The hydrodynamic journal bearing is still one of the most geometrically simple mechanical
components, yet highly reliable and efficient and, above all, unique in what concerns to heavy
duty – high load, high speed – support of rotating shafts.
Analytical studies, not only to understand the physical basis of its performance, but also to
develop practical tools for an expedite design, as well as to assure its reliability and improved
efficiency, were object of the early developments in fluids’ hydrodynamic sciences, since the
late XIX century, and are still been refined and improved on the XXI century.
Historical marks can be flagged as (i) simplified analytical resolutions of the hydrodynamic
pressure distribution; (ii) computerized iterative resolution of the full pressure development
equations; (iii) introduction of the lubricant feeding conditions; (iv) analysis of the thermal
aspects and its influence on viscosity; (v) localized aspects of fluid flow, due to
thermal/viscous phenomena and geometrical particularities.
This evolution led to increased accuracy on the performance predictions and to safer and
higher efficiency of the designed components. On the other hand, analysis became more
specific in use and, particularly with the introduction of the thermo-hydrodynamic analysis,
led to the need of ‘tailored’ solutions to a given set of specific conditions. As a consequence,
methods lost much of their ‘universality’ and ease of use to the common and sporadic
designer.
This work intents to make a first evaluation of the response of three prediction methods – a
commercial and widely used isothermal approach and an isothermal and a thermohydrodynamic
procedures, these former developed at UMinho over the last years – in an
attempt to highlight the variability of the predictions of the main performance parameters by
the use of simpler and rapid methods, when compared with those based on more complex and
accurate analysis, and their eventual influence on an efficient and reliable design solution
