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Materials, surface roughness of bearing and shaft, and journal misalignment affect the seizure load of journal bearing. To improve the load carrying capacity of bearing and obtain better friction pair, this paper studies experimentally the seizure loads of a gray iron journal bearing and two kinds of aluminum alloy journal bearings under both aligned and misaligned conditions. Three shafts are used to study the effects of journal surface roughness and DLC coating. The journal center locus is recorded. Results show that the combination of DLC coating and the aluminum alloy with lower hardness has the largest seizure load and inclined angle, followed by the combinations of DLC coating and gray iron, and 40Cr steel and gray iron. The surface roughness values of bearing and shaft have a considerable negative effect on seizure load, especially for aligned condition. [ABSTRACT FROM AUTHOR]

The double parabolic profiles can help journal bearing to reduce bushing edge wear, but it also reduces load carrying capacity and increases friction loss. To overcome these drawbacks, in this study, a multiobjective optimization of journal bearing with double parabolic profiles and groove textures is researched under steady operating conditions using Taguchi and grey relational analysis methods. Firstly, a lubrication model with journal misalignment, elastic deformation, asperity contact, thermal effect is established and formation cause of drawbacks is illustrated. Then, an orthogonal test with considering six factors, i.e., groove number, groove depth, groove length, axial width of double parabolic profiles, radial height of double parabolic profiles and groove location is conducted, meanwhile the effects and significances of each factor on response variables are revealed. Finally, an optimal parameters combination of six factors is determined by grey relational analysis, which gives maximum load carrying capacity and minimum friction loss. Overall, this study may give guidance on journal bearing design to enhance its tribological performance. [ABSTRACT FROM AUTHOR]

The textures on the bushing surface have important effects on the performance of journal bearing. In this study, the effects of double parabolic profiles with groove textures on the hydrodynamic lubrication performance of journal bearing under steady operating conditions are investigated theoretically. The journal misalignment, asperity contact and thermal effects are considered, while the profile modifications due to running-in are neglected. The Winkler/Column model is used to calculate the elastic deformation of bushing surface and the adiabatic flow hypothesis is adopted to obtain the effective temperature of lubricating oil. The numerical solution is established by using finite difference and overrelaxation iterative methods, and the rupture zone of oil film is determined by Reynolds boundary conditions. The numerical results reveal that the double parabolic profiles with groove textures with proper location and geometric sizes can increase load carrying capacity and reduce friction loss under steady operating conditions, which effectively overcome the drawbacks of double parabolic profiles. This novel bushing profile may help to reduce the bushing edge wear and enhance the lubrication performance of journal bearing. [ABSTRACT FROM AUTHOR]

The increasing ecological awareness and stringent requirements for environmental protection have led to the development of water lubricated journal bearings. For the investigation of water-lubricated journal bearings, a new structured mesh movement algorithm for the CFD model is developed and based on this method, the nonlinear transient hydrodynamic force model is established. Then, with consideration of velocity perturbation, a method to determine dynamic coefficients and linear hydrodynamic forces is promoted. After validation of static equilibrium position and stiffness coefficients, a comparative linear and nonlinear hydrodynamic force analysis of multiple grooves water-lubricated journal bearings (MGWJBs) is conducted. The calculation results indicate that the structured mesh movement algorithm is suitable for the dynamic characteristics investigation of water-lubricated journal bearings. And the comparative study shows that there is a considerable difference between the linear and nonlinear hydrodynamic forces of MGWJBs. Further investigation should be carried to evaluate the dynamic responses of rotor supported by MGWJBs under difference force models. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The bushing profiles have important effects on the performance of journal bearing. In this article, the effects of plain profile, double conical profile, and double parabolic profile on the elastohydrodynamic lubrication of the journal bearing under steady operating conditions are investigated. The journal misalignment and asperity contact between journal and bushing surface are considered, while the modification of the bushing profiles due to running-in is neglected. Finite element method is used for the elastic deformation of bushing surface, while the numerical solution is established by using finite difference method and overrelaxation iterative method. The numerical results reveal that the double parabolic profile with appropriate size can significantly increase the minimum film thickness and reduce the asperity contact pressure and friction, while the maximum film pressure, load-carrying capacity, and leakage flow rate change slightly under steady operating conditions. This study may help to reduce the edge wear and prolong the service life of the journal bearing. [ABSTRACT FROM AUTHOR]

The proposed work is concerned with the theoretical and numerical investigation of the lubricant rheology effects on the steady-state behavior of a plain finite compliant journal bearing operating under isothermal conditions. In the present investigation, the couple-stresses due to the presence of improving viscosity index (VI) additives, the viscosity-pressure (piezoviscosity effect) as well as the density-pressure (compressibility effect) variations are considered. The hydrodynamic lubrication theory is based on the V.K. Stokes micro-continuum mechanics which takes into account the size of macro-molecular chains added to the basic oil. The Barus and Dowson-Higginson laws were used to express the viscosity-pressure and density-pressure variations. Using the classical assumptions of lubrication, a modified Reynolds' equation is derived and solved numerically by the finite difference method. The displacement field at the fluid film bearing liner interface due to pressure forces is determined using the elastic thin liner model. The proposed work is concerned with the theoretical and numerical investigation of the lubricant rheology effects on the steady-state behavior of a plain finite compliant (elastic liner) journal bearing operating under isothermal conditions and laminar flow. The obtained results show that the couple-stresses have significant effects on the hydrodynamic performance characteristics such as the pressure field, the carrying capacity, the attitude angle and friction number especially when the viscosity-pressure variation is considered. Moreover, it is also shown that the compressibility of lubricant doesn't affect the hydrodynamic characteristics. [ABSTRACT FROM AUTHOR]

In the present paper, the influence of wear on the performance of 2-lobe slot entry restrictor bearing has been investigated theoretically. The equation of fluid flow field has been solved by using Galerkin's technique of FEM. In this study, Dufrane's wear model has been used to consider the change in bush geometry due to wear. The performance of 2-lobe slot entry restrictor bearing is studied for both symmetric and asymmetric slot configurations. The simulated results of the study indicate that the wear defect substantially changes the performance of 2-lobe slot entry journal bearing systems. A proper choice of bearing geometry and bearing configuration (12 slots and 6 slots per row) may partially compensate the loss occurred due to wear. [ABSTRACT FROM AUTHOR]

The journal bearing is a complex system with high film convergence and with cavitation hy-drodynamic phenomena. The surface texturation influence study on journal bearing performances requires unavoidably experimental investigations followed by a numerical modelling of the problem. This work consists in modellization and understanding of the journal bearing characteristics in both cases of presence or absence of textures onto the bearing surface. The finite difference method is used as numerical approach in the analysis. The textured bearing performance enhancement passes essentially by an improvement of a minimum film thickness, a maximum pressure and a friction torque through an appropriate surface texture geometry and appropriate texture distribution on the contact surface. It is found that the simulations results are in good concordance with litteratures. The texture area position on the bearing surface is the primary endpoint for journal bearing performance enhancement. The best design of textured area depends strongly on the geometrical parameters and the journal bearing operating conditions. [ABSTRACT FROM AUTHOR]

Hydrodynamic journal bearings supporting high mass rotating machinery are subjected to low rotational speeds during start-up or idling phases. These working conditions need a hydrostatic pressure contribution to ensure a correct load capacity when the hydrodynamic pressure is not established yet. This is possible by means of hydrostatic lift pockets. These pockets avoid mechanical damages via sufficient film thickness from start-up to hydrodynamic working conditions. In a first part, it is showed how an existing isothermal 3D hydrodynamic numerical modelling of tilting pad bearing has been adapted to take into account the lift pocket impact on static bearing performance. This approach is only valid for low rotational speeds, when inertia step pressure effects (rises or drops) at the film-pocket edge can be neglected compared to the total bearing pressure pattern. Then, numerical simulations have been performed, from 1 to 200 rpm with pockets and from 75 to 200 rpm without pockets. The results have been compared and discussed in terms of pressure fields and bearing static performance such minimum film thickness, friction torque or rotor center position. Therefore, the interest of such lift pockets has been highlighted. Finally, calculations with and without pockets have been carried out in case of a strong bearing misalignment. As a result, the benefits of the lift pockets in this configuration are also significant in terms of static performance. [ABSTRACT FROM AUTHOR]

Tilting-Pad Journal Bearings (TPJB) are commonly used on high-performance turbomachinery due to their excellent stability properties at high speed when compared to other designs for oil film bearings. Hence, efforts have been made to improve the accuracy for the available models for these mechanical devices, achieving nowadays an elasto-thermo-hydrodynamic formulation. On the other hand, the basic design of the Tilting-Pad Journal Bearing has been modified in order to transform it into a smart machine element. One approach to do so is to inject pressurized oil directly into the bearing clearance through holes drilled across the bearing pads. By adjusting the injection pressure, it is possible to modify the dynamic characteristics of the bearing. A controllable lubrication regime is obtained, allowing to expand the operational boundaries of the original design. This work focuses on presenting an elasto-thermo-hydrodynamic model (ETHD) for the Tilting-Pad Journal Bearing, including the effect of the controllable lubrication system. The basic model is validated by comparing its results against theoretical and experimental results available in the literature. Then, the validated code is used to show the benefits of applying a controllable lubrication regime, by means of the modification of the thermal and dynamic behaviour of the bearing. [ABSTRACT FROM AUTHOR]

There has been a number of initiatives launched in the field of lubrication as potential sources of improvements in energy efficiency in a wide range of engineering products, plant and processes. Attention is being focussed on bearings to improve both performance and efficiency in fields such as automotive, machine tools, industrial and power generation plant. This paper reviews some of the background to these drives and illustrates how a novel design of adjustable fluid film hydrodynamic journal type bearing shows promise to both improve performance and save energy. Theoretical modelling and practical tests have demonstrated clear improvements over conventional fluid film bearings, along with a number of other characteristics offering benefits that may be of interest to designers and users of such bearings. [ABSTRACT FROM AUTHOR]

This paper presents thermohydrodynamic solutions for a finite-width journal bearing with single axial groove on the crown by considering turbulent effects in lubricant film. Appropriate governing equations and boundary conditions are used for the fluid flow and heat transfer process occurring in finite full journal bearings. A general computer program is developed to numerically solve the set of governing equations. Results are provided for THD characteristics of journal bearing in terms of Reynolds number, clearance ratio and eccentricity ratio. Good agreement with published experimental results was achieved. The results indicate that the bearing temperature field and pressure field are considerably influenced by the journal bearing parameters. [ABSTRACT FROM AUTHOR]

A theoretical investigation of the static and dynamic behaviour of a rigid plain journal bearing lubricated by oils containing polymer additives considering misalignment defect is presented. The lubricating oils which are non-Newtonian are modelled as couple-stress fluids. According to the V. K. Stokes' micro-continuum theory which takes into account the size of particles, these fluids are characterized by two physical constants, namely the dynamic viscosity (μ) and a second characteristic responsible for the couple stress in the fluid (η). The effects of the couple-stress on the static and dynamic behaviour of the plain journal bearing are studied by defining of a dimensionless couple-stress parameter. The obtained results showed that the presence of additives in the lubricant has non- negligible effects on the static and dynamic performance characteristics as well as the dynamic stability and response of the journal bearing especially at high values of couple-stresses parameter, i.e. for higher chain length of the additive molecule. However, their influence on the side leakage flow is negligible except for high values of eccentricity ratio. [ABSTRACT FROM AUTHOR]