Reduction of Aerodynamic Forcing in Transonic Turbomachinery

193 Pages·2013·11.37 MB·English

Reduction of Aerodynamic Forcing in
Transonic Turbomachinery
NumericalStudiesonForcingReductionTechniques
FLORIANFRUTH
DoctoralThesis
DepartmentofEnergyTechnology
SchoolofIndustrialTechnologyandManagement
RoyalInstituteofTechnology
Stockholm,Sweden
TRITAKRVReport13/08
ISSN1100-7990
ISRNKTH/KRV/13/08-SE
ISBN978-91-7501-870-6
©FlorianFruth,2013
Pageiii DoctoralThesis/FlorianFruth
Abstract
Due to more and more aggressive designs in turbomachinery, assuring the
structural integrity of its components has become challenging. Also influ-
encedbythistrendisbladedesign,wherelighterandslimmerblades,incom-
bination with higher loading, lead to an increased risk of failure, e.g. in the
form of blade vibration. Methods have been proposed to reduce vibration
amplitudes for subsonic engines, but cannot directly be applied to transonic
regimes due to the additional physical phenomena involved. Therefore the
present work investigates numerically the influence of two methods for re-
ducingbladevibrationamplitudesintransonicturbomachines,namelyvary-
ingthebladecountratioandclocking. Asitisknownthatclockingaffectsthe
efficiency, the concurrent effects on vibration amplitudes and efficiency are
analyzedanddiscussedindetail.
Forthecomputationalinvestigations,theproprietaryFortran-basednon-linear,
viscous 3D-CFD solver VolSol is applied on two transonic compressor cases
and one transonic turbine case. In order to reduce calculation time and to
generatethedifferentbladecountratiosascalingtechniqueisapplied.
Thefirstandmainpartofthisworkfocusesontheinfluenceofthereduction
techniquesonaerodynamicforcing. Boththechangeinbladecountratioand
clockingpositionarefoundtohavesignificantpotentialforreducingaerody-
namicforceamplitudes. Manipulationofthephasingofexcitationsourcesis
found herein to be a major contributor to the amplitude variation. The low-
eststimulusresultsareachievedforde-phasedexcitationsourcesandresults
in multiple blade force peaks per blade passing. In the case of blade count
ratiovariationitwasfoundthatblockageforhighbladecountratiosandthe
changeinpotentialfieldsizehavesignificantimpactsonthebladeforcing.For
theclockinginvestigation,threeadditionaloperatingpointsandbladecount
ratiosareanalyzedandprovetohaveanimpactontheforcereductionachiev-
ablebyclocking.
The second part of the work evaluates the influence of clocking on the effi-
ciency of a transonic compressor. It is found that the efficiency can be in-
creased,butthemagnitudeofthechangeandtheoptimalwakeimpingement
location depend on the operating point. Moreover it is shown that optimal
efficiencyandaerodynamicforcingsettingsarenotdirectlyrelated. Inorder
to approximate the range of changes of both parameters, an ellipse approxi-
mationissuggested.
Keywords: Forced Response, Aerodynamic Forcing, Efficiency, Blade Count
Ratio,Clocking

Pagev DoctoralThesis/FlorianFruth
Samanfattning
Den senaste trenden inom turbinutvecklingen mot allt mer aggressiv design
ökar svårigheten att säkerställa hållfastheten. Del av denna designfilosofi är
ävenmaskinensbeskovlingdärtrendenmotlättareochslankarebladikombi-
nationmedhögrebelastningledertillökadriskförbrottistrukturenrelaterat
till mekaniska vibrationer. Många metoder har utvecklats för reduktion av
bladvibrationer för subsoniska motorer. Dessa kan dock inte direkt tilläm-
pas för transoniska flödesområden eftersom ytterligare flödesfenomen är in-
volverade. Därför ägnas föreliggande arbete åt att numeriskt undersöka två
metoderförreduktionavbladvibrationeritransoniskaturbomachiner,nämli-
genvariationavförhållandetmellanantaletrotor-ochstatorblad(bladkvoten)
och så kallad clocking. Det är sen tidigare känt att clocking påverkar verkn-
ingsgraden och i denna studie undersöks och beskrivs effekter av clocking i
detaljbådemedavseendepåverkningsgradochvibrationsamplituder.
För de numeriska analyserna av bladlaster tillämpas den Fortran-baserade
icke-linjära, viskösa 3D CFD-lösaren VolSol på två transoniska kompressor-
fall och ett transoniskt turbinfall. För att minska beräkningstiden har den
vedertagnametodenförtangentiellskalningtillämpasidefalldårotor-stator
bladantalenintevardelbara.
Denförstaochhuvuddelenavdettaarbetefokuserarpåanalysenavpåverkan
av reduceringsåtgärderna på den aerodynamiska lasten. Både ändringar i
bladkvotenochclockingpositionharbetydandepotentialattminskadeaero-
dynamiska stimuli. Det visas att förändringar i fasrelationen mellan olika
aerodynamiska lastkällor är den huvudsakliga förklaringen till förändringar
identotalabladlastamplituden. Lägstatotalalaststimulansmedförfleralast-
topparperbladpassageuppstårnärdeenskildalastkällornaärurfas. Ifallet
för varierande bladkvoter påverkar även blockageffekter och potentialeffek-
terdenaerodynamiskalastamplitudenvidhögabladkvotstal. Undersöknin-
gen av optimala clockingen åtföljdes av variationer i tre driftpunkter samt
bladkvotsförhållanden och det visas att detta påverkade clockingresultaten
markant.
Den andra delen i studien undersöker påverkan av clocking på prestandan
i en transonisk kompressor. Det påvisas att prestandan kan höjas men stor-
lekeniprestandavinstenochoptimalkorsningspunktmellanuppströmsvak
ochnerströmsbladenberorpåoperationspunkten. Vidarevisasdetattclock-
ingpositionenerna för optimal prestanda och aerodynamisk lastning inte är
direkt korrelerade. För att approximera variationen för dessa båda parame-
trarmapclockingenföreslåsenelliptiskkorrelation.
Nyckelord: Lastdriven Resonans, Aerodynamisk Lastning, Prestanda, Blad-
kvoter,Clocking

Pagevii DoctoralThesis/FlorianFruth
Preface
The thesis presented is based on the publications listed below. In order to
present all cases in a similar manner, the methodologies and approaches of
thepublicationshavebeenpartlyadjusted.
PaperI:
FlorianF.,VogtD.M.,MårtenssonH.,MayorcaM.A.,FranssonT.H.
"InfluenceoftheBladeCountRatioonAerodynamicForcing-PartI:Highly
LoadedTransonicCompressor"
GT2010-22756,ASMETurboExpo,2010
PaperII:
FlorianF.,VogtD.M.,FranssonT.H.
"Influence of the Blade Count Ratio on Aerodynamic Forcing - Part II: High
PressureTransonicTurbine"
GT2011-46071,ASMETurboExpo,2011
PaperIII:
HosseiniS.M.,FlorianF.,VogtD.M.,FranssonT.H.
"EffectofScalingofBladeRowSectorsonthePredictionofAerodynamicForc-
inginaHighly-LoadedTransonicTurbineStage"
GT2011-45813,ASMETurboExpo,2011
PaperIV
FlorianF.,VogtD.M.,FranssonT.H.
"HarmonicForceVariationduetoChangeinBladeCountRatio-PhysicalIn-
terpretation"
S2-5,13thInternationalSymposiumonUnsteadyAerodynamics,Aeroacous-
ticsandAeroelasticityofTurbomachines,2012
PaperV
FlorianF.,VogtD.M.,BladhR.,FranssonT.H.
"Unsteady Forcing vs. Efficiency - The Effect of Clocking on a Transonic In-
dustrialCompressor"
FEDSM2013-16583,FluidsEngineeringSummerMeeting,2013

Pageix DoctoralThesis/FlorianFruth
Acknowledgements
The results within this doctoral thesis are a summary of almost five years of
researchattheDepartmentofEnergyTechnologyintheHeatandPowerDi-
vision.FirstofallIwouldliketothankProf.DamianVogtforhissupervision,
guidanceandencouragementduringthewholetime. MoreoverIwouldlike
toexpressmygratitudetoProf. TorstenFransson,formakingthisrewarding
but also exciting time at the department and in Stockholm possible. Also, I
wouldliketothankDr. BjörnLaumertwhowasalwaystherefordetaileddis-
cussionsabouttheCFDcodeandbrainstorming.
TheoverallprojectwasgraciouslysupportedandfundedbytheSwedishEn-
ergyAgency,SiemensIndustrialTurbomachineryandGKNAerospacewithin
theframeworkoftheTURBOPOWERproject. Significantcontributionswere
madebyHansMårtenssonfromGKNAerospaceandDr. RonnieBladhfrom
SiemensIndustrialTurbomachineryandIwouldliketoexpressmythanksfor
theirtechnicaladviceandguidance.
Duringthealmostfiveyears, ithasbeenmycolleaguesthatmadethisplace
sospecialtome. Thankstomycolleaguesandfriendsfromtheaeromechanic
group that made me laugh, cheered me up in the harder times and were al-
waysthereforexchangingideasortechnicaldiscussions. Maria,Nenad,An-
tonio,Lucio,MauricioandTobias-manythanks.Ofcourse,duringthecourse
of time, there are also other colleagues that became more than friends, be it
Lukas and Manuel who made me feel less home sick because of our similar
German/Austriandialectthatweshare, orJamesthatIspentagreatdealof
time with when we shared an apartment. Also thanks goes to the Venezue-
lans,RafaandMonika,thatalwaysbrightenedupthedayswiththeirhappy
mood.
HavinglivedinStockholmforsuchalongtime,Iwouldalsoliketothankoth-
ersfortheirfriendshipandthecommontimethatweshared. Beittheboul-
deringgroupwithMariaandAndreas,themanypeoplefromtheKarolinska
Institute like Tina, Mustafa, Nadim but also others such as Sanjay, Joel and
Mona. Iwishyouallthebestofluckforyourfuture,andhopethatourpaths
crossagain.
FinallyandwithgreatestgratitudeIwouldliketoaddressmyparentsandmy
brother. Yougavemelove,strengthandyourunconditionalsupport-Ican’t
thankyouenoughforthat. Tomybrother,yourdrivetoachievemoreinlife
andatworksignificantlycontributedtothepersonthatIam.