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Research Papers

Nonlinear Flutter in Fan Stator Vanes With Time Dependent Fixity

[+] Author and Article Information
R. Srivastava

 Honeywell Aerospace, Phoenix, AZ 85034rakesh.srivastava@honeywell.com

J. Panovsky

 Honeywell Aerospace, Phoenix, AZ 85034josef.panovsky@honeywell.com

R. Kielb

Department of Mechanical Engineering and Material Science, Duke University, Durham, NC 27708rkielb@duke.edu

L. Virgin

Department of Mechanical Engineering and Material Science, Duke University, Durham, NC 27708lvirgin@duke.edu

K. Ekici

Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, TN 37996ekici@utk.edu

J. Turbomach. 134(2), 021009 (Jun 23, 2011) (8 pages) doi:10.1115/1.4003253 History: Received September 24, 2010; Revised October 29, 2010; Published June 23, 2011; Online June 23, 2011

A new mechanism for fan stator vane failure in turbofan engines at high speed and high loading has been identified and reported in this paper. Highly destructive vane failures have been encountered at Honeywell in a development fan with composite stator vanes. Measured data indicated nonlinear high amplitude vibratory response in fan stator vanes on the stall side of the fan map at high speeds. Analysis showed that under certain steady loading, vane fixity at the hub could change, significantly reducing the vane natural frequency. At this lower natural frequency, the vane was found to be aeroelastically unstable, and calculated response exhibited characteristics similar to those observed during failure. An engine test conducted to validate the role of hub fixity in vane failures showed the failure to be a self-excited phenomenon and not driven by an external source of excitation. It was also shown that failures occur in vanes that are not rigidly fixed, validating the role of hub fixity in vane failures. Test results along with analysis confirm the role of time dependent hub fixity leading to the highly destructive flutter responsible for vane failures.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Measured instability boundary

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Figure 2

Catastrophic damage of stator vanes

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Figure 3

Distribution of damaged stator vanes

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Figure 4

Measured strain during a vane failure event

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Figure 5

Nonlinear single degree of freedom model: (a) vane-grommet hub fixity model and (b) bilinear hub fixity stiffness

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Figure 6

Aerodynamic damping variation with frequency for the composite vane

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Figure 7

Calculated vane response characteristics

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Figure 8

Waterfall of calculated vane response

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Figure 9

Schematic of nonlinear flutter with time dependent hub fixity

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Figure 10

Vane fixity at the hub for the second configuration

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Figure 11

Installed instrumentation

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Figure 12

Tested operating points on the fan map

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Figure 13

Measured strain response on four vanes

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Figure 14

Tested operating points on the fan map in the second configuration

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Figure 15

Measured strain response of four vanes in the second configuration

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Figure 16

Damaged vanes in the second configuration: (a) vane assembly after the second configuration test and (b) schematic of the damaged vane assembly

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Figure 17

Waterfall of Vane 32 response

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Figure 18

Time history of Vane 32 response for 52.2% open VEN

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