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Rotor instability due to loose rotating partLoosening of a rotating part from its fixed position on the shaft or a part of the stator which comes loose and begins to turn with the rotor very frequently represents machinery malfunction. The loose part becomes involved in rotative motion mostly due to dry or fluid friction, and thus its motion is very erratic. The loose part can also move axially along the shaft. Detachment of the rotating part causes changes in the rotor balance state. Most often this results in higher unbalance. During steady-state operation the effect of a loose rotating part can manifest itself through heat vibration. It can be diagnosed by observing periodic changes of amplitude and phase of the synchronous response. During start-up (or shutdown) a loose rotating part carrying some amount of unbalance may manifest its dynamic action in the form of subsynchronous vibrations, very similar to those of other instabilities. The objective of this demonstration is to observe the effect of a loose rotating part (fixed, however, in the axial direction) under both steady-state (rotor constant speed) and transient (rotor start-up or shutdown) operation. The dynamic response depends very much on the amount of damping in the system: lubrication of the loose part/shaft surfaces and addition/elimination of aerodynamic drag blades, mounted on the loose disk, significantly change the rotor response.
Document ID
Document Type
Conference Paper
Muszynska, A. (Bently Rotor Dynamics Research Corp. Minden, NV, United States)
Date Acquired
August 12, 2013
Publication Date
December 1, 1985
Publication Information
Publication: NASA. Lewis Research Center Instability in Rotating Machinery
Subject Category
Distribution Limits
Work of the US Gov. Public Use Permitted.

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NameType 19860020726.pdf STI

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IDRelationTitle19860020688Analytic PrimaryInstability in Rotating Machinery