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A NEW VISUALIZATION METHOD FOR HARMONIC UNSTEADY FLOWS IN TURBOMACHINERY
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.ORCID iD: 0000-0001-9195-793X
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
2016 (English)In: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7B, AMER SOC MECHANICAL ENGINEERS , 2016Conference paper, Published paper (Refereed)
Abstract [en]

Understanding unsteady flow processes is key in the analysis of challenging problems in turbomachinery design such as flutter and forced response. In this paper a new visualization method for harmonic unsteady flow is presented. The method illustrates the direction in which unsteady waves are traveling and transporting energy by the direct visualization of the propagating pressure waves in terms of field lines constructed from the wave group velocity. The group velocity is calculated from the unsteady flow solution by assuming that the local unsteady pressure perturbation of interest can be represented by a single harmonic unsteady wave. The applicability of the method is demonstrated for three test cases including a linear cascade of two-dimensional flat plates and a linear cascade of two-dimensional compressor blade profiles.

Place, publisher, year, edition, pages
AMER SOC MECHANICAL ENGINEERS , 2016.
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-196481ISI: 000385461300066Scopus ID: 2-s2.0-84991735542OAI: oai:DiVA.org:kth-196481DiVA, id: diva2:1049368
Conference
ASME Turbo Expo: Turbine Technical Conference and Exposition
Note

QC 20161124

Available from: 2016-11-24 Created: 2016-11-14 Last updated: 2019-01-14Bibliographically approved
In thesis
1. The Influence of Flow Leakage Modelling on Turbomachinery Blade Forcing Predictions
Open this publication in new window or tab >>The Influence of Flow Leakage Modelling on Turbomachinery Blade Forcing Predictions
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vibrations in turbomachinery engine components are undesirable as they put the structural integrity of the components at risk and can lead to failure during the lifetime of the turbomachinery engine. Vibrations arising from aerodynamic forces and stability of turbomachinery blades is assessed in the discipline of aeromechanics. Ultimately, aeromechanical considerations limit turbomachinery designs and impose constraints on innovative aerodynamic designs with highly loaded light-weight components. Besides, aeromechanical assessment of blade vibration is done at a late stage of the design process and the number of iterations in the design loop is limited. Aeromechanical calculations can have large uncertainties in the prediction accuracy, especially when made a-priori without test data or without comparable design experience to tune the analysis methods. Therefore, large safety margins are required in the design, given that only a small set of prototype engines of a chosen design can be manufactured for testing. This may result in unnecessarily conservative engines and inhibit efficient or cost-effective design.

Accurate prediction methods together with a reliable estimate of the accuracy and sensitivity of the calculations will allow designers to push the limits and to design machines with highly efficient components. Efficiency directly translates into savings in terms of operational cost, capital cost as well as reductions in emissions when fuels are used.

In the presented work the sensitivity of aerodynamic forcing to the geometry features of a tip gap, hub cavity, tip-shroud cavity and inlet guide vane partial gaps has been investigated by the means of URANS CFD computations. The results indicate that sensitivity is both feature and case dependent, and that the detailing features can significantly alter the aerodynamic forcing function. The work shows, that the features should be included in high-fidelity aerodynamic models used for aeromechanics and highlights the mechanisms in which the features affect the aeromechanic forcing.

Investigations were performed for a subsonic model steam turbine configuration in 1.5 stage simulations, for a transonic turbine stage and for a 1.5 stage transonic research compressor in a 5 row investigation. Computations were performed using time domain simulations on scaled sectors of the blade rows. Results are analysed in terms of generalised modal force, and differences in the flow-field between the investigated detailing configurations are highlighted, marking the influence of the detailing features.

Abstract [sv]

Vibrationer i turbomaskinmotorer är oönskade därför att de riskerar komponenternasstrukturella integritet och kan leda till brott under motorns livslängd.Vibrationer som har sitt ursprung i aerodynamiska krafter, såväl somaerodynamiskt kopplad stabilitet av blad i turbomaskinen studeras inom aeromekanik. I slutändan verkar aeromekaniska överväganden inskränkande i utvecklingav turbomaskiner och utgör begränsningar till innovativa aerodynamiskakonstruktioner med högbelastade lättviktkomponenter. För övrigt görsen aeromekanisk bedömning av bladvibration på en sen fas av konstruktionsprocessenoch antalet iterationer i designslingan är begränsad. Aeromekaniskaberäkningar kan komma med stor osäkerhet angående exakthet av prognoser,speciellt när de görs i förväg utan testdata eller utan jämförbar erfarenhetsom kan hjälpa till att avstämma analysmetoderna, och bara ett begränsatantal testmotorer kan tillverkas för provning.

Därför krävs stora säkerhetsmarginaler i konstruktionen. Detta kan ledatill onödigt konservativa konstruktioner och hindra effektiv eller kostnadseffektivdesign.

Noggranna prediktiva metoder tillsammans med en bra uppskattning avexaktheten och känsligheten av beräkningarna gör det möjligt för konstruktöreratt driva gränserna och konstruera maskiner med högeffektiva komponenter. Effektivitet omvandlas dessutom direkt till besparingar när det gällerdriftskostnad, kapitalkostnad och utsläppsminskningar ifall bränsle användsför att driva motorn.

I det här arbetet har aerodynamikens inflytande av att modellera geometriskadetaljeringar studerats. Rotorspetsmellanrum, navkavitet, spetskavitetoch mellanrum på styrskovlar undersöktes med hjälp av URANS CFDberäkningar.Resultaten visar att påverkan är både detaljberoende och fallberoende,och att detaljeringsfunktionerna kan väsentligt ändra den aerodynamiskainstationära kraften som utför arbete på strukturen. Denna avhandlingvisar att undersökning av geometrisk detaljer bör ingå i noggranna aerodynamiskamodeller som används för aeromekanik och markerar på vilket visdetaljer påverkar den aeromekaniska kraften.

Simuleringsundersökningar utfördes på en subsonisk ångprovturbinkonfigurationi 1,5-steg, ett transoniskt turbinsteg, och på en 1,5-steg transoniskforskningskompressor med 5 skovelrad. Beräkningar utfördes i tidsdomän påskalade sektorer av bladraderna. Resultaten analyserades med fokus på generaliseradmodalkraft. Förändringar i flödesfältet mellan de undersökta detaljeringskonfigurationernamarkeras i samband med aerodynamisk skillnad ibladkraft.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 109
Series
TRITA-ITM-AVL ; 2018:58
National Category
Engineering and Technology
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-241125 (URN)978-91-7873-060-5 (ISBN)
Public defence
2019-02-06, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish National Space Board, T7328Swedish Energy Agency, T6527
Available from: 2019-01-14 Created: 2019-01-11 Last updated: 2019-05-10Bibliographically approved

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Gezork, TobiasPetrie-Repar, PaulFransson, Torsten

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