Performance Of Fluid Film Bearings Research Articles

Experimental study on the feasibility of alternative materials for tilting pad thrust bearings operating in transition to mixed friction

In hydrodynamic bearings traditional bearing alloys: Babbitts and bronzes are most frequently utilized. Polymer sliding layers are sometimes applied as a valuable alternative. Hard diamond-like carbon (DLC) coatings, which are also considered for certain applications may show some advantages, as well. Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions, which is crucial for bearings with frequent starts and stops. Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime, including the transition to mixed friction, is described in the paper. The tests were carried out on four tilting pad bearings of different material compositions: Steel/bronze, DLC/steel, steel/polyether ether ketone (PEEK), and steel/Babbitt. The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values, and observing the changes of friction force during the transition to mixed friction regime. Analysis of the transition conditions and other results showed clear differences between the tested bearings, illustrating the feasibility of less popular material compositions for bearings operating in specific conditions. More specifically, the DLC/steel bearing was demonstrating superior performance, i.e. lower friction, transition to mixed friction occurring at higher load, and more stable performance at start-stop regime over the other tested bearings.

Effect of bearing shell deformation and ER fluid behavior on two-lobed slot-entry hybrid journal bearing

The present article deals with the effects of deformable bearing shells on the performance of lobed slot-entry hybrid journal bearing systems. The influence of the deformation coefficient [Formula: see text] has been studied using the thin liner elasticity model, which measures the flexibility of the bearing liner. Recently, smart fluid, that is, electrorheological (ER) fluid has been used in various tribological systems to obtain better performance. Therefore, the influence of ER lubricant on the bearing performance characteristics has also been studied in this work. Bingham model constitutive relation has been used to analyze the non-Newtonian behavior of ER fluid. The performance of fluid film bearings is greatly influenced by the noncircularity of the bearings. Therefore, the behavior of deformable bearing shells in a slot-entry journal bearing for lobed conditions has also been studied in the present study. The results reveal that considering deformation in the bearing shell reduces the value of frictional torque, whereas the value of stiffness coefficients and stability threshold speed increases. However, ER lubricant enhances the value of film thickness, stiffness/damping coefficients, and stability threshold speed margin.

Micro-grooved hybrid spherical thrust bearing with Non-Newtonian lubricant behaviour

Recent tribology research has primarily focused on leveraging engineered grooved surfaces to enhance the lubrication performance of tribo-contacts. The performance of fluid film bearings may be improved by using a properly designed micro-groove on the surface of bearing. This paper deals with the performance of micro-grooved hole-entry hybrid spherical thrust bearing (HSTB) considering Non-Newtonian behavior of the lubricant. To analyse the Non-Newtonian behaviour of lubricant the cubic law model has been used. The solution of the governing Reynold equation in the fluid film domain of the hole-entry hybrid spherical thrust bearing is obtained by the FEM. In this study, the influence of rectangular and circular shaped micro-groves has been analysed. The parametric analysis has also been performed to obtain the optimum attributes (i.e. w¯g,d¯g,l¯gr) of the micro-grooves for both the shapes. The present investigation shows that the performance of the hole-entry hybrid spherical thrust bearing gets enhanced by considering the micro-grooves on the surface of bearing. Furthermore, the bearings performance is affected by the geometry of the micro-groove used. The value of fluid film reaction (F¯y) and stiffness coefficient (S¯) is observed to be increased by 23.33% and 343.98% at εy = 0 and κ¯=1 for the case of rectangular-shaped micro-grooved hole-entry HSTB configuration.

Misalignment and Surface Irregularities Effect in MR Fluid Journal Bearing

Misalignment is a major issue to hampers the satisfactory operation of the journal bearing system. Perfect alignment of the journal bearing system is rather difficult to achieve due to various reasons. In actual reality, there is always some amount of misalignment that exists. In recent times, smart lubricants have come up in a big way application concerning fluid film journal bearings. The performance of fluid film bearings gets greatly affected due to misaligned journal conditions and bearing surface irregularities. The present study deals with magnetorheological (MR) lubricant behavior fluid in a hybrid slot-entry journal bearing system (SEJBs) operating under misaligned journal conditions with bearing surface irregularities. The numerically simulated result reveals that due to journal misalignment conditions, the fluid film thickness is reduced, whereas, the value of fluid film damping coefficient and frictional torque gets increased. The mutual effect of bearing surface irregularities and MR lubricant enhances the value of minimum fluid film thickness thereby reducing the chances of metal to metal contact. Further, the combined influence of MR lubricant and surface irregularities increases the damping capabilities of bearing system which helps to damp out the oscillating vibration and large excitation under dynamic circumstances.

Performance of textured spherical thrust hybrid bearing operating with shear thinning and piezoviscous lubricants

Improving the lubricating performance of tribo-pairs using engineering textured surfaces has been the main focus of tribology research in recent years. The use of a suitably designed micro-texture on the bearing surface may have a beneficial effect on the performance of fluid film bearings. In the present paper, a mathematical model of a hybrid spherical thrust bearing is developed considering the effect of shear thinning and piezoviscous behaviour of a lubricant. The modified Reynolds equation for a hybrid spherical thrust bearing configuration together with a restrictor flow equation for a capillary restrictor is solved using a finite-element method. In this work, the effect of various micro-textures shapes (spherical, circular, conical and square) and non-Newtonian lubricant behaviour having shear thinning and piezoviscous effects are analysed. The numerically simulated result shows a strong dependence on the combined effect of shear thinning and piezoviscous lubricant behaviour and a chosen geometric shape of a texture. The frictional power loss is seen to reduce nearly by 24.05%, and the stiffness gets enhanced by 11.08%.

A Study of Hole-Entry Grooved Surface Hybrid Spherical Journal Bearing Operating With Electrorheological Lubricant

Abstract The performances of the tribo-pairs are greatly influenced by introducing the grooved surfaces. Developments of the newer type of lubricants have made a great impact on the performance of fluid film bearings. This article investigates the non-Newtonian behavior of electrorheological lubricant on the performance of grooved hybrid spherical journal bearing. The effect of different arrangements of grooves, i.e., partially grooved or fully grooved on the bearing surface, has been studied. The finite element method is used to numerically simulate the results. Furthermore, a parametric study is performed for optimizing the groove attributes. The present work demonstrates that the different grooved arrangements have a substantial influence on the bearing performance. It is revealed that the provision of grooves on the bearing surface decreases frictional losses and enhances the stiffness coefficients of the bearing. Furthermore, numerically simulated results indicate that the electrorheological lubricant enhances the value of minimum fluid film thickness and the stiffness coefficients (S¯xxandS¯yy) of spherical hybrid journal bearing. Improved bearing performance can be achieved by using the optimized grooved attributes together with the electrorheological lubricant.

Magneto-rheological fluid slot-entry journal bearing considering thermal effects

In recent times, controlling the performance of fluid film bearings smartly has become an important area for the fluid film bearing designers. This study deals with the numerical simulation of a magneto-rheological fluid–lubricated two-lobe hybrid slot-entry journal bearing. To make the operating condition more exact and realistic, the influence of geometric imperfection of the journal arising from manufacturing inaccuracies and thermal effect has been considered. Dave magneto-rheological fluid model, a constitutive relation of the Bingham model, and finite element method have been used in this article to simulate the behavior of the magneto-rheological fluid in a slot-entry bearing. The results indicate that the heat generated because of viscous friction rises the temperature of the magneto-rheological fluid, which changes the bearing performance significantly. Considering barrel-shaped journal and magneto-rheological fluid (applied current, Ic = 4 A), the performance of two-lobe slot-entry bearing is superior in terms of the value of [Formula: see text] approximately by a magnitude of 2%, 41%, 181%, 168%, 75%, and 41%, respectively, as compared to that of the base bearing (smooth [Formula: see text], two-lobe bearing, operating with a Newtonian fluid, Ic = 0 A).

A Simulation Study on the Behavior of Magnetorheological Fluid on Herringbone-Grooved Hybrid Slot-Entry Bearing

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 influence the performance of bearings. In the present work, various geometric shapes of herringbone grooves (rectangular, triangular, and parabolic) with groove angles (30° and 60°) have been considered to numerically simulate the performance of slot-entry bearings. The work reported in this article deals with the numerical simulation of magnetorheological (MR) fluid–lubricated slot-entry herringbone-grooved hybrid journal bearings. Dave equation, a constitutive relation of the Bingham model, was employed to simulate the flow behavior of MR fluid. Using the finite element method (FEM), the governing Reynolds equation for a hybrid slot-entry bearing model was solved. The result shows that the use of a herringbone-grooved surface and application of MR fluid in a slot-entry bearing offers better stability and higher fluid film stiffness and minimizes frictional torque.

Effect of Fluid Compressibility on Journal Bearing Performance

An analysis was undertaken to determine the effect of fluid film compressibility on the performance of fluid film bearings. A new version of the Reynolds equation was developed, using a polytropic expansion, for both steady-state and dynamic conditions. Polytropic exponents from 1 (isothermal) to 1000 (approaching an incompressible liquid) were evaluated for two bearing numbers, selected from a range of practical interest for cryogenic application, and without cavitation. Bearing loads were insensitive to fluid compressibility for low bearing numbers, as was expected. The effect of compressibility on attitude angle was significant, even when the bearing number was low. A small amount of fluid compressibility was enough to obtain stable running conditions. Incompressible liquid lacked stability at all conditions. Fluid compressibility can be used to control the bearing dynamic coefficients, thereby influencing the dynamic behavior of the rotor-bearing system.

The influence of film temperature boundary conditions on the performance of fluid film bearings

Results are presented of a study of the effect of various film temperature boundary conditions on the performance of fluid-film bearings. A three-dimensional thermohydrodynamic analysis is applied to a square inclined pad. Conditions studied range from non-conducting boundaries to conditions for which the film alone limits heat transfer to the boundaries. The importance of the boundary temperatures is shown to depend upon the value of two dimensionless groups determined by the operating conditions. It is shown that the case of non-conducting boundaries does not necessarily lead to a lower bound prediction of pressure generation. An intermediate case considers the runner to be an isothermal surface at such a temperature as to produce zero net heat transfer to the runner. For this case it is shown that there is no “typical” apportioning of the film energy loss between conduction to the pad and that carried away by the oil.

Influence of film inlet conditions on the performance of fluid film bearings

Influence of film inlet conditions on the performance of fluid film bearings

Influence of Film Inlet Conditions on the Performance of Fluid Film Bearings

In fluid film bearings it is difficult to ensure that lubricant which has once traversed the length of the film is not immediately reintroduced at the entry end of the film. The ability of cooler feed oil to be drawn into the film is controlled by the viscosity of the hot carryover oil adhering to the runner or journal surface. A modified Reynolds equation is derived which incorporates a variation of viscosity through the thickness of the film. Application of this modified equation to the case of a square taper-film pad shows that variation of viscosity through the film thickness at film entry can have a very significant effect upon the operating conditions of a bearing.