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A New Reduced Order Modeling for Stability and Forced Response Analysis of Aero-Coupled Blades Considering Various Mode Families
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. (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)
2010 (English)In: Proceedings of ASME Turbo Expo 2010: Scottish Exhibition & Conference Centre / [ed] ASME 2010, Glasgow, UK: ASME 2010 , 2010, 1-10 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the description and application of a new method for stability and forced response analyses of aerodynamically coupled blades considering the interaction of various mode families. The method, here referred as MLS (Multimode Least Square), considers the unsteady forces due to the blade motion at different modes shape families and calculates the aerodynamic matrixes by means of a least square (L2) approximations. This approach permits the prediction of mode families’ interaction with capabilities of structural, aerodynamic and force mistuning. A projection technique is implemented in order to reduce the computational domain. Application of the method on tuned and structural mistuned forced response and stability analyses is presented on a highly loaded transonic compressor blade. When considering structural mistuning the forced response amplitude magnification is highly affected by the change in aerodynamic damping due to mistuning. Analyses of structural mistuning without aerodynamic coupling might result in over-estimated or under-estimated response when the source of damping is mainly aerodynamic. The frequency split due to mistuning can cause that mode families’ interact due to reducing their frequencies separation. The advantage of the present method is that the effect of mode family interaction on aerodynamic damping and forced response is captured not being restricted to single mode families.

Place, publisher, year, edition, pages
Glasgow, UK: ASME 2010 , 2010. 1-10 p.
Series
GT2010, GT2010-22745
Keyword [en]
aerodynamic damping, stability, flutter, forced response, ROM, aerodynamic coupling, mode family interaction, CFD, FE, Turbomachinery, aeromechanic desing
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11991DOI: 10.1115/GT2010-22745ISI: 000290927800122Scopus ID: 2-s2.0-82055201355ISBN: 978-0-7918-4401-4 (print)OAI: oai:DiVA.org:kth-11991DiVA: diva2:292476
Conference
ASME Turbo Expo 2010
Projects
TurbopowerAROMA
Note

QC 20110211

Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2012-09-05Bibliographically 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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Citation style
  • apa
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  • modern-language-association-8th-edition
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Output format
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