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Research Papers: Gas Turbines: Structures and Dynamics

Fault Analysis and Optimal Balancing of Bowing of Steam Turbine Rotor Under Long-Term Service

[+] Author and Article Information
Jingming Chen

State Key Laboratory of Control and Simulation
of Power System and Generation Equipments,
Department of Thermal Engineering,
Tsinghua University,
Beijing 100084, China
e-mail: cjm10@mails.tsinghua.edu.cn

Dongxiang Jiang

State Key Laboratory of Control and Simulation
of Power System and Generation Equipments,
Department of Thermal Engineering,
Tsinghua University, Beijing 100084, China
e-mail: jiangdx@tshinghua.edu.cn

Chao Liu

Department of Mechanical Engineering,
Tsinghua University,
Beijing 100084, China
e-mail: chaoliu13@tsinghua.edu.cn

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 2, 2015; final manuscript received March 16, 2015; published online May 12, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(11), 112503 (Nov 01, 2015) (10 pages) Paper No: GTP-15-1034; doi: 10.1115/1.4030279 History: Received February 02, 2015; Revised March 16, 2015; Online May 12, 2015

In recent years, bowing of steam turbine rotor under long time service occurs in several high-parameter units. Collected data show that the bending of the haywire rotor is increasing continuously, which results in excessive vibration in operation and even causes over-limit vibration during start-up. In order to suppress the vibration, balancing is utilized in field with the traditional approach that the balancing mass is placed in the section of the rotor close to the bearing. However, the balancing with the traditional approach could only reduce the vibration temporarily. In the long time scale, the bowing is still propagating or even gets worse after the balancing. To determine the cause of bowing and form optimal balancing approach, analysis is carried out in this work including: (i) fault cause and its treatment of bowing of steam turbine rotor under long time service is studied with elastic–plastic mechanics and creep mechanism taken in account; (ii) a case study was carried out, where the bowing process was simulated and validated with the field monitoring data; (iii) the phenomenon of the traditional balancing method was illustrated with rotordynamics analysis, where the influence of whirling is included. Based on the analysis, the cause of bowing is determined as uneven creep effect. And the balancing method would influence the whirling mode, which would worsen bowing in the traditional balancing method. Based on this conclusion, an optimized balancing method was developed to reduce the vibration and prevent bowing propagation simultaneously.

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References

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Figures

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Fig. 1

Peak–peak vibration value under working condition in one haywire unit

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Fig. 2

Peak–peak vibration value while passing critical rotating speed in a haywire unit

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Fig. 3

Steps of the deformation of bowing

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Fig. 4

Coordinates in the cross section

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Fig. 5

Temperature distribution of the bowing rotor

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Fig. 6

Von Mises equivalent stress distribution of the bowing rotor

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Fig. 7

Creep strain rate distribution of the bowing rotor

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Fig. 8

The axial deviator stress distribution

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Fig. 9

Dimensionless creep rate in the concave side and convex side

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Fig. 10

Diffuse function of creep strain in the cross section of effective zone, ϕξ=0

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Fig. 11

Schematic diagram of the shearing force and angular moment

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Fig. 12

Schematic diagram of the variation of the bending moment amplitude and the phase at ith node

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Fig. 13

Flow chart of bowing simulation

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Fig. 14

The three-dimensional model of the HP–IP rotor

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Fig. 15

Propagation of the maximum bending amount and phase

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Fig. 16

Deflection distribution in the axial direction

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Fig. 17

Schematic diagram of balancing plane in the HP–IP rotor

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