Thermal-Mechanical Life Prediction System for Anisotropic Turbine Components

[+] Author and Article Information
F. J. Cunha

Pratt & Whitney, United Technologies Corporation, East Hartford, CT 06108frank.cunha@pw.utc.com

M. T. Dahmer

Pratt & Whitney, United Technologies Corporation, East Hartford, CT 06108

M. K. Chyu

Department of Mechanical Engineering, University of Pittsburgh, Pittsburgh, PAmkchyu@engr.pitt.edu

J. Turbomach 128(2), 240-250 (Feb 01, 2005) (11 pages) doi:10.1115/1.2137740 History: Received October 01, 2004; Revised February 01, 2005

Modern gas turbine engines provide large amounts of thrust and withstand severe thermal-mechanical conditions during the load and mission operations characterized by cyclic transients and long dwell times. All these operational factors can be detrimental to the service life of turbine components and need careful consideration. Engine components subject to the harshest environments are turbine high-pressure vanes and rotating blades. Therefore, it is necessary to develop a turbine component three-dimensional life prediction system, which accounts for mission transients, anisotropic material properties, and multi-axial, thermal-mechanical, strain, and stress fields. This paper presents a complete life prediction approach for either commercial missions or more complex military missions, which includes evaluation of component transient metal temperatures, resolved maximum shear stresses and strains, and subsequent component life capability for fatigue and creep damage. The procedure is based on considering all of the time steps in the mission profile by developing a series of extreme points that envelop every point in the mission. Creep damage is factored into the component capability by debiting thermal-mechanical accumulated cycles using the traditional Miner’s rule for accumulated fatigue and creep damage. Application of this methodology is illustrated to the design of the NASA Energy Efficient Engine (E3) high pressure turbine blade with operational load shakedown leading to stress relaxation on the external hot surfaces and potential state of overstress in the inner cold rib regions of the airfoil.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

HPT blade solid model and finite element mesh

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Figure 2

Different mission cycles for commercial and military engines

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Figure 3

Overall peanut curve for strain versus temperature for a point in the blade

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Figure 4

Typical fatigue data curve

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Figure 5

Typical creep curves

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Figure 6

NASA E3 HPT blade thermal results

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Figure 7

NASA E3 HPT blade thermal-mechanical results in terms of equivalent strains

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Figure 8

Performance parameters for a typical commercial aircraft engine mission

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Figure 9

Core flow for a typical commercial aircraft engine mission

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Figure 10

NASA E3 HPT blade strain vs temperature “peanut” curve

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Figure 11

Structural transient response showing von Mises stress profile for two airfoil points: (1) External suction side point experiencing high temperatures and (2) rib point experiencing relative cold temperatures

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Figure 12

Structural transient response at (a) initial time, and (b) at 50h of hot time illustrating stress relaxation on the external points of the airfoil, and overstress on the cold rib regions of the airfoil



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