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.