Showing papers on "Fluid bearing published in 2019"
TL;DR: In this paper, the frictional behavior of plane converging bearings was experimentally and numerically studied for four texture geometries fabricated by ultra-short pulse laser texturing (single pocket, line, cross-and dot-like texture) and convergence ratios under full-film lubrication in the presence of thick oil films (up to 100μm).
98 citations
TL;DR: In this article, the influence coefficient method (ICM) was proposed to evaluate the elastic deformation, and the elastic-hydrodynamic lubrication (EHL) model of the water-lubricated micro-groove bearings was developed.
60 citations
TL;DR: In this paper, the authors identify the characteristic parameters, such as the sliding velocity, Hersey number, and friction torque or friction coefficient, when the transition of lubrication regimes occurs for different journal bearing types.
56 citations
TL;DR: In this paper, three kinds of new Koch snowflake textures were designed on the surface of the UHMWPE to try to decrease friction and prolong the service life of the bearings.
52 citations
TL;DR: In this paper, a transient hydrodynamic lubrication model is proposed to investigate the lubrication performance of micro-grooved journal bearings, considering axial flow caused by the axial reciprocating movement of the shaft.
44 citations
TL;DR: In this article, a numerical model for the lubricated full-floating pin bearings in multibody mechanical systems was developed by embedding the hydrodynamic lubrication and solid contact forces in the revolute joint clearance.
31 citations
02 May 2019
TL;DR: In this article, the optimum design parameters of chevron-shaped surface texture have been determined for the steady state performance enhancement of a hydrodynamic journal bearing for the purpose of improving the stability of the bearing.
Abstract: In the present study, the optimum design parameters of chevron-shaped surface texture have been determined for the steady state performance enhancement of a hydrodynamic journal bearing. The fluid ...
25 citations
TL;DR: In this article, a new formulation for the dynamic compliance coefficient is derived which significantly reduces these discrepancies, and possible explanations for the remaining discrepancies are discussed, and a new technique to calculate the onset speed of instability (OSI) in the frequency domain is developed.
18 citations
TL;DR: In this article, the shape of the threshold curve for a rigid rotor supported on a plain bearing is investigated. And the influence of run-up time and acceleration on the stability threshold curve is compared to the analytical expressions for the threshold curves calculated for the IS approximation.
16 citations
TL;DR: In this paper, a computational model of a hip implant based on multibody dynamics methodology and Reynold equation is developed, and it is illustrated that modifying velocities can cause friction forces to increase, significantly, compared to Goenker and Booker's.
15 citations
TL;DR: In this article, the dynamics of air bearings and aerostatic spindle system in ultra-precision machine, which mainly causes mid-spatial waviness errors, has a great effect on surface topography.
Abstract: Aerostatic bearings are of great importance for improving machining accuracy of a workpiece surface. The dynamics of air bearings and aerostatic spindle system in ultra-precision machine, which mainly causes mid-spatial waviness errors, has a great effect on surface topography. The dynamic coefficients of the thrust bearings were determined by adopting the perturbation method and finite difference method with MATLAB® software. In addition, the influences of the spindle speed and tilt angle conducted upon the dynamics of the thrust bearings were investigated in detail. The dynamic response of the spindle system, which is closely related to the performance of the thrust bearing and does not work only by the effect of the journal bearing, supported by pressured air film was obtained. The simulation analysis of spindle responses under cutting force and experiment results is well matched, and the analysis method proposed in this paper can be also applicable to other air bearing spindle systems.
TL;DR: The hydrodynamic journal bearing is an important part of rotary machine and faces many challenges such as high rotating speed, heavy specific pressure, and large temperature rise with the development of dynamic journal bearing as mentioned in this paper.
Abstract: Hydrodynamic journal bearing is an important part of rotary machine and faces many challenges such as high rotating speed, heavy specific pressure, and large temperature rise with the development o...
TL;DR: In this paper, the effects of non-Newtonian pseudo-plastic lubricants behavior, using Rabinowitsch fluid model, on static characteristics of circular self-lubricating porous journal bearings of finite length with sealed ends are highlighted.
TL;DR: In this article, a wedge-shaped structure opened on an edge of oil seal is put forward, the loss and insufficiency for hydrostatic bearing capacity are made up by using dynamic pressure, and then, hydrostatic hydrodynamic lubrication is realized.
Abstract: This paper aims to improve the bearing capacity of hydrostatic thrust bearing under working conditions of high speed and heavy load; a new wedge-shaped structure opened on an edge of oil seal is put forward, the loss and insufficiency for hydrostatic bearing capacity are made up by using dynamic pressure, and then, hydrostatic hydrodynamic lubrication is realized.,Oil film three-dimensional models of unidirectional and bi-directional hydrostatic hydrodynamic oil pad are established by using UG. The oil film pressure fields of two kinds of oil pad are simulated by using ANSYS ICEM CFD and ANSYS CFX; the pressure fields distribution characteristics are obtained, and the effects of workbench rotary speed and bearing weight on pressure field are analyzed. Also, the experimental verification is made.,The results demonstrate that with an increase in workbench rotary speed, the oil film pressure of two kinds of hybrid oil pad increases gradually, and the maximum pressure of the bi-directional one accounts for 95 per cent of the unidirectional one when the load is constant. With an increase in load, the oil film pressure of two kinds of hybrid oil pad increases gradually, the difference between them is 9.4 per cent under the condition of load of 25 t when the rotary speed is constant.,The paper can provide theoretical basis for a structure design of hybrid thrust bearing under different rotary speed and load conditions, and compensate the shortage of static pressure-bearing capacity by using dynamic pressure, improve the stability of vertical CNC machining equipment.
TL;DR: In this paper, the influence of groove shape on the hydrodynamic characteristics of a journal bearing was investigated, which can illustrate the lubrication performance of the journal bearing under different operation conditions.
Abstract: The purpose of this study is to investigate the influence of groove shape on the hydrodynamic characteristics of a journal bearing.,The computational fluid dynamics model also takes into account the cavitation phenomena and thermal effect, which can illustrate the lubrication performance of a journal bearing.,The hydrodynamic simulations of the journal bearing with the different groove shapes are conducted under different operation conditions.,Based on the numerical analysis, the suggestions are presented for groove shape selection and can be used to the design of a journal bearing under the extreme operation condition.
15 Sep 2019
TL;DR: In this paper, 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.
Abstract: 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.
TL;DR: In this article, the performance characteristics of an externally adjustable bearing with multiple bearing pads in steady state conditions were investigated, and a modified film thickness equation was used to incorporate the bearing adjustments and accurately predict the variation in film profile.
Abstract: Purpose – This study aims to investigate the performance characteristics of an externally adjustable bearing with multiple pads in steady state
conditions. The proposed adjustable bearing geometry can effectively control the hydrodynamic operation in bearing clearances by adjusting the
pads in radial and tilt directions. These pad adjustments have a significant role in improving the bearing characteristics such as load capacity,
attitude angle, side leakage, friction variable and Sommerfeld number, which will be analysed in this paper.
Design/methodology/approach – The adjustable bearing is designed with circumferentially spaced four bearing pads subjected to similar radial
and tilt adjustments. Tilt angles are applied along the leading edges of bearing pads. A modified film thickness equation is used to incorporate the
pad adjustments and accurately predict the variation in film profile. Finite difference approximation is adopted to solve the Reynolds equation and
discretize the fluid film domain.
Findings – For negative radial and tilt adjustments, higher hydrodynamic pressures are generated in bearing clearances, which increases the
bearing load capacity at different eccentricity ratios. From comparative analysis for different pad adjustments, superior bearing performance is
observed for bearing pads under negative radial and negative tilt adjustments.
Originality/value – This research presents a detailed theoretical approach to analyse the performance capability of a four pad adjustable bearing
geometry, which is not available in literatures. Improved bearing performances with negative pad adjustments can attract bearing designers to
implement the proposed adjustability-bearing concept in rotating machineries.
TL;DR: In recent years, extensive use of smart lubricants has been made in order to control the tribological performance of fluid film bearings as mentioned in this paper, and the grooved surfaces of the journal bearing greatly influen...
Abstract: In recent years, extensive use of smart lubricants has been made in order to control the tribological performance of fluid film bearings. The grooved surfaces of the journal bearing greatly influen...
01 Jul 2019
TL;DR: Based on the numerical simulation of the rough surfaces, Reynolds equation and Newton's Second Law of Motion-Force and Acceleration, the calculation model for planar thrust sliding bearing consider... as mentioned in this paper.
Abstract: Based on the numerical simulation of the rough surfaces, Reynolds equation and Newton's Second Law of Motion-Force and Acceleration, the calculation model for planar thrust sliding bearing consider...
01 May 2019
TL;DR: In this article, the safety of shipping depends on their durability and reliability, and the new legal restrictions on propeller shafts are discussed. But they do not consider the propulsion system of ships.
Abstract: Bearings of propeller shafts are very crucial elements of the propulsion system of each of the ships. The safety of shipping depends on their durability and reliability. The new legal restrictions ...
TL;DR: In this paper, a CFD-smoothed particle hydrodynamics (SPH) code is applied to simulate hydrodynamic lubrication for a linear slider bearing in the presence of a 3D rough surface.
Abstract: Rough and textured surfaces are of paramount importance for lubrication, both in nature and in technology. While surface roughness relevantly influences both friction and wear, artificial surface texturing improves the performance of slider bearings as an energy efficiency action. The simulation of hydrodynamic lubrication by taking into account complex surfaces as boundaries requires the use of computational fluid dynamics (CFD) software able to predict the pressure and the velocity profile through the thickness of the fluid and at any point within the 3D domain. In the present study, a CFD–smoothed particle hydrodynamics (SPH) code is applied to simulate hydrodynamic lubrication for a linear slider bearing in the presence of a 3D rough surface, showing the capabilities of CFD–SPH in modelling such complex interaction phenomena. Numerical assessments involve the load capacity, the 3D fields of the velocity vector, and the pressure 3D field (both within the fluid domain and at the fluid–plate interface).
TL;DR: In this article, the idea of using cooled pads with internal channels in which an external cooling fluid is circulated will be applied to a TPJB for the first time, and the results of the numerical simulations will be discussed.
Abstract: Tilting-pad journal bearings (TPJBs) are widely installed in rotating machines owing to their high stability, but some drawbacks can be noted, such as higher cost with respect to cylindrical journal bearings and thermal issues. High temperatures in the pads correspond to low oil-film thicknesses and large thermal deformations in the pads. Therefore, the restriction of the maximum temperature of the bearing is a key aspect for oil-film bearings. The temperature reduction is generally obtained by adopting higher oil inlet flowrates or suitable oil nozzles. In this paper, the idea of using cooled pads with internal channels in which an external cooling fluid is circulated will be applied to a TPJB for the first time. The three-dimensional TEHD model of the TPJB, equipped with a cooled pad, will be introduced, and the results of the numerical simulations will be discussed. Several analyses have been performed in order to investigate the influence of cooling conditions, such as the type, flowrate, inlet temperature and number of cooled pads. Two types of pad geometry with different cross-sections of the cooling circuit, namely, circular and six-square multi-channel sections, have been compared to the reference bearing with solid pads. Simple experimental tests were performed by means of a test rig equipped with a cooled pad bearing obtained with the additive manufacturing process, thus showing the effectiveness of the solution and the agreement with the predictions.
27 May 2019
TL;DR: In this paper, the authors proposed a hydrodynamic lubrication regime to limit wear and promote minimal friction by sliding the journal bearings of an engine journal bearing, but this regime is not suitable for all engine journal bearings.
Abstract: Ideally, engine journal bearings are expected to operate under hydrodynamic lubrication regime to limit wear and promote minimal friction by sliding. Nevertheless, engine journal bearings fail sinc...
TL;DR: In this paper, the dynamics of a radial bearing and aerostatic spindle system in an ultraprecision fly-cutting machine are analyzed using the MATLAB® software, and the simulation results show that the rotating speed has a little impact on stiffness but having a great impact on damping.
Abstract: The dynamics of a radial bearing and aerostatic spindle system in an ultraprecision fly-cutting machine cause mid-spatial waviness errors, which have a significant effect on surface topographies. Air bearings, which are externally pressurized, comprise two journal bearings and two thrust bearings with orifice restrictors. The dynamic coefficients of the radial bearings are obtained by adopting the perturbation and finite difference methods with the MATLAB® software. In addition, the influences of the spindle speed and tilt angle on the dynamics of the radial bearings are investigated in detail. The simulation results show that the rotating speed has a little impact on stiffness but having a great impact on damping, and the theoretical values of static stiffness are almost the same as the experimental values. The dynamic responses of the spindle system supported by pressurized air film are obtained, and the simulation analysis of spindle responses under cutting forces is also well matched to the experiment results.
TL;DR: In this article, a method for reducing the friction of high-precision system, air bearings have been widely used for various industrial applications, however, their small damping leads to poor in-position stabilisation.
Abstract: As a method for reducing the friction of high-precision system, air bearings have been widely used for various industrial applications. However, their small damping leads to poor in-position stabil...
TL;DR: In this article, the impact of bearing ovalization on the dynamics of a planar slider-crank mechanism with a hydrodynamic bearing located between the connecting rod (conrod) and the crank was investigated.
01 Jul 2019
TL;DR: Experimentation is an effective approach to study the dynamic coefficients of journal bearings because experimental results are more reliable than theoretical calculations as discussed by the authors, which is the case for most of the articles.
Abstract: Experimentation is an effective approach to study the dynamic coefficients of journal bearings because experimental results are more reliable than theoretical calculations. Dynamic coefficients ide...
TL;DR: In this article, a general CFD-based frequency response method for obtaining the dynamic coefficients of hydrodynamic bearings is presented, which is grounded in experimental parameter identification methods and is verified for an extremely long, slider bearing geometry as well as short and long journal bearing geometries.
Abstract: A general, CFD-based frequency response method for obtaining the dynamic coefficients of hydrodynamic bearings is presented. The method is grounded in experimental parameter identification methods and is verified for an extremely long, slider bearing geometry as well as short and long journal bearing geometries. The influence of temporal inertia on the dynamic response of the bearings is discussed and quantified through the inclusion of added mass coefficients within the mechanical models of the hydrodynamic bearing films. Methods to separate the dynamic stiffness into static stiffness and added mass contributions are presented and their results compared. Harmonic perturbations are applied to the bearings at varying frequencies to determine the frequency dependence of the dynamic coefficients and to facilitate the decomposition of the dynamic stiffness into its constituents. Added mass effects are shown to be significant for the extremely long slider bearing geometry and negligible for the short and long journal bearing geometries under operating conditions motivated by those typical of marine bearings.
TL;DR: In this article, a hydrodynamic lubrication analysis for connecting rod big-end bearing is conducted, where the effects of engine speed, operating condition, lubricant viscosity and oil temperature on tribological performance of big end bearing have been examined.
Abstract: A hydrodynamic lubrication analysis for connecting rod big-end bearing is conducted. The effects of engine speed, operating condition, lubricant viscosity and oil temperature on tribological performance of big-end bearing have been examined. Force equilibrium is solved to define instantaneous eccentricity between journal and bearing to have accurate estimation of oil film thickness at interface of connecting rod big-end bearing and crankpin. Connecting rod big-end is treated as π film hydrodynamic journal bearing and finite difference scheme is applied to calculate generated hydrodynamic pressure and frictional power loss at each crank angle. Beside the development of analytical formulation, well-known Mobility model introduced by Booker has been employed to be compared with the analytical model. The presented analytical model reduces the complexity and the numerical effort with respect to Mobility method, thus shortening the computation time. The simulation results show good agreement between analytical model, Mobility approach and experimental data.
31 Mar 2019
TL;DR: In this paper, the effect of the change in bearing radial clearance with pressure variation of the fluid (lubricant) in a hydrodynamic journal bearing was carried out using the Galerkin Finite Element Method (GFEM).
Abstract: This work entails the parametric study of the effect of the change in bearing radial clearance with pressure variation of the fluid (lubricant) in a hydrodynamic journal bearing was carried out. The classical Reynolds Equation was used to represent the pressure behaviour in the bearing. This study was carried out using the Galerkin Finite Element Method (GFEM). The result obtained shows that the pressure increases from the ambient pressure which is taken to be zero and increases significantly till 145.3737 0 . At this point, the pressure is maximum with 1.955 MPa and then drop until it gets to 180 0 where the pressure equals the ambient pressure. Between angular displacements of 180 0 and 360 0 there were also pressure variations which were equal in magnitude with those between 0 0 and 360 0 but with different direction. From the foregoing, it is observed that as the radial clearance increases, the pressure in the bearing drops significantly. Therefore, in the design of journal bearings, the radial clearance should a high as possible to reduce the pressure in the bearing. The result obtained shows a strong positive correlation with existing result in literature.