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Development and Validation of a Numerical Tool for the Aeromechanical Design of Turbomachinery
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Heat and Power Technology)
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 [en]
aeromechanical design, turbomachinery, numerical tool, reduced order modeling, mistuning, ROM, aero-structure coupling, CFD, FEM, methods
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-11992ISBN: 978-91-7415-561-7 (print)OAI: oai:DiVA.org:kth-11992DiVA: diva2:292486
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
List of papers
1. Effect of scaling of blade row sectors on the prediction of aerodynamic forcing in a highly-loaded transonic compressor stage
Open this publication in new window or tab >>Effect of scaling of blade row sectors on the prediction of aerodynamic forcing in a highly-loaded transonic compressor stage
Show others...
2009 (English)In: PROCEEDINGS OF THE ASME TURBO EXPO 2009, VOL 6, PTS A AND B, 2009, 535-546 p.Conference paper, Published paper (Refereed)
Abstract [en]

An investigation of the sensitivity of a geometrical scaling technique on the blade forcing prediction and mode excitability has been performed. A stage of a transonic compressor is employed as test object. A scaling ratio is defined which indicates the amount of scaling from the original geometry. Different scaling ratios are selected and 3D Navier Stokes unsteady calculations completed for each scaled configuration. A full annulus calculation (non-scaled) is performed serving as reference. The quantity of interest is the generalized force, which gives a direct indication of the mode excitability. In order to capture both up- and downstream excitation effects the mode excitability has been assessed on both rotor and stator blades. The results show that first harmonic excitation can be predicted well for both up- and downstream excitation using moderate amount of scaling. On the other hand, the predictions of second harmonic quantities do show a higher sensitivity to scaling for the investigated test case.

Keyword
aeromechanical design, unsteady forces, CFD, turbomachinery, blade row interaction, scaling, aerodynamic forcing, fluid structure interaction
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-11958 (URN)10.1115/GT2009-59601 (DOI)000277070700055 ()2-s2.0-77953225029 (Scopus ID)978-0-7918-4887-6 (ISBN)
Conference
54th ASME Turbo Expo 2009, Orlando, FL, JUN 08-12, 2009
Projects
Turbopower (TurboVib)AROMA
Note
QC 20110222Available from: 2010-02-08 Created: 2010-01-29 Last updated: 2011-03-24Bibliographically approved
2. Numerical tool for prediction of aeromechanical phenomena in gas turbines
Open this publication in new window or tab >>Numerical tool for prediction of aeromechanical phenomena in gas turbines
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
Keyword
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:nbn:se:kth:diva-11959 (URN)
Conference
ISABE 2009
Projects
AROMATurbopower (TurboVib)
Note

QC 20110324

Available from: 2010-02-08 Created: 2010-01-29 Last updated: 2017-03-24Bibliographically approved
3. A New Reduced Order Modeling for Stability and Forced Response Analysis of Aero-Coupled Blades Considering Various Mode Families
Open this publication in new window or tab >>A New Reduced Order Modeling for Stability and Forced Response Analysis of Aero-Coupled Blades Considering Various Mode Families
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
Series
GT2010, GT2010-22745
Keyword
aerodynamic damping, stability, flutter, forced response, ROM, aerodynamic coupling, mode family interaction, CFD, FE, Turbomachinery, aeromechanic desing
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-11991 (URN)10.1115/GT2010-22745 (DOI)000290927800122 ()2-s2.0-82055201355 (Scopus ID)978-0-7918-4401-4 (ISBN)
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

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Citation style
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