Host: The Japan Society of Mechanical Engineers
Name : Dynamics and Design Conference 2023
Date : August 28, 2023 - August 31, 2023
This paper presents a computational evaluation of the stability for the flexible rotor by using the open-loop characteristics with the block diagram. The developed method for the stability evaluation has two advantages from the general: the unnecessary of exclusive analysis codes, and the easily understanding of the vibration model. The developed method was applied to the examination rotor which has caused the self-excitation vibration and concluded that the stability limit speed of the examination rotor could be calculated quantitively by using the 2-DOF model of the rotor and the sliding bearing. After that, the 2-DOF model was expanded to the 3-DOF model in consideration of the flexible foundation. It was then confirmed that the stability could be established visually by using the vector locus and the distance vector locus of the dB polar diagram from the open-loop characteristics. Finally, the steam turbine rotor supported on the tilting pad bearing was evaluated by the 2-DOF and 3-DOF models, which concluded that use of the tilting pad bearing makes the turbine rotor always stable without depending on placing on flexible foundation or not. For the case study adopting the cylindrical bearing instead of the tilting pad bearing, both models became unstable.
These instability phenomena behave as the oil whips corresponding to the first bending rotor natural frequency of the 2-DOF, and the foundation whips of its first natural frequency of foundation mode in the 3-DOF.
