1544. Synchronous and subsynchronous vibration under the combined effect of bearings and seals: numerical simulation and its experimental validation

Wanfu Zhang1, Jiangang Yang2, Chun Li3, Ren Dai4, Ailing Yang5

1, 3, 4, 5School of Energy and Power Engineering, University of Shanghai for Science and Technology,
Shanghai 200093, China

2National Engineering Research Center of Turbo-Generator Vibration, Southeast University,
Nanjing 210096, Jiangsu Province, China

1Corresponding author

E-mail: 1zwf5202006@163.com, 2jgyang@seu.edu.cn, 3lichunusst@163.com, 4dairen@usst.edu.cn, 5alyang@usst.edu.cn

(Received 20 October 2014; received in revised form 5 December 2014; accepted 3 February 2015)

Abstract. A three-dimensional computational fluid dynamics (CFD) model of a labyrinth seal was established in order to investigate the influence mechanism of combined effects between bearings and labyrinth seals on the dynamic characteristics of the rotor-bearing-seal system. The dynamic coefficients of the labyrinth seal for various rotating speeds were calculated. Results show that the absolute values of cross-coupled coefficients increase with the increasing rotating speed, while the absolute values of direct coefficients decrease slightly. The positive preswirl at the inlet tends to intensify the increase of cross-coupled coefficients and the decrease of direct coefficients. The negative preswirl shows the opposite effect. A finite element model was further setup. Results show that the labyrinth seal has a large influence on the synchronous response of rotor in the resonant region due to its damping effect. For other speeds, it has a minor effect. The labyrinth seal may promote the instability of the rotor-bearing-seal system. The subsynchronous vibration increases significantly when the seal force is taken into account. The system stability can be generally enhanced by introducing the negative preswirl at the inlet. Results also show that the detrimental influence of the labyrinth seal can be compensated by using suitable bearings. A proper bearing configuration can be designed to reduce the risks of rotordynamic instabilities due to seals. An experimental test was finally performed, and it shows good agreements with the numerical simulation.

Keywords: labyrinth seal, vibration, stability, CFD, rotor-bearing-seal system.

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Cite this article

Zhang Wanfu, Yang Jiangang, Li Chun, Dai Ren, Yang Ailing Synchronous and subsynchronous vibration under the combined effect of bearings and seals: numerical simulation and its experimental validation. Journal of Vibroengineering, Vol. 17, Issue 2, 2015, p. 662‑673.

 

© JVE International Ltd. Journal of Vibroengineering. Mar 2015, Volume 17, Issue 2. ISSN 1392-8716