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Research Papers

Self-Excited Blade Vibration Experimentally Investigated in Transonic Compressors: Rotating Instabilities and Flutter

[+] Author and Article Information
F. Holzinger

Institute of Gas Turbines and
Aerospace Propulsion,
Technische Universität Darmstadt,
Darmstadt 64295, Germany
e-mail: holzinger@glr.tu-darmstadt.de

F. Wartzek

Institute of Gas Turbines and
Aerospace Propulsion,
Technische Universität Darmstadt,
Darmstadt 64295 Germany

M. Jüngst, H.-P. Schiffer

Institute of Gas Turbines and
Aerospace Propulsion,
Technische Universität Darmstadt,
Darmstadt 64295, Germany

S. Leichtfuss

Turbo Science,
Darmstadt 64295, Germany

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 15, 2015; final manuscript received November 26, 2015; published online January 5, 2016. Assoc. Editor: Rakesh Srivastava.

J. Turbomach 138(4), 041006 (Jan 05, 2016) (9 pages) Paper No: TURBO-15-1148; doi: 10.1115/1.4032163 History: Received July 15, 2015; Revised November 26, 2015

This paper investigates the vibrations that occurred on the blisk rotor of a 1.5-stage transonic research compressor designed for aerodynamic performance validation and tested in various configurations at Technische Universität Darmstadt. During the experimental test campaign, self-excited blade vibrations were found near the aerodynamic stability limit of the compressor. The vibration was identified as flutter of the first torsion mode and occurred at design speed as well as in the part-speed region. Numerical investigations of the flutter event at design speed confirmed negative aerodynamic damping for the first torsion mode, but showed a strong dependency of aerodynamic damping on blade tip clearance (BTC). In order to experimentally validate the relation between BTC and aerodynamic damping, the compressor tests were repeated with enlarged BTC for which stability of the torsion mode was predicted. During this second experimental campaign, strong vibrations of a different mode limited compressor operation. An investigation of this second type of vibration found rotating instabilities to be the source of the vibration. The rotating instabilities first occur as an aerodynamic phenomenon and then develop into self-excited vibration of critical amplitude. In a third experimental campaign, the same compressor was tested with reference BTC and a nonaxisymmetric casing treatment (NASCT). Performance evaluation of this configuration repeatedly showed a significant gain in operating range and pressure ratio. The gain in operating range means that the casing treatment successfully suppresses the previously encountered flutter onset. The aeroelastic potential of the NASCT is validated by means of the unsteady compressor data. By giving a description of all of the above configurations and the corresponding vibratory behavior, this paper contains a comprehensive summary of the different types of blade vibration encountered with a single transonic compressor rotor. By investigating the mechanisms behind the vibrations, this paper contributes to the understanding of flow-induced blade vibration. It also gives evidence to the dominant role of the tip clearance vortex in the fluid–structure-interaction of tip critical transonic compressors. The aeroelastic evaluation of the NASCT is beneficial for the design of next generation casing treatments for vibration control.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Blade vibration: flutter (M1)

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Fig. 2

Flow-induced vibration (from Ref. [3])

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Fig. 3

Transonic compressor at TU Darmstadt

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Fig. 4

Unsteady instrumentation with schematic rotor (from Ref. [13])

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Fig. 5

Flutter (M2) and rotating stall at design speed, identical operating point

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Fig. 6

Transonic compressor stage with LC (schematic illustration)

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Fig. 7

Investigated compressor speed lines and limiting phenomena (schematic NASCT extension)

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Fig. 8

LC: rotating instability

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Fig. 9

Comparison of structural behavior between LC and RC at last stable operating point LC

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Fig. 10

Comparison of aerodynamic behavior between LC and RC at last stable operating point LC (schematic illustration of rotor blades)

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Fig. 11

Transonic compressor stage with RC, Ref. [17]

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Fig. 12

RC: rotating stall

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Fig. 14

Transonic compressor stage with NASCT (schematic illustration)

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Fig. 15

Comparison of structural behavior between RC and NASCT at last stable operating point RC

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Fig. 16

Comparison of aerodynamic behavior between RC and NASCT at last stable operating point RC (schematic illustration of rotor blades)

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Fig. 17

NASCT: flutter (M1)

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