23/11/2011 23/11/2011 Doctoral Doctoral Thesis Thesis “ “ UNSTEADY ROTOR UNSTEADY ROTOR - - STATOR STATOR INTERACTION IN AN AXIAL INTERACTION IN AN AXIAL TURBOMACHINE TURBOMACHINE ” ” D. Jes D. Jes ú ú s Manuel Fern s Manuel Fern á á ndez Oro ndez Oro Dtor Dtor : Prof. Carlos : Prof. Carlos Santolaria Santolaria Morros Morros
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23/11/201123/11/2011
Doctoral Doctoral ThesisThesis
““UNSTEADY ROTORUNSTEADY ROTOR--STATOR STATOR INTERACTION IN AN AXIAL INTERACTION IN AN AXIAL
TURBOMACHINETURBOMACHINE””
D. JesD. Jesúús Manuel Ferns Manuel Fernáández Orondez Oro
DtorDtor: Prof. Carlos : Prof. Carlos SantolariaSantolaria MorrosMorros
22/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
TableTable ofof ContentsContents
33/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
ThisThis unsteadyunsteady pressurepressure fieldfield isisa a consequenceconsequence ofof thethe bladesblades
motionmotion ofof thethe rotor.rotor.
UNSTEADY UNSTEADY TURBOMACHINERY TURBOMACHINERY
FLOWFLOW
1.1.-- Even, an Even, an inviscidinviscid, adiabatic flow (reversible) is exchanging enthalpy , adiabatic flow (reversible) is exchanging enthalpy (work) due to the existence of an unsteady pressure field.(work) due to the existence of an unsteady pressure field.
2.2.-- Mechanical vibrations and unsteady forces also appear due to thMechanical vibrations and unsteady forces also appear due to the e time variations of the pressure field.time variations of the pressure field.
3.3.-- Aerodynamically generated noise is associated to the pressure Aerodynamically generated noise is associated to the pressure fluctuations inside the fluctuations inside the turbomachineturbomachine. .
55/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
Non Non relatedrelated totoSpeedSpeed RotationRotation
TransitionalTransitionalOperationOperation ––
Speed Range Speed Range VariationsVariations
TurbulenceTurbulence
ROTORROTOR--STATOR INTERACTIONSTATOR INTERACTION
TurbomachineryTurbomachinery flows are highly flows are highly unsteady because of the relative unsteady because of the relative motion of rotor and stator stages.motion of rotor and stator stages. In general, unsteadiness may be viewed as a combination of two processes: the INVISCID POTENTIAL EFFECTINVISCID POTENTIAL EFFECTand the PERIODIC PASSING OF PERIODIC PASSING OF WAKESWAKES generated by the upstream blade rows. The former is due to the relative motion of the rotors with relative motion of the rotors with respect to the statorsrespect to the stators, and this effect becomes stronger when the gap between rotor and stator is small. The latter arises from the interaction interaction of the blade boundary layers with the of the blade boundary layers with the vortices shedvortices shed from the blunt trailing edge of upstream blade rows, and from the variation of the angle of attack at the leading edge due to the wake velocity deficit. All these All these unsteady features and the unsteady features and the interaction between them make the interaction between them make the simulation of unsteady simulation of unsteady turbomachineryturbomachinery flows a highly flows a highly challenging task. (C.HIRSCH)challenging task. (C.HIRSCH)
PERIODIC PASSING PERIODIC PASSING OF WAKESOF WAKES
ROTORROTOR--STATOR STATOR INTERACTIONINTERACTION
•• Axial Axial gapgap variationsvariations. . PitchPitch effecteffect..•• CircunferentialCircunferential variationsvariations in total in total pressurepressure duedue toto thethe bladesbladesdownstreamdownstream response.response.•• Time Time circunferentialcircunferential variationsvariations andand response response toto anan uniformuniform inletinletconditionsconditions..
t t
““A steady flow pattern in a relative frame of A steady flow pattern in a relative frame of
reference with a velocity gradient in the reference with a velocity gradient in the tangential direction generates an unsteady tangential direction generates an unsteady
The static pressure field upstream and downstream of a blade rowis varying circumferentiallyvarying circumferentially (and radially) due to the blade loaddue to the blade load.
This causes a flow defect, which is felt as unsteady pressure waves felt as unsteady pressure waves by the relative moving blade rows. (by the relative moving blade rows. (JJööckercker, 2002), 2002)
88/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
3.3.-- SegregationSegregation ofof instantaneousinstantaneous turbulentturbulent phenomenaphenomena throughthrough a a time average time average forfor everyevery rotor rotor phasephase
4.4.-- IdentificationIdentification ofof dynamicdynamic unsteadinessunsteadiness sourcessources, , eithereither generatedgeneratedby rotor by rotor bladesblades oror generatedgenerated by stator by stator vanesvanes
2121/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
3.3.-- Experimental Experimental ResultsResults
PASSAGEPASSAGE--AVERAGED FLOWAVERAGED FLOW
FHP FHP
ADIM. AXIAL VELOCITYADIM. AXIAL VELOCITY
•• BetweenBetween thethe rowsrows (D), (D), atatnominal nominal flowflow raterate, , therethere isis a a perfectperfect homogenetationhomogenetation ofofthethe flowflow, , justjust brokenbroken by by stator stator wakeswakes. . BothBoth axial axial gapsgaps..
•• Rotor Rotor downstreamdownstream (R), (R), thethestator stator wakeswakes are are clearlyclearlypresentpresent, more , more diffuseddiffused andandadvectedadvected, , butbut perfectlyperfectlyvisible.visible.
•• BoundaryBoundary layerlayer zoneszones: : ForFor(D), (D), widewide boundaryboundary atat tiptip. . InsteadInstead, , forfor (R), (R), thethe hubhubboundaryboundary layerlayer seemsseems toto be be thickerthicker. .
•• FIRST RESULTS !!FIRST RESULTS !!
2222/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
•• SpatialSpatial DiscretizationDiscretization: : up up toto 350,000 350,000 cellscells. 12,000 . 12,000 cellscells//passagepassage. . HybridHybridmeshmesh. O. O--GridGrid aroundaround thethe bladesblades. . GridGrid accuracyaccuracy analysisanalysis..•• Temporal Temporal DiscretizationDiscretization: : 5.34*105.34*10--55 s. 468 time s. 468 time stepssteps/rotor /rotor rev.rev. ((1313xx99x4).x4).•• NumericalNumerical SchemeScheme: : SIMPLE algorithm for pressureSIMPLE algorithm for pressure--velocity coupling, upwind velocity coupling, upwind discretizationsdiscretizations and second order implicit scheme for the time dependent term.and second order implicit scheme for the time dependent term.•• TurbulenceTurbulence modelingmodeling: : LESLES--(k(k--εε))RSM RSM comparisoncomparison. .
•• SpatialSpatial DiscretizationDiscretization: : up up toto 1,800,000 1,800,000 cellscells. 3,000 . 3,000 cellscells//passagepassage 3D. 3D. HybridHybridmeshmesh. O. O--GridGrid aroundaround thethe bladesblades. [100x35x25].. [100x35x25].•• Temporal Temporal DiscretizationDiscretization: : 1.068*101.068*10--44 s. 234 time s. 234 time stepssteps/rotor /rotor rev.rev. ((1313xx99x2).x2).•• NumericalNumerical SchemeScheme: : SIMPLE algorithm for pressureSIMPLE algorithm for pressure--velocity coupling, upwind velocity coupling, upwind discretizationsdiscretizations and second order implicit scheme for the time dependent term.and second order implicit scheme for the time dependent term.•• TurbulenceTurbulence modelingmodeling: : LESLES--(k(k--εε))RSM RSM comparisoncomparison. .
5.5.-- GAP AXIAL MODIFICATIONS GAP AXIAL MODIFICATIONS andand OFFOFF--DESIGN CONDITIONS DESIGN CONDITIONS havehave beenbeen includedincludedin in thethe studystudy toto determine determine thethe influenceinfluence ofof thesethese parametersparameters. General . General conclusionsconclusionspointpoint out out thatthat::
•• BothBoth parametersparameters modifymodify WAKEWAKE--ROTOR ROTOR unsteadyunsteady patternspatterns..•• WAKEWAKE--WAKEWAKE featuresfeatures are are lessless affectedaffected by by gapgap reductionreduction andand badlybadly relatedrelated totopartialpartial load load perfomanceperfomance..
7.7.-- TheThe constructionconstruction ofof thethe DETERMINISTIC STRESS TENSOR in DETERMINISTIC STRESS TENSOR in bothboth fixedfixed andandmovingmoving referencereference framesframes has has concludedconcluded thisthis workwork. . AboutAbout thisthis issueissue, , itit can be can be saidsaidthatthat::
•• DeterministicDeterministic unsteadyunsteady featuresfeatures are more are more pronouncedpronounced atat thethe stator.stator.•• BladeBlade--toto--bladeblade tensor has tensor has revealedrevealed thatthat stator stator wakewake corecore isis unaffectedunaffected by by circumferentialcircumferential pressurepressure gradientsgradients generatedgenerated by by thethe rotor.rotor.•• BetweenBetween thethe rowsrows, similar , similar valuesvalues toto ReynoldsReynolds stressesstresses are are encounteredencountered forforDeterministicDeterministic StressesStresses ((formerformer studiesstudies).).•• DeterministicDeterministic unsteadinessunsteadiness sourcessources havehave beenbeen indentifiedindentified, so , so allall correlationscorrelationscan be can be usedused as as inputinput data data forfor a a steadysteady RANS RANS simulationsimulation..
CONCLUSIONSCONCLUSIONS
8.8.-- WAKE RECOVERY WAKE RECOVERY processprocess has has beenbeen outlinedoutlined, , withwith thethe goalgoal ofof obtainingobtaining ananestimationestimation onon thethe residual residual deterministicdeterministic kinetickinetic energyenergy associatedassociated toto stator stator wakeswakesatat downstreamdownstream rotor rotor locationslocations..
6464/64/64““Unsteady RotorUnsteady Rotor--Stator Interaction in an Axial TurbomachineStator Interaction in an Axial Turbomachine””. .
Doctoral Thesis Doctoral Thesis -- GijGijóón. n. AprilApril, 7th, 2005. University of Oviedo., 7th, 2005. University of Oviedo.
1.1.-- ANALYSIS OF THE ROTORANALYSIS OF THE ROTOR--STATOR CONFIGURATION, as STATOR CONFIGURATION, as wellwell as as thethe formerformerstatorstator--rotor rotor stagestage..
FUTURE WORKFUTURE WORK
2.2.-- NUMERICAL SOLUTION ENHACEMENT NUMERICAL SOLUTION ENHACEMENT throughthrough RADIAL GAP RADIAL GAP modellingmodelling. . AlsoAlso, , improvementimprovement ofof 3D 3D meshesmeshes qualityquality ((mainlymainly, , highhigh dense dense zoneszones atat bladeblade passagespassages), in ), in orderorder toto improveimprove LES LES characteristicscharacteristics ((y+y+ restrictionsrestrictions criterioncriterion))
4.4.-- INTRODUCTION OF CLOCKING EFFECTS, INTRODUCTION OF CLOCKING EFFECTS, throughthrough considerationconsideration ofof largerlargermachines machines withwith more more thanthan justjust oneone single single stagestage..
23/11/201123/11/2011
Doctoral Doctoral ThesisThesis
““UNSTEADY ROTORUNSTEADY ROTOR--STATOR STATOR INTERACTION IN AN AXIAL INTERACTION IN AN AXIAL
TURBOMACHINETURBOMACHINE””
D. JesD. Jesúús Manuel Ferns Manuel Fernáández Orondez Oro
Prof. Carlos Prof. Carlos SantolariaSantolaria MorrosMorros