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Research Papers

Measurement and Evaluation of Shaft Torsional Vibrations Using Shaft Instantaneous Angular Velocity

[+] Author and Article Information
Jindrich Liska

NTIS—European Centre of Excellence,
University of West Bohemia,
Pilsen 30100, Czechia
e-mail: jinliska@ntis.zcu.cz

Jan Jakl

NTIS—European Centre of Excellence,
University of West Bohemia,
Pilsen 30100, Czechia
e-mail: jjakl@ntis.zcu.cz

Sven Kunkel

NTIS—European Centre of Excellence,
University of West Bohemia,
Pilsen 30100, Czechia
e-mail: kunkel@ntis.zcu.cz

Manuscript received June 26, 2018; final manuscript received July 9, 2018; published online December 7, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(4), 041029 (Dec 07, 2018) (5 pages) Paper No: GTP-18-1357; doi: 10.1115/1.4041006 History: Received June 26, 2018; Revised July 09, 2018

Online evaluation of possible failures of a turbine is a key factor for a successful long-term turbine operation. Fluctuations of generator air-gap torque, caused for example by nonstationary conditions of electrical power grid, influence shaft torsional vibrations as well as rotating blades vibrations. Symptoms of shaft torsional vibrations are not measurable by normally used relative shaft vibrations sensors, so special measurement must be used. The direct consequence of shaft torsional vibrations is local acceleration or deceleration of shaft circumference when it is measured by a stationary sensor. This paper deals with a measurement method using an optical probe measuring the passage of black and white stripes of a zebra tape, which is stuck on the rotor. The shaft torsional vibrations manifest themselves as a phase modulation of the optical probe output signal, so the sampling rate influence the achievable resolution of the calculated shaft vibrations. The presented method for the calculation of the shaft torsional vibrations is based on the evaluation of shaft instantaneous angular velocity. The advantage of this method is a direct compensation of possible nonregular geometry of the zebra tape. The analysis of shaft torsional vibrations evaluation using this method is supplemented by two case studies from the authors' current work.

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Copyright © 2019 by ASME
Topics: Vibration , Signals
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References

Walker, D. N. , and Giesecke, H. , 2005, “ Steam Turbine-Generator Torsional Vibration Interaction With the Electrical Network: Tutorial,” Electric Power Research Institute, Paolo Alto, CA, Product ID. 1011679.
Walker, D. N. , Adams, S. L. , and Placek, R. J. , 1981, “ Torsional Vibration and Fatigue of Turbine-Generator Shafts,” IEEE Trans. Power Appar. Syst., 100(11), pp. 4373–4380. [CrossRef]
Walker, D. N. , Bowler, C. E. J. , Jackson, R. L. , and Hodges, D. A. , 1975, “ Results of Subsynchronous Resonance Test at Mohave,” IEEE Trans. Power Appar. Syst., 94(5), pp. 1878–1889. [CrossRef]
Halliwell, N. A. , 1996, “ The Laser Torsional Vibrometer: A Step Forward in Rotating Machinery Diagnostics,” J. Sound Vib., 190(3), pp. 399–418. [CrossRef]
Huster, J. , Eckert, L. , and Pohle, F. , 1999, “ Calculation and Measurement of Torsional Vibrations in Large Steam Turbosets—New Technique,” Noise and Vib. Worldwide, 30(3), pp. 5–11.
Walker, D. , 2003, Torsional Vibration of Turbomachinery, McGraw-Hill Professional, New York, pp. 125–130.
Resor, B. R. , Trethewey, M. W. , and Maynard, K. P. , 2005, “ Compensation for Encoder Geometry and Shaft Speed Variation in Time Interval Torsional Vibration Measurement,” J. Sound Vib., 286(4–5), pp. 897–920. [CrossRef]
Diamond, D. H. , Heyns, P. S. , and Oberholster, A. J. , 2016, “ Online Shaft Encoder Geometry Compensation for Arbitrary Shaft Speed Profiles Using Bayesian Regression,” Mech. Syst. Signal Process., 81, pp. 402–418. [CrossRef]

Figures

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Fig. 1

Simulated zebra tapes: ideal (top), missing segment (middle) and nonequidistant stripes (bottom)

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Fig. 2

Angular intervals between zebra-tape stripes in the three simulated cases

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Fig. 3

Detection times—simulated data

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Fig. 4

The evaluated angular velocity signals

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Fig. 5

Zebra tape attached to the shaft circumference and the optical probe bracket

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Fig. 6

Detection times—measured data

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Fig. 7

Detection times—detail of Fig. 6

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Fig. 8

Instantaneous angular velocity during grid transient at the nuclear power plant

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Fig. 9

Spectrogram of the instantaneous angular velocity signal at the nuclear power plant

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Fig. 10

Instantaneous angular velocity during grid transient at the coal-fired power plant

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Fig. 11

Spectrogram of the instantaneous angular velocity signal at the coal-fired power plant

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