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

The independent effects of excitation frequency and excitation magnitude on experimentally derived bearing coefficients for a highly preloaded three-lobe journal bearing were studied. The effect of excitation frequency was determined by applying external dynamic forces at half-synchronous, synchronous, and twice synchronous frequencies with respect to the operating speed. Effect of excitation magnitude was independently determined by applying either three or four different amplitudes of excitation force to the bearing resulting in orbit sizes ranging up to 30% of clearance. Applying static forces to the bearing housing controlled the Sommerfeld number, and thus, the static operating position. Data was reduced as linear dynamic coefficients, and presented relative to excitation frequency and excitation magnitude over a range of Sommerfeld numbers from 0.2 to 3.0 and operating eccentricities from 0.3 to 0.9. In general, neither excitation frequency nor excitation magnitude was shown to have a measurable effect over the ranges studied.