Theoretical and Experimental Dynamic Characteristics of a Highly Preloaded Three-Lobe Journal Bearing

Abstract

The predicted performance of a three-lobe journal bearing with a preload factor of 0.75 is compared with the measured performance. Operating eccentricity and dynamic coefficients versus Sommerfeld number are compared for three shaft speeds and various steady loads. Numerical results are based on a model which solves the Reynolds equation and allows for a variety of thermal effects including circumferential and cross-film viscosity and temperature variation. The linearized coefficients are experimentally determined by an average magnitude and phase method using synchronous, sinusoidal excitations. Comparisons of journal position show good agreement (within 9.5%) for Sommerfeld numbers below 0.7 and increasing disagreement (30 % or greater) at higher Sommerfeld numbers. Agreement in journal position improves as load and shaft speed increase. At Sommerfeld numbers less than 0.4 to 0.7, agreement between the numerical and experimental dynamic coefficients is very good, typically within the uncertainty of the measured data. The magnitude and slope of the coefficients vs. Sommerfeld number match well. Disagreement in coefficient magnitude by as much as 100% is seen at high Sommerfeld numbers, although there is general agreement in the trend for predicted coefficients vs. Sommerfeld number.

Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997

KEY WORDS:

• Hydrodynamic Bearings
• Journal Bearings
• Multi-Lobe Bearings
• Hydrodynamic Lubrication

Notes

Presented as a Society of Tribologists and Lubrication Engineers paper at the World Tribology Congress in London, United Kingdom, September 8–12, 1997