individual project dissertation

DESIGN AND MANUFACTURE GAS TURBINE BLADE ARUNTHIHAN RAMAJEYAN
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FACULTY OF SCIENCE, ENGINEERING
AND COMPUTING
School of Aerospace and Aircraft Engineering
BSc (Hons) DEGREE
IN
BSc Aerospace Engineering
Name: Arunthihan Ramajeyan
ID Number: K1359820
Project Title: DESIGN AND MANUFACTURE GAS TURBINE
BLADE
Date: April 2016
Supervisor: Dr Hossein Mirzaii
WARRANTY STATEMENT
This is a student project. Therefore, neither the student nor Kingston University makes any
warranty, express or implied, as to the accuracy of the data or conclusion of the work
performed in the project and will not be held responsible for any consequences arising out of
any inaccuracies or omissions therein.

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DECLARATION
I, the undersigned ArunthihanRamajeyanstudentof BScHonoursdegree inAerospace Engineering
herebydeclare thatthe projectworkpresentedinthisreportismyownworkand has beencarried
out underthe supervisionof DrHosseinMirzaii of KingstonUniversityLondon.
Thiswork hasnot beenpreviouslysubmittedtoanyotheruniversityforanyexamination.
Word count: 6853
Name: ArunthihanRamajeyan
StudentID: K1359820
Date: 25/04/2016

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ACKNOWLEDGEMENTS
Firstand foremost,Iwouldlike toexpressmysinceregratitude to mymodule supervisor,DrHossein
Mirzaii,whohas beenguidingme throughoutthisproject.Hisadvice andguidance made me give my
bestto complete thisproject.He sharedhisexpertisewithme,whichgave me abetter
understandingof the conceptandalso hisfriendlinessmade me enjoythisproject.Itisthe main
reasonwhichledme to finishthisprojectsuccessfullytothe bestof myability.
I wouldalsolike tothankthe lab technicians,Mr.MartinTheobald,Mr Dean WellsandMr. Dave
Haskell forguidingandhelpingme complete my3Dprintedcomponentsandforhelpingme
throughoutthe investmentcastingprocess. Iwouldliketoexpressmysincere gratitude tomyfamily
and mycolleague Mr.NirojanParanjothywhodidthe same projectwithme.

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ABSTRACT
There are somany methodsof castingalloys,turbine bladesare manufacturedbyinvestmentcasting
methodor normallyaslost-wax method.The investmentcastingmethodwasdevelopedover5500
yearsago and can trace itsroots back to bothancientEgyptand China.Thisis the keymethodwhich
isusedpresentlyinAviationindustryformanufacturingthe gasturbine blades.Investmentcasting
methodismainlyusedbecause ithaswide range of advantages.Itformsthe componentwith
undercuts,canproduce a verysmoothsurface whichisformedwithoutapartingline inthe
componentandaccuracy. Thisdissertationlooksdetailedintothe theoretical andpractical side of
designingmethodusedwiththe aidof SolidWorks andinvestmentcastingmethod.
AIMS AND OBJECTIVES
The endmostaimof thisprojectisto DesignandManufacture Gas turbine blade
 Researchmethodsof casting
 Create the designof Gas turbine blade
 Manufacturingthe turbine blade usinginvestmentcastingmethod
 Researchmaterialsandtheireffectivenessonturbine blades
METHODOLOGY
The methodsthat I’mgoingto use to achieve myaimsandobjectivesare asfollows:
 Create a designof turbine blade asa tree designusingSolidWorks
 Create the 3D printedobjectusing3Dprinter.
 Create the final metal blade usinginvestmentcastingmethod

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Contents
DECLARATION .............................................................................................................................. 2
ACKNOWLEDGEMENTS ................................................................................................................. 3
ABSTRACT....................................................................................................................................4
AIMS AND OBJECTIVES.............................................................................................................. 4
METHODOLOGY........................................................................................................................ 4
1 INTRODUCTION ......................................................................................................................... 9
2 Gas Turbine engine.................................................................................................................. 10
2.1 Types of jet engines........................................................................................................... 12
2.1.1 Turbojet..................................................................................................................... 12
2.1.2 Turboprops................................................................................................................. 13
2.1.3 Turbofans................................................................................................................... 13
2.1.4 Turboshafts ................................................................................................................ 14
2.1.5 Ramjets...................................................................................................................... 15
2.2 Gas turbine design......................................................................................................... 15
2.2.1 Fans ........................................................................................................................... 16
2.2.2 Compressor................................................................................................................ 16
2.2.3 Combustion chamber.................................................................................................. 17
2.2.4 Turbine....................................................................................................................... 17
2.3 Gas Turbine blade ............................................................................................................. 19
2.4 Turbine Blade failure ......................................................................................................... 21
2.4.1 High cycle fatigue........................................................................................................ 21
2.4.2 Environmental attack.................................................................................................. 22
2.4.3 Creep damage............................................................................................................. 22
2.4.4 Erosion/Wear............................................................................................................. 22
2.5 Materials used .................................................................................................................. 23
2.6 Cooling system.................................................................................................................. 24
3. Methods of Casting............................................................................................................. 25
3.1.1 Sand casting................................................................................................................... 25
3.1.2 Die casting..................................................................................................................... 26
3.1.3 Shell Mould Casting........................................................................................................ 27
3.1.4 Lost foam casting............................................................................................................ 27
3.1.5 Investment Casting......................................................................................................... 28

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3.1.6 Cooling systems.............................................................................................................. 30
3.2 Designing Process ................................................................................................................. 30
3.3 SolidWorks Design....................................................................................................... 32
4. Manufacturing Process........................................................................................................ 34
4.2 Investment Casting Process ................................................................................................... 35
4.2.1 Silicon Mould making...................................................................................................... 35
4.2.2 Making the Wax model................................................................................................... 37
4.2.3 Ceramic Coating............................................................................................................. 39
5 CONCLUSION........................................................................................................................... 40
6 References .............................................................................................................................. 42
Figure 1 Newton's third law......................................................................................................... 10
Figure 2(Durham, 2012) .............................................................................................................. 11
Figure 3Turbojet engine.............................................................................................................. 12
Figure 4Turboprop...................................................................................................................... 13
Figure 5Turbofans....................................................................................................................... 14
Figure 6Turboshaft ..................................................................................................................... 14
Figure 7Ramjets.......................................................................................................................... 15
Figure 8Design............................................................................................................................ 15
Figure 9Compressor.................................................................................................................... 16
Figure 10Combustion chamber.................................................................................................... 17
Figure 11Turbine ........................................................................................................................ 18
Figure 12Impulse Turbines.......................................................................................................... 18
Figure 13Impulse and Reaction turbines ...................................................................................... 19
Figure 14Gas turbine blades........................................................................................................ 20
Figure 15HCF blade..................................................................................................................... 21
Figure 16Creep damage curve..................................................................................................... 22
Figure 17Sand casting................................................................................................................. 26

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Figure 18Die Casting................................................................................................................... 26
Figure 19Shell mould casting....................................................................................................... 27
Figure 20Lost Foam Casting......................................................................................................... 27
Figure 21Investment casting method........................................................................................... 29
Figure 22Turbine blade design..................................................................................................... 31
Figure 23Turbine blade aero foil design ....................................................................................... 31
Figure 24Turbine blade side view................................................................................................. 31
Figure 25Aerofoil view with the dimensions in mm....................................................................... 32
Figure 26Aerofoil blade twist angle 9˚.......................................................................................... 32
Figure 27Blade heights 1.76 in..................................................................................................... 32
Figure 28Blade view.................................................................................................................... 32
Figure 29Blade root.................................................................................................................... 33
Figure 30blade root side view...................................................................................................... 33
Figure 31Final blade views.......................................................................................................... 33
Figure 32Final blades with the tree.............................................................................................. 33
Figure 33UP BOX ........................................................................................................................ 34
Figure 34Removing off the Turbine blade..................................................................................... 35
Figure 35Turbine bladeswith the sheet ....................................................................................... 35
Figure 36Mould box.................................................................................................................... 35
Figure 37Silicon mould Cut into half............................................................................................. 36
Figure 38Breaking off the Mould box........................................................................................... 36
Figure 39Silicon settling .............................................................................................................. 36
Figure 40Pouring Silicon into the mould box................................................................................. 36
Figure 41Mixing silicon with curing agent..................................................................................... 36
Figure 42Assembly...................................................................................................................... 38
Figure 43Wax blades and tree..................................................................................................... 38

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Figure 44Wax blades................................................................................................................... 38
Figure 45Wax Tree model ........................................................................................................... 38
Figure 46Wax poured.................................................................................................................. 38
Figure 47ceramic coating left to dry............................................................................................. 39
Figure 48Ceramic first coating..................................................................................................... 39
Table 1Failure Severity................................................................................................................ 21
Table 2(Tantalum - element information, properties and uses, no date) ........................................ 23

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1 INTRODUCTION
Anyaircraft whichmovesthroughairismovedbythe force calledthrust.“Foreveryaction,there is
an equal andopposite reaction”accordingtoIsaac Newton’sthirdlaw of motion. Whenanytwo
objectsgetinterface witheachother,whetheritgetsdirectlyinteractedorat a distance,theyexert
forceseachother equally.
Anydevice whichconvertsheatenergyof fuel intomechanical energyisknownasengine orheat
engine.Engine iswidelyusedinautomobileindustries oran engine canbe evencalledasthe heart
of automobile.Tomake anaircraft move forward,there needtobe a pushingforce or thrustwhich
iscreatedby makingthe air accelerate betweenthe frontandthe backof the engine. Anydevice
whichconvertsheatenergyof fuel intomechanical energyisknownasengine orheatengine.Engine
iswidelyusedinautomobile industriesoranengine canbe evencalledasthe heartof automobile.
To make an aircraft move forward,there needtobe a pushingforce orthrust whichiscreatedby
makingthe air accelerate betweenthe frontandthe backof the engine.Itconvertsthe energyfrom
burningfuel bythree elementswhichithasinit. Theyare compressor,combustorandturbine.A gas
turbine cancreate thrustby acceleratingairormake electricity,turnpumpsandshippropellersby
drivinggenerators. (reserved,2016)
The turbine blade isa verycomplex shape whichconsistsof arootat the bottomof the blade.Ithas
an aerofoil shape whichextractsthe thermal energyfromthe hotexhaustgases.The rootof the
blade isattachedto a disc.There will be hundredsof bladesattachedinasingle disc,whichiscalled
a stage.There are several stagesineachsectionof the engine.(IMPRESSeducation:Circularmotion,
no date)

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2 Gas Turbine engine
As I indicatedabove inmyintroduction,“Foreveryaction,there isanequal andopposite reaction”.
To explainitwithanexample,asyousitina chair, yourbodyacts withone force on the chair, and
the chair reacts withanotherforce onyour body.Itis that “whenyousitin a chair,the force of
gravityisbalancedbythe force of the chairpushingup”(Newton’sThirdlaw of motion:Examplesof
the relationshipbetween twoforces- video&lessontranscript,2003).
BasicallyGasturbine enginesare usedfortwopurposes,firstforpowerproductionandsecondlyfor
generatingthrustforaircraft.Theyare very simple;theyhave three simplepartswhichare
Compressor,combustionareaandturbine.Compressorcompressesthe incomingairtohigh
pressure.Combustionareaiswhere the fuel andproduceshigh-pressure,high-velocitygas.Turbine
extractsthe energyfromthe high-pressure,high-velocitygasflowingfromthe combustionchamber.
To elaborate itbriefly, agasturbine engine movingforwardusesasimple principle.Justlike the
reactionforce producedbya balloon,the reactionforce producedbythe highspeedjetatthe tail of
the jetengine makesitmove forward.The higherthe speedof the jetthe greaterthe thrustforce.
The thrust force makesan aircraftmove forward.Such highspeedisachievedbyacombinationof
Figure 1 Newton's third law

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techniques.If youcanheatthe incomingairto a hightemperature,itwillexpandtremendouslyand
will create the high-velocityjet.Forthisprocess,acombustionchamberisused.The fuel isburntin
the combustionchamber.Effective combustionrequiresairtobe moderatelyhightemperatureand
pressure.Tobringthe air to thiscondition,asetof compressorstagesare used.The rotatingblades
of the compressoraddenergytothe fluidandits temperature andpressure rise toalevel suitable to
sustaincombustion.The compressorreceivesthe energyforthe rotationfromaturbine whichis
placedrightafterthe combustionchamber.The compressorandturbine are attachedto the same
shaft.The highenergyfluidthatleavesthe chambermakesthe turbine bladesturn.
The turbine bladeshave aspecial airfoil shape whichcreatesliftforce andmake themturn.Asthe
turbine absorbsenergyfromthe fluiditspressuredrops. Throughthese stepsareallyhothigh
speedairemittedthroughthe exitof the engine.(LearnEngineering,2015)
Figure 2(Durham, 2012)

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2.1 Types of jet engines
2.1.1 Turbojet
The term ‘turbojet’iscommonlyusedforanumberof enginessuchasturbojet,turboprop,turbofan
and turboshaft,because all of themuse acommonprinciple.Insimpleterms,asengine ejectsburnt
mixture backwardsaforwardforce is createdonthe engine of the aircraft.Inthiscase,greaterthe
backwardforce the greaterthe forwardforce. (Turbojetengines,2011)
The basic ideaof turbojetengine issimple.FirstAiristakenintothe frontof the engine and
compressedto3 to 12 times of its original pressure incompressor.Thenfuel isaddedtothe airin
the combustionchamberand burnedina combustionchambertoraise the temperature of the fluid
mixture toabout1,100˚F to 1,300˚F. The hot air ispassedthrougha turbine,whichdrivesthe
compressor. If the turbine andcompressorare efficientenough,the pressure atthe turbine willbe
nearlytwice the atmosphericpressure.Thispressurewhichisexcessissentthentothe nozzle to
produce a high-velocitygaswhichproducesthrust.Increase in thrustcanbe obtainedbyusinga
afterburner.Afterburnerisa secondchamberwhichispositionedafterthe nozzle.Thisincrease in
temperature iswill increase about40percentinthrust at take-off.
The turbojetisalsoknownas a reactionengine.Inareactionengine,The turbojetsucksairinand
squeezesorcompressesit.Thenthe gasesflow throughthe turbineandmake itspin.These gases
bounce back andshoot outof the rear of the exhaust, whichpushesthe plane forward. (Engines,no
date)
Figure 3Turbojet engine

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2.1.2 Turboprops
Turbopropenginesare usedinsome transportaircraftand small airliners.A turbopropengine hasa
propellerattachedinit.The hotgasesturn the turbine atthe back,and thisturns a shaftthat rotates
the propeller. The turbopropconsistsof acompressor,combustionchamber,andthe turbine like a
turbopropto run the turbine,Sothatthe turbine createspowertodrive the compressor.The
turboproppropulsionefficiency ishigherthancomparedwithaturbojetengine forspeedsbelow
500 mph.Recentturbopropengineshave lotsof bladeswithfewerdiameterstogive amore
efficientoperationathigherflightspeeds.Inaturbopropengine the bladesare scimitar-shapedwith
swept-backleadingedge inthe blade tips. (Engines,nodate)
2.1.3 Turbofans
A turbofanconsistsof a large fanat the frontside of the engine whichisusedtosuck inair. Normally
the air flowsaroundthe outside of the engine whichwill make itgive itmore thrustatlow speeds
and formakingit quitter.Ina turbofanonlysome airgoesintothe combustionchamber,the
remainderpassesthroughafan,low-pressure compressor,andisejecteddirectlymixedwiththe
gas-generatorexhausttoproduce a hotjet whereasall the airenteringthe intake passesthrough
the gas generator,whichismade upwiththe compressor,combustionchamberandturbine.It
Figure 4Turboprop

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achievesthisbyincreasingthe total air-massflow andreducingthe velocitywithinthe total energy
supplyasthe same. (Engines,nodate)
2.1.4 Turboshafts
Thisengine ismuchlike aturbopropsystem.Itprovidespowerforahelicopterwithoutdrivinga
propellerinit.Thisturbopropengineisdesignedsothathelicopterrotor speedisfree of the rotating
speedof the generatorandisnot dependentwithit.Evenwhenthe generatorisvariedtomodulate
the amountof powerreduced,the turboproppermitsthe rotorspeedtobe keptinthe same level.
(Engines,nodate)
Figure 5Turbofans
Figure 6Turboshaft

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2.1.5 Ramjets
The ramjetis the simplestjetengine whichhasnomovable partin it. Airenteringitiscompressedby
the movementof the vehicle.Ithasa longduct intowhichfuel isfedat a controlledrate.The fuel is
ignitedbythe incomingheatedcompressedair.A Ramjetwill onlystartworkabove a speedof 485
km/h.The Ramjetismore fuel efficientthanturbojetsandturbofansabove Mach3 makingthem
betterforuse on missiles. (Darling,nodate)
2.2 Gasturbinedesign
Figure 7Ramjets
Figure 8Design

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2.2.1 Fans
The fan inthe frontof the engine anditisa gas turbine whichdrawsair intothe engine;it
compressesthe bypassstreamtoproduce 80 percentof the engine’sthrust,andfeeds airtothe gas
turbine core. (reserved,2016a)
2.2.2 Compressor
The compressorisdrivenbythe turbine.Itrotatesat highspeed,addingenergytothe airflow and
compressingintoasmallerspace.Socompressingthe airincreasesthe pressureinside the engine.
The purpose of a compressoristo increase the pressure of the airinside the gasturbine engine.
Thenit sendsthe compressedairintothe combustionchamber. (reserved,2016a)
The compressorisassumedto containfourteenstagesof rotorblades andstatorvanes.Inan axial
flowcompressor,eachstage normallybooststhe pressurefromthe previousstage.A singlestage of
compressionconsistsof asetof rotorbladesattachedon a disk,followedbystatorvanesattached
to a stationaryring.
In general,the compressorrotorbladesconvertmechanical energyintogaseousenergy.
Figure 9Compressor

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2.2.3 Combustionchamber
The combustionchamberisthe area inside the enginewhere the fuel orairmixture iscompressed
and ignited. Itisnormallyformedonone side bythe shape castintothe cylinderhead,inthe other
side bythe top of the piston.The chamberisat its smallestdimensionwhenthe pistonisattop-
dead-centre.Andatthistime the fuel/airwillbe ina conditionwhere itisreadytobe ignited.
2.2.4 Turbine
There are fourstagesina turbine. The turbine convertsthe gaseousenergyof the burnedfuel/air
mixture outof the combustorintomechanical energytodrive the compressor,throughareduction
gear,the propeller.Itconvertsgaseousenergyintomechanical energybyexpandingthe hot,high-
pressure gasestoa lowertemperature andpressure.Eachstage consistsof stationaryvaneswhich
are followedbyrotatingblades.The vanesandbladesare airfoilsthatprovide forasmoothof the
gases.As the airstreamentersthe turbine fromthe combustionsection,itisacceleratedbythe
stator vanesinthe firststage.Thenthe stator vanesformthe convergentductsthatconvertthe
gaseousheatand pressure energyintohighervelocitygasflow.
Figure 10Combustion chamber

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As the highvelocitygasflowsacrossthe turbine blades,the gaseousenergyisconvertedto
mechanical energy.ATthisstage velocity,temperatureandpressure of the gasare compromisedto
rotate the turbine togenerate powerfromthe engine. (FUNDAMENTALSOFGASTURBINE ENGINES,
2010)
There are twobasictypesof steamturbines,impulseturbinesandreactionturbines,inwhichhe
bladesare designedtocontrol the speed,pressure anddirectionof the steamasitpassesthrough
the turbine.
2.2.4.1 ImpulseTurbines
The steam jetsare keptat the turbine’sbucketshapedrotorbladesdirectlywhere the pressure
exertedbythe jetscausesthe rotorto rotate andthe velocityof the
streamto reduce as itimpartsits kineticenergytothe blades. But
the blades change the directionof flowof the steamhoweverits
pressure remainsthe same asitpassesthroughthe rotor bladesas
the gap betweenthe bladesare constant.Therefore Impulse
turbinesare knownasconstant pressure turbines.Sothe nextseries
Figure 11Turbine
Figure 12Impulse Turbines

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of fixedbladesreversesthe directionof the steambefore itpassestothe secondrow of moving
blades.
2.2.4.2 ReactionTurbines
The rotor bladesof the reactionturbine are more like aerofoils;theyare arranged where the cross
sectionin-betweenthe chambersformed are fixedbladeswhichreducesthe inletside of the blades.
The chambersbetweenbladesformnozzles sothatasthe steamprogressesthroughthe chambers,
itsvelocityincreasesandthe pressure decreases.Alsothe pressure decreasesinboththe fixedand
movingblades.Soasthe steamenters ina jetinbetweenthe rotorblades, the steamcreatesa
reactive force onthe bladeswhichinturncreatesthe turningmomentonthe turbine rotor justlike
ina steamengine. (Shukla,2013)
2.3 Gas Turbine blade
Turbine blade isthe rotatingcomponentwithinthe turbine whichgiveschallengestothe designand
manufacturingcommunities. Itisan individual componentwhichmakesthe turbinesectionof agas
turbine engine.Bladesare responsible forextractingenergyfromthe hightemperature,high
Figure 13Impulse and Reaction turbines

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pressure gasproducedbythe combustor.Theyare exposed tomore toughenvironmentsinagas
turbine.
Therefore turbine bladesare carefullydesignedtoresistall these toughconditionsandmake upwith
the suitable material whichcanresistall these conditions.There are some more methodsdone to
withstandall these problemssuchascoolingsystem, boundarylayer,thermal bearingcoatingsand
internal airchannels. The Gasturbine blade isdesignedinanaerofoil designandreformedinsucha
waywhere itprovidesequal space betweenadjacentblades. The areaof the cross-sectionof each
blade isfixedbythe allowedstressinthe material usedandbythe size of the holeswhichisrequired
for blade coolingpurpose.The trailingedge of the blade isdesignedthininconsideringpreventingit
fromblade crackingwhichmay occur due to the change intemperature while the engine works.
One of the mostimportant thingsconsideredingasturbine blade isattachingthe blade tothe
turbine discbecause the stressinthe discaroundthe fixingandinthe blade root has a key
behaviouronthe limitingrimspeed.
Thisdesignof fixingthe blade tothe discwhichisusedinmostof the gas turbine enginespresently
isknownas ‘fir-tree’fixing,whereasinpastthe blade isfixedbythe de Laval bulbrootingfixing. This
‘fit-free’ensuresthatthe loadingonthe blade isshared byall the serrations.The blade isfree inthe
serrationswhenthe turbine isstill andis rigidinthe rootby centrifugal loadingwhenthe turbine is
rotating.A shroudisfittedatthe tip of the blade anda small
segmentismade upat the tipof the blades whichformsa
tangential ringaroundthe blade whichisformed toreduce the loss
of efficiencythroughgasleakage acrossthe blade tips.(166837
EB161 rolls royce the jet engine fifth edition gazoturbinnyy
dviga, no date)
Figure 14Gas turbine blades

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2.4 Turbine Blade failure
Failure meansthata thingdoesnotmeetits desirable objective;inthiscase a turbine blade failure
meansthat it’snolongersuitable foruse butcan be usedtill the limitedamountof time givenforit
to be used.
2.4.1 Highcyclefatigue
Highcycle fatigue isthe mainproblemof a turbine blade it isgenerallycausedaerodynamic
excitationsandby self-excitedvibrationandflutterwhichisbecause of the repeatedcyclingof the
loadon a structural member.HCFdamage occurs whenthe stresslevelsare above the fatigue
strength.Itoccurs aftera numberof loadcyclesthat resultsincracking.The crack will thengradually
increase throughthe material witheachstresscycle.
Table 1Failure Severity
Figure 15HCF blade

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2.4.2 Environmental attack
The environmentshouldbe consideredinturbineblade failure astheyare exposedtobe damaged
fromoxidation,corrosionandsulphidation. Itdoesnotleadthe blade toa enormousfailure butit
has a role init whichcan slowlydamage the blade withtime.
2.4.3 Creepdamage
Thisdamage occurs whenthe blade isoperatedovertimeunderhighstressesandtemperature.Asa
roughrule,a 15° increase inblade metal temperaturecutscreeplife by50 percent.Thisshowsthe
importance of effective cooling. ([CSL STYLE ERROR: reference with no printed form.])
2.4.4 Erosion/Wear
Thiscause catastrophicblade failure rarely,butitcontributestosome otherblade failureswhichcan
cause a blade replacement.Inadditiontothe primarydamage causedbyerosion,areductioninthe
surge margincan occur if the tipsof the bladesgetseverelyeroded.
Figure 16Creep damage curve

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2.5 Materials used
Moderngas turbineshave the mostadvancedtechnologyinall aspects,Turbine bladesare exposed
to the extreme operatingcondition. Itisexposedtoaround1400°C – 1500°C, highpressure,high
rotational speed,vibration,small circulationareaandsoon.
So to overcome it,Gasturbine bladesare made usingadvancedmaterialsandsuperalloysthat
containsupto ten significantelements,itconsistsof rectangularlocksof stone stackedinaregular
array withnarrow seriesof cementtostickthemtogether.Presentlytantalumisusedreplacing
intermetallicformof titanium whichhasbeenusedinthe past. (NEW TECHNOLOGY USED IN
GAS TURBINE BLADE MATERIALS, no date)
Tantalumis an incrediblyuseful metal with uniquepropertiesthatmake itthe choice fora range of
placesto be usedwhere strength,durability,corrosion,resistance,ductilityandahighmeltingpoint
are critical. (Tantalum (Ta), 2015).
Table 2(Tantalum - element information, properties and uses, no date)

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Since the 950’s, 250°C of allowablemetal temperatureshasbeenyieldedfromwroughtto
conventionallycastto directionallysolidifiedtosinglecrystal turbine blades.Inthe otherside,
coolingdevelopmentshave nearlydoubledthe temperature whichentersthe turbine.
If metallurgical developmentcanbe exploitedbyreducingthe coolingairquantitythisisa
potentiallyimportantperformance enhancer.
2.6 Cooling system
Turbine bladespresentlyfocustoonblade coolingsystemwhichisimportanttoreduce the blade
metal temperature toacceptable levelsforthe materialsincreasingthermalcapabilityof the engine.
Turbine blade coolingisclassifiedintotwosectionssuchasinternal coolingsystemandexternal
coolingsystem.
Internal blade cooling:It iswhere the heatis removedbya variation of convectionand
impingementcoolingconfigurations,wherehighvelocity airflowsandhitsthe innersurface of the
turbine blades.
External blade cooling:It is where coldairisinjectedthroughthe coolingholesof the external
surface of the turbine blade surface tocreate a thinfilmcoolinglayer.
Howeverinbothcasestheyare implementedtokeepthe entire bladecool enoughtoensure that
the hightemperature doesnotdamage the blades.There are more sub-partsinsideInternalcooling
systemandExternal coolingsystemwhichisnotnecessarytoexplaininthe reportasit isnot done in
throughoutproject.Thisisa general brief of how coolingsystemsworkandthe purpose of it. (2016,
2014)

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3. Methods of Casting
Castingisa manufacturingwhichismostlyusedtomake more complex methods.Itisaprocessin
whichnormallyliquidmaterial ispouredintoamould,whichhasahollow cavityof the desired
shape inwhichwe expectoursolidfinishedmaterial shouldbe.Thenthe solidifiedpartisejectedor
brokenoutof the mouldto complete the casting process.Inmyproject,Ihave usedinvestment
castingmethodto manufacture the gasturbine blade.Sointhisreportas ittakesmore time,Ihave
explainedthe typesof castingasan overview summarisingand concentratedmore onInvestment
castingmethod. Basictypesof casting:Sand casting,Die casting,Shell mould casting,lost-foam
casting,and investmentcasting.
3.1.1 Sand casting
It isa metal castingprocesscharacterisedbyusingsandasthe mouldmaterial. Inadditiontothe
sand,clay ismixed withthe sand.The mixture ismoistenedwithwater,sometimeswithsome other
substancestodevelopstrengthandplasticityof the claytomake the combinationsuitable for
moulding. The word‘sandcasting’isreferredtoanobjectproducedbythe sand castingprocess.
Over70% of all metal castingsare producedbya sand castingprocess.Thiscastingmethodis
relativelycheapandobstinate evenforsteel foundryuse.
Basic Process:
 Place a patternin sandto create a mould.
 Incorporate the patternand sandin a gatingsystem.
 Remove the pattern
 Fill the mouldcavitywithmoltenmetal
 Allowthe metal tocool

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 Breakaway the sand mouldandremove the casting.
3.1.2 Die casting
It isa meal castingprocesswhichforcesmoltenmetal underhighpressure intoamouldcavity.The
mouldcavityismade usingtwohardenedsteel dieswhichworksmore similarlike aninjection
mouldduringthe process.
Figure 17Sand casting
Figure 18Die Casting

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3.1.3 Shell Mould Casting
It isa metal castingprocessinmanufacturingindustryinwhichthe mouldisathinhardenedshellof
sand andthermosettingresinbinder,withsome other material.
3.1.4 Lost foam casting
It isa type of evaporative-patterncastingwhichissimilartoinvestmentcastingexceptinthisfoamis
usedforthe patterninsteadof wax.
Figure 19Shell mould casting
Figure 20Lost Foam Casting

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3.1.5 Investment Casting
Investmentcastingwhichisalsoknownaslostwasinvestmentcasting,isaprecisioncastingprocess
usedto create more complex metal partsfromalmostanyalloys.The use of thiscastingmethod
acceleratedin1940s as a resultof demandfor specialisedtools.FollowingWorldWarII,the
technique expandedintomanyindustrial andcommercial applications.
The term “investment”referstoceramicmaterialsthatare usedto buildahollow shell intowhich
moltenmetal ispouredintomake castings. (InvestmentcastingFAQs,nodate)
Requirementsforinvestmentcasting:
 Metal die
 Wax
 Ceramic slurry
 Furnace
 Molten metal
Advantages:
 Reliability– It providesreliableprocesscontrolsand
repeatabilitythatare maintainedfromcastingtocasting.
 Tolerances– It holdstolerancesof ±.005˚
 AmortizationLowers toolingcost – It is lowerthanother
castingtoolingcosts.
 Better for the Environment – It is producedfrom9 wax
patternswhichinmostcases can be reclaimedandused
again.

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 Intricate Design– Can easilyincorporate featuressuchas
logos,productID’s/numbers,andlettersintotheir
component. (Advantagesof investmentcastingvs.Sand
casting,die casting,nodate)
Process:
 Patterncreation – The wax patternsare typically injected moulded into a metal die and are
formed as one piece.
 Mould creation – This “pattern tree” is dipped into slurry of fine ceramic particles, coated
with more coarse particles, and dried to form a ceramic shell around the patterns.
 Pouring – The mould is pre-heated in a furnace to approximately 1000˚C and the molten
metal is poured from a ladle into the gating system of the mould, filling the mould cavity.
 Cooling– Afterthe mouldisfilled,the moltenmetal is allowed to cool and solidify in to the
shape of the final casting.
 Castingremoval – Afterthe moltenmetal hascooled,the mouldis broken and the casting is
removed.
 Finishing – Heat treatment or grinding or sand blasting the part at the gates to harden the
final part. (CustomPartNet, 2009)
Figure 21Investment casting method

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3.1.6 Cooling systems
Turbine bladeslifetime isreducedasitis exposedtoveryhottemperatures.Therefore,turbine
coolingisnecessarytoincrease the bladesworkingtime.Due tothe contributionandthe
developmentof turbine coolingsystemsthe turbinehasbeenlastedlong. Turbine bladecoolingis
classifiedintotwosections;theyare internal coolingsystemandexternalcoolingsystem.
Internal coolingsystem:It is where the heatisremovedbya variationof convectionand
impingementcoolingconfigurations,wherevelocityairflowsandhitsthe innersurface of the
turbine blades.
External Coolingsystem:It iswhere the coldair isinjectedthroughthe filmcoolingholeswhichare
on the external blade surface tocreate athinfilmcoolinglayer.
Internal coolingsystemandexternal coolingsystemare implementedtothe turbine blade tokeep
the entire blade cool andensure thattemperature gradientswithinthe blade are kepttoan
acceptable level. (2016,2014)
3.2 Designing Process
The turbine blade isan aero foil shape andwhendesigningaturbine blade,eachstage of the blade
has differentdimensions.FirstIcouldn’tfindarealisticdesignof aturbine blade,asthisisa design
and manufacturingproject,struggledinfindingthe realisticdimension.Discussedwiththe lab
techniciansandfinallyfoundthe actual blade whichisusedinthe Universitylab.Gotthe dimensions
of the blade usedmore accuratelywithadigital Verniercalliper.Beloware the Designof the Turbine
blade used.

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Figure 23Turbine blade aero foil design Figure 22Turbine blade design
Figure 24Turbine blade side view

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3.3 SolidWorks Design
The SolidWorkssoftware isa3D mechanical design,whichallowstodesignanythree Dimensional
objects.Belowisthe blade androotdesignwhichwasdesignedusingthe SolidWorkssoftware.
Figure 26Aerofoil blade twist angle 9˚
Figure 25Aerofoil view with the dimensions in
mm
Figure 28Blade view Figure 27Blade heights 1.76 in

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Figure 29Blade root Figure 30blade root side view
Figure 31Final blade views
Figure 32Final blades with the tree

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4. Manufacturing Process
4.1 Start of manufacturing process – 3D printing
My final designof the turbine bladeisconfirmedbymysupervisorandwasreadyto the 3D printing
process. The 3D printerdoesthe 3D printingprocedure automaticallywhenwe importthe CAD
designtoit.The universityprovidedme the 3D printer,inwhichthe masterpiece 3Dprintedmodel is
printedoutas an ABSplasticturbine blade. The 3D printerwhichprintedmyblade isknownasUP
BOX. UP BOX specifications:
 Material used– ABS plastic
 Resolution– 100 microns
Dimension of the UP BOX:
 Width– 255 mm
 Height– 205 mm
 Depth – 205 mm
To printit out the firststepI didwas,savedthe file inSTL formatand sentitto the labtechnician
Mr. Dave Haskell.Then Openedthe CatalystEXsoftware andmodifiedthe dimensionsinthe
software tokeepitwithinthe machine requirements.Selectedprintpropertiesandadjusted
resolutionandorientationasthe labtechnicianinstructedme todo.The machine calculated
howmuch material will be usedandthe estimateddurationof the printing.The durationof my
blade tobe printedtook10 hours.Set the machine toprint, the machine printedmyblade all
nightand I tookit outthe followingdayinthe morning. The 3D printedturbine blade wasfixed
to the ABS plasticsheetinsidethe UPBOX,removed the blade sheetandunwantedmaterials
usingpliers,shears andascraper off the blade.
Figure 33UP BOX

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4.2 Investment Casting Process
4.2.1 Silicon Mould making
The firststepto start off made a mouldbox withthe suitable dimensionsof the turbine blade to
attach it fixedinside the bladewiththe aidof wires.The box must wideron eitherside bythe same
lengthof the blade andthe heightof the blade shouldbe three timesthe heightof the blade.
Length 136mm
Width 103mm
Height 100mm
Table 37 Dimensions
Aftermakingthe mouldbox,the blade mustbe keptinside the bladestable sothatitstaysstill when
pouringthe siliconinsidethe box.Todothis,Drilledsome holesinthe
blade andin the root of the blade.Kept the blade usingcopperwires
inside the blade andheldathickmetal at the bottomof the root sothat
wax will be pouredinitand the copperwiresare usedso that afterthe
Figure 35Turbine blades with the
sheet Figure 34Removing off the
Turbine blade
Figure 36Mould box

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siliconmouldiscomplete,the coppercanbe removedandthe copperholeswill be usedasair
pocketsto suckout air whenpouringthe wax.
The turbine blade istapedmakinga partingline before itwaskeptinsidethe mouldbox sothat
whencuttingthe siliconmould,the partinglinewill make iteasytocut the siliconblade.
Calculated the volume of the silicon to be poured in to the mould box
Length × Width × Height
136 mm × 103 mm × 100 mm
Volume =1400800 mm3
Volume =1400.8 cubic centimetres
Withthe helpof the labtechnician,mixedcuringagentwiththe Silicon.Amountof curingagent
mixedwas10% of the siliconwhichis 140.08 cubic centimetresandmixeditwiththe hardenerto
allowitto settle.Aftermixingthem,keptitinthe vacuumchamberto remove anyair inside with
settingupit to -1 bar pressure.Afterit,pouredthe siliconintothe box andkeptitinthe vacuum
chamberagainso that it removes anymore airtrappedin it.The mouldbox withthe siliconiskept
inside the vacuumchamberovernighttosettle andtakenoutthe followingdaymorning.
Nextdaymorningremoved the mouldbox off afterthe siliconmixturesettledovernight. Cutthe
siliconmouldintohalf,anditisveryimportanttocut the siliconmouldandwiththe splittingline
where the tape wasput. Sothat the mould canbe easilyopenedandclosedforwax pouring.
Figure 41Mixing
silicon with curing
agent
Figure 40Pouring
Silicon into the
mould box
Figure 39Silicon
settling
Figure 38Breaking
off the Mould box
Figure 37Silicon
mould Cut into
half

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4.2.2 Making the Wax model
Aftercutting,tookoutthe ABSplastic3D printedblade andtree designout,sprayedmouldrelease
inboth the siliconmouldwhere the wax blade the tree designsiliconmouldsticks.Sprayedmould
release inboththe siliconmouldwhere the wax blade sticksinandstapledbothtogethertightlyso
that the wax blade isstable inside the wax mouldandtapedittightly.Putthe topof the moulds with
tape so that the excess moltenwax doesnotoverflow.
In the afternoon,afterkeepingthe mouldinthe ovenforcouple of hourswiththe temperature of
30˚C to be warm and recycledwax whichwaskeptina separate ovenat100˚C to be melt.Poured
wax in the mouldswiththe helpof labtechnicianinthe hole of where athickmetal wasplacedas in
the mouldmakingprocessabove.Usedgravitymethodtopourthe wax intothe mould as the lab
techniciantoldme inpastyears it isthe waytheywere beingdoinginthismethod.Keptthe mould
so that the wax to be cooledand settledforthree hoursinthe mouldproperly.
Safety precautions:
 Lab coat
 Safety boots
 Pair of gloves
 Safety goggles
Afterthree hours,Separatedthe mouldoff andtookthe wax blade andtree designout.The wax
tree designwasa successinthe firstpouringasthe wax blade hassome airbubblesinit.It is
because the airrisesdidnot release the airoutproperly.Followingdaymorning,made the moulds
readyfor the secondpouringasin the firstprocessmentionedabovebutwithmakingthe airrising
holesmore clearsothat the blade doesnotgetany air bubblesinit.

38 K1359820
Pouredwax inthe moulds.Sawthe air risesfilledwiththe wax properlyinthe secondpouring.After
keepingthe blade tocool foranothercouple of hours, separatedthe mouldsoff andtookoutthe
wax models.Thistime,blade wasnotupto the desiredlevel.Discussedwiththe labtechnician
aboutthe problemandcame to a conclusionof pre-heatingthe siliconmouldat35˚C warm so that
the wax can flowthroughall the complex parts. Afterkeepingittocool foranothercouple of hours,
separatedthe wax model off the mould.Itstill didn’tcome tothe desiredlevel.Thenrealisedthe
bladeshassome complex partsinwhichwax can’t flow throughthe gravitymethodof pouring. Did
sevenpouringof wax andfourof the blades were goodenoughtoprogresswiththe nextprocessas
time wasa probleminthisprocess.Itneedsquite more patience inthisprocesstogetthe desired
level of outcome. Startedassemblingprocess,attachedthe wax turbinebladestothe tree design
usinghotgun. Usedhot glue gunto attach two turbine bladesinatree.
Figure 46Wax
poured
Figure 45Wax Tree
model
Figure 44Wax blades Figure 43Wax blades and
tree
Figure 42Assembly

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4.2.3 Ceramic Coating
This process consists of three steps which is coating, stuccoing and hardening. It is a
repeated process in which the wax model is dipped in the ceramic. The first step of ceramic
coating is to get the amount of ceramic which is going to be used in the tree design. Used
340 ml of ceramic material with 470 ml of binder and stirred together.
The initial idea is to coat the turbine blades for about three to four layers with the time
interval of forty to forty five minutes with the ceramic mixture.
Future works to be done:
 Complete the wax coating
 Burnout/ De-Wax
 Pour molten metal and Break the Ceramic Coating
Figure 49Ceramic first coating Figure 48ceramic coating left
to dry
Figure 47 Ceramic
coated blade

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5 CONCLUSION
The gas turbine blade isa unique componentwithanaerofoil designwhichundergoes more tough
environmentssuchashightemperaturesandpressures,whereasexposedtoapproximately1500
degree C. The turbine blade experiences majorfailureslike creepandfatigue failureswhichisdue to
highdynamicstressescausedbyvibrationandresonance withinthe operatingrange.These failures
leadto the endof the life of blade aswell.Toovercome this,Engineersworkhardtopreventthese
failure problemsby implementingcoolingsystemsandmanufacturingthe bladesinmetallicalloys,
such as nickel basedalloys,whichhashighmeltingpoint,toughnessandlightweight.
The turbine blade ismanufacturedusinginvestmentcastingmethod,whichisaprocessthat needs
more patience.Thisprocessisa verylengthyprocess,beingafuture engineerthisprocessgave alot
of experience inpatience andatthe same time learnedhow tomanage time withwork.Thisprocess
alsogave quite muchexperienceinworkingasan engineerwithatechnicianinthe lab.
In thisthe author of thisreportlikestoshare the successandproblemsfacedinthisproject.Tostart
off with,Designingthe blade wasthe secondsteptothisprojectinwhichbackgroundresearch
playedamajor role forthe authoras thisis the firstindividual projectexperienced. Fordesigningthe
turbine blade,dimensionswere needed.Itwasone of the biggestchallengesfacedasall the turbine
blade manufacturingcompaniesdidnothelptogive the dimensions.Mailedandtriedtocontact
more than tenmanufacturingcompanies,still notevenasingle companyrepliednorgave their
blade dimensions.Asthe projecthadalimitedamountof time tomanufacture the turbine blade,
starteddesigningthe blade withanappropriate designchose andwithsome assumptions.
At the middle of the designingprocess,MrDave Haskell,labtechnicianfoundaturbine blade and
gave as thisprojectwas alreadybeendiscussedwithhim.Thentookthe dimensionsof the turbine

41 K1359820
blade anddesignedthe blade withall accurate dimensionsandgotapprovedbythe Supervisorfor
the designcreatedusingSolidWorks.
Once the designisdone,tookthe blade designtothe labtechnicianasit wasalreadybeendiscussed
withthemformakingthis project.Unfortunately,due torepairin3D printerittookquite a couple of
weekstogetthrough3D printingprocess.Asthe 3D printingmachine startedworking,startedthe
manufacturingprocess.The labtechnicianswerebusy because mostof the studentsusedlabfor
theirfinal projectsandthe techniciansgave time forthisprojectas3 days ina weekwhich wasnot
enoughtofinishthisprojectassome of the wax modelswere failure. Labtechnician,MrDave
Haskell alsotoldthatthismanufacturingprocesstakesonlytwotothree weekstobe finishedbut
thenwhenmethimtwomonthsago but inthe endtheywere all busy. The factor whichaffectedthis
projectalsoincludesnotplanningproperlyasthe supervisoradvised.Thisprojectcouldnotbe
finishedontime includesthe reasonthatitwas noteasyas itwas thoughtto be.
Future works to be done:
It isthe simplestparttobe done comparingthiswhole projectwhichcanbe done inthe following
week.Asmentionedabove withsomelabissuesthe processtooksome more time thanthe
expecteddate of deliverable.Two stepsawayfromfinishingthisproject,theyare finishingthe shell
formingwithceramicandmetal model making.

42 K1359820
6 References
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Durham,P. (2012) THE GASTURBINE ENGINE.Availableat:
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InvestmentcastingFAQs(nodate) Available at:
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Shukla,V.(2013) Instrumentationengineering.Availableat:
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