Performance Of Journal Bearing Research Articles

Effect of texture on hydrodynamic journal bearing performance under starvation lubrication

The effect of texture on tribological properties of journal bearings operating under starvation lubrication conditions is studied in this paper. The P-θ model with mass conservation boundary conditions is used to accurately predict the oil film distribution in the full oil film/starvation region of the textured bearing. The effects of various degrees of starvation lubrication on the tribological performance parameters, such as eccentricity, attitude angle, full film area, and friction coefficient, are discussed in textured bearings. The results show that the effect of texture on the bearing performance is affected by starvation lubrication conditions: (1) The effect severity varied with starvation levels; (2) The texturing still improved the operating performance of the journal bearing in the case of weak starvation; (3) Texturing increased the bearing load carrying capacity and reduced the friction coefficient, improving safety and preventing safety accidents due to oil supply problems.

Analysis of the Performance of Chamfered Finite-Length Journal Bearings under Dynamic Loads

Misalignment is one of the most common challenges that the normal operation of journal bearings faces. This type of problem may be the result of a wide range of reasons, such as bearing wear, shaft deformation, and errors related to the manufacturing and installation process. The main undesirable consequences of the misalignment, such as pressure rise and lubricant film reduction, are concentrated on the bearing edges. Therefore, chamfering the bearing edges reduces such misalignment-related drawbacks. This work presents a novel numerical solution to the problem of finite-length journal bearing considering edge chamfering. This solution involves the determination of the levels of lubricant layer thickness and pressure distribution in addition to the journal trajectory under impact load with the related stability limits. The finite difference method is used in this solution, and the equations of motion are also solved numerically using the Runge–Kutta method. The Results of this novel analysis show that chamfering the bearing edges increases the film thickness and reduces pressure spikes associated with the system operation under the case of 3D misalignment. Furthermore, the chamfered bearing shows a wide stability range under impact loads, where the normal bearing is unstable as the critical speed increases by 26.98%, which has positive consequences on the journal’s trajectory.

Tribological properties of MoS2 particles as lubricant additive on the performance of statically loaded radial journal bearings

It is very important to reduce power losses for plain bearings used in industry and especially in automobiles. In recent years, inorganic compounds have been added to the engine oils to reduce friction in plain bearings and increase their performance. In this study, the effects of additive oil obtained by adding 1% by weight Molybdenum Disulfide (MoS2) to the base hydraulic (or lubricating) oil (Shell Tellus 10) on the statically loaded radial journal bearing performance were experimentally investigated. As a result of experiments, it was determined that MoS2 added engine oil showed less friction behavior by forming a better oil film compared to the base oil at increasing bearing load and temperatures, and therefore exhibited less wear and power loss.

Research on Start-Stop Performance of Journal Bearing Based on an Isothermal and Mixed Lubrication Model With Different Acceleration and Deceleration Forms in Consideration

Abstract In order to explore the influence of different acceleration and deceleration forms on the bearing performance during acceleration and deceleration, an isothermal and mixed lubrication model for journal bearings was established. In this model, the fluid mechanics was solved by the Reynolds equation with mass conservation boundary condition, while the contact mechanics was predicted by Greenwood and Tripp (GT) contact model. By the developed model and using different functions of the shaft speed, the start-stop performances of the journal-bearing system under different acceleration scenarios were analyzed. The effects of working conditions, lubrication oil temperature, and bearing structure parameters on the start-stop performance of the journal-bearing system were studied. It was found that the larger starting acceleration can help the journal-bearing system enter the hydrodynamic lubrication faster in the acceleration phase. In the deceleration phase, slow deceleration helps the journal-bearing system maintain hydrodynamic lubrication for a longer time. The higher final speed, lower lubrication oil temperature, and lower bearing clearance can make the journal-bearing system have a better performance in the start-stop process.

Investigation of Microflow Effects in Textures on Hydrodynamic Performance of Journal Bearings Using CFD Simulations

Adequately designed and positioned surface textures are recognized as a promising way to increase load-carrying capacity and reduce frictional losses of journal bearings. The aim of this work is to analyze the local lubrication mechanisms of textures in journal bearings from microflow perspective, while considering the interactions between textures and the film formation in the whole bearing. For this purpose, hydrodynamic lubrication models of textured journal bearings are built. The results show that placing textures downstream of the high-pressure region leads to a reduced friction force, with a less severe loss of load-carrying capacity. The effects of textures on the load-carrying capacity include the positive micro-hydrodynamic pressure effect and the negative effect caused by the discontinuity of the high-pressure region. The micro-hydrodynamic pressure of textures can be generated on one hand by limiting pressure drop (cavitation) in the divergent gap and on the other hand by the inertia effect. For the friction, the vortex inside textures affects the friction force by influencing the maximum shear stress at the minimum oil film. In turn the vortex is influenced by the bearing lubrication film. The research provides the fundamental reference and theoretical basis for the design and optimization of textured journal bearings.

Performance of conical hydrodynamic journal bearing under the worn-out condition

PurposeWhere combined radial and axial loads act on the bearing, the conical journal bearing is best suited. Large turbines, generators, compressors and other machinery perform better while using conical hydrodynamic journal bearings (CHJBs). The bearings worn out and the performance suffered because of regular use and numerous start and stop operations.Design/methodology/approachThe performance of CHJB is evaluated using both analytical and experimental methods in this paper. The analytical method for resolving Reynolds equation uses spherical coordinate system and finite element analysis. On the CHJB test rig, data is collected for different radial loads with 10°, 20° and 30° semi-cone angles using hydraulic oil of viscosity grade ISO VG46.FindingsThe findings of this paper demonstrate that at various semi-cone angles for worn-out bearings, the maximum pressure developed increases with increasing radial load.Originality/valueThis paper provides analytical and experimental performance of CHJBs considering the effect of abrasive wear that is caused because of frequent start and stop operations of machine. The results of wear impact on CHJBs will be helpful for researchers and design engineers.

Effect of microridges on the performance of three-lobe journal bearing considering cavitation and lubricant compressibility

This study presents a numerical study of the effect of microridges on the performance of the three-lobe journal bearing considering lubricant compressibility and cavitation effects. A mathematical model based on the Reynolds equation that has been modified to take into account the effects of lubricant compressibility and cavitation has been proposed to achieve the primary goal of this work. Lubricant compressibility is considered by using lubricating oils with different bulk moduli while Elord's algorithm was used to consider the effect of cavitation. The governing equations for finite length journal bearing lubricated with Newtonian oil in laminar flow and isothermal condition are numerically discretised using the finite difference method and solved by using a suitable prepared computer program. The performance of the rough and smooth bearings was compared for plain and three-lobe journal bearings. The numerical model was demonstrated by comparing the pressure distribution for smooth and microridges three-lobe journal bearing with that published by El-Said et al. and they were found in good agreement. It was found that the pressure and the load were considerably enhanced and the coefficient of friction decreased by 15 % for three-lobe journal bearing with microridges in comparison with that of smooth surfaces.

Analiza performansi eliptičnog ležaja podmazanog eksperimentalno karakterizovanim nano-mazivom s obzirom na toplotni efekat korišćenjem CFD tehnike

This study uses computational fluid dynamics (CFD) to quantitatively examine the performance of an elliptical journal bearing (EJB) lubricated with TiO2 and ZnO nano-lubricant considering thermal effect. In an experiment, nanoparticles with particle concentrations varying from 0 to 2 weight percent are mixed with SAE15W40 engine oil to create these lubricants. The impact of weight fractions, rotational speed, eccentricity, and ellipticity ratios on the thermal performance of the EJB has been examined. The Kreger-Dougherty model is employed to understand the effects of oil film temperature as well as nanoparticle concentration on lubricant viscosity. The pressure and temperature determined by (Dang 2020) and (Wang 2021were evaluated against the CFD model with good agreement. The findings show that for 2 wt% nanoparticles, e of 0.6 and N of 5000 rpm, the load-carrying capacity increased by 5.5% and 4% and the side leakage flow decreased by 24.4% and 18%.

Ferrofluid squeeze film lubrication: surface roughness effect

PurposeThis study aims to investigate the combined effects of roughness and ferrofluid lubricant on finite journal bearing load capacity and squeeze time.Design/methodology/approachThe stochastic theory of Christensen is applied to study the surface roughness effect. The Shliomis model is used to take into account the effects of the rotational viscosity of ferromagnetic particles and their magnetic moment. A finite wire located in the center of the shaft produces the applied magnetic field. A developed computing code allows predicting the effect of the surface roughness on the performance of the considered journal bearing. The good agreement with the results of the literature validates the used approach.FindingsThis study shows that unlike longitudinal roughness, the presence of transverse roughness makes the use of ferrofluid more beneficial in terms of increasing the performance of finite journal bearings. This increase is more significant for large relative eccentricities, which present an ideal confinement.Originality/valueThis study shows the effect of two surface roughness patterns on the squeezing performance of a finite journal bearing lubricated by a ferrofluid.

Impact of partial surface waviness on the tribological performance of hydrodynamic journal bearing

AbstractIn this paper, the static performance analysis of journal bearing having full and partial surface waviness has been presented. The surface waviness is to be considered in the full, first half, second half, and pressure‐increasing and decreasing regions of the bearing for analysis. The effect of surface waviness is considered by modifying the lubricant flow governing Reynolds equation with the film thickness equation and it is solved with the finite element method to get performance parameters like bearing load capacity, friction coefficient, and so forth operating under eccentricity ratios range of 0.2–0.8. The waviness geometrical parameters like waviness numbers and amplitudes are also considered in circumferential, axial, and both directions in the selected regions. The maximum performance has been found for waviness in the full and pressure‐increasing region in the circumferential direction at a high eccentricity ratio.

Effect of Engineered Roughness on the Performance of Journal Bearings Lubricated by Bingham Plastic Fluid Using Computational Fluid Dynamics (CFD)

A journal bearing is a machine element that is used to keep the shaft rotating about its axis. The increasing demand for journal bearing applications in high-speed machines that are efficient and economical has resulted in the need for improvements to the acoustic and tribological performance of journal bearings. In order to improve the tribological and acoustic performance, this study aims to propose a novel journal bearing design by introducing a roughness condition in a specific zone of the stationary bearing surface. In addition, the impact of the application of engineered roughness on the performance of Bingham-plastic-lubricated bearings is investigated in more detail. Considering the effect of cavitation, the analysis was conducted using a 3D computational fluid dynamics (CFD) model of a journal bearing. In comparison with the Reynolds equation—which is inertialess—for lubrication analysis, the use of a 3D CFD model based on Navier–Stokes equations reflects more detailed flow characteristics. Moreover, in this work, variations in the area of surface roughness were employed, resulting in various roughness patterns on the surface of the journal bearing, so that the acoustic and tribological performances of the journal bearing were anticipated to be enhanced. The findings of this study show that under non-Newtonian lubrication of the bearing, the engineered roughness has a strong effect in altering the tribological performance. Furthermore, the well-chosen roughened surface was proven to be more pronounced in enhancing the load support and reducing the friction force. The simulation results also show that using an engineered surface has little effect on the noise of the bearing.

Evaluation and Application of an Engineering Calculation Method of the Static Performance of an Aerostatic Journal Bearing with Multiple Orifice-Type Restrictors

A simplified calculation method is evaluated to calculate the static performance of an aerostatic journal bearing with multiple orifice-type restrictors. This method adopts a one-dimension flow assumption and is a fast calculation method to design journal bearings in engineering by directly linking the structural parameters and performance parameters affecting radial bearings with nonlinear equations. In addition, this method is verified with computational fluid dynamics by two actual case studies, and it is found that the LCC difference between those two methods is less than 5% for a 200 mm diameter spindle, and less than 10% for a 100 mm diameter spindle. Subsequently, the influence of a key parameter ζi on the static performance of journal bearings is explained theoretically. This method is much easier and more intuitive compared with numerical computational methods. Furthermore, it promotes the application of aerostatic journal bearings.

Surface topography effect on tribological performance of water-lubricated journal bearing under mixed-EHL regime

Water-lubricated journal bearings (WLJB) are one of the important components of the stern tube shaft. Surface topography of WLJB is an important aspect in the design of stern tube shaft, and significantly affects the lubrication characteristics of WLJB. This work aims to investigate the effect of non-Gaussian surface topography on tribological performance of water-lubricated journal bearing (WLJB) under mixed-elastohydrodynamic lubrication (mixed-EHL) regime. The non-Gaussian flow factors, and a normalized Weibull probability density function is used to tackle the non-Gaussian roughness in hydrodynamic and asperity contact models respectively. From results, it is observed that skewness (S sk ) significantly affects both asperity contact pressure and hydrodynamic pressure along circumferential direction of bearing. It is concluded that for skewness, S sk = −1 to 1, lambda ratio falls between 1 to 3. The relation between altitude angle and skewness is established. The effect of bearing length to diameter (L/D) ratio on lubrication performance of WLJB is also discussed in detail.

Thermal Analysis and Static Lubrication Performance Study of Liquid Metal Journal Bearing

The temperature distribution of liquid metal journal bearing system in X-ray tube of medical CT machine was simulated by using simulation software, and the working temperature of the herringbone groove liquid metal journal bearing was initially determined. On this basis, the lubricating properties of the liquid metal lubricant were analyzed. The lubrication model of herringbone groove liquid metal journal bearing with Galinstan liquid metal as lubricant was established, and the influence of herringbone groove structure parameters on the static lubrication performance of liquid metal journal bearings was analyzed. The results show that the Galinstan liquid metal has good high temperature stability and can act as a reliable lubricant in the high temperature working environment of the medical CT machine X-ray tube.

Experimental and Numerical Study on Mixed Lubrication Performance of Journal Bearing Considering Misalignment and Thermal Effect

The shaft misalignment under mixed lubrication is an important factor affecting the running performance of the bearing, which can occur under heavy load and unsatisfactory assembly. This paper presents a misaligned journal mixed lubrication model coupling for the asperity contact effect, elastic deformation, viscosity–temperature, and viscosity–pressure effect. The finite difference method was employed to calculate the model, and an experimental apparatus designed in this paper was used to test the friction and temperature characteristics of the specimens. The results show that the pressure field, film thickness, and elastic deformation of the bearing conformed to asymmetric distribution along the axial direction under misalignment conditions and there was a notable end side effect. In addition, the frictional force and side leakage flow were evidently enhanced with the increase in the inclination angle in a certain range. The experimental results showed that there was a visible wear phenomenon on the end sides of the bush and shaft. The research results are beneficial for understanding the mixed lubrication mechanism of misaligned journal bearing.

Modelling and Analyzing the Performance of Journal Bearing with TiO2 and CuO Nanoparticle as Lubricant Additives

Modelling and Analyzing the Performance of Journal Bearing with TiO2 and CuO Nanoparticle as Lubricant Additives

Transient-mixed lubrication model numerically for friction and wear of journal bearings under heavy load during start-up

Purpose Friction and wear are very important factors in predicting the performance of journal bearings, particularly under heavy load in start-up processes. However, there are few relevant studies on the numerical model. This study aims to establish a transient-mixed lubrication model to predict the performance of journal bearings, focusing on the friction and wear behavior under heavy load during start-up. Design/methodology/approach The average Reynold equation, three-dimensional energy equation, shear stress model for friction and Archard model for wear are coupled in the transient model by finite difference method. The linear wear simulation method is bought out to reduce the update times and the calculation time. Findings The different start-up accelerations and linear wear times set are compared and discussed, which indicates a reasonable start-up acceleration is necessary for journal bearings under heavy load during start-up, and setting linear wear times is an effective method to reduce the simulation time significantly. Furthermore, the wear profile in the start-up process spreads in both the clearance and circumferential directions, but mainly in the clearance direction, which increases the minimum film thickness and affects the friction performance. Originality/value This study is of great significance for the numerical prediction of the transient performance of journal bearings during start-up considering friction and wear.

Minimizing Misalignment Effects in Finite Length Journal Bearings

This paper focuses on a method to reduce the detrimental effects that occur due to the misalignment in journal bearings by approaching it with the more complete model of a finite length bearing. Such a drawback is quite common in industrial applications, and it is generally accepted that misalignment causes a significant thinning in the film thickness in the area that is close to the bearing edges. Therefore, removing a certain volume of material from the inner surface of the bearing (bushing) over a distance that is at the bearing edges provides an additional clearance to compensate for the clearance reduction that is due to misalignment. A numerical solution that is used in this work is based on the finite difference method where the Reynolds boundary conditions are considered in the solution scheme, thereby, using an iterative procedure to identify the cavitation zone. A three-dimensional misalignment model is incorporated in the solution in order to provide a more realistic presentation of the deviations and errors that there are in comparison with the ideal aligned case. It has been found in the present work that the edge modification increases the thickness of the lubricant layer considerably and reduces the pressure spikes that are associated with the presence of misalignment. The suggested design also reduces the coefficient of friction in comparison with that of the misaligned case. Furthermore, this method helps in reducing the asymmetry of the hydrodynamic pressure field that results from the misalignment. This method enables the operation of journal bearings over a wider range of misalignment levels without sacrificing the load-carrying capacity of the bearing by maintaining a relatively thicker layer of lubricant at the critical positions that are not so due to the effects of misalignment.

Implementation of the Elrod Algorithm in Practical Design of an Axial Lubricant Supply Groove in Journal Bearings

Abstract The Elrod algorithm was implemented to study the effects of axial lubricant supply groove parameters, i.e., groove length, width, and location, on the performance of a one-axial groove journal bearing, taking into consideration thermal effects. The results and presented recommendations will assist bearing designers in determining the groove’s preferred angular location and main dimensions to achieve a solution in terms of low total power loss and high minimum film thickness. It is suggested that with regard to low total power loss and high minimum film thickness, for a lighter loaded bearing, the axial groove should be located in the angular range of 100–140 deg to the load line with a groove length ratio Lg/L over 0.6 or the angular range of 300–350 deg with an Lg/L over 0.75. For a heavier loaded bearing, it is suggested that the groove be placed at the angular range of 80–115 deg with an Lg/L over 0.6.

Performance of rough surface hydrodynamic circular and multi-lobe journal bearings in turbulent regimes

This article deals with the steady and dynamic performance analysis of rough surface circular and multi-lobe journal bearings operating with non-Newtonian lubricant in turbulent regimes. The numerical solution of Reynold's equation was obtained using the finite element method. To account for surface roughness, the Patir and Cheng model was used, and fluid turbulent behavior was modeled using the turbulent theory as proposed by Ng and Pan. The non-Newtonian behavior of the lubricant is presented by the Rabinowitsch fluid model, and JFO boundary conditions are used to solve Reynold's equation, considering gaseous cavitation. The bearing with micro-roughness has been considered in numerical analysis and transverse roughness has been reported to improve bearing performance indices. Among the different bearing design configurations, the two-lobe bearing configuration provides significantly improves the minimum film thickness, hydrodynamic pressure, and dynamic parameters. The presence of turbulent flow and transverse surface roughness produces a synergistic effect that enhances the minimum film thickness, stiffness, and damping parameters of journal bearings. This study provides a detailed comparison between various bearing designs and recommends the use of two-lobe bearings for high-speed applications.