Abstract
This paper presents a numerical approach for the analysis of hydrodynamic radial journal bearings. The effect of shaft and housing elastic deformation on pressure distribution within oil film is investigated. An iterative algorithm that couples Reynolds equation with a plane finite elements structural model is solved. Temperature and pressure effects on viscosity are also included with the Vogel-Barus model. The deformed lubrication gap and the overall stress state were calculated. Numerical results are presented with reference to a typical journal bearing configuration at two different inlet oil temperatures. Obtained results show the great influence of elastic deformation of bearing components on oil pressure distribution, compared with results for ideally rigid components obtained by Raimondi and Boyd solution.
Highlights
Journal bearings are machine elements in which the applied force is entirely supported by an oil film pressure
Can be somewhat oversimplified, considering for example that the deformation of journal bearing components under the imposed oil film pressure is expected to produce a change in the real lubrication gap and a modification in the resultant pressure distribution
In light of the above considerations, the present paper aims to present a general numerical approach to study the behavior of hydrodynamic radial journal bearings, by including in the analysis the effect of the aforementioned aspects
Summary
Journal bearings are machine elements in which the applied force is entirely supported by an oil film pressure. Several design charts are available in literature [3, 4], which provide journal bearing operation parameters as a function of Sommerfeld number S=(r/c)2(μN/pm), defined in terms of shaft radius r and rotational speed N, while pm=F/(LD) is the average (specific) pressure defined as the ratio of the applied radial force F and the nominal projected area (L is the length of journal bearing) Such diagrams were determined by R&B through numerical solution of Reynolds equation under the hypothesis of constant temperature (and viscosity) of lubrication film and under the assumption of perfectly rigid components (shaft and support). This would allow a more realistic estimate of the overall stress distribution on journal bearing components (shaft and housing), compared to other approaches (see for example [7]) that are based on approximate analytical (asymptotic) solutions of Reynolds equation
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