Hydrodynamic Journal Bearings Research Articles

Design optimization of vein-bionic textured hydrodynamic journal bearing using genetic algorithm

Design optimization of vein-bionic textured hydrodynamic journal bearing using genetic algorithm

Environmentally acceptable lubricants (EAL) compared with a reference mineral oil as marine stern tube bearing lubricant – Experimental and theoretical investigations

The purpose of this research is to indicate the potential differences in bearing characteristics resulting from the application of different lubricant types with the same viscosity grade. The effect of different environmentally acceptable lubricants (EALs) on hydrodynamic journal bearing properties is studied experimentally and compared to the properties obtained after lubrication with a reference mineral oil. The results of the studies proved that a bearing lubricated with EALs had practically the same properties as one lubricated with mineral oil. The calculations for the tested bearing system showed that the variations of selected lubricant parameters, such as specific heat or thermal conductivity, do not significantly affect the properties of the bearing, i.e. the minimum film thickness or power losses.

Effect of rectangular rough dimples of textured surface on tribological behavior of a hydrodynamic journal bearing

The geometry and location of the textures can affect the hydrodynamic bearing and coefficient of friction for the journal bearing case. The present study deals with the analysis of the effect of texture containing dimples in rectangular forms with the introduction of micro-dimples at the same time (considered as roughness). The relationship between texture (dimples) and micro-texture (micro-dimples) is based on two key geometric parameters (roughness ratio and micro-dimples ratio). Numerical modeling is used to analyze the effect of rectangular texture, its geometry (with variation of these ratios) and its location on the tribological behavior in steady-state régime. The results indicate that a rectangular texture with roughness (micro-dimples) can considerably improve the performance of journal bearing.

Effect of texture shapes and additives in lubricants on the dynamic characteristics of the hydrodynamic journal bearing

PurposeThis study aims to understand how the texture shape, number of textures and addition of nanoparticle additives in lubricants impact the dynamic characteristics of journal bearing by comparing six different texture shapes like triangle, chevron, arc, circle, rectangle and elliptical applied in pressure-increasing region under various geometrical and operating conditions.Design/methodology/approachThe finite element method approach has been employed to solve governing Reynold’s equation, assuming iso-viscous Newtonian fluid, for computation of performance parameters like stiffness and damping coefficient, threshold speed, etc. By using a regression model, the impact of adding nanoparticles Al2O3 and CuO to the base lubricant on viscosity variation is calculated for selected temperature ranges and weight fractions of nanoparticles.FindingsThe arc-shaped texture with an area density of 28.27%, eccentricity ratio of 0.2 and texture depth of 0.6 exhibited 35.22% higher direct stiffness and 41.4% higher damping coefficient compared to the lowest value in the circle-shaped texture. Increasing the number of arc-shaped textures on the bearing surface with low area density led to declining stiffness and damping parameters. However, with nanoparticle additives, the arc-shaped texture further showed 10.75% and 8.11% improvement in stiffness and 9.99% and 4.87% enhancement in damping coefficient for Al2O3 and CuO, respectively, at 90 °C temperature and 0.5% weight fraction.Originality/valueBy understanding the influence of texture shapes on the dynamic characteristics, engineers can design bearings that exhibit improved stability and enhance overall performance.

Modelling and Simulation of Aerodynamic Cylindrical Bearings Using ANSYS Hydrodynamic Bearing Element Types

Modern power engine concepts and environmental restrictions demand oil-free lubrication of rotors, for example, by gas bearings. However, the stiffness and damping properties ruling the rotor’s dynamics are poorly documented for aerodynamic bearings and simple calculation methods are lacking. Based on the similarity between aerodynamic and hydrodynamic journal bearings, it is investigated to what extent the hydrodynamic bearing element types of the commercial FE program ANSYS are also suitable for air bearings. Within these elements, the compressibility of the gas is neglected. After verification of the ANSYS hydrodynamic element types with literature data for cylindrical hydrodynamic bearings, the stiffness and damping coefficients of a cylindrical aerodynamic bearing are calculated by using the ANSYS hydrodynamic element types. In the examined speed range, the results agree well with literature data that consider gas compressibility. Therefore, the FE elements designed for hydrodynamical journal bearings may also be used for simulating cylindrical aerodynamic bearings. The presented calculation approach provides a compact and easy-to-use method for rotordynamic simulations with cylindrical aerodynamic bearings in a single development environment.

Analysis of the Turbulent Lubrication of a Textured Hydrodynamic Journal Bearing

In order to investigate the turbulent lubrication performance of a textured hydrodynamic journal bearing (THJB), a model of turbulent lubrication was established in this paper. The variations in the Reynolds number, oil film thickness, oil film pressure, bearing capacity, attitude angle, and side leakage flow with structural and working parameters were studied, and the axis whirl orbit was further analyzed. The results show that turbulent lubrication is suitable for the actual operating conditions of THJBs. The Reynolds number decreases with the eccentricity ratio in the pressure-bearing zone but increases with rotational speeds, whereas the variation in the maximum oil film pressure increases and the minimum oil film thickness decreases with the eccentricity ratio under various Reynolds numbers. The bearing capacity decreases with the dimple diameter, depth, oil film thickness, and clearance ratio but increases with the length/diameter ratio and dimple spacing. As the eccentricity ratio increases, the attitude angle decreases, but the side leakage flow increases. In addition, the system tends to be unstable as the rotational speed and length/diameter ratio increase, and the friction and wear on the surface are three-body friction. This work not only helps in analyzing the characteristics of a THJB under actual operating conditions but also provides support for research on the simulation of THJB’s lubrication mechanism of THJB via computational fluid dynamics.

Static Characteristics of Water-Lubricated Hydrodynamic Spiral-Groove Journal and Thrust Bearings for Motorized Spindle

Abstract Oil-lubricated hydrodynamic bearing is a typical support for motorized spindle. However, a motorized spindle supported by the oil-lubricated hydrodynamic bearing has disadvantages regarding high-temperature rise and low rotational speed. To overcome this problem, this technical brief proposes novel water-lubricated hydrodynamic spiral groove bearings for the motorized spindle. A rotor-bearing static model for the motorized spindle was established considering the external loads and the tilting effect of bearings. An experimental prototype for the motorized spindle was developed, and the theoretical calculation and experimental research on the bearing static characteristics were carried out. The result shows that the water-lubricated hydrodynamic spiral groove bearings have significant advantages in terms of low-temperature rise, good high-speed performance, and moderate spindle stiffness, together with the inherent low manufacture cost and high rotation accuracy of the bearings, and the proposed bearings can be a potential alternative to the fluid bearing for the high-speed motorized spindle.

Numerical analysis of finite bearing operating under non-Newtonian lubricant and flow turbulence effect

The purpose of this work is to evaluate the combined influence of turbulence and shear-thinning/shear-thickening lubricant on the steady-state characteristics of hydrodynamic journal bearings. The modified Navier–Stokes equation for linear turbulence and non-Newtonian (shear-thinning as well as shear-thickening aspect) lubricants are solved using a finite element method to acquire load capacity, attitude angle, friction coefficient variable, total oil flow, and temperature rise variable for distinct combined values of the flow behavior index and Reynolds number. This work utilizes the Navier–Stokes equation with Ng–Pan's linear turbulence and shear-thinning/shear-thickening lubricant models, which is very helpful in predicting the performance characteristics of hydrodynamic bearings under harsh industrial operating conditions. The results show that the combined presence of non-Newtonian lubricant and turbulence in the flow significantly affects the steady-state performance parameters of such type of bearing compared to existence of individual presence of turbulence and non-Newtonian lubricant in the clearance space. This work helped to provide better insight into the operation of journal bearings in a severe environment owing to the high speed and changes in the nature of lubricant.

ANALYSIS OF FLOW AND TEMPERATURE DISTRIBUTION IN JOURNAL BEARING LUBRICATED WITH VEGETABLE OIL

The use of vegetable oil as a sustainable alternative to mineral oil in lubrication applications has garnered considerable attention. This research focuses on evaluating three different vegetable oils, namely palm mid olein (PMO), refined bleached deodorized palm oil (RBDPO), and rapeseed oil, for their effectiveness in lubricating a hydrodynamic journal bearing. The study examines key performance factors such as pressure, temperature, load-carrying capacity, and coefficient of friction. Computational fluid dynamics (CFD) is employed to compare the lubricating capabilities of the vegetable oils against engine oil. Rapeseed oil emerges as the most promising option among the vegetable oils, displaying notable advantages. It demonstrates a 22.12% higher pressure, 26.37% higher load-carrying capacity, and 0.37% higher temperature distribution compared to PMO. In contrast, while engine oil exhibits a 16.67% higher pressure distribution and 35.8% higher load-carrying capacity, it also comes with a drawback of 44.29% higher coefficient of friction compared to other vegetable oils. It is worth noting that the simulation results have been validated through experimental data, leading to the conclusion that engine oil surpasses vegetable oils in terms of pressure and temperature distribution.

Time History of Maximum Bearing Temperature Based on a Simplified Thermohydrodynamic Lubrication Theory

An overshoot phenomenon of bearing temperature in hydrodynamic journal bearings may be observed during a sudden start-up experiment. This phenomenon implies that the maximum bearing temperature in acceleration operation may exceed the predicted one which can be predicted accurately by applying a state-of-the-art steady state thermohydrodynamic lubrication (THL) model. This paper presents the maximum bearing temperature including the one during acceleration operation by using a simplified THL model that is newly proposed for a transient THL analysis. It is found that the overshooted temperature can be qualitatively predicted by using the transient THL model that incorporates properly the interaction between the motion of journal center and the viscous dissipation, even if it is a simple model. Next, the transient temperature during slow acceleration operation and also those toward higher dimensional steady state journal rotational speed are calculated and they are found to be in qualitative agreement with the measurements. The oil film characteristics such as oil film pressure, temperature and thickness after reaching the steady state equilibrium do not depend on the value of initial journal eccentricity ratio in the transient analysis. However, when the values are different, the characteristics immediately after starting rotation change largely. In the case of the value 1.00, it is found to give a prediction that agrees qualitatively with the characteristics measured in the experiment.

Performance of hydrodynamic textured journal bearing with the combined influence of elastic deformation and pseudo-plastic lubricant

This study outlines the performances of finite-length journal bearing with textured liner, shear-thinning Rabinowitsch lubricants, and considers the elastic deformation of the bearing liner. The yielded nonlinear Rabinowitsch-Reynolds PDE system has been solved using the finite difference method combined with Elrod’s algorithm for the case of cylindrical textures. The static performance of hydrodynamic lubrication, in this case, involves different parameters such as depth of texture, eccentricity ratio, elastic deformation factor, rheological index, etc. Results showed that, at a fixed eccentricity ratio, texturing of the bearing’s converging area enhances significantly the load-carrying capacity and reduces the friction coefficient compared to the smooth bearing surface (up to [Formula: see text] in load capacity and [Formula: see text] in friction coefficient). On the other hand, using a lubricant with more pronounced shear-thinning behavior and/or elastic liner reduces the journal bearing performances (up to [Formula: see text] in load capacity and [Formula: see text] in pressure). By applying the optimization technique (particle swarm optimization), an optimal arrangement of textures that can compensate for these losses in performance even at high eccentricity has been found. This optimal texture with dimensionless dimple’s depth set to 1 [Formula: see text] improves the load capacity with [Formula: see text] for a lubricant with a rheological index [Formula: see text] and elastic bearing liner with deformation parameter [Formula: see text].

Theoretical and experimental study on the stability of water lubricated high speed journal bearing with lobe pockets

The stability problem prevents the application of water lubricated journal bearing in high speeds conditions. To improve the bearing performance, the lobe pocket with Archimedes helix profile is designed in the water lubricated hydrostatic and hydrodynamic hybrid journal bearing. Bearing stiffness coefficients, damping coefficients and threshold speed are investigated with considering turbulence. Effects of radius clearance, pocket parameters, water supply pressure, restriction parameter and external load are analyzed. The results indicate that decreasing radius clearance and increasing pocket depth both improve the bearing stability, while there are optimal values for pocket widths. The water supply pressure and orifice diameter increase the threshold speed at low speeds. The results obtained provide useful information for designing high stability journal bearings.

Thin films in hydrodynamic lubrication regime: The Osiris friction setup.

A model hydrodynamic lubrication tribometer consisting of two hydrodynamic journal bearings working under thin film conditions was developed to investigate the mechanisms of hydrodynamic friction with low-viscosity fluids and the role of surface effects. A small nominal radial clearance of about 5 µm was considered between the two surfaces. This fully instrumented setup provides in situ information on the sheared fluid film in terms of simultaneous measurements of film thickness; localization and extension of the cavitation zone, with a resolution of 30°; nominal friction torques up to 0.5 Nm, with an accuracy of 0.05 mNm; temperature; and the position of the shaft for velocities up to 12 000 rpm. To illustrate the capability of the Osiris tribometer, thin hydrodynamic film measurements were performed on smooth surfaces. The results are presented here, and the thermal effects, acceleration, and inertia contributions are discussed. Finally, the influence of the surface topography using textured surfaces was demonstrated and the role of adsorbed layers on the surface due to fluid formulation was highlighted.

CFD analysis of hydrodynamic journal bearing with Bingham plastic lubricant considering roughness

CFD analysis of hydrodynamic journal bearing with Bingham plastic lubricant considering roughness

Investigation on acoustic, thermal, and tribological properties of hydrodynamic journal bearing with heterogeneous rough/smooth surface

High level of noise limits the reliability of the lubricated journal bearing. In the current paper, the possibility of bearing design with a heterogeneous rough/smooth surface is explored using the computational fluid dynamics (CFD) approach to improve tribological and acoustic performance. A parametric analysis is conducted to determine the optimal surface roughness level, the cavitation pressure, and the ratio of length to the diameter of the journal. The effect of the presence of a roughened pattern on the thermal behavior of the lubricant, friction force, noise level, and cavitation phenomena was also studied in depth. The main finding of the present study is that when conventional journal bearing fails in generating the load support for concentric conditions, the heterogeneous rough/smooth bearing has a beneficial effect by increasing the load-carrying capacity. Furthermore, the high level of surface roughness can significantly increase the load-carrying capacity while decreasing frictional forces and acoustic power. However, the roughness does not dramatically change the maximum temperature (less than 1%). The numerical results also suggest that the variation in vapor saturation pressure has a negligible effect on the maximum temperature, friction force, and noise level.

Energy-Conserved Hydrodynamic Lubricated Components with Wall Slippage

The hydrodynamic thrust slider and journal bearings as well as hydrodynamic lubricated gears with the merit of energy conservation by the wall slippage are reviewed. The principle for designing these hydrodynamic contacts is to artificially set the wall slippage on the stationary surface in the hydrodynamic inlet zone. To design the wall slippage on the moving surface in the hydrodynamic outlet zone can also give additional benefits. The technical merits of these mechanical components are the improved load-carrying capacity and the lowed friction coefficient, i.e., the energy conservation due to the wall slippage. Owing to the designed wall slippage, the carried load of the hydrodynamic step bearing can be increased by 200%~400% while its friction coefficient can be reduced by 50%~85%, and the load-carrying capacity of the hydrodynamic journal bearing can be increased by nearly 100% while at the same time, its friction coefficient can be reduced by more than 60%. For hydrodynamic lubricated gear contacts, by covering ultrahydrophobic or oilphobic coatings on the slower moving surface, the friction coefficient can be approaching to vanishing and the contact load-carrying capacity can be increased very significantly for large slide-roll ratios under medium or heavy loads.

Cooled pads with bioinspired gyroid lattice for tilting pad journal bearings: Experimental validation of numerical model for heat transfer

Hydrodynamic journal bearings are essential components for industrial rotating machineries. Continuously growing specific power allows more compact and efficient machines to be obtained, by reducing the environmental footprint of production plants. The aim of this work is to provide a new design of an innovative pad for Tilting Pad Journal Bearings (TPJBs) with an embedded cooling circuit, able to limit the oil film temperature. As a result, specific load can be increased leading to a possible downsizing of the bearing and reduction of lubricant quantity. The heat exchange in the cooling circuit of the pad has been enhanced using bioinspired gyroid lattice. The thermo-mechanical study of the pad has been performed with both numerical and experimental analysis. The resulting thermal and mechanical performances have been calculated and discussed. The tested components have been manufactured in stainless steel by using a metal 3D printing technology, based on polymer-metal feedstock extrusion. A performance analysis is conducted to catch differences between the nominal and the printed geometry. The prototype is able to dissipate the generated heat with a higher efficiency, and the pressure drop inside the cooling circuit can be estimated with the numerical model here proposed.

Multiscale Analysis of Hydrodynamic Journal Bearing Considering the Effect of the Physically Adsorbed Boundary Layer

Multiscale Analysis of Hydrodynamic Journal Bearing Considering the Effect of the Physically Adsorbed Boundary Layer

Analysis of Nonlinear Time-Domain Lubrication Characteristics of the Hydrodynamic Journal Bearing System

The nonlinear time-domain lubrication characteristics of the hydrodynamic journal bearing system are studied in this paper. The motion equation of the hydrodynamic journal bearing system is established based on the balance of the relationship among the water film force, journal inertia force, and external load. The water film pressure distribution of the sliding bearing is calculated by the finite difference method. Firstly, the variation law of the water film pressure distribution with time under the external periodic load is calculated considering the inertial force of the journal. The influence of the initial eccentricity on the orbit of the journal center is studied. Secondly, the maximum water film pressure, the orbit of the journal center, eccentricity, water film pressure, and the minimum water film thickness of the bearing under the action of circumferential and unidirectional periodic external loads are calculated, and the effects of inertial force and rotational speed on the dynamic characteristics of the bearing are analyzed. Finally, the water film dynamic characteristics under low speed and heavy load are studied. The result shows that the pressure of the dimensionless water film caused by inertial force is reduced by 7 to 10 percent at the rotational speed between 200 r/min and 800 r/min, which means that the influence of inertia force cannot be ignored.

Effect of lubricant inertia on steady-state characteristics of textured hydrodynamic journal bearing

PurposeThis paper aims to investigate the effects of inertia of the lubricant on the performance parameters of journal bearings textured with spherical-shaped textures.Design/methodology/approachThe lubricant is assumed to be Newtonian, and the flow is considered laminar. Considering the lubricant inertia effects, the modified Reynolds equation is discretized using the finite difference method and solved with the Gauss–Seidel successive over-relaxation scheme using the progressive mesh densification method.FindingsThe results from this numerical study indicate that the lubricant inertia improves textured journal bearing performance characteristics significantly. The improvement is more significant in the case of heavily loaded bearings. Furthermore, it is observed that protruded texturing in journal bearings shows better results compared to dimple textured journal bearings.Originality/valueUnderstanding the effect of lubricant inertia is essential for efficiently designing textured journal bearings. Thus, the results shown here would be helpful for the researchers and the bearing designers.