Abstract
Performance investigation of oil journal bearings is of particular importance given the growing use of them as a support for rotary components in a wide range of industrial machines. Frictional forces and shear stresses, which are proportionate to the velocity of lubricating layers at different points in the bearing space, provide the basis for changing temperature conditions. Various factors such as rotational velocity increase, slip width reduction, and small heat transfer coefficient of lubricant cause intensification of lubricant temperature changes. In the present study, with using computational fluid dynamic (CFD) thermohydrodynamic (THD) numerical simulations, the effect of nanoparticles on the performance features of plain journal bearings is evaluated. Particularly, 3D simulation of a journal bearing is implemented using CFD which considerably improves the accuracy of results, coupled with conjugate heat transfer model for metal parts of bearings. Reynolds equation model is used to calculate the oil-film pressure developed in hydrodynamic journal bearings by applying the nano-based lubricants. The configuration of thrust bearing consists of six pads in this study. In order to reduce the modeling complexity and computational cost and because of the symmetrical geometry of the pads, simulation of a single pad is considered instead of the entire domain. In this study, TiO2 nanoparticle with different volume fraction percentages are used. The parameters that are changed to evaluate the performance of the bearing include volume fraction percentage of the nanoparticle, type of lubricant, and rotational speed. Based on the results, for all different lubricant types, the dissipation power, average shear stress, and temperature rise are increased with augmenting the rotational speed. By increasing the rotational speed from 500 to 1500 rpm, the average shear stress increases by more than 100%, 120%, and 130% for DTE 26, DTE 25, and DTE 24 lubricant types, respectively. Moreover, by increasing the rotational speed from 500 to 1500 rpm, the dissipation power, and temperature rise are increased around 600% and 800%, respectively. Furthermore, increasing nanoparticles volume fraction from 0% to 10%, increases all parameters by approximately 10% for all lubricant types and in all rotational speeds.
Highlights
The main difference between machines and structures are moving parts such as bearings.In bearings, this movement is generally resisted by friction on machine joints, and the work required to sustain motion is largely converted to heat due to the shear generated between the static and dynamic parts
Considering that the effects of lubricant temperature variations and heat transfer currents formed between the rotor, lubricant, and shell on the static and dynamic performance of bearings can lead to more realistic results of journal bearing performance, research on this issue has grown significantly in the last decade
3D simulation of a journal bearing is implemented using computational fluid dynamic (CFD) which considerably improves the accuracy of results, coupled with conjugate heat transfer model for metal parts of bearings [28]
Summary
The main difference between machines and structures are moving parts such as bearings In bearings, this movement is generally resisted by friction on machine joints, and the work required to sustain motion is largely converted to heat due to the shear generated between the static and dynamic parts. This movement is generally resisted by friction on machine joints, and the work required to sustain motion is largely converted to heat due to the shear generated between the static and dynamic parts Such heat generation may lead to joint deformation, which can further impose defects on operational conditions including physical contact and freedom of movement. It is crucial to improve the performance of bearings to obtain higher workability from machines This necessitates investigations on working conditions and the influence of different important parameters on bearings. Considering that the effects of lubricant temperature variations and heat transfer currents formed between the rotor, lubricant, and shell on the static and dynamic performance of bearings can lead to more realistic results of journal bearing performance, research on this issue has grown significantly in the last decade
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