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Lubricated contact performance can be improved by using a textured surface as well as a hydrophobic surface. A procedure to obtain the optimal partially textured journal bearing combined with the hydrophobic coating is presented through the computational fluid dynamics (CFD) codes. In this study, lubricated hydrophobic textured contacts with and without cavitation modeling are discussed. The cavitation phenomena in the lubricant is modeled using a multiphase model of “mixture” to obtain a realistic condition. The effect of dimple depth, as well as the eccentricity ratio, on the tribological performance, is of particular interest. It is found that the tribological performance is greatly influenced by the multiphase flow cavitation scheme. When cavitation modeling is taken into account, higher load support is noted. Furthermore, the simulation results show that a hydrophobic textured surface with a shallow depth (d/hmin<1) seems to be better for enhancing the tribological performance. Meanwhile, for the case of the low eccentricity ratio, there is an optimal dimple depth giving the highest load support. The findings explored in this work can be considered as a theoretical basis to increase the performance of hydrophobic textured journal bearing. [ABSTRACT FROM AUTHOR]

This study experimentally investigates the influence of cavitation effect caused by surface texture on the lubrication performance of friction pairs. In order to verify and research the cavitation phenomenon induced by surface texture, cavitation images are collected by visual experimental apparatus. The results show that the surface texture will induce the cavitation of the lubricating oil under certain speed and load conditions, gas bubbles will be generated at the outlet of the dimples, and the cavitation will affect the lubrication performance of the friction pair. When the texture depth is close to the oil film thickness, it has the best effect in terms of inducing cavitation and promoting lubrication. And it is found in the experiments when area density of texture is 8% and the square dimples are arranged at inlet area of the sample, the best effect of the surface texture can be obtained. [ABSTRACT FROM AUTHOR]

Partial texturing of the surface of journal bearings have been proven very beneficial in terms of friction coefficient. In the present work, the load support of the hydrodynamic textured journal bearing combined with artificial slippage is fully characterized by means of computational fluid dynamics (CFD) simulations based on the numerical solution of the Navier-Stokes equations for incompressible flow. In order to model slippage, the enhanced user-defined-function (UDF) code is developed. Realistic boundary condition is employed by implementing the mixture multiphase model to model a cavitation in the bearing. The numerical analysis is performed under the condition of different groove depths, eccentricity ratios and slippage placements along the textured area of bearing. The simulation results including hydrodynamic pressure and load support are gained and compared for conventional smooth parameters. A reference to determine optimal groove depths as well as best artificial slippage placement of textured bearing under different conditions of loading are proposed. Based on the present results, favorable slippagetextured journal bearing design can be assessed. [ABSTRACT FROM AUTHOR]

This note addresses the effect of surface ellipticity on self-acting partial arc journal bearings under steady load and sinusoidal oscillation accounting for mass conserving cavitation. A generalized Warner bearing (GWB) formulation developed in a previous publication is employed for computational efficiency. A set of non-dimensional design charts and a sample application show that bearing performance, as measured by cyclic-minimum film thickness ratio, is substantially improved with an elliptical sleeve at small oscillation amplitudes typically found in practice. The results also suggest that a fully hydrodynamic lubrication regime can be established at small oscillation amplitudes from a wearing-in process of the sleeve surface. • Rapid solution method for transient mass-conserving hydrodynamic lubrication. • Focus is on steadily loaded oscillating journal bearings. • Elliptically shaped sleeve enhances bearing performance. • Development of fully hydrodynamic lubrication from a running-in wear process. • Applications include two-stroke wristpin bearings and servo-actuators. [ABSTRACT FROM AUTHOR]

Purpose - The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach - Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings - Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and so does friction loss. Therefore, coordination deformation ability of whole engine block is favorable to mean load. In the whole block model, friction contact happens on both upper shell and lower shell positions. In addition, average oil film fill ratio at the key position becomes smaller in the whole engine block model, and consequently increases the chances of cavitations erosion more. So, wearing resistance of both upper and lower shells and anti-cavitations erosion ability must be enhanced simultaneously. Originality/value - Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the CMS method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an EHD-mixed lubrication model of the main bearings for the diesel engine is built, which can predict the lubrication of journal bearings more accurately. [ABSTRACT FROM AUTHOR]

This paper described unique hysteresis phenomena that appear in the hydrodynamic lubrication properties of dimpled thrust bearings. A seal-type thrust bearing specimen was textured with dimples. The load-carrying capacity and frictional torque were measured with a constant film thickness and compared to those of a dimple-free specimen. For examining the size of cavitation bubbles that occurred in various conditions, the lubricating area was observed during experiments. The used dimpled specimen produced the load-carrying capacity, and it exhibited an interesting hysteresis phenomenon, the difference in the values in the increasing and decreasing processes of rotational speed. The visualization test results revealed that the size of cavitation bubbles occurring within the dimples strongly affected this phenomenon. In addition, the dimpled specimen was able to reduce the frictional torque compared to the dimple-free specimen. However, the frictional torque did not show the hysteresis loop similar to that shown in the load-carrying capacity. [ABSTRACT FROM AUTHOR]

In the present work, a numerical model is developed to investigate the influence of wear and misalignment on the bearings of a stationary diesel engine. The model implemented considers the effects of surface wear on the bearing, cavitation effects, and surface roughness. For the numerical analysis, changes in the surface roughness of σ = 0.75   μ m , σ = 1   μ m , and σ = 1.25   μ m are defined, and changes in the bearing load of 50%, 75%, and 100%. The results demonstrated that increasing the surface roughness intensifies the bearing wear, which represents 18% and 140% of the bearing clearance for the roughness of σ = 1   μ m and σ = 1.25   μ m , respectively. Additionally, the surface roughness causes a considerable increase in the bearing wear rate. The results described a maximum wear rate of 20   μ m / s . In general, increasing the bearing load by 25% doubles the hydrodynamic pressure conditions increases friction force by 33%, and reduces lubrication film thickness by 12%. The analysis of the angle of deflection, ϕ x and ϕ y , shows that the moment and the degree of misalignment tend to increase significantly with the increase in the magnitude of the angle ϕ y . Negative angles of deflection, ϕ x , produce a greater increase in the degree of misalignment and the moment. This implies a greater chance of contact with the bearing surface. In conclusion, the proposed methodology serves as a reliable tool to simultaneously evaluate key parameters on the tribological behavior of bearings that further extend their endurance and minimize wear damage. [ABSTRACT FROM AUTHOR]