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Analytical and Finite Element Modeling of Rubbing Phenomena in Rotors

Alvandi, Mahdi | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42381 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Behzad, Mahdi
  7. Abstract:
  8. Rotor contact with a stationary element of a rotating machine and the subsequent rubbing at the contact area is a serious malfunction that may lead to the machine’s catastrophic failure. In the past decades, many studies have been done on the rubbing phenomena, its different regimes and its various consequences on the machine performance and safety. However, most of them have used a simple model to investigate the rubbing interaction between the rotor and the stator. This simple model consists of the Jeffcott rotor, as a model for the real rotors, and a rigid annular block surrounding the rotor, as a model for the real stators. The objective of this thesis is to build an algorithm to investigate the rubbing contact between the rotor and any deformable stator with any arbitrary geometry. Toward this goal, the contact finite element approach is employed. This algorithm should be derived so that it can treat the dynamics of contact between the rotor, with rigid circular cross section, and a set of nodes, belonging to the deformable body of the stator. First, the two individual finite element models of the rotor and the stator are coupled via Lagrange multiplier method, and then the constrained equation of motion is numerically solved. Next, an analytical approach of partial rubbing, adopted from the literature, is extended in order to verify the proposed algorithm. The two results are presented in the form of orbits and then compared. Good agreement is seen under different conditions achieved by changing normalized parameters such as clearance, stator stiffness, friction coefficient, rotational speed and damping coefficient. Finally, the subsynchronous vibration due to partial rubbing is demonstrated. The algorithm of rotor-to-stator rubbing can more realistically model the stationary parts of turbomachinery
  9. Keywords:
  10. Wear ; Rotors ; Lagrange Coefficient ; Stator ; Contact Finite Element

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