Thermal modelling of the lemon-bore hydrodynamic bearing

The lemon-bore hydrodynamic lubricated journal bearing is a bearing type which is commonly used in high-speed machinery. This is because the lemon-bore bearing is less susceptible to self-excited vibrations or instability than the plain cylindrical bearing at high speeds, while remaining easy to manufacture. However, the increased viscous shear will result in a higher increase in the temperature in the lubricating film.In this paper a finite element analysis is presented which has been used to calculate the pressure and temperature distribution in the lubricating film of a lemon-bore journal bearing. This thermo-hydrodynamic (THD) model is an inverse model, that is, a model in which the shaft eccentricity and attitude angle are calculated given a certain known and prescribed load and load angle. A novel, simple and fast mass-conserving cavitation algorithm has been used in order to calculate the pressure and mass fraction distribution in the lubricating film, and consequently accurately describes the heat flow in the cavitated areas. Furthermore, care has been taken to accurately model the heat to and from the oil supplies.This model has been used to check the design of the lemon bearings in a specific naval application. The results of this model are compared with those obtained using the bearing manufacturer's design code. The influence of several operating and design parameters is studied, particularly with respect to the maximum temperature. The results of this parameter study have been used to suggest design improvements for this particular application.