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Forced Response Analysis of a Mistuned, Compressor Blisk Comparing Three Different Reduced Order Model Approaches
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.
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2017 (English)In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, no 6, article id 062501Article in journal (Refereed) Published
Abstract [en]

Accurate structural modeling of blisk mistuning is critical for the analysis of forced response in turbomachinery. Apart from intentional mistuning, mistuning can be due to the manufacturing tolerances, corrosion, foreign object damage, and in-service wear in general. It has been shown in past studies that mistuning can increase the risk of blade failure due to energy localization. For weak blade to blade coupling, this localization has been shown to be critical and higher amplitudes of vibration are expected in few blades. This paper presents a comparison of three reduced order models (ROMs) for the structural modeling of blisks. Two of the models assume cyclic symmetry, while the third model is free of this assumption. The performance of the reduced order models for cases with small and large amount of mistuning will be examined. The benefits and drawbacks of each reduction method will be discussed.

Place, publisher, year, edition, pages
ASME Press, 2017. Vol. 139, no 6, article id 062501
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-208227DOI: 10.1115/1.4035209ISI: 000399391400008Scopus ID: 2-s2.0-85026923145OAI: oai:DiVA.org:kth-208227DiVA, id: diva2:1116881
Funder
Swedish Energy Agency
Note

QC 20170628

Available from: 2017-06-28 Created: 2017-06-28 Last updated: 2018-05-14Bibliographically approved
In thesis
1. Development of Accurate Reduced Order Models in a Simulation Tool for Turbomachinery Aeromechanical Phenomena
Open this publication in new window or tab >>Development of Accurate Reduced Order Models in a Simulation Tool for Turbomachinery Aeromechanical Phenomena
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Modern gas turbines are still vulnerable to vibrations when operated at certain speeds. This unstable environment can lead to high cycle fatigue (HCF) and damage several of the components inside the turbine. Since engineers are striving to increase the turbines’ efficiency with thinner and more complex blade shapes, these critical speeds will always be present. For these reasons, aeromechanical analyses that is the study of structural and aerodynamic forces need to be assessed with a high level of accuracy. Since this type of analysis are very computational expensive, reduced order models (ROMs) are utilized to decrease the degrees of freedom (DoF) for a faster computation without compromising the accuracy. The present work focuses on cyclic and noncyclic ROMs implemented in an already existing aeroelastic tool, with different characteristics in their condensation and ease of usage depending on the analysis.

 

The AROMA (Aeroelastic Reduced Order Model Analysis) tool has been previously developed to predict the fatigue life of turbomachinery blades with the use of ROMs. The aim of this work has been to improve the tool in terms of accuracy, flexibility and speed, by employing additional reduction methods capable to predict forced responses analysis of large industrial-size models.

 

The understanding of an aeroelastic phenomena would not be complete if mistuning is not considered in the analysis. A mistuned bladed-disk means that all its sectors do not share the same mass and stiffness properties, which in reality this is the case. Mistuning can be addressed as probabilistic, taking into account the manufacturing tolerances and wear of the bladed disk, or it can be assessed as deterministic, also known as intentional mistuning.

 

The latter is achieved to increase the flutter stability by breaking the circumferential traveling waves modes due to energy confinement, and also to have a certain understanding of the forced response amplitude, which helps in designing for worst and best case scenarios.

 

The ROMs that have been incorporated in the AROMA tool are known as the component mode synthesis (CMS) and subset nominal mode (SNM) approaches. The CMS is split into two branches, these are the fixed- and freeinterface methods known as Craig-Bampton (CB) and Craig-Chang (CC), respectively. An intensive study with numerical and experimental validation has been performed for these three reduction methods. The outcome of the study is that each of these methods have their own drawbacks and benefits depending on the aeromechanical analysis problem. The SNM showed that it produces fast computations, with high level of accuracy when the mistuning level is low. On the other hand, a novel and unique approach, Craig-Chang multisubstructuring (CCMS), demonstrated fast computations and high accuracy when the mistuning level is high.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 68
Series
TRITA-ITM-AVL ; 2018:7
Keyword
flutter, forced response, high cycle fatigue, reduced order models, ROM, craig-bampton, mistuning, tuned, mistuned, cyclic, noncyclic, craig-chang, free-interface. fixed-interface, subset nominal mode, SNM, CBMS, CCMS, CCC, CBC, FEM, CMS, modal, eigen, modeshapes, aeroelasticity, aeromechanical, tool, turbomachinery, turbine, compressor, AROMA
National Category
Aerospace Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-227658 (URN)978-91-7729-750-5 (ISBN)
Public defence
2018-06-07, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180514

Available from: 2018-05-14 Created: 2018-05-09 Last updated: 2018-05-15Bibliographically approved

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