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Numerical tool for prediction of aeromechanical phenomena in gas turbines
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Heat and Power Technology)
KTH, School of Industrial Engineering and Management (ITM), Energy Technology. (Heat and Power Technology)
VOLVO Aero Corporation, Trollhättan, Sweden.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Heat and Power Technology)
2009 (English)In: 19th ISABE Conference / [ed] ISABE, Montreal: American Institute of Aeronautics and Astronautics Inc. , 2009, 1-11 p.Conference paper, Published paper (Refereed)
Abstract [en]

A numerical tool for aeromechanic design is presented. The output of the tool is the fatigue risk of the critical blade obtained by the Haigh diagram, and stability curves for the stability analyses. The tool integrates results from commercial Computational Fluid Dynamics (CFD) and Finite Element (FE) solvers. It uses a Reduced Order Modeling (ROM) technique in order to account for mistuning effects in an efficient way. The description of the numerical tool and an overview of typical results are presented in this paper. The applicability of the tool in the industrial design process is discussed as well as the outlook of the targeted capabilities.

Place, publisher, year, edition, pages
Montreal: American Institute of Aeronautics and Astronautics Inc. , 2009. 1-11 p.
Keyword [en]
aeromechanical design, fluid-structure interaction, ROM, mistuning, aerodynamic damping, unsteady forces, aerodynamic forcing, blade row interactiong, High Cycle Fatigue, CFD, FEM, Turbomachinery, Aeroelasticity
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11959OAI: oai:DiVA.org:kth-11959DiVA: diva2:291114
Conference
ISABE 2009
Projects
AROMATurbopower (TurboVib)
Note

QC 20110324

Available from: 2010-02-08 Created: 2010-01-29 Last updated: 2017-03-24Bibliographically approved
In thesis
1. Development and Validation of a Numerical Tool for the Aeromechanical Design of Turbomachinery
Open this publication in new window or tab >>Development and Validation of a Numerical Tool for the Aeromechanical Design of Turbomachinery
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In aeromechanical design one of the major rules is to operate under High Cyclic Fatigue (HCF) margins and away from flutter. The level of dynamic excitations and risk of HCF can be estimated by performing forced response analyses from blade row interaction forces or Low Engine Order (LEO) excitation mechanisms. On the other hand, flutter stability prediction can be assessed by calculation of aerodynamic damping forces due to blade motion. In order to include these analyses as regular practices in an industrial aeromechanical design process, interaction between the fields of fluid and structural dynamics must be established in a rather simple yet accurate manner. Effects such as aerodynamic and structural mistuning should also be taken into account where parametric and probabilistic studies take an important role.

The present work presents the development and validation of a numerical tool for aeromechanical design. The tool aims to integrate in a standard and simple manner regular aeromechanical analysis such as forced response analysis and aerodynamic damping analysis of bladed disks.

Mistuning influence on forced response and aerodynamic damping is assessed by implementing existing model order reduction techniques in order to decrease the computational effort and assess results in an industrially applicable time frame.  The synthesis program solves the interaction of structure and fluid from existing Finite Element Modeling (FEM) and Computational Fluid Dynamics (CFD) solvers inputs by including a mapping program which establishes the fluid and structure mesh compatibility. Blade row interaction harmonic forces and/or blade motion aerodynamic damping forces are inputs from unsteady fluid dynamic solvers whereas the geometry, mass and stiffness matrices of a blade alone or bladed disk sector are inputs from finite element solvers. Structural and aerodynamic damping is also considered.

Structural mistuning is assessed by importing different sectors and any combinations of the full disk model can be achieved by using Reduced Order Model (ROM) techniques. Aerodynamic mistuning data can also be imported and its effects on the forced response and stability assessed. The tool is developed in such a way to allow iterative analysis in a simple manner, being possible to realize aerodynamically and structurally coupled analyses of industrial bladed disks. A new method for performing aerodynamic coupled forced response and stability analyses considering the interaction of different mode families has also been implemented. The method is based on the determination of the aerodynamic matrices by means of least square approximations and is here referred as the Multimode Least Square (MLS) method.

The present work includes the program description and its applicability is assessed on a high pressure ratio transonic compressor blade and on a simple blisk.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2010. 52 p.
Series
Trita-KRV, ISSN 1100-7990 ; 2010:01
Keyword
aeromechanical design, turbomachinery, numerical tool, reduced order modeling, mistuning, ROM, aero-structure coupling, CFD, FEM, methods
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-11992 (URN)978-91-7415-561-7 (ISBN)
Presentation
2010-02-18, D3, Lindstedtsv 5 (Entréplan), KTH, Stockholm, 09:00 (English)
Opponent
Supervisors
Projects
TurbopowerAROMA
Note
QC 20110324Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2011-03-24Bibliographically approved
2. Numerical Methods for Turbomachinery Aeromechanical Predictions
Open this publication in new window or tab >>Numerical Methods for Turbomachinery Aeromechanical Predictions
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In both aviation and power generation, gas turbines are used as key components. An important driver of technological advance in gas turbines is the race towards environmentally friendly machines, decreasing the fuel burn, community noise and NOx emissions. Engine modifications that lead to propulsion efficiency improvements whilst maintaining minimum weight have led to having fewer stages and lower blade counts, reduced distance between blade rows, thinner and lighter components, highly three dimensional blade designs and the introduction of integrally bladed disks (blisks). These changes result in increasing challenges concerning the structural integrity of the engine. In particular for blisks, the absence of friction at the blade to disk connections decreases dramatically the damping sources, resulting in designs that rely mainly on aerodynamic damping. On the other hand, new open rotor concepts result in low blade-to-air mass ratios, increasing the influence of the surrounding flow on the vibration response.

 

This work presents the development and validation of a numerical tool for aeromechanical analysis of turbomachinery (AROMA - Aeroelastic Reduced Order Modeling Analyses), here applied to an industrial transonic compressor blisk. The tool is based on the integration of results from external Computational Fluid Dynamics (CFD) and Finite Element (FE) solvers with mistuning considerations, having as final outputs the stability curve (flutter analysis) and the fatigue risk (forced response analysis). The first part of the study aims at tracking different uncertainties along the numerical aeromechanical prediction chain. The amplitude predictions at two inlet guide vane setups are compared with experimental tip timing data. The analysis considers aerodynamic damping and forcing from 3D unsteady Navier Stokes solvers. Furthermore, in-vacuo mistuning analyses using Reduced Order Modeling (ROM) are performed in order to determine the maximum amplitude magnification expected. Results show that the largest uncertainties are from the unsteady aerodynamics predictions, in which the aerodynamic damping and forcing estimations are most critical. On the other hand, the structural dynamic models seem to capture well the vibration response and mistuning effects.

 

The second part of the study proposes a new method for aerodynamically coupled analysis: the Multimode Least Square (MLS) method. It is based on the generation of distributed aerodynamic matrices that can represent the aeroelastic behavior of different mode-families. The matrices are produced from blade motion unsteady forces at different mode-shapes fitted in terms of least square approximations. In this sense, tuned or mistuned interacting mode families can be represented. In order to reduce the domain size, a static condensation technique is implemented. This type of model permits forced response prediction including the effects of mistuning on both the aerodynamic damping as well as on the structural mode localization. A key feature of the model is that it opens up for considerations of responding mode-shapes different to the in-vacuo ones and allows aeroelastic predictions over a wide frequency range, suitable for new design concepts and parametric studies.

Place, publisher, year, edition, pages
Stockholm: Royal Institute of Technology, 2011. 127 p.
Series
Trita-KRV, ISSN 1100-7990 ; 11:08
Keyword
Aeromechanics, numerical tools, methods, turbomachinery, aeroelasticity, gas turbines, vibrations
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-48418 (URN)978-91-7501-135-6 (ISBN)
Public defence
2011-12-15, M2, Brinellvägen 64, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Turbopower, AROMA
Note
QC 20111125Available from: 2011-11-25 Created: 2011-11-18 Last updated: 2011-11-25Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
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Output format
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