Influence of Pad Pivot Friction on Tilting-Pad Journal Bearing Measurements—Part I: Steady Operating Position©

This paper presents measured results for the eccentricity ratios for two tilting-pad journal bearing. Comparison between a bearing with spherical seated ball and socket pad pivots and one with line contact rocker-back pad pivots is made. The bearings have a length to diameter ratio of 0.75, offset ratios of 0.50, preloads of about 0.320, a journal diameter of 70 mm and a radial machined pad clearance of 113.0 μm. Measurements were made for a range of speed-load conditions encompassing a Sommerfeld number range of 0.1 to 2.0. Comparison of the eccentricity magnitude for the two bearing agreed within uncertainty levels. For the bearing with rocker-back pad pivots, the journal attitude angle with respect to the applied load direction is nearly zero. Attitude angles range from 13° to 33° for the bearing with spherical seated ball and socket pad pivots. The deviation from zero attitude angle for this bearing increased with increasing speed. A hypothesis for larger pad pivot friction in the ball and socket pivot is presented to explain the variation in attitude angle between the two bearings.