Thermal characteristics of misaligned finite journal bearings

Adiabatic analysis of a journal bearing is presented for maximum allowable misalignment with a length:diameter ratio of one. The direction of journal misalignment is allowed to vary up to the axialplane containing the load vector. Reynolds and energy equations are solved simultaneously using finite differences, considering both axial and spiral oil inlet conditions. The results show that bearing behaviour is significantly affected by journal misalignment. It is also noted that thermal effects are more pronounced for bearings with axial rather than spiral oil inlet grooves. The isothermal Reynolds equation is commonly used to predict performance of misaligned journal bearings. 'Bearing performance', however, is now used in a wider sense than was meant originally;it includes the bearing temperature distribution or at least the maximum bearing temperature, in addition to the usual performance parameters of load capacity,journal position and power loss. Different methods have been proposed to take into account thermal effects x . The simplest uses isothermal theory to calculate an effective temperature and the corresponding viscosity through an evaluation of the dissipated power 2 . A theoretical method was proposed by Dowson a in which he derived a generalized Reynolds equation to include variations of the lubricant properties. In this paper the effect of journal misalignment on bearing performance is studied taking account of thermal effects. The number of analyses available on misaligned bearings is small compared with the extensive literature on journal bearings in general. In a previous work by the authors 4 it was shown that journal misalignment has a pronounced effect on bearing performance, particularly when hmin approaches zero (touch at a point). Earlier works s-7 have discussed the problem of misalignment in journal bearings and the possible hydrodynamic consequences. Their results, however, are limited to isothermal solutions. The present work provides solutions for finite journal bearings, in which the magnitude of the misalignment is maximum (bearing journal contact), while the direction of misalignment (journal skewness) may vary up to a direction normal to the axial plane containing the load vector. It is assumed that the heat generated within the lubricant film is carried exclusively by the fluid. The effect of misalignment on the load, friction, and maximum oil temperature is considered. Analysis