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Partial rotor-to-stator rub demonstrationA rotor radial rub typically occurs in seals or at a blade tip or shroud when there is insufficient clearance, high vibration, or the shaft equilibrium position has been displaced to effectively limit the clearance (eccentricity). There are two extreme cases of radial rubs: full annular rub, when the rotor maintains continuous contact with the seal, etc.; and a partial rub, when the contact occurs during a fraction of the precession period. They both involve similar physical phenomena such as friction and modification of stiffness. In partial rubs with consecutive impacts, a significant average value of radial force is generated. This results in shaft average displacement in the direction opposite the rub location. The rotor rig demonstrates the characteristics of a partial lateral rub of varying severity and location. These characteristics include: (1) subharmonic components as a function of rotative speed/first balance resonance ratio and radial force; (2) higher harmonic content as a function of severity; (3) increased average rotor stiffness resulting in increased first balance resonance speed; and (4) change in overall orbital pattern as a sum of the unbalance response (1x) and subharmonic response (1nx).
Document ID
Document Type
Conference Paper
Grissom, R. (Bently Nevada 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 19860020725.pdf STI

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IDRelationTitle19860020688Analytic PrimaryInstability in Rotating Machinery