Rotordynamic Performance Predictions of Tilting Pad Journal Bearing with Rocker-Back Pivots and Comparison with Published Test Results

Abstract

In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs)with rocker-back pivots, and we compare the predictions to recently published predictions and test data. Thepresent TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress the-ory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and load-on-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection andstiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thicknessand peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pres-sure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiff-ness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficientsincrease as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speedincreases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well withthe test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. Ingeneral, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamicperformance compared to previously reported models.Keywords: damping(감쇠), pivot stiffness(피벗 강성), rocker-back pivot (로커-백 피벗), stiffness( 강성), tiltingpad journal bearing(틸팅 패드 저널 베어링)