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Research Papers

Numerical Investigation of Abradable Coating Removal in Aircraft Engines Through Plastic Constitutive Law

[+] Author and Article Information
M. Legrand

 Structural Dynamics and Vibration Laboratory, Department of Mechanical Engineering, McGill University, 817 Sherbrooke St West, Montréal, Québec H3A 2K6, Canadamathias.legrand@mcgill.ca

A. Batailly

 Structural Dynamics and Vibration Laboratory, Department of Mechanical Engineering, McGill University, 817 Sherbrooke St West, Montréal, Québec H3A 2K6, Canadaalain.batailly@mcgill.ca

C. Pierre

 Structural Dynamics and Vibration Laboratory, Department of Mechanical Engineering, McGill University, 817 Sherbrooke St West, Montréal, Québec H3A 2K6, Canadachristophe.pierre@mcgill.ca

These conditions written in a vector form have to be read coordinate by coordinate for each interface DoF where contact is treated.

J. Comput. Nonlinear Dynam 7(1), 011010 (Sep 26, 2011) (11 pages) doi:10.1115/1.4004951 History: Received March 01, 2011; Revised August 04, 2011; Published September 26, 2011; Online September 26, 2011

In the field of turbomachines, better engine performances are achieved by reducing possible parasitic leakage flows through the closure of the clearance distance between blade tips and surrounding stationary casings and direct structural contact is now considered as part of the normal life of aircraft engines. In order to avoid catastrophic scenarios due to direct tip incursions into a bare metal housing, implementation of abradable coatings has been widely recognized as a robust solution offering several advantages: reducing potential nonrepairable damage to the incurring blade as well as adjusting operating clearances, in situ, to accept physical contact events. Nevertheless, the knowledge on the process of material removal affecting abradable coatings is very limited and it seems urgent to develop dedicated predicting numerical tools. The present work introduces a macroscopic model of the material removal through a piecewise linear plastic constitutive law which allows for real time access to the current abradable liner profile within a time-stepping approach of the explicit family. In order to reduce computational loads, the original finite element formulation of the blade of interest is projected onto a reduced-order basis embedding centrifugal stiffening. First results prove convergence in time and space and show that the frequency content of the blade response is clearly sensitive to the presence of abradable material. The continuous opening of the clearance between the blade tip and the casing due to the material removal yields larger amplitudes of motion and new scenarios of structural divergence far from the usual linear conditions provided by the well-known Campbell diagrams.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Low pressure compressor. Courtesy of CFM International.

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Figure 2

Blade under investigation with eight anticipated boundary nodes undergoing contact constraints and abradable removal conditions

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Figure 3

Campbell diagrams with centrifugal stiffening: reduced-order model (- -) and full finite element model with no parametrization of the stiffness matrix (—)

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Figure 4

Blade interface node and associated geometrical profile

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Figure 5

Plasticity constitutive laws controlling the ductility of the abradable coating

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Figure 6

Casing distortion in the radial direction

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Figure 7

Final abradable profiles for two densities after twenty rounds of the blade

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Figure 8

Radial displacement of interface node 1

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Figure 9

First natural modes of the blade

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Figure 10

Blade response spectrum

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Figure 11

Maps of the final abradable profiles with respect to Ω for interface node 1 after twenty rounds of the blade

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Figure 12

Final abradable profiles for E=1 (—) and E=10 (- -) at respective critical rotational frequency for k=4 after twenty rounds

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Figure 13

Coordinates (‖Y‖,Ωc) versus E and K

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Figure 14

Abradable coating wear patterns

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Figure 15

Blade spectrum with tangential efforts for E=10 and K=4.55

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Figure 16

Spectrograms of the blade response

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