Effect of Preset on the Performance of Finite Journal Bearings Supporting Rigid and Flexible Rotors

Abstract

A large number of cylindrical bearings are manufactured in two halves and assembled in such a way that there exists a possibility that the center may get displaced along the parting line. Very little published data are available on the effect of this displacement on the performance of journal bearings. This paper is directed toward the theoretical study of the static and dynamic behavior of the finite displaced lobe or “offset” bearings where the displacement or “preset” is either accidental due to the faulty manufacture or intentional to improve the performance. It has been found that the static dynamic properties of journal bearings are greatly influenced by preset. Data on load capacity, dynamic coefficients and stability are presented in this paper for several values of preset, L/D ratio and shaft flexibility. Offset bearings are found to be much more stable in comparison to conventional cylindrical journal bearings, specially for low loads.