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Research Papers: Gas Turbines: Structures and Dynamics

Exploration of NDE Properties of AMB Supported Rotors for Structural Damage Detection

[+] Author and Article Information
Jerzy T. Sawicki1

Center for Rotating Machinery Dynamics and Control (RoMaDyC), Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214j.sawicki@csuohio.edu

Dmitry L. Storozhev2

Center for Rotating Machinery Dynamics and Control (RoMaDyC), Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214

John D. Lekki

 NASA Glenn Research Center, 21000 Brookpark Road, Brookpark, OH 44135-3191john.d.lekki@nasa.gov

1

Corresponding author.

2

Currently at GE Energy; e-mail: dmitry.storozhev@ge.com

J. Eng. Gas Turbines Power 133(10), 102501 (Apr 25, 2011) (9 pages) doi:10.1115/1.4002908 History: Received May 16, 2010; Revised June 11, 2010; Published April 25, 2011; Online April 25, 2011

This paper addresses self-diagnostic properties of active magnetic bearing (AMB) supported rotors for online detection of the transverse crack on a rotating shaft. In addition to pure levitation, the rotor supporting bearing also serves as an actuator that transforms current signals additionally injected into the control loop into the superimposed specially selected excitation forces into the suspended rotor. These additional excitations induce combination frequencies in the rotor response, providing unique signatures for the presence of crack. The background of theoretical modeling, experimental, and computer simulation results for the AMB supported cracked rotor with self-diagnostic excitation forces are presented and discussed.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

(a) Photo of experimental test rig, (b) schematic with dimensions in [mm], (c) finite element model of the rotor

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Figure 2

Undamped critical speed map for AMB rotor system

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Figure 3

Magnified view of the shaft with EDM cut: (a) with no shim and (b) with an inserted shim

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Figure 4

Static deflection of the rotor due to its weight

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Figure 5

SIMULINK model of the rotor supported on conical AMBs

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Figure 6

Transfer function for single axis for the developed controller

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Figure 7

(a) Simulated and (b) experimental orbits of the uncracked rotor supported on conical AMBs at spin speed of ω=1560 rpm without (top row) and with (bottom row) force injection

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Figure 8

Measured total magnetic force in one axis of the nondrive bearing without and with excitation force

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Figure 9

Experimental time responses of the healthy and 40% cracked rotors running at 1560 rpm without ((a) and (b)) and with ((c) and (d)) external excitation force of 5 N at 18.6 Hz applied at W-axis of a nondrive end bearing

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Figure 10

Comparison between experimental frequency responses of the healthy (dotted line) and 25% cracked (solid line) rotors at spin speed of ω=26 Hz and excitation force of 5 N with various frequencies, measured at the nondrive end bearing

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Figure 11

Comparison between experimental frequency responses of the healthy (dotted line) and 40% cracked (solid line) rotors at spin speed of ω=26 Hz and excitation force of 5 N with various frequencies, measured at the nondrive end bearing

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Figure 12

Experimental frequency responses of the healthy (dotted line) and 40% cracked (solid line) rotors at spin speed of ω=26 Hz (a) without and (b) with excitation force of 5 N near the combinational frequency of 70.6 Hz

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Figure 13

Experimental frequency responses of the healthy (dotted line) and 40% cracked (solid line) rotors at spin speed of ω=26 Hz (a) without and (b) with excitation force of 5 N near the combinational frequency of 111.4 Hz

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Figure 14

Experimental responses of the healthy (dotted line) and 40% cracked (solid line) rotors at spin speed of ω=26 Hz with excitation force of 5 N at 50.1 Hz measured with accelerometer mounted on nondrive end bearing housing

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Figure 15

Comparison between simulated (dotted line) and experimental (solid line) frequency responses of the 40% cracked rotor at spin speed of ω=26 Hz and excitation force of 5 N with various frequencies measured at the nondrive end bearing

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