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Study of Snubbing Mechanism Using Finite Element Method

[+] Author Affiliations
Jingming Chen, Dongxiang Jiang

Tsinghua University, Beijing, China

Paolo Pennacchi, Steven Chatterton

Politecnico di Milano, Milan, Italy

Paper No. DETC2014-35184, pp. V008T11A054; 7 pages
doi:10.1115/DETC2014-35184
From:
  • ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference
  • Volume 8: 26th Conference on Mechanical Vibration and Noise
  • Buffalo, New York, USA, August 17–20, 2014
  • Conference Sponsors: Design Engineering Division, Computers and Information in Engineering Division
  • ISBN: 978-0-7918-4641-4
  • Copyright © 2014 by ASME

abstract

In the rotating machineries, large vibrations of a blade would result in fatigue crack, which is a great threaten to the safety. Therefore, it is of great importance to reduce the blade vibrations. Snubbing technique is a possible solution to this problem. A tiny gap is left between the shrouds of adjacent blades. While the forced vibration makes the relative displacement between two neighboring blades exceed the gap, the contact happens at the contact face of the shrouds, accompanied with friction and energy dissipation, which restricts the vibration.

In this paper, a simplified model for a set of rotor blades is established, by using finite element method. The contact between the adjacent shrouds is considered. In this way, snubbing phenomenon can occur under forced vibration. Based on the model, modal analysis has been conducted. The 8x rev. frequency has been chosen as the excitation frequency. Under a certain amplitude of sine excitation, the circumferential vibration of the blades has been simulated. The vibration has been analyzed in the time domain. As expected, the blade motion is divided into four different states in one period. They are: non-contact, rebounding, sticky and escaping state. The four states had different mechanical and motion characteristics.

The motion pattern for the set of blades has been also analyzed and the wave spreading along the bladerow has been described. Because of the snubbing mechanism, the waveform was distorted into serrated shape.

Copyright © 2014 by ASME

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