BEARINGS WITH COMPRESSIBLE FLUID

Abstract

Gas lubrication has interesting and important engineer-ing applications which are the motivating reasons for the expanding research in this area. The gas bearings have the advantage of negligible friction losses, cleanliness and, when air is used, easy availability of lubricant. The wear in gas-lubricated bearings is extremely low, a factor which contributes to their long life: These bearings do not contaminate the surroundings and can very well be employed in the presence of severe radiation. Precisely for these reasons the gas bearings find use in electric motors, machine tools, equipment for gas liquefaction, ultracentrifuges, textile machines, turbocompressors and high precision instru-ments such as inertial guidance system for rockets and space ships. The gas bearings encounter two familiar shortcomings, low loadcarrying capacity and hydrodynamic instability. The problem of instability is more pronounced at lover eccentricities, for example in vertical shafts where load support is not a requirement. The Reynolds equation for compressible fluid received a lot of attention from the scientists engaged in theoretical investi-gation in this area. Analytical (closed form) solutions of Reynolds equation are based on the assumption of infinitely .long bearing. Methods such as electrical analogy and analog - iv- field plotter were used for the solution of externally pressurized gas bearings and only a limited experimental work has been done in studying the performance of gas bearings. The numerical methods, particularly those based on finite differences, have been extensively employed to solve gas bearing flow-fields. A limitation of the finite difference method is that for every bearing configuration of interest, a. preferred coordinate system for which lubrication boundaries conform with constant coordinate lines, may not exist. In such situations special procedures for the non-conforming boundary segments have to be devised. In addition, where abrupt variations of film thickness exist, auxiliary conditions, such as continuity of flow have to be invoked...