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Research Papers: Gas Turbines: Structures and Dynamics

Aeromechanical Modeling of Rotating Fan Blades to Investigate High-Cycle and Low-Cycle Fatigue Interaction

[+] Author and Article Information
Priyanka Dhopade

School of Engineering and
Information Technology,
University of New South Wales Canberra,
Canberra 2600, Australia
e-mail: priyanka.dhopade@eng.ox.ac.uk

Andrew J. Neely

School of Engineering and
Information Technology,
University of New South Wales Canberra,
Canberra 2600, Australia
e-mail: a.neely@adfa.edu.au

1Corresponding author.

2Present address: Osney Thermo-Fluids Laboratory, University of Oxford, Department of Engineering Science, Osney Mead, Oxford, OX2 0ES, UK.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 25, 2014; final manuscript received September 20, 2014; published online November 28, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(5), 052505 (May 01, 2015) (12 pages) Paper No: GTP-14-1439; doi: 10.1115/1.4028717 History: Received July 25, 2014; Revised September 20, 2014; Online November 28, 2014

Gas turbine engine components are subject to both low-cycle fatigue (LCF) and high-cycle fatigue (HCF) loads. To improve engine reliability, durability and maintenance, it is necessary to understand the interaction of LCF and HCF in these components, which can adversely affect the overall life of the engine while they are occurring simultaneously during a flight cycle. A fully coupled aeromechanical fluid–structure interaction (FSI) analysis in conjunction with a fracture mechanics analysis was numerically performed to predict the effect of representative fluctuating loads on the fatigue life of blisk fan blades. This was achieved by comparing an isolated rotor (IR) to a rotor in the presence of upstream inlet guide vanes (IGVs). A fracture mechanics analysis was used to combine the HCF loading spectrum with an LCF loading spectrum from a simplified engine flight cycle in order to determine the extent of the fatigue life reduction due to the interaction of the HCF and LCF loads occurring simultaneously. The results demonstrate the reduced fatigue life of the blades predicted by a combined loading of HCF and LCF cycles from a crack growth analysis, as compared to the effect of the individual cycles. In addition, the HCF aerodynamic forcing from the IGVs excited a higher natural frequency of vibration of the rotor blade, which was shown to have a detrimental effect on the fatigue life. The findings suggest that FSI, blade–row interaction and HCF/LCF interaction are important considerations when predicting blade life at the design stage of the engine. The lack of available experimental data to validate this problem emphasizes the utility of a numerical approach to first examine the physics of the problem and second to help establish the need for these complex experiments.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Schematic of simplified engine mission spectrum [1]

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Fig. 2

Schematic of aeromechanical simulation flow process

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Fig. 3

Flow chart for temporal scheme of coupled solvers Ansys and Cfx

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Fig. 4

IGV-rotor grid at midspan

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Fig. 5

Single edged crack under tension

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Fig. 6

Unsteady maximum pressure fluctuations on isolated rotor and IGV-rotor cases at the leading edge, 98.6% span

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Fig. 7

Frequency spectrum of unsteady pressure fluctuations at leading edge, 98.6%, span for IGV-rotor and IR cases

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Fig. 8

Mach number profiles upstream of rotor inlet showing progression of IGV wake passing and corresponding flow field of rotor at 98.6% span

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Fig. 9

Fluctuations in maximum displacement in the x, y, and z directions over five revolutions of rotor for case with upstream IGV (SR) and IR

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Fig. 10

Orientation of coordinate axes with respect to rotor blade

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Fig. 11

Frequency spectrum of maximum displacement fluctuations for upstream IGV and IR with peaks at natural frequencies

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Fig. 12

Fluctuations in maximum stress in the x, y, and z directions over five revolutions of rotor for case with upstream IGV (SR) and IR

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Fig. 13

Frequency spectrum of stress fluctuations for upstream IGV and IR with peaks at natural frequencies

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Fig. 14

Crack growth curves for the narrow chord blade with upstream IGVs

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Fig. 15

Crack growth curves for the combined HCF/LCF case for narrow chord blade with upstream IGVs and IR for a single edge crack geometry

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Fig. 16

Relationship between Mach number and dynamic pressure at flutter conditions

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