Research on lubrication performance and dimensional tolerance of engine main shaft journal bearings based on oil film formation ability

To understand the engine main bearings’ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic(TEHD) reaction on engine main bearings is investigated. The calculated method of main bearing’s thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic(EHD) and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.

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Review for "Research on Lubrication Performance and Dimensional Tolerance of Engine Main Shaft Journal Bearings Based on Oil Film Formation Ability"

High-viscosity plastic fluids and polymer liners are expected to improve the lubrication and load-carrying performance of low-speed and heavy-load journal bearings. The objective of this paper is to investigate the elastohydrodynamic lubrication performance of compliant journal bearings lubricated with non-Newtonian plastic fluids (following the Herschel-Bulkley model) using computational fluid dynamics (CFD) and fluid-structure interaction (FSI) methods. The following data are obtained: fluid film pressure, total bearing deformation, cavitation volume fraction, bearing capacity, and coefficient of friction. The simulation results are in close agreement with the data reported in the existing literature. A comparative analysis of the lubrication characteristics of journal bearings with Babbitt metal, PEEK, and PTFE liners at varying rotational speeds is presented. The effects of yield stress, power-law index, elastic modulus, and liner thickness on the lubrication characteristics are investigated. The results indicate that the power-law index of non-Newtonian plastic fluids has a greater influence on the bearing lubrication performance than the yield stress. Increasing the power-law index could improve the bearing capacity and reduce the coefficient of friction. The research provides a theoretical basis for the application of non-Newtonian plastic fluid-lubricated polymer journal bearings in low-speed and heavy-load equipment.

Purpose This work aims to explore the combined effects of boundary slip and texturing on hydrodynamic journal bearings and identifies optimized slip and texture patterns to improve the performance of journal bearings. Design/methodology/approach The quadratic programming technique is used to study the influence of boundary slip on the lubrication performance of a two-dimensional journal bearing. A numerical model is used to analyze the effect of the cylindrical texture shape on the characteristics of journal bearings. It is concluded that the combination of slip and texture can be an effective approach to improve the performance of hydrodynamic journal bearings. Findings The results show that there is an interfacial shear stress (perfect slip surface) and that the role of the slip regime is to reduce friction. Numerical analyses indicate that the location and size of the slip and texture zone have a large effect on journal bearings. A comparison of the distribution forms of various texture–slip combinations indicates that the full texture–slip combination can prominently reduce the load-carrying capacity and that the “forward-slip backward-texture” configuration can considerably improve the performance of journal bearings. Originality/value The combined effects of boundary slip and texture on hydrodynamic journal bearings are meticulously examined. The patterns of the slip and texture are optimized, which can substantially improve the journal bearing performance.

ABSTRACTThe lubricant properties have a significant influence on the static and dynamic performance characteristics of journal bearing such as load-carrying capability, minimum fluid film thickness, maximum pressure, lubricant flow rate, damping coefficients, stiffness coefficients, etc. The present document reviews the behaviour of various lubricants such as power-law lubricants, couple stress lubricants, micropolar lubricants, ionic liquid lubricants and space lubricants. The influence of these lubricants on the performance of hydrostatic, hydrodynamic and hybrid journal bearings is discussed. An effort is made to develop the understanding to choose the suitable lubricant for journal bearings for different journal bearing configurations. Journal bearings operated with non-Newtonian lubricants have shown better performance compared to Newtonian lubricants. Ionic liquid lubricants have shown high potential in vacuum applications and extreme temperature environment such as in bearings of spacecraft moving mechanical assemblies.

Journal bearings are critical components designed to facilitate the smooth and consistent rotation of shafts around specific axes. To meet the demands for efficient and cost-effective applications in high-speed machinery, it is imperative to enhance the tribological performance of journal bearings. This study investigates the impact of multistep texture geometry and partial surface roughness on the tribological behavior of journal bearings fabricated from steel. Experimental analyses were performed using Newtonian fluids across varying rotational speeds to evaluate the interplay between geometry and material properties. To further explore these dynamics, a three-dimensional computational fluid dynamics (CFD) model integrated with fluid–structure interaction (FSI) was employed, accounting for the effects of cavitation and material deformation under elastohydrodynamic lubrication conditions. The study also introduced partially rough surface boundary conditions to the multistep journal bearings, hypothesizing their potential to enhance lubrication performance. Results demonstrate that surface texture and roughness significantly influence the elastohydrodynamic lubrication and overall tribological performance of steel journal bearings. Additionally, variations in rotational speed were found to have a pronounced effect on lubrication efficiency. These findings provide valuable insights into optimizing journal bearing design for high-performance applications.

Bearings might be damaged due to shock loads caused by disturbances, in addition to static loads. In this study, a flexible structure was applied to enhance the lubrication characteristics of misaligned journal bearings subjected to impact loads. When an impact load is added to the bearing, a misaligned journal bearing has a high possibility of metal-to-metal contact. It might also lead to failure. Misalignment can occur at any time during bearing operation. A flexible structure is applied to the end of the bearing as a way to improve lubrication performance in a system where impact loads might be applied. The bearing’s lubrication performance was numerically assessed under unsteady-state conditions. An elastohydrodynamic lubrication analysis was conducted, taking into account elastic deformation. The lubrication characteristics of misaligned journal bearings were compared with the dimensionless minimum film thickness. The flexible structure and elastic modulus of the bearing were investigated so that it could support the load without contact according to the change in the maximum magnitude of the impact load. When subjected to oil film pressure, this flexible structure underwent elastic deformation, resulting in enlargement of the oil film. A misaligned journal bearing with a suitable flexible structure provided stable lubrication without metal-to-metal contact, even under shock load conditions. The flexible structure was incorporated into the high-load-bearing region of the journal bearing as a groove. Therefore, the application of a flexible structure in misaligned journal bearings can effectively enhance lubrication performance in misaligned conditions and under shock loads.

A comprehensive summary of the vibration diagnosis techniques used to detect the wear of the main journal bearings in a diesel engine is presented. The load of the main journal bearing, the minimum thickness of the oil film, the oil film pressure and the locus of the crankshaft centre have been calculated based on the measured thermal parameters. Simulated wear experiments for the main journal bearing have been carried out in laboratory conditions. The strain and vibration on the main journal pedestals in the vertical direction were measured under various working conditions. The strain signals on the main journal bearing pedestal are related to the oil film forces, damped by the lubricant oil. The excitation sources and the vibration characteristics of the main journal bearing pedestal system were analysed by measuring the vibration signals. The relationships between the feature parameters of the vibration signals and the wear conditions of the main journal bearing have been obtained. It is promising, therefore, to develop and apply the vibration diagnosis technique further to detect the wear conditions of the main journal bearings online.

The applications of nano-lubricants in journal bearing are found to be capable of improving load-carrying capacity and reducing friction. Many numerical and experimental investigations have been performed to find the effect of nano-lubricants on the performance of the journal bearing. In this paper, a state-of-the-art review is done of the articles of numerical and experimental assessments of the effect of nano-lubricants on the performance of journal bearings. Here research articles are classified on the basis of nanoparticles used as nano-additive, which are further classified in the category of numerical and experimental study. It is seen that the application of nano TiO2, CuO and Al2O3 based nano-lubricants gives much higher load-carrying capacity than the base lubricants. This article concludes by discussing the effect of different nanoparticle-based nano-lubricants on the performance characteristics of the journal bearing and mathematical models used for numerical investigations.