Orifice compensated multirecess hydrostatic/hybrid journal bearing system of various geometric shapes of recess operating with micropolar lubricant

The objective of the present paper is to study analytically the performance of four-pocket orifice compensated hydrostatic/hybrid journal bearing system of various geometric shapes of recess operating with micropolar lubricant. The modified Reynolds equation for micropolar lubricant is solved using FEM and the Newton-Raphson method along with appropriate boundary conditions. The results suggest that the influence of micropolar effect of lubricant on bearing performance is predominantly affected by the geometric shape of recess and restrictor design parameter. Therefore, the bearing designer must judiciously choose an appropriate geometric shape of recess in order to get an overall enhanced bearing performance.     

Influence of micropolar lubricants on the performance of slot-entry hybrid journal bearing

A theoretical study concerning the slot-entry hybrid journal bearing lubricated with micropolar lubricants is presented. The modified Reynolds equation for micropolar lubricant is solved using finite element method along with equation of lubricant flow through slot-entry restrictors as a constraint together with appropriate boundary conditions. It has been observed that a slot-entry hybrid journal bearing operating with micropolar lubricant shows an increase in the value of minimum fluid film thickness and a reduction in the value of coefficient of friction as compared to a corresponding similar slot-entry hybrid journal bearing operating with Newtonian lubricant.     

A study of slot-entry hydrostatic/hybrid journal bearing using the finite element method

A theoretical study concerning the static and dynamic performance of hydrostatic/hybrid journal bearing compensated by slot restrictor has been presented using the finite element method (FEM). Results have been presented for a double row symmetric as well as asymmetric configurations for different values of slot width ratios (SWR) and external load ( ). In order to have a better understanding of their performance vis-à-vis other non-recessed bearing configurations, the performance characteristics of slot-entry journal bearings have been compared with that of similar hole-entry compensated journal bearings using capillary, orifice and constant flow valve restrictors for the same bearing geometric and operating parameters. The comparative study indicates that asymmetric slot-entry journal bearings provide an improved stability threshold speed margin compared with asymmetric hole entry journal bearings compensated by capillary, orifice and constant flow valve restrictors.     

Effect of non-Newtonian behaviour of lubricant and bearing flexibility on the performance of slot-entry journal bearing

This work describes the theoretical study concerning the effect of non-linear behaviour of the lubricant on the performance of a slot-entry journal bearing. The analysis considers the generalized Reynolds equation governing the flow of lubricant having variable viscosity in the clearance space and the three dimensional elasticity equations governing the displacement field in the bearing shell, and equation of flow of lubricant through slot restrictor. The non-Newtonian lubricant is assumed to follow the cubic shear stress law ( ). Bearing performance characteristics have been presented for a typically selected values of non-linearity factor ( ) and deformation coefficient ( ). It has been observed that the combined effect of non-linearity factor ( ) and bearing flexibility ( ) affects the performance characteristics of slot-entry journal bearing quite significantly.     

Performance analysis of micropolar lubricated journal bearings using GDQ method

In this work generalized differential quadrature (GDQ) method as a simple, efficient and high order numerical technique is used for the solution of modified Reynolds equation to obtain the performance of micropolar lubricated hydrodynamic circular and noncircular lobed journal bearings. Effects of micropolarity of the lubricant as well as noncircularity parameter (preload) of the bearings are investigated. Comparing the GDQ method results with the results of FDM/FEM, good agreement between them is observed. The results also show that though the micropolarity of the lubricants improves the performance of the bearings, however, the rate of enhancement is affected by noncircularity of the bearings.     

Influence of elastic effects on the performance of slot-entry journal bearings

Modern high-performance machines require bearings to operate under stringent conditions. For bearings operating under heavy loads, the bearing deformations can no longer be neglected as they are comparable to the order of magnitude of the fluid film thickness. This paper describes the performance of slot-entry hydrostatic/hybrid journal bearings by considering bearing shell flexibility in the analysis. The relevant governing equations have been solved by the finite element method. Slot-entry journal bearings of two separate configurations have been studied over a wide range of bearing operating and geometric parameters. Elastic effects are found to significantly affect the static and dynamic performance characteristics of the bearing studied. The study indicates that, for given operating conditions, to get optimum performance of a bearing proper selection of the bearing flexibility parameter (), the concentric design pressure ratio () and the type of bearing configuration (symmetric/asymmetric) are essential.     

Static and dynamic analysis of elastohydrodynamic elliptical journal bearing with micropolar lubricant

In this paper the effect of deformation of the bearing liner on the static and dynamic performance characteristics of an elliptical (two-lobe) journal bearing operating with micropolar lubricant is presented. Lubricating oil containing additives and contaminants is modeled as micropolar fluid. A generalized form of Reynold's equation is derived from the fluid flow and diffusion equations. Finite element technique is used to solve the modified Reynold's equation governing the flow of micropolar lubricant in the clearance space of the journal bearing and the three-dimensional elasticity equations governing the displacement field in the bearing shell. The static and dynamic characteristics of the bearing are computed for a wide range of deformation coefficient which takes into accountant the flexibility of bearing liner by treating operating lubricant as (i) Newtonian and (ii) micropolar. The computed results show that the increasing volume concentration of additives and mass transfer of additives produce significant changes on the performance characteristics.     

On the steady-state performance of misaligned hydrodynamic journal bearings lubricated with micropolar fluids

The present work deals with the micropolar lubrication theory to the problem of the steady-state characteristics of hydrodynamic journal bearings considering two types of misalignment, e.g. axial (vertical displacement) and twisting (horizontal displacement). Using a finite difference method, the steady-state film pressures are obtained by solving modified Reynolds equation based on the micropolar lubrication theory. With the help of the steady-state film pressures, the steady-state performance characteristics in terms of load-carrying capacity, misalignment moment and friction parameter of a journal bearing are obtained at various values of eccentricity ratio, degree of misalignment and micropolar fluid characteristic parameters viz. coupling number and non-dimensional characteristic length.     

Influence of lubricants on the performance of journal bearings – a review

ABSTRACT

The lubricant properties have a significant influence on the static and dynamic performance characteristics of journal bearing such as load-carrying capability, minimum fluid film thickness, maximum pressure, lubricant flow rate, damping coefficients, stiffness coefficients, etc. The present document reviews the behaviour of various lubricants such as power-law lubricants, couple stress lubricants, micropolar lubricants, ionic liquid lubricants and space lubricants. The influence of these lubricants on the performance of hydrostatic, hydrodynamic and hybrid journal bearings is discussed. An effort is made to develop the understanding to choose the suitable lubricant for journal bearings for different journal bearing configurations. Journal bearings operated with non-Newtonian lubricants have shown better performance compared to Newtonian lubricants. Ionic liquid lubricants have shown high potential in vacuum applications and extreme temperature environment such as in bearings of spacecraft moving mechanical assemblies.     

Static and dynamic performance characteristics of an orifice compensated hydrostatic journal bearing with non-Newtonian lubricants

This paper presents a theoretical study of the performance characteristics of hydrostatic rigid orifice compensated multirecess journal bearings using non-Newtonian lubricants. The generalized Reynolds equation governing the flow of lubricant having variable viscosity has been solved using the finite element method and iterative procedure. The static and dynamic performance characteristics are presented for non-Newtonian lubricants of which constitutive equation has been represented by the cubic shear stress law. The non-linearity factor () in the cubic shear stress law significantly influences the bearing performance characteristics, particularly the dynamic characteristics.     

Linear stability analysis of hydrodynamic journal bearings under micropolar lubrication

The dynamic characteristics of hydrodynamic journal bearings lubricated with micropolar fluids are presented. The modified Reynolds equation is obtained using the micropolar lubrication theory. Applying the first order perturbation of the film thickness and steady state film pressure, the dynamic characteristics in terms of the components of stiffness and damping coefficients, critical mass parameter and whirl ratio are obtained with respect to the micropolar property for varying eccentricity ratios and slenderness ratios. The results show that micropolar fluid exhibits better stability in comparison with Newtonian fluid.     

Influence of wear on the performance of a multirecess conical hybrid journal bearing compensated with orifice restrictor

In the present work, an analytical study concerning the influence of wear on the performance of a four-pocket hybrid conical journal bearing compensated with an orifice restrictor has been presented. The Reynolds equation governing the flow of lubricant in the clearance space of bearing has been solved using FEM and the Newton Raphson method. The static and dynamic performance characteristics have been presented for the various values of external load, wear depth parameter and for the various values of semi-cone angle. The numerically simulated results suggest that, the performance of the conical bearing is greatly affected by the wear defect.     

Performance analysis of flexible multirecess hydrostatic journal bearing operating with micropolar lubricant

This paper presents the analytical study of the effect of the bearing shell flexibility on the performance of multirecess hydrostatic journal bearing system operating with micropolar lubricant. The modified Reynolds equation for the flow of micropolar lubricant through constant flow valve‐compensated hydrostatic journal bearing has been solved by finite element technique based on Galerkins method, and the resulting elastic deformation in the bearing shell due to fluid‐film pressure has been determined iteratively, in which the deformation coefficient accounts for the bearing shell flexibility. The computed results suggest that the influence of the micropolar effect on bearing performance characteristics is significantly affected by the bearing shell flexibility. Copyright © 2012 John Wiley & Sons, Ltd.     

Micropolar fluid squeeze film lubrication of finite porous journal bearing

In this paper, the effect of micropolar fluid on the static and dynamic characteristics of squeeze film lubrication in finite porous journal bearings is studied. The finite modified Reynolds equation is solved numerically using the finite difference technique and the squeeze film characteristics are obtained. According to the results obtained, the micropolar fluid effect significantly increases the squeeze film pressure and the load-carrying capacity as compared to the corresponding Newtonian case. Under cyclic load, the effect of micropolar fluid is to reduce the velocity of the journal centre. Effect of porous matrix is to reduce the film pressure, load-carrying capacity and to increase the journal centre velocity.     

A study of the lubricating effectiveness of micropolar fluids in a dynamically loaded journal bearing (T1516)

The lubricating effectiveness of micropolar fluids in a dynamically loaded journal bearing is studied. On the basis of the theory of micropolar fluids, the modified Reynolds equation for dynamic loads is derived. Results from the numerical analysis indicated that the effects of micropolar fluids on the performance of a dynamically loaded journal bearing depend on the size of material characteristic length and the coupling number. It is shown, compared with Newtonian lubricants, that under a dynamic loading the micropolar lubricants produce an obvious increase in the oil film pressure and oil film thickness, but a decrease in the side leakage flow. It is also shown that the friction coefficient for a dynamically loaded journal bearing with micropolar fluids is in general higher than that of Newtonian fluids, which is not the same as the results for a steadily loaded journal bearing. Furthermore, a parametric study of flow and friction for different mass parameters keeping micropolar parameters fixed is undertaken. It is indicated that, with the increase of the mass parameters, the crank angles corresponding to the maximum flow are changed and the maximum friction coefficients are obviously decreased either for the Newtonian fluids or for the micropolar fluids.     

Influence of oil type on the performance characteristics of a two‐axial groove journal bearing

The use of environmentally adapted lubricants (EALs) is a subject of growing interest to industry as legislation increasingly demands the replacement of mineral oil lubricants. Vegetable‐based fluids are widely seen as providing lubricants from a renewable source, as well as meeting demands for improved biodegradability. However, at present, utilization of such fluids is limited due to their rapid oxidation. EALs produced from other base stocks (i.e. synthetic esters) have been shown to provide performance benefits in hydrodynamic thrust bearings. In the present study, a hydrodynamic journal bearing test rig has been employed to compare the performance of three EALs (a VG32 saturated ester, rapeseed base fluid and a propylene glycol dioleate) relative to three mineral turbine oils (ISOVG32, ISOVG46 and ISOVG68) in the hydrodynamic regime. Results are given in terms of temperature, power loss and minimum film thickness. The impact of oil viscosity index is also discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Performance characteristics of a centrally loaded 120° partial journal bearing using pseudoplastic lubricants

The additive mixed oils, which are classified as non-Newtonian fluids, are widely used in many lubrication systems. During the past decade, several analyses of plane journal bearings using non-Newtonian lubricants have been reported, although no work has been reported on partial bearings. This paper attempts to fill this void. The non-Newtonian lubricant is taken to be pseudoplastic and two types of rheological model, based on a cubic shear stress law and a shear strain rate power law, have been considered. The computed results reported here are dimensionless and include the static as well as the dynamic characteristics of the bearing     

Analysis of hybrid journal bearing for non‐Newtonian lubricants

The performance characteristics of capillary compensated hole‐entry hybrid journal bearing systems have been studied theoretically. The analysis considers the generalized Reynolds equation governing the flow field of lubricant, having variable viscosity, taking the equation of lubricant flow through a capillary restrictor as constraint. The non‐Newtonian lubricant is assumed to follow the cubic shear stress law. The results obtained from the study suggest that bearing static performance characteristics can be optimized for the particular bearing operating conditions by proper selection of parameters such as bearing land width ratios (ā_b), the restrictor design parameter (C̄_s2), and the non‐linearity factor (K̄). Copyright © 2006 John Wiley & Sons, Ltd.     

Adiabatic solutions for a misaligned journal bearing with non-Newtonian lubricants

Adiabatic solutions are presented for a finite width, hydrodynamic, misaligned journal bearing with non-Newtonian lubricants, obeying the power law model. The film viscosity is taken to be an exponential function of temperature. The performance characteristics of a misaligned journal bearing with slenderness ratio of unity are obtained for various values of non-Newtonian power law index n in the range 0.4 to 1.2, eccentricity ratio in the range 0.2 to 0.8, and misalignment angles of 0.0001 and 0.0002 rad. The adiabatic solutions show that the load-carrying capacity is greatly reduced when compared with that given by the isothermal solutions. In addition, thermal effects are found to be more pronounced for higher values of flow behaviour index n, higher eccentricity ratios and larger misalignment angles.     

Analysis of orifice compensated non-recessed hole-entry hybrid journal bearing operating with micropolar lubricants

A numerical study concerning the performance of non-recessed hole-entry hybrid journal bearing lubricated with micropolar lubricants is presented. The modified Reynolds equation governing the flow of micropolar lubricant in the bearing clearance space is solved using Finite Element Method along with appropriate boundary conditions. Dependence of bearing performance characteristics upon the bearing operating, geometric and micropolar parameters, over a range, has been analyzed. The numerically simulated results are pointed to the choice of restrictor design parameter, for the chosen combination of micropolar parameters of lubricant, in order to obtain optimum values of fluid film stiffness coefficients.