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Research Papers: Gas Turbines: Structures and Dynamics

Vibration Diagnosis Featuring Blade-Shaft Coupling Effect of Turbine Rotor Models

[+] Author and Article Information
Norihisa Anegawa

Department of Mechanical Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa, Japang46076@nda.ac.jp

Hiroyuki Fujiwara

Department of Mechanical Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa, Japanhiroyuki@nda.ac.jp

Osami Matsushita

Department of Mechanical Engineering, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa, Japanosami@nda.ac.jp

J. Eng. Gas Turbines Power 133(2), 022501 (Oct 26, 2010) (8 pages) doi:10.1115/1.4001980 History: Received March 19, 2010; Revised March 29, 2010; Published October 26, 2010; Online October 26, 2010

As is well known, zero and one nodal diameter (k=0 and k=1) modes of a blade system interact with the shaft system. The former couples with torsional and/or axial shaft vibrations, and the latter with bending shaft vibrations. This paper addresses the latter. With respect to k=1 modes, we discuss, from experimental and theoretical viewpoints, in-plane blades and out-of-plane blades attached radially to a rotating shaft. We found that when we excited the shaft at the rotational speed of Ω=|ωbωs| (where ωb is the blade natural frequency, ωs the shaft natural frequency, and Ω is the rotational speed), the exciting frequency ν=ωs induced shaft-blade coupling resonance. In addition, in the case of the in-plane blade system, we encountered an additional resonance attributed to deformation caused by gravity. In the case of the out-of-plane blade system, we experienced two types of abnormal vibrations. One is the additional resonance generated at Ω=ωb/2 due to the unbalanced shaft and the anisotropy of bearing stiffness. The other is a flow-induced, self-excited vibration caused by galloping due to the cross-sectional shape of the blade tip because this instability disappeared in the rotation test inside a vacuum chamber. The two types of abnormal vibrations occurred at the same time, and both led to the entrainment phenomenon, as identified by our own frequency analysis technique.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Phenomenon of the blade-shaft coupled resonance

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Figure 2

Test rigs having in-plane or out-of-plane blades

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Figure 3

In-plane mode of nodal diameter k=1

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Figure 4

Out-of-plane mode of nodal diameter k=1

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Figure 5

Campbell diagram of in-plane blade vibration (ωb0=21.5 Hz, ωs=8 Hz)

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Figure 6

Waveforms of in-plane blade (Ω=35 rps)

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Figure 7

Resonance-curve of in-plane blade due to gravity excitation

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Figure 8

Campbell diagram of out-of-plane blade vibration (ωb0=21.5 Hz, ωs=18 Hz)

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Figure 9

3D plot of out-of-plane blade vibration

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Figure 10

Waveform and orbit of out-of-plane blade vibration (Ω=13.5)

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Figure 11

Resonance-curve of out-of-plane blade due to unbalance and anisotropy of bearing stiffness

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Figure 12

Configuration of rectangle tip mass of out-of-plane blade

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Figure 13

The rotor set in a vacuum chamber

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Figure 14

Campbell diagram of out-of-plane blade vibration in a vacuum chamber

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Figure 15

Our signal processing for Campbell diagram analysis

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Figure 16

Time history response of forced self-excited system

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Figure 17

Beats and entrainment

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Figure 18

3D amplitude plot of forced self-excited vibrations

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