Tilting Pad Journal Bearing - Measured and Predicted Stiffness Coefficients

This paper presents measured and calculated characteristics of a tilting pad journal bearing suitable for high speed machinery. Descriptions are given of the experimental techniques used with this variety of bearing and the theoretical model for predicted performance.

Measured values of pad temperature, eccentricity, attitude angle, and the four stiffness coefficents are given for a range of loads and rotational speeds. Data are given for both load on pad and between pad configurations, the two principle loading arrangements.

Comparisons are made between the measured and predicted bearing tempatures and stiffness coefficients over a wide range of values.

Introduction

Tilting pad journal bearings have been used to support rotating shafts for a considerable number of years. They are more expensive and occupy a larger space than a corresponding conventional plain bearing. Nonetheless, they have been, and continue to be, selected by designers in applications where their superior stability, especially in the high speed/low load condition, is a paramount consideration.

Consequently, as with plain bearings, their widespread use has preceded knowledge of their performance characteristics and reliable theoretical models thereof. It is only in relatively recent times that the performance of tilting pad journal bearings has been studied. Theoretical studies (1) – (3) have been reported, and in particular Jones and Martin (4) have indicated the effect of changes in various geometrical paramenter upon performance. Within the last few years, results of a number of experiemental studies (5) – (9) have been published. Notwithstanding, there remains a scarcity of data.

This paper presents a contribution to this knowledge by comparing the measured performance of a typical tilting pad journal bearing with the predicted characteristics. Data are given for both the common operating configurations of load on and load between pads.