Characteristics Of Journal Bearings Research Articles

Elastic Deformation Effects on the Thermo-Hydrodynamic Aspect of Porous Journal Bearings

In this paper, the effects of porous bush elastic deformation on the static characteristics of finite porous journal bearing are investigated using Darcy’s law. The modified Reynolds equation applied to thermo-hydrodynamic problems is modified by considering the viscosity variation along the film thickness. The film pressure distribution and other characteristics such as the load carrying capacity and attitude angle are obtained by solving the governing equations numerically. Obtained results showed that deformation is considerable in the maximum pressure zone, and the elastic deformation will decrease the load carrying capacity. The viscosity variation parameter tends also to decrease the load carrying capacity.

Effect of surface roughness, viscosity-pressure relationship and elastic deformation on lubrication performance of misaligned journal bearings

Purpose– Current lubrication analyses of misaligned journal bearings were generally performed under some given preconditions. To make the lubrication analysis closer to the actual situation and usable to the journal bearing design, the purpose of this paper was to calculate the lubrication characteristics of misaligned journal bearings considering the viscosity-pressure effect of the oil, the surface roughness and the elastic deformation of the journal bearing at the same time.Design/methodology/approach– The lubrication of bearings was analyzed using the average Reynolds equation. The deformation of the bearing surface under oil film pressure was calculated by a compliance matrix method. The compliance matrix was established by finite element analysis of the bearing housing. The viscosity-pressure and viscosity–temperature equations were used in the analysis.Findings– The oil viscosity-pressure relationship has a significant effect on the lubrication of misaligned journal bearings. The surface roughness will affect the lubrication of misaligned journal bearings when the eccentricity ratio and angle of journal misalignment are all large. The directional parameter of the surface has an obvious effect on the lubrication of misaligned journal bearings. The deformation of the bearing surface has a remarkable effect on the lubrication of misaligned journal bearings.Originality/value– The lubrication characteristics of misaligned journal bearings were calculated considering the viscosity-pressure effect of the oil, the surface roughness and the elastic deformation of the journal bearing at the same time. The results of this paper are helpful to the design of the bearing.

Numerical study of twin groove journal bearings performance under steady-state condition

The thermohydrodynamic characteristics of journal bearings with two axial grooves are investigated by means of computational fluid dynamics technique. The equations governing the problem are those of continuity, momentum and energy, which are discretised using hybrid scheme and solved simultaneously employing the SIMPLE algorithm. The novelty of the present model resides mainly in the fact that it was able to accurately predict the temperature profile of twin groove plain hydrodynamic journal bearings to a degree that, to the authors' knowledge, has not been obtained so far, particularly in the inactive portion of the bearing and in the vicinity of grooves. This has been accomplished by performing a computational fluid dynamics analysis in which no relevant simplifications have been made to the governing equations along with the use of a detailed cavitation algorithm. This allowed to perform a reliable assessment of the influence of lubricant feeding conditions and to confirm their relevance for bearing design. Copyright © 2014 John Wiley & Sons, Ltd.

Comparison of static performance characteristics of different configurations of slot-entry hybrid journal bearing operating with non-Newtonian lubricants

Purpose – The slot-entry hybrid journal bearings have been successfully used in various engineering applications because of their good performance over wide range of speed and load, besides their relative simplicity in manufacturing. Most of the research work pertaining to non-recessed journal bearing assumes standard symmetric and asymmetric configurations. However, many more configurations are possible by changing the position of slot which may improve the performance of the slot-entry journal bearing. In the present work study of static performance characteristics of slot-entry journal bearing of different configuration has been carried out. The paper aims to discuss these issues. Design/methodology/approach – FEM has been used to solve the Reynolds equation governing the flow of lubricant in the bearing clearance space along with the restrictor flow equation. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The performance characteristics of slot-entry hybrid journal bearings are computed by developing a computer program. Findings – The simulated results of bearing characteristics parameters in terms of minimum fluid-film thickness and bearing flow have been presented for the wide range of various values of non-linearity factor and external load. It is found that there is an increase in the oil requirement for slot-entry hybrid journal bearing with the specified operating and geometric parameters, when the viscosity of the lubricant decreases due to the non-Newtonian behavior of the lubricant. The effect of the decrease in the viscosity of the lubricant due to non-Newtonian behavior of the lubricant diminishes the attitude angle. The computed performance characteristics are helpful for the bearing designer while choosing a particular configuration of bearing. Research limitations/implications – The performance characteristics have been computed by considering the non-Newtonian lubricants. The thermal effects have been ignored in the analysis so as to obviate the mathematical complexity. Originality/value – Get idea from already published manuscripts.

Numerical and Experimental Research on Dynamic Characteristics of Tilting-pad Journal Bearing of Pivot Stiffness and Damping

In view of the characteristic of the tile which swings and slightly vibrates through geometric direction of preload, an analytical model for vibration of entire dynamic characteristics of tilting pad bearing and its corresponding simplified dynamic model of 8 parameters are made. Based on this theory, the tilting-pad journal bearing of pivot stiffness and damping is designed. The resilient pads are set between the tiles and the bearings, thus, the pivots of the tiles are put on the resilient pads and a small clearance is left between the resilient pads and the bearings. Therefore, the oil can be shared by the small clearance and the bearing lubrication system, and that can cause squeeze film damping effect which improves the damping coefficient of the system. According to different processing technic, two kinds of tilting-pad journal bearing of pivot stiffness and damping are designed, and their dynamic characteristics are worked out by numercial and experimental research. The result shows that the tilting-pad journal bearing of pivot stiffness and damping can increase the first-order damping of rotor-bearing system and thus improve system's stability obviously.

1113 しゅう動面に四角穴を有するジャーナル軸受の油膜動特性の数値解析(OS11-3 機械要素とトライボロジー,オーガナイズドセッション11:「機械要素とトライボロジー」)

1113 しゅう動面に四角穴を有するジャーナル軸受の油膜動特性の数値解析(OS11-3 機械要素とトライボロジー,オーガナイズドセッション11:「機械要素とトライボロジー」)

Nonlinear dynamic characteristics of journal bearing–rotor system considering the pitching and rolling motion for marine turbo machinery

Rotating machinery in marine engine systems experiences the base excitation and the additional gyroscopic moment from the pitching and rolling motion of the ship. For some cases, the motion can cause the rotor system damage. The nonlinear model of the journal bearing–rotor system for marine turbo machinery considering the pitching and rolling motion is established by coupling the basement motion and nonlinear oil film force together. Then the nonlinear dynamic characteristics for the system with the unbalanced mass are studied. By employing the Newmark method, the dynamic response of the rotor-bearing system is simulated. The orbit diagram, spectrum diagram, waterfall diagram, amplitude versus rotating speed diagram and the bifurcation diagram are obtained. The effect of the pitching and rolling motion on the journal bearing–rotor system is investigated. The results indicate that the additional stiffness matrix, additional gyroscopic and additional exciting force vector will act on the journal bearing–rotor system, which are generated from the pitching and rolling motion for marine turbo machinery. The dynamic characteristics of the system such as destabilizing angular velocity will be changed by affecting the nonlinear oil film force.

A Novel Friction Model Basing on Journal Bearing Theory for Reciprocating Compressor

The paper presents a comprehensive friction model of reciprocating compressor which is able to evaluate friction losses in moving parts. The model consists of crankshaft, connecting rod and piston all supported by bearings as well as the piston ring/cylinder interface viewed as sliding friction. Hydrodynamic lubrication theory reveals relationship between load and friction coefficient and was demonstrated to be helpful to give insight to the lubrication characteristics of journal bearing. The model gave the composition of friction losses, friction coefficient dynamic change with orbiting angle and effect of oil viscosity on compressor performance. The results showed that the friction losses of piston ring/cylinder interface and the rod big end bearing was most part of the friction losses and it was necessary to choose suitable oil viscosity to reach the optimum compressor performance.

Static performance characteristics of hybrid journal bearings with plugged entry holes

PurposeThis paper aims to investigate the effect of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricants. The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor. The non‐Newtonian lubricant is assumed to follow the power law. The performance characteristics are computed for the two values of power law index (n=1.0 and 0.566). The computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing.Design/methodology/approachFinite element method has been used to solve generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and equation of flow of lubricant through constant flow valve restrictor.FindingsThe computed results indicate that the blockage of holes during operation will not be the likely causes for the imminent failure of a well‐designed non‐recessed hole‐entry hybrid journal bearing. The bearing configuration with plugged holes provides sufficient fluid film thickness and low power requirement as less lubricant is required to be pumped in the bearing.Originality/valueTo the best of the author's knowledge, no study which considers the influence of plugging of holes on the static performance characteristics of a constant flow valve compensated hole‐entry hybrid journal bearing system operating with Newtonian and non‐Newtonian lubricant is yet available in the literature.

Behavior of micropolar lubricated lobe bearings: influence of non‐circularity parameters

PurposeThe purpose of this paper is to analyse the static performance characteristics of lobe journal bearings lubricated with a micropolar fluid, considering effect of non‐circularity. Number of lobes and their preload value are the non‐circularity parameters considered in the present study. The bearings undertaken for the investigation are two, three and four‐lobe symmetric journal bearings with finite width.Design/methodology/approachFor this purpose, modified form of Reynolds equation is derived, based on Eringen's micropolar fluid theory and it is solved numerically using finite element method (FEM). The effect of the non‐circularity parameters of bearings on the steady‐state performance characteristics such as load carrying capacity, attitude angle, coefficient of friction and side leakage flow are presented and discussed.FindingsThe results show that the number of lobes and their preload value can influence the performance of lobe bearings. It is seen that, in order to provide certain improvement over simple cylindrical bearings, the non‐circularity parameters of lobe bearings must be chosen correctly. There is no single optimum profile for multi‐lobe bearing application.Originality/valueLobe bearings, compared with simple circular bearings, offer several geometric parameters to designers. These parameters must be chosen correctly, so that the requirements of a specific application can be fulfilled.

Numerical analysis of turbulent lubrication in plain full journal bearings

Purpose – The purpose of this paper is to assess the turbulent thermohydrodynamic (THD) performance characteristics of an axially grooved finite journal bearing for a variety of simulated operating conditions.

Characteristics of journal bearings with anisotropic slip

The effects of anisotropic slip on the lubrication performances of journal bearings are analyzed. The anisotropic slip boundary conditions on bearing surfaces or/and on journal surfaces are modeled from Navier slip boundary condition with orthogonal principal slip lengths. The modified Reynolds equation considering anisotropic slip is then derived and solved numerically by the finite element method. The effects of principal slip lengths on the load capacities and friction force of journal bearings are discussed. The related Couette and Poiseuille flow correctors in the modified Reynolds equation and in the shear stress are presented to assist our discussion.

Experimental Study on the Lubrication Characteristics of Porous Journal Bearings with Hydrodynamic Shape Forming at Annular Surface under Shaft Unsteady Condition (Examination into the Whirling Behavior of Shaft at Pivot Supported Condition by Analyzing the Frequency Spectrum of Time History Waveform with Parameter of Gradient on Starting Revolution Speed Changes)

Experimental Study on the Lubrication Characteristics of Porous Journal Bearings with Hydrodynamic Shape Forming at Annular Surface under Shaft Unsteady Condition (Examination into the Whirling Behavior of Shaft at Pivot Supported Condition by Analyzing the Frequency Spectrum of Time History Waveform with Parameter of Gradient on Starting Revolution Speed Changes)

Mathematical models for the viscosity-temperature relationship of the lubricants containing nanoparticles and its applications to journal bearings

In this paper, various mathematical models obtained for relationship between viscosity and temperature for the lubricants containing nanoparticles is presented. These models are used to predict the static performance characteristics of journal bearing operating under lubricants containing nanoparticles. The nanoparticles used for the present work are CuO, CeO2 and Al2O3. Viscosity models for the nanolubricants are developed with the available experimental data. These models are essential for the computation of performance characteristics of journal bearings. The modified Reynolds and energy equations are used to obtain pressure and temperature distribution across the lubricant film and these equations are solved by using the finite-element method and a direct iteration scheme. The static performance characteristics of journal bearing are computed for various values of eccentricity ratios and aspect ratios. The computed results show that addition of nanoparticles increase the viscosity of lubricants and in turn load capacity of journal bearing.

Influence of an oil supply process on the characteristics of plain journal bearings

In this paper, we present some experimental data on characteristics of plain journal bearings at different variants of oil supply inlet pipe arrangement and relative values of the shaft rotation speed and inlet pipe pressure. Also established is the significant growth of oil consumption when the inclination angle of the inlet throttling element axis is increased.

Analysis of static and dynamic performance characteristics of THD journal bearing operating under lubricants containing nanoparticles

In this paper, the static and dynamic performance characteristics of journal bearing in terms of load capacity, attitude angle, end leakage, frictional force, threshold speed and damped frequency are presented when the bearing operating under lubricants, which contain nanoparticles and viscosity of these lubricants varies with temperature. The nanoparticles used for the present work are copper oxide (CuO), cerium oxide (CeO2) and aluminum oxide (Al2O3). Viscosity models for the lubricants are developed with the available experimental data. The modified Reynolds and energy equations are used to obtain pressure and temperature distribution across the lubricant film and these equations are solved by using the finiteelement method and a direct iteration scheme. The static and dynamic performance characteristics of journal bearing are computed for various values of eccentricity ratios for isoviscous and thermoviscous lubricants. The computed results show that in isoviscous case, addition of nanoparticles does not change performance characteristics considerably but in thermoviscous case, changes are significant.

Evaluation of the finite journal bearing characteristics, using the exact analytical solution of the Reynolds equation

A very recent analysis of the exact analytical solution of the Reynolds equation for the lubrication of the plain journal bearing with finite length is used in the current work in order to evaluate the impedance forces of the fluid film and define them in closed form analytical expressions. The main journal bearing design parameters such as the eccentricity ratio, the location of the minimum fluid film thickness, the location of the maximum pressure and the stiffness and damping coefficients are evaluated under the recent analytical definition of the lubricant pressure distribution and presented in charts as functions of the Sommerfeld number, comparing them with the past and recent literature.

Simulating transient wear characteristics of journal bearings subjected to mixed friction

This article describes a calculation model for the simulation of the transient wear characteristics of journal bearings subjected to mixed friction. For predetermined time steps the local wear is calculated for circumference and width. The resulting changes to the gap geometry then flow directly into the further calculation process. The solid contact load ratio and boundary friction ratio in the mixed friction area are calculated on the basis of real rough surfaces. Modifications to the rough surfaces resulting from the running-in process are taken into consideration. In addition the microhydrodynamic effects, elastic deformations of the bearing environment and mass conserving cavitation are also recorded. The calculation model’s potential is demonstrated by means of an unsteady loaded conrod bearing.

THERMOHYDRODYNAMIC PERFORMANCE OF A JOURNAL BEARING WITH 3D-SURFACE ROUGHNESS AND FLUID INERTIA EFFECTS

This theoretical work describe the combined influence of surface roughness, thermal and fluid-inertia effects on performance characteristics of hydrodynamic journal bearing. The average Reynolds equation that modified to include the surface roughness, viscosity variation due to temperature rise in lubricant fluid-film and fluid-inertia is used to obtain pressure field in the fluid-film. The matched solutions of modified average Reynolds, energy and conduction equations are obtained using finite element method and appropriate iterative schemes. The effects of surface roughness parameter, roughness orientation, and roughness characteristics of opposing surfaces on circumferential fluid-film pressure distribution, load carrying capacity and stability threshold speed of the bearing are studied by considering thermal and fluid-inertia effects.

Influence of turbulence on the static characteristics of conical journal bearings

Analytical formulas are presented for the static characteristics of conical hydrodynamic and hydrostatic bearings, with variable thermophysical properties and a two-phase lubricant, when turbulence is disregarded or taken into account.