Effects of Excitation Frequency and Orbit Magnitude on the Dynamic Characteristics of a Highly Preloaded Three-Lobe Journal Bearing

Abstract

The independent effects of e.rcitation frequency and escitariorr n~agnitltde on esperin~entally derived hearing coeficier~ts for a highly preloaded three-lobe jo~rrnal hearing were studied. The effect of escitation fieq~ret~cy was determined by applying e,~ternal dynamic forces at half-synchronous, synckrono~ts, and twice synchronorrsfrequencies with respect to the operatitlg speed. Effect of e,vcitation nlcrgninrde ~l a s independently deternzirled by applying either three or forrr dtfferent an~plitudes of e.vcitatiort force to the hearing resulritrg in orbit sizes ranging tip to 30% of clearance. Applying static forces to the hearing housing controlled the Somniet$elrl nrm~her, and thus, the static operating position. Data Presented as a Society of Tribologists and Lubrication EngineersPaper at the STLEIASME Tribology Conference in San Francisco, CA October 21-24,2001 Final manuscript approved June 12,2001 Review led by Gregory Kostrzewsky was reduced as linear dynaniic coefficients, and presented relative to excitation frequency and excitation niagtiilude over a range of Sonlnlerfeld numbers from 0.2 to 3.0 and operating eccentricities from 0.3 to 0.9. In general, neither excitation frequency nor e.rcitatioti magttitrtde was shown to have a nieasurahle efSEct over the ranges studied.

A Review on Application of Dynamic Parameters of Journal Bearing for Vibration and Condition Monitoring

“…The uncertainty analysis was based on subsequent bearing identification experiments, including 2-axial groove bearings [57,58]; other studies of the 3-lobe bearing include testing of the linearity assumption the effect of load orientation on coefficients [59,60], three independent shaft orbits and the orbits resulting in the lowest uncertainty were used to identify bearing coefficients for a 3-lobe journal bearing with 0.75 preload [61,62] and five-pad tilting pad bearings [63][64][65][66]. The five-pad tilting pad tests have included the effect of pad pivot friction [63] and varying preload [64] on identified bearing coefficients.…”

Identification Methods and Test Results for Tilting Pad and Fixed Geometry Journal Bearing Dynamic Coefficients – A Review

“…The optimal points in shaft orbits to extract the bearing parameters were addressed, which are related to numerical conditioning. The uncertainty analysis was used on subsequent bearing identification experiments, including 2-axial groove bearings [31,32], 3 lobe bearings [7,8,17,30], and five-pad tilting pad bearings [46,47,63,69]. Typical uncertainties in identified bearing coefficients were 3-20 percent, depending on the experiment.…”

“…Three independent shaft orbits were produced, and the orbits resulting in the lowest uncertainty were used to identify bearing coefficients for a 3-lobe journal bearing with 0.75 preload [17,30]. Other studies of the 3-lobe bearing include testing of the linearity assumption the effect of load orientation on coefficients [7,8].…”