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Research Papers

Influence of Multiphysical Effects on the Dynamics of the High Speed Mini Rotors—Part II: Results

[+] Author and Article Information
Emre Dikmen1

Department of Applied Mechanics, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlandse.dikmen@utwente.nl

Peter J. M. van der Hoogt, André de Boer

Department of Applied Mechanics, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

Ronald G. K. M. Aarts

Department of Mechanical Automation, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

1

Corresponding author.

J. Vib. Acoust 132(3), 031011 (May 04, 2010) (7 pages) doi:10.1115/1.4000788 History: Received May 04, 2009; Revised November 26, 2009; Published May 04, 2010; Online May 04, 2010

In Part I of this work, a theoretical analysis showed that the surrounding air in the closed confinement between rotor and casing has a significant effect on the dynamic behavior of high speed minirotors. In order to validate the developed theoretical model, an experimental setup is designed and the dynamic behavior of the rotor with medium gap confinement is studied. The experimental setup has flexible supports, which consist of beams with adjustable length. The support stiffness is changed by altering the beam length. Modal analysis of the rotor is done in free-free conditions in order to test the capability of the rotordynamic model without the supports and multiphysical effects. The experimental and simulation results agree well with a difference of 1%. Then modal analysis of the whole structure is done at standstill and during operation in the absence of the casing. In this way, multiphysical effects are eliminated and only support effects on the dynamics of the structure are observed. The supports appear to have significant effect on the natural frequencies of the flexural modes of the system. Different support modeling techniques are studied and adequate equivalent models are obtained. These models are then implemented into the structural model of the rotor. Finally, multiphysical effects are tested at different speeds with different support stiffnesses. Experiments are performed with and without the casing for determining the change in the natural frequencies and onset of instability. The surrounding fluid has a significant effect on the stability of the system while the natural frequencies do not change significantly. The experimental and theoretical results are in fair agreement for predicting the natural frequencies and the onset of instability.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 11

First support model

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Figure 12

Second support model

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Figure 13

ANSYS model of the support

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Figure 14

Modal analysis results with and without casing

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Figure 15

Spectrum maps—support beam length: 80 mm

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Figure 16

Spectrum measurements at different speeds

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Figure 17

Amplitude of velocity spectrum at different rotor speeds

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Figure 18

Theoretical prediction of the onset of instability—support beam length: 80 mm

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Figure 10

Modal analysis results with different beam lengths

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Figure 9

Experimental modal analysis of the complete system

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Figure 8

FRFs of the support with different beam lengths

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Figure 7

Modal analysis of the isolated support

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Figure 6

Frequency response function of the free rotor

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Figure 5

Modal analysis of the free rotor

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Figure 4

Measurement setup

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Figure 3

Flexible supports

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Figure 2

The dimensions of the rotor

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Figure 1

The complete experimental setup

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