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Lubricants
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Fluid-Film Lubrication II
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Fluid-Film Lubrication II

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

Deadline for manuscript submissions: closed (20 May 2019) | Viewed by 22914

Special Issue Editor

Prof. Dr. Romeo Glovnea

E-Mail Website
Guest Editor
Head of Department of Engineering and Design, School of Engineering and Informatics, University of Sussex, Brighton, UK
Interests: lubrication; mechanical transmissions; rheology; solid-body mechanics; tribology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In a paper that famously set the foundation of the theoretical analysis of lubrication, Osbourne Reynolds stated: "The fact that a little grease will enable almost any surface to slide for a time has tended doubtless to obscure the action of the revolving journal to maintain the oil between the surfaces at the point of pressure.  And yet, although only now understood, it is this action that has alone rendered our machines and even our carriages possible." This is the essence of fluid-film lubrication; the lubricant is forced in a converging gap between two solid surfaces, generating enough pressure to support appreciable loads. This is by now well documented and practically exploited in sliding and rolling bearings, allowing for smooth and efficient operation of mechanisms and machines.

Phase one of this Special Issue on “Full Film Lubrication” was a great success thus; we have decided to launch volume two, with the same aims of publishing the latest research into the mechanisms of fluid-film lubrication, and lubricants in new experimental and modelling approaches to the behavior of such systems.

Dr. Romeo Glovnea
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

  • Fluid film
  • Lubrication
  • Lubricants
  • Bearing
  • Rolling Sliding
  • Experimental
  • Modelling
  • Materials

Published Papers (6 papers)

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Research

16 pages, 5361 KiB  
Article
Assessment of Shaft Surface Structures on the Tribological Behavior of Journal Bearings by Physical and Virtual Simulation
by Michael Pusterhofer, Florian Summer, Michael Maier and Florian Grün
Lubricants 2020, 8(1), 8; https://doi.org/10.3390/lubricants8010008 - 15 Jan 2020
Cited by 6 | Viewed by 2801
Abstract
Optimizing the surface topography of cast iron crankshafts offers the opportunity to use this material as an alternative to steel in high-performance combustion engines. In the past, this was not possible due to the higher wear on bearing shells and the higher friction [...] Read more.
Optimizing the surface topography of cast iron crankshafts offers the opportunity to use this material as an alternative to steel in high-performance combustion engines. In the past, this was not possible due to the higher wear on bearing shells and the higher friction losses in relation to forged steel shafts. In order to find an optimized shaft micro topography, the friction and wear behavior of steel and cast iron shafts with different surface treatments were compared to each other, using a combined physical (experimental) and a virtual (computational) simulation approach. The experiments were carried out with a rotary tribometer using a journal bearing test configuration with the possibility to test real-life bearing shells and shaft specimens, manufactured from real-life crankshafts. In the experiments, a polished steel shaft with low bearing wear was effective. The optimization of cast iron crankshafts by a novel surface treatment showed a significant reduction of bearing wear in relation to the classical surface finishing procedures of cast iron shafts. A computational simulation approach, considering the real-life micro topography by using the Navier–Stokes equations for the calculation of micro hydrodynamics, supports the assessment of fluid friction. The virtual simulation shows, in accordance to the experimental results, only a minor influence of the investigated shaft topographies on the fluid friction. Further optimization of shaft surfaces for journal bearing systems seems possible only by the usage of patterned micro topographies. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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14 pages, 3889 KiB  
Article
Squeeze Flow of Bingham Fluids through Reticulated, Compressed Foams
by Petrică Turtoi, Mircea D. Pascovici and Traian Cicone
Lubricants 2019, 7(10), 86; https://doi.org/10.3390/lubricants7100086 - 27 Sep 2019
Cited by 1 | Viewed by 3139
Abstract
The paper presents experimental and theoretical results for the planar squeeze flow of a finite volume of viscoplastic material through a highly deformable porous layer. The central zone of an annular disc made of a reticulated polyurethane foam with high porosity (ε [...] Read more.
The paper presents experimental and theoretical results for the planar squeeze flow of a finite volume of viscoplastic material through a highly deformable porous layer. The central zone of an annular disc made of a reticulated polyurethane foam with high porosity (ε > 0.97) was fully filled with tooth paste. The porous disc placed between two flat, impermeable, parallel, and rigid discs was subjected to compression and the normal force was recorded. After compression, the radial extension of the squeezed fluid was measured. The visualisation of the compressed disc managed to provide evidence of a tortuous flow inside the porous structure. An original analytical model is proposed for the prediction of the front of the flow inside the porous layer and corresponding resistant normal force. The model combines the Covey and Stanmore (1981) model for squeeze flow of a Bingham fluid inside the central zone, with an original approach for flow through the reticulated foams, based on the concept of “equivalent flow tubes” with variable tortuosity. This explorative investigation is of interest for innovative shock absorbers. The model validity covers both low and high plasticity numbers and was experimentally validated for low speed. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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28 pages, 7618 KiB  
Article
Evaluation of Transient Response of Turbochargers and Turbines Using Database Method for the Nonlinear Forces of Journal Bearings
by Athanasios Chasalevris and Jean-Charles Louis
Lubricants 2019, 7(9), 78; https://doi.org/10.3390/lubricants7090078 - 03 Sep 2019
Cited by 13 | Viewed by 3598
Abstract
The paper extents the fluid film bearing database method to arbitrary fixed bearing profiles including floating ring bearings. The method is applied to evaluate rotordynamic response of an automotive turbocharger, modeled as rigid rotor, and of a turbine-generator shaft train for power generation [...] Read more.
The paper extents the fluid film bearing database method to arbitrary fixed bearing profiles including floating ring bearings. The method is applied to evaluate rotordynamic response of an automotive turbocharger, modeled as rigid rotor, and of a turbine-generator shaft train for power generation modeled as flexible rotor through the transient transfer matrix method. The methodology claims to render drastically faster evaluation of transient response of rotating systems with nonlinear bearings regardless the complexity of the bearing models implemented. The computational time of transient response is similar to this when short bearing expressions are used. Turbocharger rotordynamic simulation considers the use of nonlinear bearing models as mandatory, and several case studies have to be performed for the definition of key design parameters of floating ring bearings. The bearing database method offers the tool for a severe total time reduction in rotordynamic calculations, with the possibility to implement advanced thermohydrodynamic bearing models to the rotordynamic algorithm as fast as short bearing approximation formulas. Furthermore, the rotordynamic design of large turbine shaft trains is still based on linear harmonic analysis which leads to conservative designs. The database method aims to include the transient response of nonlinear rotor models as a standard procedure in the rotordynamic design of large shaft trains, which nowadays is avoided due to high time cost and complexity. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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15 pages, 5804 KiB  
Article
Reproducibility of Gaseous Phase Area on Journal Bearing Utilizing Multi-Phase Flow CFD Analysis under Flooded and Starved Lubrication Conditions
by Masayuki Ochiai, Fuma Sakai and Hiromu Hashimoto
Lubricants 2019, 7(9), 74; https://doi.org/10.3390/lubricants7090074 - 27 Aug 2019
Cited by 7 | Viewed by 3663
Abstract
It is important to predict the gaseous phase area of journal bearing. However, a detailed calculation method for such gaseous phase areas has not yet been proposed. In this study, the gaseous-phase areas in small bore journal bearings under flooded and starved lubrication [...] Read more.
It is important to predict the gaseous phase area of journal bearing. However, a detailed calculation method for such gaseous phase areas has not yet been proposed. In this study, the gaseous-phase areas in small bore journal bearings under flooded and starved lubrication conditions are analyzed in terms of the computational fluid dynamics (CFD) of two-phase flow while using a volume of fluid (VOF) method. Furthermore, the influence of surface tension and vapor pressure conditions were investigated, and the analytical and experimental results were compared. The analytical results of VOF for vapor pressure and surface tension were observed to be consistent with the experimental observations under both flooded and starved lubrication conditions. Furthermore, under starved lubrication condition, the analytical results agree well with the observed results for the interface of the oil film and cavitation upon the rupture of the oil film. While using these results, CFD analysis of the two-phase flow of the VOF can be conducted in terms of vapor pressure and surface tension to estimate the gaseous-phase areas of journal bearings under flooded and starved lubrication conditions. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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19 pages, 6971 KiB  
Article
A Computational Fluid Dynamics Study on Shearing Mechanisms in Thermal Elastohydrodynamic Line Contacts
by Marko Tošić, Roland Larsson, Janko Jovanović, Thomas Lohner, Marcus Björling and Karsten Stahl
Lubricants 2019, 7(8), 69; https://doi.org/10.3390/lubricants7080069 - 12 Aug 2019
Cited by 9 | Viewed by 5788
Abstract
A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier–Stokes equations are solved by [...] Read more.
A computational fluid dynamics (CFD) model of the thermal elastohydrodynamically lubricated (EHL) line contact problem has been developed for the purpose of exploring the physical processes that occur inside a thin EHL film subjected to shearing motion. The Navier–Stokes equations are solved by using the finite volume method (FVM) in a commercial CFD software, ANSYS Fluent. A set of user-defined functions (UDF) are used for computing viscosity, density, heat source, temperature of moving surfaces and elastic deformation of the top roller according to well-established equations commonly used in the EHL theory. The cavitation problem is solved by taking into account multiphase mixture flow. The model combinations of Houpert and Ree–Eyring and of Tait and Carreau were used for modeling the non-Newtonian behavior of Squalane and the results were compared. Both rheological models suggest the existence of shear-band and plug-flow at high fluid pressure. Due to the differences in viscosity at GPa-level pressure, the chosen model has substantial influence on the computed shear stress and temperature distributions in the high-pressure region. This shows the importance of using correct rheology information in the whole range of pressure, temperature, and shear strain rate. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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21 pages, 889 KiB  
Article
A CFD-Based Frequency Response Method Applied in the Determination of Dynamic Coefficients of Hydrodynamic Bearings. Part 1: Theory
by Troy Snyder and Minel Braun
Lubricants 2019, 7(3), 23; https://doi.org/10.3390/lubricants7030023 - 11 Mar 2019
Cited by 6 | Viewed by 3367
Abstract
A general, CFD-based frequency response method for obtaining the dynamic coefficients of hydrodynamic bearings is presented. The method is grounded in experimental parameter identification methods and is verified for an extremely long, slider bearing geometry as well as short and long journal bearing [...] Read more.
A general, CFD-based frequency response method for obtaining the dynamic coefficients of hydrodynamic bearings is presented. The method is grounded in experimental parameter identification methods and is verified for an extremely long, slider bearing geometry as well as short and long journal bearing geometries. The influence of temporal inertia on the dynamic response of the bearings is discussed and quantified through the inclusion of added mass coefficients within the mechanical models of the hydrodynamic bearing films. Methods to separate the dynamic stiffness into static stiffness and added mass contributions are presented and their results compared. Harmonic perturbations are applied to the bearings at varying frequencies to determine the frequency dependence of the dynamic coefficients and to facilitate the decomposition of the dynamic stiffness into its constituents. Added mass effects are shown to be significant for the extremely long slider bearing geometry and negligible for the short and long journal bearing geometries under operating conditions motivated by those typical of marine bearings. Full article
(This article belongs to the Special Issue Fluid-Film Lubrication II)
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