Date of Completion

7-31-2013

Embargo Period

7-26-2018

Keywords

tuning, resonance, frequency, perturbation

Major Advisor

Kazem Kazerounian

Co-Major Advisor

Kevin Murphy

Associate Advisor

Eric Jordan

Associate Advisor

Horea Ilies

Field of Study

Mechanical Engineering

Degree

Doctor of Philosophy

Open Access

Campus Access

Abstract

In multi-stage engine design, it is difficult – or impossible – to design a rotating component free of resonance. But it is imperative to tune the interfered frequencies outside of the engine operating speed range, in order to avoid high cycle fatigue. This dissertation develops a methodology for accomplishing this design task.

The first part of the work presents an approach for tuning of a single natural frequency of a turbine blade subjected to excitation generated by unsteady pressure in the operating speed range. Structural perturbations are performed in a way that only the eigenvalue of choice changes significantly, while producing only small disturbances to the other natural frequencies that lie outside of the operating speed range. This design technique is referred to as the Guided Tuning of Turbine Blades method (GTTB).

The second part of the work presents an approach on the tuning two adjacent excited frequencies of a bladed-disc such as an impeller which has two sets of blades of different chord lengths, namely long and splitter blades. Two solutions are presented. The first one involves the reduction of the inter-blade coupling through stiffening the disc structure followed by individual blade tuning. The second solution is based upon the eigenvalue veering or non-coalescent property of the asymmetric cyclic sector of the structure.

Validated through test measurements, this work indicates that a 5% to 10% shift of the eigenvalues is achievable in order to avoid resonance as normally encountered in engineering practice.

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