicalaction of the piston within the

cylinder.


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TWO STROKE CYCLE


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FOUR STROKE CYCLE


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DIES

EL ENGINE

Dieselengine usestheheatproducedby compressionto

ignitethemixtureofairand

diesel fuel.


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Dieselengineappearsinthreetypes, low-speedengine,

medium-speedengine

high-speedengine


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Thelow-speedengineis characterizedby

ratedspeedsintherangeof 0-400 rpm.

Itisatwo-strokeenginesuperchargedby

exhaust-gasturbochargers


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Themedium-speedenginerunsintherangeof4001000 rpm. Itisa four-

strokeenginesuperchargedby

exhaust-driventurbochargers.


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High-speedenginerunsintherange

of 1000-2000 rpm.


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Dieselenginesarealsooftwo

typesaccordingtotheirpistons;

trunkpiston

barrelpiston


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Dieselenginesareheavierthangasolineenginesbecauseoftheextra

strengthrequiredto containthehigher

temperaturesand compressionratios.


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The diesel engine differs from thegasoline engine in that the ignition of

fuel is caused by compression ofair in

its cylinders instead ofby a spark.


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The speed and power of the diesel arecontrolled by varying the amount of fuel

injected into the cylinder, not the amount of

air admitted as in the gasoline engine.


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GAS TURBINEGas turbine engines are extremely simple and

has three main parts;

a compressorto compress the incoming air tohigh pressure,

a combustion chamberto burn the fuel andproduce high pressure and

a turbine to extract the energy from the highpressure, high velocity gas flowing from thecombustion chamber


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The gas turbine is used as main propulsion

engine at naval ships and supertankers becauseofthe high power

but

it has low manoeuvring capability. Therefore, it

is combined with a diesel engine for highcapability ofmanoeuvring.


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ANSWER THE QUESTIONS

1-Whatarethemaintypesofengine?


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2-How doesaninternal combustionengine work?


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3-Whatdothetwostrokeand fourstroke

termsreferto?


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4-Canyou comparedieselengine withgasturbine?


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Etymology

Diesel


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SOME WORD

S

Combustion (n)- Burning

Expand (v) - Tobecomelargerinsize,

volumeorquantity

Ignite (v) - Starttoburnorburstinto flames


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Reciprocate (v) - Tomovebackand

forthRotary (n) - Occurringaroundanaxis

Rotate (v) - Turnaroundanaxis

Velocity (n) - Speed


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Complete the diagram showing

diesel engine types.


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B- Complete the definitions

using the words below.Internal combustion engine / boiler / compressor / crankshaft /

diesel engine

1-A.isadevicethatsupplieshotsteam forsteamengine.

2-A isadevicethat convertstheback-and-forthmotionofthepistontorotarymotion forpropulsion

3- isanenginetypethat converts chemicalenergyoftheburning fuelintomechanicalenergy.

4-A isanenginethat usestheheatproducedbycompression.

5-A.isadevicethat compressestheincomingairtohighpressure


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1-What statement is not true

regarding the steam engines?

a. Steamengines usessteam.

b. Steamengines convertheatenergyinto work.

c. Pistonrotatesina cylinderto

reciprocatethe crankshaft

d. Boilerssupplyhotsteam.

e. Steamenginesarenot common.


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1-What statement is not true

regarding the steam engines?

c. Pistonrotatesina cylinderto

reciprocatethe crankshaft


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1-Which one is used for

propulsion on ships?

a. steamengineb. steamturbine

c.gasturbine

d.dieselenginee.all


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1-Which one is used for

propulsion on ships?

e.all


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3-combustion, compression,

stroke. The terms are related to

a. steamturbine

b. turbine

c. boiler

d. internal combustionenginee. reciprocatingsteamengine


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3-combustion, compression,

stroke. The terms are related to

d. internal combustionengine


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4-What does the term

stroke refer to?

a. combustion

b. pistonmotioninthe cylinder

c. ignition

d. compressione. rotarymotion


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4-What does the term

stroke refer to?

b. pistonmotioninthe cylinder


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5-Which is not a characteristic

of diesel engines?

a. Dieselengines canbeeithertrunkpistontypeor

barrelpistontype.

b. Theignitionis causedbysparkc. Theyareheavierthangasturbines.

d. Thepoweris controlledbyvaryingtheamountof

injected fuel.

e. Dieselenginesoperateatvariousspeedssuch

aslow,mediumorhigh.


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5-Which is not a characteristic

of diesel engines?

b. Theignitionis causedbyspark


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6-Which is not true about

gas turbines?a. Gasturbineshavehighmaneuvering

capability

b. They consistof compressor,turbineandcombustion chamber

c. Theyarelighterthandieselengines

d. Theirignitionis causedbysparke. Theyare usedatnavalshipsand

supertankers.


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6-Which is not true about

gas turbines?

a. Gasturbineshavehighmaneuvering

capability

.


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7-Which is the most common

propulsion engine for merchant

ships?

a. steamengine

b. steamturbine

c. gasturbine

d. nuclearpowere. dieselengine


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7-Which is the most common

propulsion engine for merchant

ships?

e. dieselengine

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Unit III Main Engine