On the Instability Threshold of Journal Bearing Supported Rotors. (3rd February 2014)

• Record Type: Journal Article
• Authors: Mendes, Ricardo Ugliara; Cavalca, Katia Lucchesi
• Other Names: Heshmat Hooshang Academic Editor.
• Is Part Of: International journal of rotating machinery. Volume 2014(2014)
• Publication Date: 2014-02-03
• Subjects: Machinery -- Periodicals; Rotary combustion engines -- Periodicals; Turbines -- Periodicals; Hydraulic machinery -- Periodicals; 621.82
• DOI: 10.1155/2014/351261
• Languages: English
• ISSNs: 1023-621X

Abstract

Abstract : Journal bearing supported rotors present two kinds of self-excited vibrations: oil-whirl and oil-whip. The first one is commonly masked by the rotor unbalance, hence being rarely associated with instability problems. Oil-whip is a severe vibration which occurs when the oil-whirl frequency coincides with the first flexural natural frequency of the shaft. In many cases, oil-whip is the only fluid-induced instability considered during the design stage; however, experimental evidences have shown that the instability threshold may occur much sooner, demanding a better comprehension of the instability mechanism. In this context, numerical simulations were made in order to improve the identification of the instability threshold for two test rig configurations: one on which the instability occurs on the oil-whip frequency, and another which became unstable before this threshold. Therefore, the main contribution of this paper is to present an investigation of two different thresholds of fluid-induced instabilities and their detectability on design stage simulations based on rotordynamic analysis using linear speed dependent coefficients for the bearings.