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Research Papers

Casing Treatment and Blade-Tip Configuration Effects on Controlled Gas Turbine Blade Tip/Shroud Rubs at Engine Conditions

[+] Author and Article Information
Corso Padova

Gas Turbine Laboratory, The Ohio State University, Columbus, OH 43235padova.1@osu.edu

Michael G. Dunn, Jeffery Barton

Gas Turbine Laboratory, The Ohio State University, Columbus, OH 43235

Kevin Turner, Alan Turner, Darin DiTommaso

 GE Aviation, Cincinnati, OH 45215

J. Turbomach 133(1), 011016 (Sep 22, 2010) (12 pages) doi:10.1115/1.4000539 History: Received April 14, 2009; Revised July 29, 2009; Published September 22, 2010; Online September 22, 2010

Experimental results obtained for an Inconel® compressor blade rubbing bare-steel and treated casings at engine speed are described. Since 2002 a number of experiments were conducted to generate a broad database for tip rubs, the Rotor-Blade Rub database obtained using the unique experimental facility at the The Ohio State University Gas Turbine Laboratory. As of 2007, there are seven completed groups of measurements in the database. Among them a number of blade-tip geometries and casing surface treatments have been investigated. The purpose of this paper is to provide a detailed interpretation of this database. Load cell, strain, temperature, and accelerometer measurements are discussed and then applied to analyze the interactions resulting from progressive and sudden incursions of varying severity, defined by incursion depths ranging from 13μm to 762μm (from 0.0005 in. to 0.030 in.). The influence of blade-tip speed on these measurements is described. The results presented describe the dynamics of rotor and casing vibro-impact response at representative operational speeds similar to those experienced in flight. Force components at the blade tip in the axial and circumferential directions are presented for rub incursions ranging in depth from very light (13μm) to severe (406μm). Trends of variation are observed during metal-to-metal and metal-to-abradable contacts for two airfoil tip shapes and tip speeds 390 m/s (1280 ft/s) and 180 m/s (590 ft/s). The nonlinear nature of the rub phenomena reported in earlier work is confirmed. In progressing from light rubs to higher incursion, the maximum incurred circumferential load increases significantly while the maximum incurred axial load increases much less. The manner in which casing surface treatment affects the loads is presented. Concurrently, the stress magnification on the rubbing blade at root midchord, at tip leading edge, and at tip trailing edge is discussed. Computational models to analyze the nonlinear dynamic response of a rotating beam with periodic pulse loading at the free-end are currently under development and are noted.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Overview of the spin-pit facility

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Figure 3

Typical center load cell measurements

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Figure 4

Typical strain gauge measurements

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Figure 5

Typical tip temperature measurements

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Figure 6

Casing after rubs of group 1 (steel-on-steel) experiments (1 mil=0.001 in=25.4 μm)

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Figure 7

Coat-1 rubs, group 3

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Figure 8

Coat-1 rubs, group 2, 254 μm (0.010 in.) incursion

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Figure 9

Coat-2 rubs, group 6, 254 μm (0.010 in.) high-speed incursion

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Figure 10

Coat-2 rubs, group 6, 559 μm (0.022 in.) incursion

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Figure 11

Coat-2 rubs, group 7, 254 μm (0.010 in.) incursion

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Figure 12

Coat-2 rubs, group 7, 533 μm (0.021 in.) incursion

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Figure 13

Recorded loads, group 1

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Figure 14

Recorded loads, groups 1, 5, and 6

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Figure 15

Recorded loads, rub speed effect, groups 7 and 8

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Figure 16

Recorded loads, effect of incursion progression

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Figure 17

(a) Axial component of tip force on airfoil, group 1 and 2 conditions. Incursion: ε=140 μm (0.0055 in.). And (b) circumferential component of tip force on airfoil, group 1 and 2 conditions. Incursion: ε=140 μm (0.0055 in.).

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Figure 18

Percent magnification of midchord root stresses on airfoil at selected frequencies

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