Lubrication Of Journal Bearings Research Articles

Analysis of Misaligned Journal Bearing Lubrication Performance with Consideration of Couple Stress Lubricant Area and Viscosity-pressure Effect

Analysis of Misaligned Journal Bearing Lubrication Performance with Consideration of Couple Stress Lubricant Area and Viscosity-pressure Effect

Lubrication of journal bearings by shear thinning lubricants using different constitutive models

The lubrication of hydrodynamic journal bearings using shear thinning fluids is investigated analytically by comparing three different constitutive models. Whilst journal bearings have been in use for a long time, they are still fundamental components of the most advanced mechanical systems, and will remain so for a long time to come. In particular, the modified Reynolds equations for the power-law (Ostwald-de Waele), the Carreau and the Cross models were derived based on the perturbation method. The three models were used to calculate the pressure distribution and the load carrying capacity, and their results were compared and discussed. It is shown that at high shear rates (i.e., high shaft speeds) the Carreau and Cross models, which better describe the rheology of shear-thinning fluids, yield higher magnitudes of the pressure than the power-law model, while at low shear rates the three models are in better agreement.

The combined effect of couple stresses, variable viscosity and velocity-slip on the lubrication of finite journal bearings

Abstract We examine the combined effect of variable viscosity, velocity slip, and the couple stress lubricant on a finite journal bearing. In our model, we utilize the Stokes micro-continuum theorem, the Barus formula, and an artificial (homogeneous) slip surface to improve the lubrication performance. Three cases of slip have also been considered: on the journal, the bearing, and both journal and bearing. The finite difference method is used to solve the equations numerically. The results indicate that the highest pressure occurs with slip on the bearing, and the lowest pressure occurs with slip on the journal. A high piezo-viscosity enhances the pressure and load-carrying capacity. Also, the slip parameter improves the load-carrying capacity. With slip on the bearing only, the frictional parameter decreases significantly.

Effect of groove shape on the hydrodynamic lubrication of journal bearing considering cavitation

PurposeThe purpose of this study is to investigate the influence of groove shape on the hydrodynamic characteristics of a journal bearing.Design/methodology/approachThe computational fluid dynamics model also takes into account the cavitation phenomena and thermal effect, which can illustrate the lubrication performance of a journal bearing.FindingsThe hydrodynamic simulations of the journal bearing with the different groove shapes are conducted under different operation conditions.Originality/valueBased 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.

Chebyshev wavelets approach for the squeeze film lubrication of long porous journal bearings with couple stress fluids

Chebyshev wavelets approach for the squeeze film lubrication of long porous journal bearings with couple stress fluids

The Effects of Palm Oil with Nanoclay Additive in Hydrodynamic Journal Bearing Lubrication

In the present study, palm oil has been tested to study its capability as a lubricant to replace commercial mineral oil. To enrich the performance, nanoparticles additives were added. Previous studies proved that by adding the small size of additives into lubricating oil can lessen the friction and improve anti-wear properties. In this research, the size of the nanoparticle used was below 20nm. Four ball tester following ASTM D4072-94 was conducted to determine the optimum concentration of palm oil bio-lubricant with Nano-clay additive ranged from 0.02% to 0.08%wt. The results discovered that 0.04wt% of Nano-clay additive added into palm oil was the optimum concentration of the lubricant with the coefficient of friction 0.081, which recorded 16% reduction as compared to mineral oil (20W-40) – the reference lubricant. It also shows good anti-wear ability which the wear scar diameter was improved by 32%. The oil was then tested in journal bearing to characterize the hydrodynamic lubrication properties. The properties that have been observed were the coefficient of friction, pressure profile and temperature profile. The results showed that modified palm oil with Nano-clay provided better performance with low coefficient of friction (reduced more than 50% as compared to mineral oil) and also temperature profile (reduced up to 20% compared to mineral oil). As for the pressure profile, even slightly higher pressure recorded for palm oil due to lower viscosity, yet the pressure was improved with the presence of Nano-clay additive. In overall, it had been proven that palm oil with Nano-clay additive shows massive potential as an alternative lubricant to the same range with the current industrial mineral oil.

Viscosity Change and its Effect on Pressure Distribution in Hydrodynamically Lubricated Journal Bearing

In this work, a parametric study of the change in lubricant viscosity with pressure variation of fluid (lubricant) in a hydrodynamic journal bearing was carried out. This study was carried out using the Finite Element Method (FEM) and this was used to analyse the pressure behaviour of the bearing was presented using the classical Reynolds Equation. From the result, it was observed that at the beginning of the bearing where the pressure was equal to the ambient pressure, the pressure increases thereafter till about 0.01875m where the pressure was at maximum. From this point to the other trailing end of the bearing, the pressure decreases to the ambient pressure at L = 0.025m. At the early stage in the bearing, the pressure increase was seen not to be that significant. This was usually between the ranges of 0 ≤ L ≤ 0.00625m. From this point onward, the pressure begins to increase significantly. The reverse was the case when the bearing’s angular displacement was in the range of 1800 ≤ L ≤ 3600. The result also shows a linear relationship between viscosity and pressure. The result obtained when compared with relevant literature shows a strong positive agreement.

Experimental Study on an Influence of Bearing Geometry and TiO2 Nanoparticle Additives on the Performance Characteristics of Fluid Film Lubricated Journal Bearing

Experimental Study on an Influence of Bearing Geometry and TiO2 Nanoparticle Additives on the Performance Characteristics of Fluid Film Lubricated Journal Bearing

Coupling transient mixed lubrication and wear for journal bearing modeling

Abstract A transient Mixed Lubrication-Wear coupling model (MLW coupling model) is developed to investigate the mixed lubrication and wear performances of journal bearings, and a wear experiment for journal bearing is performed to support the validity of the developed numerical model. In the coupling numerical model, the transient interaction between the behaviour of mixed lubrication and wear is considered by incorporating the wear depth distribution, which is determined by the developed friction fatigue wear model, into the film gap equation. The evolutions of the worn surface profile, wear rate, fluid pressure and asperity contact pressure over operating time are calculated by the developed numerical model. The simulated results demonstrate that the transient wear process affects the distribution trend of lubrication performances significantly, and a worn surface profile may exist that provides an optimal tribology performance of journal bearings. The simulated results also demonstrate that there are two wear stages, identified by initial and steady wear stage, of journal bearings under mixed lubrication condition. Furthermore, the effects of the input parameters, including the radius clearance(C), surface roughness (σ), asperity curvature radius (β) and boundary friction coefficient(μc), on the predicted mixed lubrication and wear performance are evaluated.

The Granular Lubricated Journal Bearing: Evidence of Lift Formation

This work demonstrates that granular flows (i.e., macroscale, noncohesive spheres) entrained into an eccentrically converging gap can indeed actually exhibit lubrication behavior as prior models postulated. The physics of hydrodynamic lubrication is quite well understood and liquid lubricants perform well for conventional applications. Unfortunately, in certain cases such as high-speed and high-temperature environments, liquid lubricants break down making it impossible to establish a stable liquid film. Therefore, it has been previously proposed that granular media in sliding convergent interfaces can generate load carrying capacity, and thus, granular flow lubrication. It is a possible alternative lubrication mechanism that researchers have been exploring for extreme environments, or wheel-regolith traction, or for elucidating the spreadability of additive manufacturing materials. While the load carrying capacity of granular flows has been previously demonstrated, this work attempts to more directly uncover the hydrodynamic-like granular flow behavior in an experimental journal bearing configuration. An enlarged granular lubricated journal bearing (GLJB) setup has been developed and demonstrated. The setup was made transparent in order to visualize and video capture the granular collision activity at high resolution. In addition, a computational image processing program has been developed to process the resulting images and to noninvasively track the “lift” generated by granular flow during the journal bearing operation. The results of the lift caused by granular flow as a function of journal rotation rate are presented as well.

Effect of the axial movement of misaligned journal on the performance of hydrodynamic lubrication journal bearing with rough surface

Generally, the movement of journal along the direction of bearing axis under the combined action of various factors is neglected in the lubrication study of bearing, which is quite different from the actual working condition of bearing in the shaft-bearing system. In this paper, with a comprehensive consideration of the axial movement of journal, the surface topography of journal and bearing and the misalignment of journal, a new model about the hydrodynamic lubrication of misaligned journal bearing is established based on the average Reynolds equation. Considering the effect of the axial movement of misaligned journal, the lubrication characteristics parameters of rough journal bearing is presented and mainly discussed. The results show that the axial movement of misaligned journal has a distinct effect on the bearing lubrication characteristics. The influence of the axial movement of misaligned journal on the bearing lubrication characteristics is slightly reduced when considering the surface roughness.

A semi analytical approach in thermal analysis of Hydrodynamic lubrication of journal bearing

Abstract Hydrodynamic lubrication of journal bearing considering rotation of the journal including the effects of temperature is studied in this work. It describes the theoretical analysis of power law fluid film lubrication of journal. A semi analytical solution is obtained by solving the continuity equation and momentum equation along with thermal energy equation under isothermal boundaries. The obtained results are compared and found that they are in good agreement with the results available in the literature. Further, the delta profile which is the location of the points of zero velocity gradients is also presented in order to get the simplified form the Reynolds and energy equations. The obtained results are compared with the experimental results and seen to be a good agreement with the effect of temperature.

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.

Theoretical and Experimental Analyses of Directly Lubricated Tilting-Pad Journal Bearings With Leading Edge Groove

Flooded lubrication of tilting-pad journal bearings provides safe and robust operation for many applications due to a completely filled gap at the leading edge of each pad. Direct lubrication by leading edge grooves (LEG) located on the pads represents an alternative to restrictive end seals to ensure these conditions at the entrance to the convergent lubricant film. A theoretical model is presented that describes the specific influences of LEG design on operating characteristics. First, in contrast to conventional tilting-pad journal bearing designs, the LEG is a self-contained lube oil pocket, which is generally connected to an outer annular oil supply channel. Consequently, each LEG can feature a specific speed and load-dependent effective pocket pressure, which influences the pad tilting angle. Second, the thermal inlet mixing model must consider the specific flow conditions depending on the main flow direction within the film as well as the one between outer annular channel and pocket. The novel LEG model is integrated into a comprehensive bearing code and validated with test from a high performance test rig for a four tilting-pad bearing in load between pivot orientations. Within the investigated operating range good agreement between theoretical and experimental data is achieved if all boundary conditions are accurately considered. Additionally, the impact of single simplifications within the model is studied and evaluated. Finally, the test data are compared to results from the same test bearing with modified lubricant oil supply conditions in order to identify specific properties of LEG design.

Lubricant Rheological Behavior Effect Analysis on the Performance of Finite Porous Self- Lubricating Journal Bearings

In this paper, the hydrodynamic lubrication of finite porous self-lubricating journal bearings is investigated taking into account the rheological lubricant behavior effect. The modified Reynolds equation is derived by considering both the fluid flow in the porous matrix and the lubricant rheological behavior where Darcy’s law and power- law model were used. Governing differential equations were solved numerically using the finite difference method. Static characteristics are obtained by considering three types of lubricants: pseudo-plastic, dilatant and Newtonian fluids. Obtained results showed that the power law index, n, has important effects on the performance of porous and non-porous bearings. An improvement in the fluid bearing characteristics (load capacity, pressure) is observed for dilatant fluids (n>1) while these characteristics decreased for pseudo-plastic fluids (n

Computational Investigation of Oil Film Pressure Profile in Journal Bearings

Lubrication of journal bearing in ship shafting systems is facing a problem in the slow speed range, where oil film created pressure depends on shaft speed, among many other factors. Hence, the slower the speed the lower the pressure will be, which shifts lubrication from hydrodynamic to boundary one. An experimental journal bearing test rig (JBTR) has been designed and established to simulate typical journal bearing for ship’s shafting system. A theoretical validation study has been undertaken and good agreement with the test rig pressure readings was found. The test rig is capable of carrying out wide range of tests to investigate oil film pressure profile dependence on many parameters regarding design modification, oil properties, material properties, and many other factors. A new Computational Fluid Dynamic (CFD) model has been built for the sake of coupling future experimental investigations with computerized ones. The CFD model was created using the well-known CFD package Ansys ver. 15.0. The effect of shaft speed on oil film pressure profile was studied using the CFD model as a verification test. The model results were contrasted to the experimental results and an acceptable deviation range was found.

Influence on Journal Bearing Considering Wall-Slip in EHL

Based on the line contact Elastohydrodynamic model and the limiting shear stress model of the journal bearing, the limiting shear stress at the contact interface of bearing, shaft and lubricant is discussed. And the effects of limiting shear stress on the film thickness, the pressure profile and friction coefficient are analyzed. The effect of wall-slip on elastohydrodynamic lubrication of journal bearings is discussed when the shear stress at the interface of solids and liquids reaches its limiting value. The results show that different wall-slip types will produce different lubrication states and the wall-slip of shaft interface will increase the oil film thickness in the sliding region. On the contrary, the wall-slip of the bearing interface will decrease the oil film thickness. The friction coefficient will decrease when the wall-slip occurs and the degree is greater at the interface of shaft than bearing.

Thermo-hydrodynamic performance of tilted non-circular micropolar lubricated journal bearings

PurposeThe purpose of this study is to examine the thermo-hydrodynamic performance of tilted non-circular journal bearings lubricated with a micropolar fluid. The investigated bearing types are two- and three-lobe journal bearings with finite length.Design/methodology/approachFor this purpose, modified Reynolds, energy and three-dimensional Laplace equations are solved numerically by using generalized differential quadrature method. The effects of micropolarity characteristics of lubricants, such as characteristic length and coupling number, as well as tilt angle as a design parameter, on the performance of non-circular two- and three-lobe journal bearings are studied.FindingsThe results show that the tilt angle can affect the temperature and pressure profiles causing variation in the performance of non-circular bearings. Increasing coupling number and decreasing characteristic length cause the load-carrying capacity to decrease because of the increase in maximum oil temperature of the fluid film of lubricant and decrease in the minimum oil base viscosity. So, it is possible to select suitable values of tilt angle for achieving optimum performance of these bearings.Originality/valueThe non-circular bearings suggest several design parameters such as tilt angle for designers. By considering thermal effects for micropolar lubricant, the requirements of a specific application can be fulfilled.

Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings

Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces when the threshold speed is overcome by the rotational speed, can generate rotor lateral self-excited vibrations known as “oil whirl” or “oil whip”. These instabilities derive from the interaction between the rotor and the sliding bearing and they are typically sub-synchronous and they contribute to eventual rubbing between rotor and stator with consequent damage to the rotating machines. For these reasons, the aim of this paper is to numerically investigate the differences in the dynamic behaviour of a flexible rotor supported by cylindrical lubricated journal bearings. The study considers two different cases, uncavitated and cavitated lubricated films, in order to develop an original Matlab-Simulink algorithm for the numerical solution of the differential non-linear equations of motion of the unbalanced flexible rotor supported on hydrodynamic journal bearings. The bearings were modelled as uncavitated and cavitated (π-Film) short bearings derived from classical Reynolds’ theory. Dynamic simulation allowed prediction of the shape and size of the orbit performed by the system and evaluation of the vibrating phenomena exerted by the rotor during the motion. The results show that cavitation completely modifies the behaviour of the system in every aspect. The analysis of the diagrams obtained showed that the proposed algorithm provides consistent results and represents a valuable instrument for dynamic analysis of rotating systems.

CFD analysis of partial slip effect on the performance of hydrodynamic lubricated journal bearings

Slip modification of the lubricated bearing such hydrophobic coating has proven to improve the hydrodynamic performance. The present paper investigates the effect of partial slip on the journal bearing performance using computational fluid dynamic (CFD) approach. The eccentricity ratio and the placement of slip area are of particular interest. It was shown that the partial slip placement on the convergent region of the bearing generally improves the hydrodynamic performance lubrication by increasing load support. It was also found that introducing partial slip on the divergent area decreases the lubrication performance of journal bearing.