REDUCED ORDER MODEL OF MISTUNED BLADED DISKS USING THE KRYLOV-SUBSPACE COMBINEDWITH THE CRAIG-BAMTON REDUCTION TECHNIQUE

REDUCED ORDER MODEL OF MISTUNED BLADED DISKS USING THE KRYLOV-SUBSPACE COMBINEDWITH THE CRAIG-BAMTON REDUCTION TECHNIQUE

Pohle, M. Sc. L.; Scheidt, Dr.-Ing. Lars Panning-von; Wallaschek, Prof. Dr.-Ing. Jörg

Full Article:

In order to analyze the effects of mistuning of blisks, the frequency response function (FRF) has to be calculated as quickly as possible and with high accuracy. Therefore, commonly used finite element models with more than 106 degrees of freedom (DOF) have to be reduced to a model with only a few DOF. A usual way in literature is using reduced order models (ROM) like a modal reduction. This is either slow, inaccurate, or the possible extension to non-linearity is difficult. In this paper a new method of model reduction for mistuned turbine blades is introduced and the benefits are shown. The model of the blisk is separated into individually mistuned blades and a tuned disk where the latter is analyzed as a cyclic system. Analog to the Craig-Bampton reduction technique the system is divided into master- and slave-DOF. The introduced technique is the reduction based on the Krylov-Subspace-Method which performs better in terms of accuracy than the modal reduction if the Two-Side-Arnoldi algorithm is used. Afterwards, the reduced tuned model is mistuned by a variation of Youngs modulus which is the most popular way to introduce mistuning. This reduced system can be further described by modal reduction to decouple the equation of motion and describes the full system with as few DOF as possible. Finally, the paper gives a comparison of the standard Craig-Bampton-reduction and the combined Krylov-Craig-Bampton-method in terms of computational accuracy and efficiency to show the benefits of the new method.

In order to analyze the effects of mistuning of blisks, the frequency response function (FRF) has to be calculated as quickly as possible and with high accuracy. Therefore, commonly used finite element models with more than 106 degrees of freedom (DOF) have to be reduced to a model with only a few DOF. A usual way in literature is using reduced order models (ROM) like a modal reduction. This is either slow, inaccurate, or the possible extension to non-linearity is difficult. In this paper a new method of model reduction for mistuned turbine blades is introduced and the benefits are shown. The model of the blisk is separated into individually mistuned blades and a tuned disk where the latter is analyzed as a cyclic system. Analog to the Craig-Bampton reduction technique the system is divided into master- and slave-DOF. The introduced technique is the reduction based on the Krylov-Subspace-Method which performs better in terms of accuracy than the modal reduction if the Two-Side-Arnoldi algorithm is used. Afterwards, the reduced tuned model is mistuned by a variation of Youngs modulus which is the most popular way to introduce mistuning. This reduced system can be further described by modal reduction to decouple the equation of motion and describes the full system with as few DOF as possible. Finally, the paper gives a comparison of the standard Craig-Bampton-reduction and the combined Krylov-Craig-Bampton-method in terms of computational accuracy and efficiency to show the benefits of the new method.

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DOI: 10.5151/meceng-wccm2012-18187

Referências bibliográficas

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Como citar:

Pohle, M. Sc. L.; Scheidt, Dr.-Ing. Lars Panning-von; Wallaschek, Prof. Dr.-Ing. Jörg; "REDUCED ORDER MODEL OF MISTUNED BLADED DISKS USING THE KRYLOV-SUBSPACE COMBINEDWITH THE CRAIG-BAMTON REDUCTION TECHNIQUE", p-899-908. In: In Proceedings of the 10th World Congress on Computational Mechanics [= Blucher Mechanical Engineering Proceedings, v. 1, n. 1]. São Paulo: Blucher, 2014.
ISSN 23580828, DOI 10.5151/meceng-wccm2012-18187