Oil-lubricated Journal Bearing Research Articles

Performance improvement of an oil-lubricated journal bearing using bionic-textures fused micro-pockets

Abstract This article investigates the static and dynamic performances of bionic-textures fused micro-pocketed journal bearing considering cavitation. The new bionic textures placed inside the micro-pocket towards the trailing side has been conceived inspired from the skins of freshwater fish. The mass conservation satisfying partial differential lubrication equations for the static and dynamic pressures are discretized using finite volume method (FVM) followed by simultaneous solution of the system equations using the Fischer-Burmeister-Newton-Schur (FBNS) and the Broyden's method with Sherman-Morrison formula. The minimum film thickness, friction force, temperature rise, dynamic coefficients, effective damping and stiffness, critical mass and system characteristic roots have been explored with new conceived bores and the numerical results have also been compared with conventional plain and conventional pocketed bore bearings. Significant static and dynamic performance improvements have been found in presence of bionic textures fused micro-pocketed bores in comparison to conventional bores.

Lithium Based Grease with Additives as an Alternative Lubricant for Conventionally Oil Lubricated Journal Bearings of Sugarcane Crushing Mills

The purpose of this work was to examine the tribological issues related to failure of heavily loaded split journal bearings sugarcane crushing mills. . It was also identified that hydrodynamic fluid film was not formed due to low speed of journal. Regime of lubrication for such journal bearings is thin film lubrication. In such situations journal and bearing surface has physical contact and adhesive or abrasive wear may occur. For such situations grease lubrication can be adopted for journal bearings. Suitability of Lithium Grease with additives as lubricant for sugarcane crushing mills is verified using four ball tester machine.

Monitoring Journal-Bearing Faults: Making Use of Motor Current Signature Analysis for Induction Motors

Most of the failures in oil-lubricated journal bearings are associated with mechanical instabilities produced by lubrication-system problems or bearing wear and result in increased shaft vibration. Therefore, monitoring the journal-bearing condition in the field relies mainly on the analysis of proximity-probe or accelerometer signals. However, not all motors with journal bearings are equipped with such mechanical sensors due to cost or environmental restrictions. In this article, we evaluate the feasibility of applying motor current signature analysis (MCSA) for the remote monitoring of mechanical instabilities in journal bearings produced by oil-whirl and bearing-clearance problems. In addition, we present a small-scale journal-bearing test setup that can be implemented in low-voltage motors for testing journal-bearing faults under controlled conditions. An experimental study on a sealless fuel-pump motor operating in the field and on the custom-built journal-bearing motor test setup shows that MCSA can remotely monitor journal-bearing oil whirl and excessive clearance to prevent motor failure. The results of vibration analysis are also presented for comparative evaluation.

Approximate solution of oil film load-carrying capacity of turbulent journal bearing with couple stress flow

The instability of the rotor dynamic system supported by oil journal bearing is encountered frequently, such as the half-speed whirl of the rotor, which is caused by oil film lubricant with nonlinearity. Currently, more attention is paid to the physical characteristics of oil film due to an oil-lubricated journal bearing being the important supporting component of the bearing-rotor systems and its nonlinear nature. In order to analyze the lubrication characteristics of journal bearings efficiently and save computational efforts, an approximate solution of nonlinear oil film forces of a finite length turbulent journal bearing with couple stress flow is proposed based on Sommerfeld and Ocvirk numbers. Reynolds equation in lubrication of a finite length turbulent journal bearing is solved based on multi-parametric principle. Load-carrying capacity of nonlinear oil film is obtained, and the results obtained by different methods are compared. The validation of the proposed method is verified, meanwhile, the relationships of load-carrying capacity versus eccentricity ratio and width-to-diameter ratio under turbulent and couple stress working conditions are analyzed. The numerical results show that both couple stress flow and eccentricity ratio have obvious influence on oil film pressure distribution, and the proposed method approximates the load-carrying capacity of turbulent journal bearings efficiently with various width-to-diameter ratios. This research proposes an approximate solution of oil film load-carrying capacity of turbulent journal bearings with different width-to-diameter ratios, which are suitable for high eccentricity ratios and heavy loads.

A Variable Viscosity Approach for the Evaluation of Load Carrying Capacity of Oil Lubricated Journal Bearing with TiO2 Nanoparticles as Lubricant Additives

Influence of TiO2 nanoparticle lubricant additive on the load carrying capacity of a journal bearing is studied. Increase in lubricant viscosity due to presence of TiO2 nanoparticles is modelled using a modified Krieger-Dougherty viscosity model. Validity of modified Krieger-Dougherty model in simulating the viscosities of TiO2 nanoparticle dispersions in engine oil is experimentally verified. The pressure distribution and load carrying capacity are theoretically evaluated using a modified Reynolds equation for various TiO2 nanoparticle concentrations and aggregate sizes. Results reveal an increase in load carrying capacity of journal bearing using TiO2 nanoparticle lubricant additive as compared to plain oils without nanoparticle additive.

Order reduction and nonlinear behaviors of a continuous rotor system

An isotropic flexible shaft, acted by nonlinear fluid-induced forces generated from oil-lubricated journal bearings and hydrodynamic seal, is considered in this paper. Dimension reductions of the rotor system were carried out by both the standard Galerkin method and the nonlinear Galerkin method. Numerical simulations provide bifurcation diagrams, spectrum cascade, orbits of the disk center and Poincare maps, to demonstrate the dynamical behaviors of the system. The results reveal transitions, or bifurcations, of the rotor whirl from being synchronous to non-synchronous as the unstable speed is exceeded. The non-synchronous oil/seal whirl is a quasi-periodic motion. In the regime of quasi-periodic motion, the “windows” of multi-periodic motion were found. The investigation shows that the nonlinear Galerkin method has an advantage over the standard one with the same order of truncations, because the influences of higher modes are considered by the former.

Analysis of oil-lubricated herringbone grooved journal bearing with trapezoidal cross-section, using a spectral finite difference method

A modified Reynolds equation for an oil-lubricated journal bearing is derived, including curvature effect under a lubrication theory, and the curvature effect on characteristics of the journal bearing is discussed. In addition, in case of a herringbone-grooved journal bearing with trapezoidal cross-sections, the modified Reynolds equation is solved, using a spectral finite difference method to get characteristics such as variation of load capacity and attitude angle for trapezoidal angles of from 1.8 through 7.2 degrees.

Noise analysis of oil-lubricated journal bearings

The objective of the paper is to provide a procedure for calculating the noise of oil-lubricated journal bearings. In order to obtain acoustical properties of the bearing, a non-linear analysis including rotor imbalance is performed for a rotor-bearing system. Sound pressure levels of the bearing are obtained through frequency analysis of pressure fluctuations calculated from the non-linear analysis using a transmission theory of plane waves. Results show that the sound pressure level of the bearing increases with the rotational speed of the rotor, although the whirl amplitude of the rotor is decreased at high speed. The noise-estimating procedure presented in the paper could be an aid in the evaluation and understanding of acoustical properties of oil-lubricated journal bearings.

Two-dimensional finite difference solution for externally pressurized journal bearings of finite length

A two-dimensional finite difference solution was used to predict the performance of finite length externally pressurized oil-lubricated journal bearings with several supply holes. The generalized Reynolds equation was solved numerically to obtain the effects of the bearing design parameter, eccentricity ratio and speed parameter on bearing performance. Performance curves are presented for a double-feeding plane bearing compensated by orifice restrictors. The bearing load-carrying capacity, stiffness, lubricant flow rate and frictional torque due to bearing rotation increase with increase in the bearing design parameter, eccentricity ratio and speed parameter. The attitude angle increases with increase in the bearing design parameter and is generally stable at high values of the eccentricity ratio and speed parameter. Hydrodynamic and centrifugal actions are present at higher values of the eccentricity ratio and speed parameter.

A Study on the Unstable Vibration Phenomena of a Reduction Gear System, Including the Lightly Loaded Journal Bearings, for a Marine Steam Turbine

Rotatory machines such as turbines and compressors, almost invariably, include several power transmission gears. The relation between the torsional vibration and the gear transmission mechanism supported by the oil-lubricated journal bearings, however, has never been elucidated. The unstable vibration phenomena (different from ordinary phenomena such as oil whirl, oil whip and so forth) were observed in the locked train type reduction gear system of a marine steam turbine while it was subjected to running conditions with no load. The unstable vibration phenomena are assumed to be due to the self-exciting vibration system which is caused by both the oil film characteristics of the journal bearings which support the reduction gears and the torsional vibration system. The results of the calculations using a dynamic model provide a satisfactory explanation of the phenomena. According to the authors' research, the unstable vibration phenomena are strongly influenced by the torsional rigidity of the system.

The Influence of Oil Lubricated Journal Bearings on the Dynamics of Rotating Systems

SYNOPSIS A computer program representing a shaft and rotor whirling in bearings which allows for realistic oil film boundary conditions and non-circular bearing profiles has been developed. It gave good agreement with experimental results published by Brown and France. With the aim of increasing understanding of the influence of bearing profile on system instability, the program calculates the timewise variation of the energy in translational motion supplied to the rotor by oil film forces. One case is illustrated.

Distortion of a Squeeze Film Bearing

The paper shows theoretically the influence of elastic deformation of a long bearing on the squeeze action of a full oil-lubricated journal bearing. Thick liners and those with a thickness radius ratio of 0–2 (Poisson's ratio of 0–4) are considered at constant load. For a given dimensionless load value a decrease in the peak pressure is predicted, together with increases in the eccentricity ratio and minimum film thickness. The time to squeeze from the centre of the bearing to a given film thickness is also increased.Next, a thick bearing and shaft, or bearing alone, are considered at constant squeeze rate, and at a given value of dimensionless load a decrease in peak pressure, an increase in eccentricity ratio, and an unaltered value of minimum film thickness are predicted.

On the Vibrations of Horizontal Shaft Supported in Oil Lubricated Journal Bearings

Based on a pressure solution for an infinitely long journal bearing clarified in the previous paper, the vibrations of a rotating shaft which is supported in oil lubricated journal bearings is investigated theoretically and experimentally. The results are as follows : 1) A system in which a rigid shaft is supported in oil lubricated journal bearings has in general an angular natural frequency slightly less than ω/2 (ω is angular velocity of rotating shaft). Although the free vibration with angular frequency about ω/2 is stable at low rotational speeds, it becomes self-excited when the rotational speed increases to a high enough value. 2) In the case of a flexible shaft, the system has three angular natural frequencies, one of which is slightly less than ω/2 and the others are nearly equal to Ω (Ω is a fundamental angular frequency of flexural vibration of the shaft). Only one of the vibrations with frequency Ω becomes unstable when the rotational speed increases above about twice the critical speed of the shaft.