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Lubricants
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Friction and Lubrication of Sliding Bearings
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Friction and Lubrication of Sliding Bearings

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (31 October 2017) | Viewed by 71610

Special Issue Editor

Prof. Dr. Michel Fillon

E-Mail Website
Guest Editor
Department of Mechanical Engineering and Complex Systems, Pprime Institute, CNRS - University of Poitiers - ISAE-ENSMA, SP2MI - Téléport 2, 11 Boulevard Marie et Pierre Curie, BP 30179, CEDEX, F86962 Futuroscope Chasseneuil, France
Interests: thermal effects in hydrodynamic journal and thrust bearings; non-laminar regime; transient effects; risk of bearing seizure; misalignment effects; thermal and mechanical deformations; dynamically loaded bearings; mixed lubrication; lubrication of textured surfaces and wear of hydrodynamic bearings; PTFE and PEEK layered journal and thrust tilting pad bearings; theoretical analyses and numerical simulations under THD or TEHD regime and experimental analyses
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue came as the natural consequence of the great success of the previous Special Issue, “Friction and Lubrication of Bearings”.

Every year, billions of bearings of all kinds are working worldwide. Without exaggeration, bearings are by far the most common machine elements. From miniature bearings used in watches to huge sliding bearings used in hydro turbines, bearings are present in almost every possible aspect of our lives.

The role of bearings is to guide and support surfaces in relative motion and at the same time, to reduce friction. At a first glance, this may seem a simple task. However, not only does this task involve complex, physical, chemical, mechanical, and energetic phenomena, this role is of paramount importance in our current efforts to increase the efficiency of machines, to extend their working lives, and to protect the environment.

The significant research into all aspects of bearing operations has been extensive in the last century. However, the drive for better quality and longer-lasting bearings and the use of new materials, designs, and lubricants enable continuous research and add new knowledge to engineering science. The current Special Issue is aimed at the latest developments concerning lubrication mechanisms and lubricants and the effect of working parameters upon their functionality and the modelling of their behavior.

Dr. Michel Fillon
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Lubricants is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bearing
  • sliding
  • modeling
  • hydrodynamic lubrication
  • hydrostatic lubrication
  • journal bearings
  • thrust bearings
  • gas bearings
  • water lubricated bearings
  • materials
  • lubricants

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Published Papers (12 papers)

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Research

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19 pages, 7488 KiB  
Article
Dynamic Performances of Foil Bearing Supporting a Jeffcot Flexible Rotor System Using FEM
by Benyebka Bou-Saïd, Mustapha Lahmar, Ahcène Mouassa and Bachir Bouchehit
Lubricants 2020, 8(2), 14; https://doi.org/10.3390/lubricants8020014 - 4 Feb 2020
Cited by 13 | Viewed by 5002
Abstract
Aerodynamic bearings have received considerable attention in recent decades and are increasingly being used in applications where high speed, low loads and high precision are required. Aerodynamic applications mainly concern auxiliary power units (APU) and air-conditioning machines (ACM). From the industrial point of [...] Read more.
Aerodynamic bearings have received considerable attention in recent decades and are increasingly being used in applications where high speed, low loads and high precision are required. Aerodynamic applications mainly concern auxiliary power units (APU) and air-conditioning machines (ACM). From the industrial point of view, the static and dynamic characteristics of these bearings rotating at very high speed must be determined. According to the literature, studies carried out on this type of bearing consider the elastic deformations of the foils due to the pressure generated in the air film. The linear approach is from time to time adopted for the prediction of the dynamic behavior of these bearings, which is not always justified. This paper aims to present a step towards a better mastery of the non-linear dynamic behavior of a flexible rotor-air bearing system. We will focus on finite element modeling (FEM) of the non-linear isothermal elasto-aerodynamic lubrication problem in the case of a radial bearing operating in a dynamic regime. We will present the effects of rotational speed, unbalance eccentricity, and rotor mass on the non-linear response of rigid and compliant bearings. We use a partitioned approach which treats fluid and structure as two computation domains solved separately; reducing the development time needed for a monolithic code which is difficult to manage when the geometries or the physical properties of the problem to be treated become complex. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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18 pages, 23297 KiB  
Article
Thermal–Hydrodynamic Behaviour of Coated Pivoted Pad Thrust Bearings: Comparison between Babbitt, PTFE and DLC
by Konstantinos Katsaros, Dimitrios A. Bompos, Pantelis G. Nikolakopoulos and Stephanos Theodossiades
Lubricants 2018, 6(2), 50; https://doi.org/10.3390/lubricants6020050 - 17 May 2018
Cited by 7 | Viewed by 5693
Abstract
The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study [...] Read more.
The hydrodynamic lubrication and thermal analysis of tilting pad thrust bearings has been a major subject for many studies in the field of tribology. There is only a limited number of studies regarding thrust bearings with coated surfaces. The purpose of this study is to build a parametric, iterative algorithm in order to perform a complete thermal and hydrodynamic lubrication analysis for pivoted pad thrust bearings with coatings. The analytical model is mainly based on the energy, continuity and Navier–Stokes equations, which are solved numerically with the Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC) method. The analysis focuses on a single pivoted pad of the thrust bearing. The thermal properties of the coating material are taken into account and the resulting thermal and flow fields are solved. The basic hydrodynamic and tribological characteristics are calculated for an uncoated, a Babbitt coated, a PTFE coated and a diamond like carbon (DLC) coated pivoted pad thrust bearing. The pressure and the film thickness distribution, as well as the load capacity and the frictional forces, are determined for several pad positions and velocities of the rotor. A mineral oil lubricant is used to estimate the shear thinning or thickening effects on the pad tribological performance. The results indicate that pads coated with PTFE and DLC show lower friction forces compared to the common steel and Babbitt applications. At the same time, the DLC coating seems to affect the bearing’s flow and thermal fields less than the PTFE, making it more suitable for thrust bearings applications. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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15 pages, 1215 KiB  
Article
A Novel Approach for Modeling Surface Effects in Hydrodynamic Lubrication
by Michael Pusterhofer, Philipp Bergmann, Florian Summer, Florian Grün and Clemens Brand
Lubricants 2018, 6(1), 27; https://doi.org/10.3390/lubricants6010027 - 12 Mar 2018
Cited by 13 | Viewed by 5426
Abstract
The common approach for the flow factor calculation is based on using the Reynolds equation to simulate the micro-level flow. However, for structured surfaces the fluid flow cannot be represented correctly, due to the assumptions made when deriving the Reynolds equation. In this [...] Read more.
The common approach for the flow factor calculation is based on using the Reynolds equation to simulate the micro-level flow. However, for structured surfaces the fluid flow cannot be represented correctly, due to the assumptions made when deriving the Reynolds equation. In this work, a novel method using the Navier-Stokes equations for the calculation of the micro-level flow is presented and validated against results from Patir and Cheng. The three-dimensional lubrication gap was generated by a rough Gaussian random surface and a perfectly smooth moving counter surface, in order to be available for different numerical methods. The presented results illustrate similar trends for both the approaches. Additionally, the use of the Navier-Stokes equations allows for the observance of surface induced effects which cannot be resolved by the approach of Patir and Cheng. Furthermore, a numerical approach for a shear flow factor calculation with a rough moving surface is presented and validated against other simulation methods. While the validation is maintained with pressure- and temperature-independent density and viscosity, these effects will be taken into account for later research activities of textured surfaces. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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13 pages, 6015 KiB  
Article
Improvement of Thrust Bearing Calculation Considering the Convectional Heating within the Space between the Pads
by Monika Chmielowiec-Jablczyk, Andreas Schubert, Christian Kraft, Hubert Schwarze, Michal Wodtke and Michal Wasilczuk
Lubricants 2018, 6(1), 22; https://doi.org/10.3390/lubricants6010022 - 26 Feb 2018
Cited by 6 | Viewed by 5381
Abstract
A modern thrust bearing tool is used to estimate the behavior of tilting pad thrust bearings not only in the oil film between pad and rotating collar, but also in the space between the pads. The oil flow in the space significantly influences [...] Read more.
A modern thrust bearing tool is used to estimate the behavior of tilting pad thrust bearings not only in the oil film between pad and rotating collar, but also in the space between the pads. The oil flow in the space significantly influences the oil film inlet temperature and the heating of pad and collar. For that reason, it is necessary to define an oil mixing model for the space between the pads. In the bearing tool, the solutions of the Reynolds equation including a cavitation model, the energy equation and the heat transfer equation are done iteratively with the finite volume method by considering a constant flow rate. Both effects—laminar/turbulent flow and centrifugal force—are considered. The calculation results are compared with measurements done for a flooded thrust bearing with nominal eight tilting pads with an outer diameter of 180 mm. The heat convection coefficients for the pad surfaces mainly influence the pad temperature field and are adjusted to the measurement results. In the following paper, the calculation results for variable space distances, influence of different parameters on the bearing behavior and operating condition at high load are presented. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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21 pages, 13424 KiB  
Article
Design Optimization of an Automotive Turbocharger Thrust Bearing Using a CFD-Based THD Computational Approach
by Anastassios G. Charitopoulos, Roel Visser, Rob Eling and Christos I. Papadopoulos
Lubricants 2018, 6(1), 21; https://doi.org/10.3390/lubricants6010021 - 22 Feb 2018
Cited by 13 | Viewed by 11771
Abstract
In a quest to reduce fuel consumption and emissions of automotive combustion engines, friction losses from many different sources need to be minimized. For modern designs of turbochargers commonly used in the automotive industry, reduction of friction losses results in better efficiency and [...] Read more.
In a quest to reduce fuel consumption and emissions of automotive combustion engines, friction losses from many different sources need to be minimized. For modern designs of turbochargers commonly used in the automotive industry, reduction of friction losses results in better efficiency and also contributes to a faster transient response. The thrust bearing is one of the main contributors to the mechanical losses of a turbocharger. Therefore, it is crucial to optimize the design of the thrust bearing so that it has minimum friction losses while keeping sufficient thrust carrying capacity. One of the main challenges of turbocharger thrust bearing design, is that rotation speed is not fixed: the turbocharger may have a rotation speed which varies between 0 to as much as 250 kRPM. Moreover, the thrust bearing generates considerable heat, which changes the temperature of the oil film and its surroundings. In the present work, the design of the thrust bearing of an automotive turbocharger has been optimized. A CFD-based Thermohydrodynamic (THD) computational approach has been developed, taking into consideration heat dissipation, conjugate heat transfer throughout the bearing domain including the surrounding parts, as well as shear thinning and cavitation in the lubricant domain. An optimizer has been coupled to the CFD solver, with the aim of identifying bearing designs with reduced friction losses. Two bearing concepts have been evaluated: a taper-land design—which is a commonly applied thrust bearing concept—as well as a pocket bearing design. The resulting optimum pocket designs exhibit improved performance, in comparison to the optimum taper-land design. The present results indicate that (a) the pocket design concept can substantially contribute to further reducing the friction losses of a turbocharger, and (b) optimal design parameters of pocket bearings depend on the specific application (size, operating conditions), therefore detailed calculations should be performed to verify optimum performance. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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24 pages, 6621 KiB  
Article
Experimental and Numerical Analysis on the Seizure of a Carbon-Filled PTFE Central Groove Journal Bearing during Start-Up Period
by Bálint Pap, Michel Fillon, Maxence Guillemont, Lionel Bauduin, Joseph Chocron, Patrice Gédin and Ludwig Biadalla
Lubricants 2018, 6(1), 14; https://doi.org/10.3390/lubricants6010014 - 26 Jan 2018
Cited by 12 | Viewed by 5179
Abstract
During the start-up period, if the journals bearing bushing and shaft materials have different heat conductivities, the thermal expansion of the shaft might be more rapid than that of the bushing. This reduces the radial clearance between the bearing components and generates higher [...] Read more.
During the start-up period, if the journals bearing bushing and shaft materials have different heat conductivities, the thermal expansion of the shaft might be more rapid than that of the bushing. This reduces the radial clearance between the bearing components and generates higher shear stresses in the lubricating fluid, which can lead to bearing seizure, resulting in the deterioration of the journal bearing. (1) First, we present an experimental case study of the seizure of a central groove journal bearing with a carbon-filled polytetrafluoroethylene (PTFE) bushing and a steel shaft; (2) Then, a static thermoelastohydrodynamic (TEHD) simulation is compared to Cristea’s experiments (Cristea, A.-F., 2012); (3) Then, a pseudo-transient TEHD simulation is performed in order to numerically predict the observed phenomena on the test rig; (4) Finally, the evolution of the oil flow rate and the bushing temperatures during the start-up period determined with the pseudo-transient TEHD modelling are compared to the experimental data of the test rig. The pressure field is determined with the thermohydrodynamic (THD) Elrod’s modelling, with Vijayaraghvan’s robust solver algorithm. The pseudo-transient temperature field in the bearing components as well as the thermal and mechanical deformations are calculated with a commercial software. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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16 pages, 3287 KiB  
Article
EHD Effects in Lubricated Journal Bearing
by Pavel Pavlovich Usov
Lubricants 2018, 6(1), 12; https://doi.org/10.3390/lubricants6010012 - 23 Jan 2018
Cited by 3 | Viewed by 3833
Abstract
This paper presents a numerical analysis of the influence of deformation of infinite parallel cylindrical solids in partial journal bearing on the oil film characteristics. The stationary elastohydrodynamic EHD problems for three design models of bearings are considered: (1) The bearing in which [...] Read more.
This paper presents a numerical analysis of the influence of deformation of infinite parallel cylindrical solids in partial journal bearing on the oil film characteristics. The stationary elastohydrodynamic EHD problems for three design models of bearings are considered: (1) The bearing in which the basic contribution to the elastic displacement of the surface brings the thin elastic liner; (2) The elastic cylinder and the elastic bushing which is modeled by the elastic space with a cylindrical cut; (3) The elastic cylinder and the elastic bushing in the presence of the thin elastic liner with a small module of elasticity. It is shown that when the minimum film thickness is fixed and deformations of the elastic solids increase, then the load capacity increases, reaches a maximum, and then decreases. The deformation of solids can raise load capacity many times over. When the deformation of solids increases from zero, the pressure distribution changes from the distribution of pressure in the case of rigid bodies to the distribution of pressure which takes place with the dry contact of elastic bodies. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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23 pages, 462 KiB  
Article
Comparison of Perturbed Reynolds Equation and CFD Models for the Prediction of Dynamic Coefficients of Sliding Bearings
by Troy Snyder and Minel Braun
Lubricants 2018, 6(1), 5; https://doi.org/10.3390/lubricants6010005 - 10 Jan 2018
Cited by 24 | Viewed by 5586
Abstract
The accuracy and utility of rotordynamic models for machinery systems are greatly affected by the accuracy of the constituent dynamic bearing models. Primarily, the dynamic behavior of bearings is modeled as linear combination of mass, damping, and stiffness coefficients that are predicted from [...] Read more.
The accuracy and utility of rotordynamic models for machinery systems are greatly affected by the accuracy of the constituent dynamic bearing models. Primarily, the dynamic behavior of bearings is modeled as linear combination of mass, damping, and stiffness coefficients that are predicted from a perturbed Reynolds equation. In the present paper, an alternative method using Computational Fluid Dynamics (CFD) with a moving boundary is used to predict the dynamic coefficients of slider bearings and the results are compared with the more commonly employed perturbed Reynolds equation model. A linear slider bearing geometry is investigated and the results serve as precursors to similar investigations involving the more complex journal bearing geometries. Time and frequency domain methods for the estimation of dynamic coefficients are shown to give comparable results. For CFD with a moving boundary, temporal inertia is found to have a significant effect for a reduced, squeeze Reynolds number less than one. The temporal inertia effect is captured through an added mass coefficient within the dynamic model of the bearing. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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15 pages, 10200 KiB  
Article
Characterization of High-Power Turbomachinery Tilting Pad Journal Bearings: First Results Obtained on a Novel Test Bench
by Enrico Ciulli, Paola Forte, Mirko Libraschi, Lorenzo Naldi and Matteo Nuti
Lubricants 2018, 6(1), 4; https://doi.org/10.3390/lubricants6010004 - 6 Jan 2018
Cited by 15 | Viewed by 5502
Abstract
Tilting pad journal bearings are usually employed in turbomachines for their stable behavior at high rotational speeds. Devoted test rigs have been realized to validate the predictions of theoretical models. However, the design of new high-performance and large-size bearings needs to be supported [...] Read more.
Tilting pad journal bearings are usually employed in turbomachines for their stable behavior at high rotational speeds. Devoted test rigs have been realized to validate the predictions of theoretical models. However, the design of new high-performance and large-size bearings needs to be supported by experimental investigations on high-performance large test rigs. The main characteristics of a recently built facility for testing large tilting pad journal bearings with diameters from 150 to 300 mm are described in this work. The test rig is versatile and can be used to test bearings of different size, configurations and to investigate the influence of many parameters, even the effect of misalignment. Sample results of the static characterization of a four-pad high-performance tilting pad journal bearing are reported evidencing some transient effects. A few sample dynamic results are also reported. The presented experimental results demonstrated the capabilities of the rig for investigating the static and the dynamic characteristics of the bearings accurately measuring slow and fast variables. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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3840 KiB  
Article
Field Tests on Hydrodynamic and Hybrid Operation of a Bidirectional Thrust Bearing of a Pump-Turbine
by Michał Wasilczuk, Michał Wodtke and Leszek Dąbrowski
Lubricants 2017, 5(4), 48; https://doi.org/10.3390/lubricants5040048 - 15 Dec 2017
Cited by 5 | Viewed by 4623
Abstract
In vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from [...] Read more.
In vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The research into fluid film thrust bearings has been quite extensive over the years, comprising theoretical studies of bearing properties with the use of more and more sophisticated calculation codes. On the other hand, the availability of experimental field data on bearing operation is limited, for obvious reasons. In this paper the authors present part of the results of extensive field tests of a large bearing of a pump-turbine they have conducted in a pumped storage power plant. Hopefully this data will be of interest to other researchers to compare theoretical predictions to measurement data. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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5837 KiB  
Article
Damage Equivalent Test Methodologies as Design Elements for Journal Bearing Systems
by Florian Summer, Philipp Bergmann and Florian Grün
Lubricants 2017, 5(4), 47; https://doi.org/10.3390/lubricants5040047 - 14 Dec 2017
Cited by 15 | Viewed by 5145
Abstract
The current paper addresses the field of experimental research of journal bearing systems. In this regard, the challenges are dealt with concerning simultaneous testing with a close correlation to the industrial application and with a high resolution of tribological processes. Concerning this aspect, [...] Read more.
The current paper addresses the field of experimental research of journal bearing systems. In this regard, the challenges are dealt with concerning simultaneous testing with a close correlation to the industrial application and with a high resolution of tribological processes. Concerning this aspect, two damage equivalent laboratory test methodologies for journal slide bearing systems are presented, and their ability to visualize certain performance parameters of bearing systems are emphasized (for instance friction performance, (start stop) wear processes, and seizure events). The results clearly emphasize that the applied methodologies provide accurate findings regarding specific effects of selective parameters/changes on the performance of bearing systems, such as polymer overlays may result in improved mixed friction sliding conditions if designed properly, and they provide superior start stop wear resistance; the use of specific corrosion inhibitors can successfully prevent tribo-corrosion on bronze bearings; a decrease of oil viscosity increases solid friction share but decreases fluid friction; lubricant anti-wear additives are able to improve seizure resistance and sliding properties of bearing systems depending on formulation harmonization; and novel bearing material coatings, e.g., sputtered SnCu, can significantly improve emergency running capabilities. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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Review

Jump to: Research

12 pages, 2328 KiB  
Review
Controllable Sliding Bearings and Controllable Lubrication Principles—An Overview
by Ilmar F. Santos
Lubricants 2018, 6(1), 16; https://doi.org/10.3390/lubricants6010016 - 7 Feb 2018
Cited by 26 | Viewed by 6316
Abstract
Hydrodynamic and aerodynamic lubrication regimes in their controllable forms have been intensively investigated over the last two decades. With the aim of reducing friction and improving thermal, static, and dynamic characteristics of radial sliding bearings, different types of electro-mechanical actuators have been coupled [...] Read more.
Hydrodynamic and aerodynamic lubrication regimes in their controllable forms have been intensively investigated over the last two decades. With the aim of reducing friction and improving thermal, static, and dynamic characteristics of radial sliding bearings, different types of electro-mechanical actuators have been coupled to such bearings. Depending on (i) the actuator type; (ii) the actuation principle, i.e., hydraulic, pneumatic, piezoelectric or magnetic among others; and (iii) how such an actuator is coupled to the sliding bearings, different regulation and control actions of fluid film pressure and lubricant flow can be obtained. The most common actions are: (a) the control of the injection pressure to modify the fluid film pressure statically as well as dynamically; (b) the adjustment of the angle and direction of injection flow (mostly passive action); (c) the control of the sliding bearing gap and its preload via moveable and compliant sliding surfaces; and (d) the control of the lubricant viscosity. All four parameters, i.e., pressure, flow (velocity profiles), gap and viscosity, are explicit parameters in the modified form of Reynolds’ equations for active lubrication. In this framework, this paper gives one main original contribution to the state-of-the-art of radial sliding bearings and controllable lubrication: a comprehensive overview about the different types of controllable sliding bearings and principles used by several authors. The paper ends with some conclusive remarks about advantages and drawbacks of the different design solutions for controllable sliding bearings and the main challenges to be overcome towards industrial applications. Full article
(This article belongs to the Special Issue Friction and Lubrication of Sliding Bearings)
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