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Investigating Nonlinear Vibration of a Turbine-Shaft in the Start-up Process Using Timoshenko Beam Theory

Arefikhah, Mohammad Reza | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54090 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Dehghani Firouzabadi, Rohollah
  7. Abstract:
  8. In this study, the nonlinear vibrations of an elastic rotor that is under the elastic support and under the follower force caused by the airflow passing through the rotating plane are investigated. The elastic shaft is modeled by the Timoshenko beam theory, which is connected to a motor through a flexible coupling and the motor increases the rotational speed of the rotor by applying torque. Gibbons’ equations have been used to model the misalignment forces. First, the kinetic energy of the rotating system is calculated nonlinearly to take into account the effect of nonlinear terms due to the rotational inertia of the system, and then the potential energy and The work of external forces on the rotor are calculated. Thereafter, the spatial and temporal variables in the energy relations are separated by the Riley-Ritz method and then the equations of motion are obtained using the Lagrange method. Through accurate investigations and analyzes that performed in the validation section, it has been shown that the obtained formulas as rotor's equations of motion give correct results and it is also well shown that the higher inertia of the rotating system, the less accurate the linear analysis response. Finally, by investigating various parameters such as the unbalance mass of the disc and shaft, the amount of stiffness of the elastic support, the position of the middle support, the amount of misalignment and follower force, The dynamic behavior of the rotating system, which includes the transverse vibrations of the rotor and how to increase the rotational speed of the rotor, has been studied and it has been observed that each of the mentioned parameters has a special effect on the dynamic behavior of the rotating system.
  9. Keywords:
  10. Nonlinear Vibration ; Misalignment ; Elastic Support ; Variable Speed Rotor Dynamic ; Transient Vibrations ; Overhung Rotor ; Timoshenko Rotor

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