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Research Papers

An Efficient Iterative Approach for the Analysis of Thermal Instabilities in Rotating Machines

[+] Author and Article Information
A. Rindi

Professor
Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: andrea.rindi@unifi.it

L. Baldassarre

General Electric Oil & Gas,
Florence 50127, Italy
e-mail: Leonardo.Baldassare@ge.com

D. Panara

General Electric Oil & Gas,
Florence 50127, Italy
e-mail: daniele.panara@ge.com

E. Meli

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: enrico.meli@unifi.it

A. Ridolfi

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: alessandro.ridolfi@unifi.it

A. Frilli

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: amedeo.frilli@unifi.it

D. Nocciolini

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: daniele.nocciolini@unifi.it

S. Panconi

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: simone.panconi@unifi.it

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received November 2, 2016; final manuscript received June 8, 2017; published online August 17, 2017. Assoc. Editor: Patrick S. Keogh.

J. Vib. Acoust 139(6), 061019 (Aug 17, 2017) (15 pages) Paper No: VIB-16-1526; doi: 10.1115/1.4037143 History: Received November 02, 2016; Revised June 08, 2017

Most of the technological developments achieved in the turbomachinery field during the last years have been obtained through the introduction of fluid dynamic bearings, in particular tilting pad journal bearings (TPJBs). However, even those bearings can be affected by thermal instability phenomena as the Morton effect at high peripheral speeds. In this work, the authors propose a new iterative finite element method (FEM) approach for the analysis of those thermal–structural phenomena: the proposed model, based on the coupling between the rotor dynamic and the thermal behavior of the system, is able to accurately reproduce the onset of thermal instabilities. The authors developed two versions of the model, one in the frequency domain and the other in the time domain; both models are able to assure a good tradeoff between numerical efficiency and accuracy. The computational efficiency is critical when dealing with the typical long times of thermal instability. The research activity has been carried out in cooperation with General Electric Nuovo Pignone SPA, which provided both the technical and experimental data needed for the model development and validation.

Copyright © 2017 by ASME
Topics: Bearings , Rotors
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References

Figures

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Fig. 1

Tilting pad journal bearing [1]

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Fig. 2

General architecture of the steady model

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Fig. 3

General architecture of the unsteady model

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Fig. 4

SOLID and BEAM rotor models

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Fig. 6

Examples of divergent and convergent loops for a given ω

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Fig. 7

Example of a temperature profile on the outer surface of the rotor in correspondence to the bearing

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Fig. 8

Example of a solution of the steady-state thermal analysis (NDE rotor fraction)

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Fig. 10

Boundary conditions

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Fig. 9

Example of rotor orbit obtained through the unsteady model

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Fig. 11

Simplified scheme of the experimental test rig

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Fig. 13

Details of the acquisition system for the rotor temperature measurement

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Fig. 14

Test procedure to capture the onset of thermal instabilities

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Fig. 15

Filtered and unfiltered experimental unbalance responses along the vertical direction, pk − pk, for the W3 configuration at the bearings midspan

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Fig. 16

Unbalance response along the vertical direction, pk − pk, for the W3 configuration obtained through the BEAM model at the bearings midspan (unbalance force applied at the bearings midspan)

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Fig. 17

Comparison between the experimental and numerical (BEAM model) vibration phase for the W3 configuration at the bearing midspan

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Fig. 18

Comparison between the orbits obtained through the steady and the unsteady BEAM models at NDE bearing location

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Fig. 19

Unbalance responses for all the considered configurations obtained through the BEAM model at NDE bearing (unbalance force applied at the overhung to excite the rotor second critical speed)

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Fig. 20

Filtered and unfiltered experimental displacements along the vertical direction for the W3 configuration at NDE bearing

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Fig. 21

Experimental rotor temperature compared with the values obtained through the proposed model scaled with respect to Tref (W3 configuration, 13,600 rpm)

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Fig. 22

Numerical results for the W3 configuration: comparison between the steady and unsteady model. (a) Rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W3 configuration, steady BEAM model, (b) rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W3 configuration, steady SOLID model, (c) rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W3 configuration, unsteady BEAM model, and (d) rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W3 configuration, unsteady SOLID model.

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Fig. 23

Filtered and unfiltered experimental displacements along the vertical direction for the W2 configuration at NDE bearing

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Fig. 24

Experimental rotor temperature compared with the values obtained through the proposed model scaled with respect to Tref (W2 configuration, 11,400 rpm)

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Fig. 25

Numerical results for the W2 configuration: BEAM models. (a) Rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W2 configuration, steady BEAM model and (b) rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W2 configuration, unsteady BEAM model.

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Fig. 26

Filtered and unfiltered experimental displacements along the vertical direction for the W1 configuration at NDE bearing

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Fig. 27

Experimental rotor temperature compared with the values obtained through the proposed model scaled with respect to Tref (W1 configuration, 13,400 rpm)

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Fig. 28

Numerical results for the W1 configuration: BEAM models. (a) Rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W1 configuration, steady BEAM model and (b) rotor vibration amplitude along the major axis of the orbit at NDE bearing for the W1 configuration, unsteady BEAM model.

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Fig. 29

Response amplitude as a function of the rotor speed for the three considered cases and their instability onsets

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Fig. 30

Shaft differential temperature inside bearing scaled with respect to Tref for the three considered configurations

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