A New Design Chart Method of Journal Bearings Based on a Simplified Thermohydrodynamic Lubrication Theory

摘要

This article proposes a new thermohydrodynamic (THD) bearing design method based on an improved version of a precedent method. The precedent method used two charts prepared in advance to easily and quickly find two crucial predicted data of the maximum bearing temperature and the effective temperature of the bearing oil film to be used later in an isoviscous Reynolds equation. Three sets of charts were prepared for three different values of journal eccentricity ratio, 0.25, 0.5, and 0.75. Which set should be used was determined based on the preliminarily obtained value of journal eccentricity ratio derived from the initially assumed bearing specifications. Two dimensionless temperature rise parametersandwere introduced for the common coordinate variables of the two charts. On the other hand, the new improved method uses a single set of charts for the two crucial temperatures for any value of journal eccentricity ratio. Furthermore, the two coordinate variables for each chart explicitly include the four well-known dimensionless numbers used in THD bearing analyses; that is, Sommerfeld number, bearing aspect ratio (L/D), Peclet number, and dimensionless temperature-viscosity index of the lubricant oil. Compared with some measurements in test rigs of cylindrical bearings, the new improved method is confirmed to predict reasonably accurate bearing performances of cylindrical bearings faster and more easily than the precedent method over a wide range of operating conditions. In conclusion, the new method is simpler, easier, and more straightforward for bearing design use than the precedent method.