Improving Tilting Pad Journal Bearing Predictions—Part II: Comparison of Measured and Predicted Rotor Pad Transfer Functions for a Rocker Pivot Tilting Pad Journal Bearing

Abstract

As described in Part I (Wilkes et al., 2012, “Improving TiltingPad Journal Bearing Predictions—Part I: Model Development and Impact of Rotor Excited Versus Bearing Excited Impedance Coefficients,â€‌ ASME J. Eng. Gas Turb. Power, 135(1), p. 012503), most analytical models for tiltingpad journal bearing (TPJBs) are based on the assumption that explicit dependence on pad motion can be eliminated by assuming harmonic rotor motion such that the amplitude and phase of pad motions resulting from radial and transverse rotor motions are predicted by rotorpad transfer functions. In short, these transfer functions specify the amplitude and phase of pad motion (angular, radial, translational, etc.) in response to an input rotor motion. Direct measurements of pad motion during test excitation were recorded to produce measured transfer functions between rotor and pad motion, and a comparison between these measurements and predictions is given. Motion probes were added to the loaded pad (having the static load vector directed through its pivot) of a 5pad TPJB to obtain accurate measurement of pad radial and tangential motion, as well as tilt, yaw, and pitch. Strain gauges were attached to the side of the loaded pad to measure static and dynamic bending strains, which were then used to determine static and dynamic changes in pad curvature (pad clearance).