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TECHNICAL PAPERS: Gas Turbines: Structures and Dynamics

Reduced-Order Modeling and Wavelet Analysis of Turbofan Engine Structural Response due to Foreign Object Damage (FOD) Events

[+] Author and Article Information
James A. Turso1

 QSS Group, Inc., 21000 Brookpark Road, Cleveland, OH 44135

Charles Lawrence

 NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135

Jonathan S. Litt

U.S. Army Research Laboratory, Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135

1

Current affiliation: Northrop Grumman Ship Systems, Advanced Capabilities Group, 6608 Sunscope Drive, Ocean Springs, MS 39564.

J. Eng. Gas Turbines Power 129(3), 814-826 (Nov 17, 2006) (13 pages) doi:10.1115/1.2718230 History: Received May 21, 2004; Revised November 17, 2006

The development of a wavelet-based feature extraction technique specifically targeting FOD-event induced vibration signal changes in gas turbine engines is described. The technique performs wavelet analysis of accelerometer signals from specified locations on the engine and is shown to be robust in the presence of significant process and sensor noise. It is envisioned that the technique will be combined with Kalman filter thermal/health parameter estimation for FOD-event detection via information fusion from these (and perhaps other) sources. Due to the lack of high-frequency FOD-event test data in the open literature, a reduced-order turbofan structural model (ROM) was synthesized from a finite-element model modal analysis to support the investigation. In addition to providing test data for algorithm development, the ROM is used to determine the optimal sensor location for FOD-event detection. In the presence of significant noise, precise location of the FOD event in time was obtained using the developed wavelet-based feature.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 2

Example FOD-event FEM model vibration response characteristics. Calculated displacements are functions of the imbalance magnitude and foreign object impact characteristics (e.g., relative speed, size, etc.).

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Figure 8

Bearing 40 accelerometer output signal corresponding to a FOD event. (a) Noise free system response. (b) System response with process and sensor noise.

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Figure 14

Wavelet transform-based vibration feature extraction implemented using an analysis and synthesis FIR filter bank

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Figure 15

Wavelet feature extracted from noisy bearing accelerometer signal at location 40. (a) Accelerometer signal. (b) Corresponding conditioned Daubechies 8 wavelet inverse transform, scale 8 approximation.

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Figure 1

DYROBES FEM schematic of turbofan rotor-bearing system

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Figure 6

Response at bearing/support location 37 to (a) a “large” FOD event (mFO=2lbm, (0.9 kg)) and (b) a “small” FOD event (mFO=0.25lbm (0.11 kg))

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Figure 7

Response at bearing/support location 39 to (a) a “large” FOD event (mFO=2lbm (0.9 kg)) and (b) a “small” FOD event (mFO=0.25lbm (0.11 kg))

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Figure 9

Power spectra of bearing 40 accelerometer output signal corresponding to a FOD event. (a) Noise free system response. (b) System response with process and sensor noise.

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Figure 10

Example bearing vibration signature and corresponding wavelet decomposition accompanying a FOD event

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Figure 11

Example of a two-scale DTWT-based signal analysis and synthesis using a FIR quadrature mirror filter bank

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Figure 12

Wavelet analysis of noise-free bearing accelerometer signal at location 40. (a) Accelerometer signal. (b) Corresponding Daubechies 8 wavelet inverse transform, scale 8 approximation.

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Figure 13

Wavelet analysis of noisy bearing accelerometer signal at location 40. (a) Accelerometer signal. (b) Corresponding Daubechies 8 wavelet inverse transform, scale 8 approximation.

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Figure 3

Coordinate system used in the FEM and reduced order state space structural models. Cyclic imbalance forces are perpendicular to the Z axis. Impulse moments due to a FOD event are about the X axis.

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Figure 4

MATLAB /SIMULINK implementation of the reduced-order turbofan rotor/bearing system structural model

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Figure 5

Steady state imbalance response comparison of 4, 10, and 25 degree of freedom (DOF) reduced-order models for two different bearing/support locations. Imbalance has an eccentricity of 0.001in. (0.0025 cm) located at the fan.

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