An investigation into the thermal mixing in journal bearings

Abstract

Flows in the thermal mixing zone of a journal bearing are investigated using the computational fluid dynamics (CFD) approach. The complexity and inertial effect of the flows inside the supply region of different configurations are considered. It is shown that these flows are highly recirculating but have almost negligible effects on the thermal mixing. The turbulent flow inside the supply region is modelled using the k-ω turbulence model. Most parts of the supply region are filled with recirculation zones and most of the injected cold oil does not immediately enter the oil film. For all configurations considered the extent of the thermal mixing zone is not confined to just above the supply groove. This zone extends some distance beyond the pockets/grooves and in some cases extends for almost the whole bearing length in the axial direction. The length of the supply region and supply pressure governs the extent of the mixing zones. To investigate the effect of various groove dimensions, locations and bearing operating conditions on the bush temperature, the supply region and oil film were considered as separate domains. This allows the difference in length scales to be resolved. The results are presented quantitatively in terms of bush temperatures and maximum temperature. A flow field inside a pocket is compared with available experimental flow visualizations.

The role of lubricant feeding conditions on the performance improvement and friction reduction of journal bearings

“…A fixed value of 0.1 has been selected after a brief parametric study. This small mixing coefficient is in agreement with the CFD study of Kosasih and Tieu [36], which concluded that although the flows occurring within the groove interior are highly recirculating, they have almost negligible effects on thermal mixing.…”

“…A higher than usual value of 750 W/m 2 K was chosen for H gr . Such value appears to be in better agreement with the highly recirculating flow found within groove regions [36,39] and indeed this allowed to replicate the strong temperature fade found experimentally in the vicinity of grooves [24].…”

Analysis of the effect of grooves in single and twin axial groove journal bearings under varying load direction

“…However, when grooves start to interfere with the pressure profile, those models will be inadequate as they will not provide a rigorous treatment of groove mixing and other phenomena taking place at the vicinity of grooves. Examples of such complex -2 -phenomena are the mixing of hot lubricant coming from upstream of the groove with fresh lubricant [9] [10] and the occurrence of reverse flow of lubricant re-entering the groove from downstream or the backflow of groove lubricant flowing upstream in the direction opposite to the journal rotation [11] [12].…”

Numerical study of twin groove journal bearings performance under steady-state condition

“…An analysis of what actually happens within the whole groove was carried out by Kosasih and Tieu . They used commercial CFD packages in order to investigate the thermal mixing occurring with different groove geometries.…”