Static Characteristics of Four-Lobe Hydrodynamic Journal Bearings with Bottom Sliding Surface Inclined Due to Manufacturing Errors

Abstract

When a manufacture error occurs, there may be a possibility of the actual size of a hydrodynamic journal bearing differing from its basic dimension. In this case, the characteristics of the hydrodynamic journal bearing can also be different from what have been expected, due to changes in oil film pressure distribution between the bearing and journal. The purpose of this study is to elucidate effects of manufacturing errors on the static characteristics of multi-lobe hydrodynamic journal bearings, whose structures are relatively simple and whose oscillation stability in the rotor shaft-bearing system is relatively strong. The study is also intended to come up with a proposal for guidelines about the optimized design for multi-lobe hydrodynamic journal bearings. This paper analyzed and examined changes in the static characteristics of a four-lobe hydrodynamic journal bearing, such as oil film pressure distribution, journal center locus, minimum oil film thickness and friction coefficient between the bearing and journal, when the position of the bottom lobe at the sliding surface is tilted from where it should be due to manufacturing errors. The results of the study showed that when the bottom lobe is tilted against the eccentric direction of the journal from the original location due to manufacturing errors, minimum oil film thickness may increase in comparison with the situation in which the lobe stays at the original location. The results also showed that friction coefficient between the journal and bearing does not change significantly in spite of manufacturing errors.