Performance of membrane compensated multirecess hydrostatic/hybrid flexible journal bearing system considering various recess shapes

The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane flow valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an elliptical recessed bearing and a triangular recessed bearing. The equation governing the flow of lubricant in a journal bearing together with 3D elasticity equation and restrictor flow equation are solved by using the Finite Element Method. The study describes the effect of recess shape, bearing flexibility and a method of compensation on the performance characteristics of a hydrostatic/hybrid journal bearing system. A comparative performance of the membrane compensated hydrostatic/hybrid journal bearing system has also been studied vis-à-vis capillary, orifice and constant flow valve restrictors. The results presented in this study amply demonstrate that the shape of recess/pocket of a hydrostatic/hybrid flexible journal bearing system affects the performance of the bearing quite appreciably and a proper selection of recess shape along with a suitable compensating device is needed to get an improved performance from the bearing.     

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.     

Performance of slot-entry hybrid journal bearings considering combined influences of thermal effects and non-Newtonian behavior of lubricant

This paper presents theoretical investigations of the thermal and rheological effects of lubricant on the performance of symmetric and asymmetric slot-entry hybrid journal bearing system. FEM has been used to solve the Reynolds equation governing flow of lubricant in bearing clearance space along with restrictor flow equation, energy equation and conduction equation using suitable iterative technique. The thermohydrostatic (THS) rheological performance of slot-entry hybrid journal bearings are studied for small temperature variation of the lubricant. The computed results reveal that variation of viscosity due to temperature rise and non-Newtonian behavior of lubricant affects the bearing performance quite significantly.     

Performance of worn non-recessed hole-entry hybrid journal bearings

Non-recessed journal bearings have been successfully used in various engineering applications because of their good performance over a wide range of speed and load, besides their relative simplicity in manufacturing. Due to many starts and stops in its lifespan, the bearing bush wears progressively on account of rubbing, which affects bearing performance. The present work is an attempt to analytically study the performance of a worn non-recessed (hole-entry) capillary-compensated hybrid journal-bearing system. 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 using suitable iterative technique. A study is conducted for two configurations, i.e., symmetrical and asymmetrical hole-entry journal-bearing system. The simulated results of bearing characteristics parameters in terms of maximum fluid-film pressure, minimum fluid-film thickness, flow rate, frictional torque, rotor dynamic coefficients, stability threshold speed and whirl frequency ratio, etc. have been presented for the wide range of various values of load and speed. The results indicate that the wear affects the bearing performance considerably; therefore, a due consideration of wear defect should be given for an accurate prediction of the bearing performance over a number of cycles. The computed results further indicate that the influence of wear defect on journal bearing performance may be minimized if a designer selects a suitable bearing configuration.     

Design of multirecess hydrostatic oil journal bearings

This paper presents computer generated design data in terms of load capacity and oil flow for multirecess hydrostatic journal bearings. The Reynolds equation for a finite bearing was solved on a high speed digital computer satisfying appropriate boundary conditions and using the finite difference method. Results for various L/D ratios, recess to bearing area ratios, number of recesses etc are presented for capillary and orifice compensated bearings.     

Analysis of Noncircular Hole-Entry Capillary-Compensated Hybrid Journal Bearing with Micropolar Lubrication

This article presents the analysis of a two-lobe hole-entry hybrid journal bearing operating with micropolar lubrication. The modified Reynolds equation governing the laminar flow of isoviscous, incompressible micropolar lubricant in the clearance space of a journal bearing system has been solved using a finite element model incorporating appropriate boundary conditions. A comparative analysis between circular and noncircular two-lobe hybrid journal bearings with capillary restrictor under Newtonian and micropolar lubrication has been presented. It is concluded that bearing performance characteristics are significantly influenced by micropolar lubrication.     

Non‐Newtonian and thermal effects in constant flow valve compensated symmetric hole‐entry hybrid journal bearing

Every high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after carefully studying both static and dynamic characteristics of the journal bearing. The present paper described the study of static and dynamic performance of a hole‐entry hybrid journal bearing system compensated with constant flow valve restrictor by considering the combined influence of thermal effects and non‐Newtonian behaviour of the lubricant. The variation of the viscosity due to the non‐Newtonian behaviour of the lubricant and temperature rise has been considered in the study. The numerical solution of the generalized Reynolds equation governing the flow of the lubricant, having variable viscosity along with the energy and heat conduction equations, was obtained using finite element method. The non‐Newtonian lubricant has been assumed to follow the cubic shear stress law. The study included the performance of a double row symmetric hole‐entry hybrid journal bearing configuration containing 12 holes per row. The results presented in this paper indicate that change in viscosity of lubricant affects the performance of the hole‐entry hybrid journal bearing system quite significantly. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Influence of surface roughness effects on the performance of non-recessed hybrid journal bearings

The effect of journal and bearing surface roughness on the performance of a capillary compensated hole-entry hybrid journal bearing system has been theoretically studied. The analysis considers the average Reynold’s equation for the solution of lubricant flow field in the clearance space of a rough surface journal bearing system. The finite element method and Galarkin’s technique has been used to derive the system equation for the lubricant flow field. The non-dimensional parameters Λ (surface roughness parameter) and γ (surface pattern parameter) have been defined to represent the magnitude of height distribution of surface irregularities and their orientation, respectively. The influence of surface roughness on the bearing performance has been studied for the transverse, isotropic and longitudinal surface patterns. The bearing performance characteristics have been computed for both symmetric and asymmetric capillary compensated hole-entry journal bearing configurations for the various values of surface roughness parameter (Λ), surface pattern parameter (γ) and restrictor design parameter ( ). The computed results indicate that the inclusion of surface roughness effects in the analysis affects the performance of a bearing quite significantly vis-à-vis smooth surface bearing. The study indicates that for generation of accurate bearing characteristic data, the inclusion of surface roughness effects in the analysis is essential.     

Misaligned journal effects in liquid hydrostatic non-recessed journal bearings

The performance characteristics of a capillary-compensated hole-entry hybrid misaligned journal bearing have been studied theoretically. The journal of the bearing is allowed to tilt on an axial plane containing the load vector and on a plane perpendicular to an axial plane containing the load vector. The journal misalignment has been accounted for by defining a pair of misalignment parameters σ and δ. The finite element method has been used to solve Reynold's equation governing the lubricant flow field in the clearance space of the journal bearing. Static and dynamic performance characteristics are presented for the different representative values of the journal misalignment parameters for both hydrostatic and hybrid modes of operation of the bearing. The bearing performance characteristics are also compared for the two hole-entry bearing configurations so as to facilitate the selection of a suitable bearing configuration by the designer. The study suggests that the journal misalignment significantly affects the performance of the hole-entry journal bearing, and for a more accurate prediction of the bearing performance it must be considered in the analysis.     

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.     

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.     

Comparative study of the performance of six-pocket and four-pocket hydrostatic/hybrid flexible journal bearings

This paper compares the performance of a six-pocket capillary compensated hydrostatic/hybrid flexible journal bearing to that of a simi ar four-pocket journal bearing. The comparison is based on theoretically computed results. The finite-element method has been used to obtain simultaneous solutions of the three-dimensional elasticity equations and the Reynolds equation. It is observed that the six-pocket journal bearing may be more efficient from a stability point of view as compared to a similar four-pocket journal system.     

Performance of an Orifice Compensated Hole-Entry Hybrid Journal Bearing System Considering Surface Roughness and Thermal Effects

The present study describes the static and dynamic performance of an orifice-compensated hole-entry hybrid journal bearing system considering the combined influence of surface roughness and thermal effects. The Dowson generalized Reynolds equation governing the flow of variable viscosity lubricant in the clearance space of a smooth journal bearing is modified using the flow factors developed by Patir and Cheng. The effects of surface roughness parameter Λ, variance ratio V?_rj, and the surface orientations vis-á-vis transverse, isotropic, and longitudinal roughness patterns on the performance characteristics of bearings are studied. The rough bearing and smooth journal combination (V?_rj = 0.0) with a transverse roughness pattern (γ = 1/6) is observed to show the largest predicted load-carrying capacity of the bearing. The smooth bearing and rough journal combination (V?_rj = 1.0) with a transverse roughness pattern shows the highest stability threshold speed margin.     

薄膜节流器动静混合径向气体轴承性能

对薄膜节流器动静混合径向气体轴承进行理论研究与数值仿真,建立薄膜节流器内气体流动模型并进行简化,采用流体阻抗法将薄膜节流器的流量表达式并与气体轴承小孔节流流量表达式联立,使用牛顿迭代法对非线性气体雷诺方程进行处理,采用有限差分法对上述方程进行离散化进而求解含有薄膜节流器小孔节流气体轴承的雷诺方程,得到薄膜节流器的气体流量分配规律,进而获得有转速和零转速下轴承承载力。数值仿真结果表明,节流器气腔高度和节流器出口直径是薄膜节流器设计的关键参数,气腔高度越小,节流器出口直径越小,承载能力越大;使用薄膜节流器后,各节流孔的入气压力均有所降低,但是各孔之间的入气压力差增大,进而显著提高气体轴承承载能力。     

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

Abstract

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.     

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.     

A Study of Non-Recessed Hybrid Flexible Journal Bearing With Different Restrictors

For bearings operating under heavy loads, the elastic deformation of bearing surface induced by fluid film pressures can no longer be neglected as it is comparable to the order of magnitude of fluid film thickness. In the present work a theoretical study describing comparative performance of non-recessed hybrid journal bearing using different flow control devices has been carried out by considering bearing shell flexibility into the analysis. The relevant governing equations have been solved using finite element method. The comparative performance of non-recessed hybrid journal bearings of two separate configurations have been studied for various values of bearing flexibility parameter (([Cbar]_d)). The results have been presented for hole-entry type journal bearings compensated by capillary, orifice and constant flow valve restrictors and for a slot-entry type journal bearing, for the same set of values of operating and geometric parameters. The computed results indicates that in order to get an improved performance of non-recessed journal bearing, a proper selection of bearing flexibility parameter (([Cbar]_d)) along with type of flow control device (i.e., capillary, orifice, constant flow valve, slot etc.) and type of bearing configuration (symmetric/asymmetric) are essential.     

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.