NDLI: Mode Evolution of Asymmetric Rotors Assembled to Flexible Bearings and Housing

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Kim, Hyunchul Shen, I. Y.
Copyright Year	2009
Abstract	This paper is to study how vibration modes of a stationary asymmetric rotor evolve when it is assembled to a flexible housing via multiple bearing supports. Prior to the assembly, vibration modes of the rotor are classified as “balanced modes” and “unbalanced modes.” Balanced modes are those modes whose natural frequencies and mode shapes remain unchanged after the rotor is assembled to the housing via bearings. Otherwise, the vibration modes are classified as “unbalanced modes.” In this paper, we first develop two mathematical criteria to identify balanced modes. For the first criteria, the rotor is subjected to fixed boundary conditions at the bearings prior to assembly. In this case, a vibration mode will be a balanced mode if the reactions at the fixed boundary vanish. For the second criterion, the rotor is subjected to free boundary conditions (including the bearing points) prior to assembly. In this case, a vibration mode will be a balanced mode if the bearing locations are nodal points of the vibration mode. These mathematical criteria are then applied to a rotor consisting of a rigid hub supporting a flexible structure, which appears in many practical applications. For balanced modes, the criteria lead to a conclusion that surface integrals of modal forces and moments at the flexible-rigid rotor interface will vanish. Moreover, these surface integrals can be conveniently calculated using finite element methods. To validate the mathematical criteria, modal testing was conducted on a disk with 4 pairs of brackets mounted on a rigid spindle, a ball-bearing spindle and a fluid-dynamic bearing spindle.
Sponsorship	International Gas Turbine Institute
Starting Page	605
Ending Page	612
Page Count	8
File Format	PDF
ISBN	9780791848876
DOI	10.1115/GT2009-59024
e-ISBN	9780791838495
Volume Number	Volume 6: Structures and Dynamics, Parts A and B
Conference Proceedings	ASME Turbo Expo 2009: Power for Land, Sea, and Air
Language	English
Publisher Date	2009-06-08
Publisher Place	Orlando, Florida, USA
Access Restriction	Subscribed
Subject Keyword	Mode shapes Fluids Vibration Ball bearings Bearings Rotors Boundary-value problems Disks Manufacturing Finite element methods Flexible structures Testing
Content Type	Text
Resource Type	Article

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