No Conventional Fluid Film Bearings with Waved Surface

Abstract

A new type of fluid film bearings called “wave bearing” has been developed since 1990’s by Dimofte (Dimofte, 1995 a; Dimofte, 1995 b). The main characteristic of the wave bearings is that they have a continuous wave profile on the stationary part of the bearing. The wave bearings can be designed as journal bearings to support radial loads or as thrust bearings for axial loads. One of the main advantages of the wave bearings is that they are very simple and easy to manufacture. In most cases they have only two parts. A journal bearing consists of a shaft and a sleeve while a thrust bearing consists of a stationary and a rotating disk. One of the bearing parts is sometimes incorporated into the machine part that is supported by the bearing. For example, the wave bearing can be used to support the gear of a planetary transmission, the bearing sleeve being incorporated into the gear (Dimofte et al., 2000). Compressible (gases) or incompressible (liquids) fluids can be used as lubricants for both the journal and thrust wave bearings. Tests were conducted with liquid lubricants (synthetic turbine oil, perfluoropolyethers –PFPE-K) and air on dedicated test rigs installed in NASA Glenn Research Centre in Cleveland, OH USA (Dimofte et al., 2000; Dimofte et al., 2005). In this chapter, the wave bearings lubricated with incompressible fluids, commonly known as fluid film wave bearings, are analysed. The performance of both journal and thrust bearings is examined. Because one of the most important properties of the wave journal bearings compared to other types of journal bearings is their improved stability, the first part of the chapter is dedicated to the study of the dynamic behaviour of the journal wave bearings. The wave thrust bearings can be used for axially positioning the rotor or to carry a thrust load. For this reason, the steady-state performance of the thrust wave bearings is analysed in the second part of the chapter.