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Research Papers

Nonlinear Time and Frequency Domain Methods for Multirow Aeromechanical Analysis

[+] Author and Article Information
M. T. Rahmati

e-mail: Mohammad.rahmati@eng.ox.ac.uk

L. He

Department of Engineering Science,
Oxford University,
Parks Road,
Oxford OX1 3PJ, UK

S. K. Krishnababu

Siemens Industrial Turbomachinery (SIT) Ltd.,
Lincoln LN5 7FD, UK

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received June 6, 2013; final manuscript received June 24, 2013; published online September 26, 2013. Editor: Ronald Bunker.

J. Turbomach 136(4), 041010 (Sep 26, 2013) (10 pages) Paper No: TURBO-13-1091; doi: 10.1115/1.4024899 History: Received June 06, 2013; Revised June 24, 2013

An unsteady Navier–Stokes solution system for aeromechanical analysis of multiple blade row configurations is presented. A distinctive feature of the solver is that unified numerical methods and boundary condition treatments are consistently used for both a nonlinear time-domain solution mode and a frequency-domain one. This not only enables a wider range of physical aeromechanical problems to be tackled, but also provides a consistent basis for validating different computational models, identifying and understanding their relative merits and adequate working ranges. An emphasis of the present work is on a highly efficient frequency-domain method for multirow aeromechanical analysis. With a new interface treatment, propagations and reflections of pressure waves between adjacent blade rows are modeled within a domain consisting of only a single passage in each blade row. The computational model and methods are firstly described. Then, extensive validations of the frequency-domain method against both experimental data and the nonlinear time-domain solutions are described. Finally, the computational analysis and demonstration of the intrarow reflection effects on the rotor aerodynamic damping are presented.

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References

Figures

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Fig. 1

Interface between a rotor domain and stator domain

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Fig. 2

Time trace constructed from the local harmonic and mean variables from an equivalent sliding plane interface

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Fig. 3

Time series containing blade vibration and blade passing disturbances

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Fig. 4

A beating period between vibration and blade passing disturbances

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Fig. 5

Nonbeating vibration and blade passing signals

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Fig. 15

The aerodynamic damping at reduced frequency of 0.4

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Fig. 14

Unsteady pressure phase angle at the reduced frequency of 0.4 and IBPA = 180 deg

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Fig. 13

Unsteady pressure coefficient at the reduced frequency of 0.4 and IBPA = 180 deg

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Fig. 12

Blade surface pressure coefficients (based on mean flow)

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Fig. 19

Local worksum distributions at suction side (“+” destabilizing, “–” stabilizing)

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Fig. 16

Computational mesh for DLR compressor stage

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Fig. 11

Computational mesh for the compressor linear cascade

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Fig. 10

Overall aerodynamic damping versus IBPA at the reduced frequency of 0.2

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Fig. 9

Unsteady pressure phase angle at reduced frequency of 0.2, IBPA = 180 deg

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Fig. 8

Unsteady pressure amplitude coefficients at reduced frequency of 0.2, IBPA = 180 deg

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Fig. 7

Surface pressure coefficients (based on mean flow)

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Fig. 6

Computational mesh for the turbine linear cascade

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Fig. 17

Amplitude of first harmonic unsteady pressure at midspan

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Fig. 18

Phase angle of first harmonic unsteady pressure at midspan

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Fig. 20

Local worksum distributions at pressure side (“+” destabilizing, “–” stabilizing)

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