Abstract: The swing characteristic of pads on four-pad tilting pad bearing is studied systematically with the guide bearing for helim circulator in fourth generation nuclear power units HTR as object. Theoretical derivation reveals that dimensionless pad pendulum angle depends on structural parameters, preload and eccentricity, but independent of viscosity of lubrication oil film, shaft rotating speed and clearance. Numerical analysis shows that: pad pendulum angle is determined by pad circumferential position relative to the load, preload and eccentricity. When the structural parameters of tilting pad bearing are constant, pendulum angle curve of pad facing the load was depend on preload, its pendulum angle increases first and then decreases with the eccentricity ratio increase while the preload less than 0.5, when the preload is greater than 0.5 its pendulum angle decreases gradually with the eccentricity ratio increase; pendulum angle curve of pad side of the load increases or decreases with the eccentricity ratio increase when the preload is smaller, and remains constant first and then decreases with the eccentricity ratio increase when the preload is greater. Pad pendulum angle has great influence on minimum oil film thickness; its value maybe negative thus leads to the minimum oil film thickness greater than fixed pad. The study results provides basis for safety operation analysis of the helim circulator.

Key words: tilting pad bearing;swing characteristic of pads;preload;minimum oil film thickness