Developments for the calculation of heavily loaded journal bearings

Abstract

This thesis describes the development of an ElastoHydroDynamic (EHD) bearing calculation. The effect of body forces is shown to be important for highly loaded bearings in reciprocating internal combustion engines. Extension of the program to rotating machinery includes an examination of instability in the shaft bearings of a turbocharger. The development of a parameter to predict cavitation damage in a bearing is promising. Several calculation results using the program are shown. These are engine main bearing and connecting rod big-end bearings and full floating bearings for a turbocharger. The calculations on the big-end bearing if a racing engine show why the designers were having difficulty understanding the correct location for the oil feed hole position. Effects of elastic deformation, thermal deformation and manufacturing/assembly deformation all have a significant effect on the extent of the oil film. A novel calculation for a cavitation damage parameter is demonstrated successfully for a heavily loaded diesel engine bearing. The importance of body forces on the oil film due to high accelerations on certain bearings is shown to be theoretically important but not yet demonstrated. The program was written with the intention to be incorporated into the sponsoring company’s range of engine design software. A part of that development process included carrying out calculations to demonstrate to customers and present papers at conferences. The results of some of these calculations have been included in this thesis. Results of a study on the effect of crankshaft geometry on racing engine viscous friction losses were reported in a paper presented at the IDETC conference in Long Beach, 2005. This study used the first version of the software which only included Rigid Hydro Dynamics (RHD) at the time but was usable. Results of a study on stability of shaft motion in high speed turbocharger bearings were reported in a paper at the 8th International Turbocharger conference in London, 2006. At this time the program was still only capable of RHD calculations but could now solve for multiple oil films simultaneously and sweep through the speed range. The studies on the effects of body forces and the development of a cavitation parameter will be presented in papers in the near future.