Special Issue "Tribology of Powertrain Systems"

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

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editor

Dr. Ramin Rahmani
E-Mail Website
Guest Editor
Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK
Interests: tribology; lubrication; friction; internal combustion engines; powertrains

Special Issue Information

Dear Colleagues,

The efficiency and durability of propulsion systems in general and internal combustion engines (ICE) and associated powertrain systems in particular have been greatly improved over past several decades. Advances in tribology have played a pivotal role in our fundamental understanding of the physics of interactions between various components in such systems. This, in turn, has resulted in the improved design of the components and the mitigation of adverse contact conditions, resulting in more environmentally-friendly products that not only meet the requirements of the ever-stringent legislations but also improve product economy and customer satisfaction.

Advances in tribology have been achieved through combined efforts in design and the use of state-of-the-art experimental tools and techniques, as well as developing novel mathematical models and computational techniques. Particular to the IC engines and associate powertrains, significant engine and drivetrain downsizing in recent decades and the use of novel engine management technologies such as cylinder deactivation (CDA) and engine stop-start technology have subjected the associated components to extreme limits of functionality.

The current Special Issue aims to bring together the most recent developments in both experimental and computational techniques with an emphasis on providing new insights into the complex physics of component interactions from a tribological perspective in order to advance our understanding in this field.

In particular, we will focus on tribological investigations of various IC engine and powertrain components, including valvetrain systems, piston ring pack, big end and crankshaft support bearings, and clutch and brake systems, as well as transmission and differential gears, bearings, seals, and tyre–road surface interactions. The potential for energy efficiency and system refinement (noise, vibration and harshness, NVH) will be of particular interest. The tribology of subsystems such as oil and fuel pumps, constant velocity (CV) joints, turbochargers, etc., are also considered.

Of particular interest will be the development of new experimental test rigs, techniques, and methodologies; component-specific contact mechanics; lubrication models; and system-level computational models. The exploration of the effect of new engine technologies, which often lead to harsh operating conditions, and the introduction of electric and hybridised propulsion systems with subsequent effects on the tribological performance of components are encouraged.

Dr. Ramin Rahmani
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 papers will be 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 1000 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

  • Tribology of internal combustion engines
  • Tribology of powertrain and drivetrain systems
  • Energy efficiency
  • Reduction of friction
  • Component durability
  • Tribology of coatings
  • Lubricant rheology and additives
  • Surface engineering (texturing)

Published Papers (6 papers)

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Research

Open AccessArticle
Study of Break-In Process and its Effects on Piston Skirt Lubrication in Internal Combustion Engines
Lubricants 2019, 7(11), 98; https://doi.org/10.3390/lubricants7110098 - 02 Nov 2019
Abstract
The piston skirt is one of the main contributors to the total mechanical loss in internal combustion engines. Usually, the skirt friction experiences a rapid change during the break-in period largely due to the wear of the machine marks or roughness against soft [...] Read more.
The piston skirt is one of the main contributors to the total mechanical loss in internal combustion engines. Usually, the skirt friction experiences a rapid change during the break-in period largely due to the wear of the machine marks or roughness against soft coatings. It is thus important to consider the effect of the change of the roughness for a realistic prediction of the piston skirt friction and system optimization. In this work, an existing model of piston skirt lubrication was improved with the consideration of a breaking in process for the most commonly used triangle machine marks. A new set of flow factors in the averaged Reynolds equation were analytically derived for the trapezoid shape formed after wear of the original triangle shape. A new asperity contact model was developed for the trapezoid shape. The calculation results reflect the trend of friction mean effective pressure (FMEP) during break-in in an engine test and showed quantitative agreement under the same amount of wear. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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Open AccessArticle
Multiphase Computational Fluid Dynamics Analysis of Hydrodynamic Journal Bearing Under the Combined Influence of Texture and Slip
Lubricants 2019, 7(11), 97; https://doi.org/10.3390/lubricants7110097 - 30 Oct 2019
Abstract
The drive to maintain the environmental sustainability and save the global energy consumption is urgent, making every powertrain system component a candidate to enhance efficiency. In this work, the combined effects of the slip boundary and textured surface in hydrodynamic journal bearing as [...] Read more.
The drive to maintain the environmental sustainability and save the global energy consumption is urgent, making every powertrain system component a candidate to enhance efficiency. In this work, the combined effects of the slip boundary and textured surface in hydrodynamic journal bearing as one of the critical components in industrial powertrain and engine systems are assessed using a multiphase computational fluid dynamic analysis that allows for phase change in a cavitation process and arbitrary textured geometry. The texture studied consists of regularly spaced rectangular dimples through two-dimensional (infinitely long) journal bearing. The modified Navier–slip model is employed to describe the slip boundary condition. A systematic comparison is made for various textured configurations varying the texture depth and the length of the texturing zone with respect to the performance of a smooth (untextured) bearing for several eccentricity ratios. The effectiveness of the texture with or without slip at enhancing the load support over a corresponding smooth bearing is investigated with the parameters. The detrimental or beneficial effect of surface texturing as well as the slip promotion is explained in terms of the mechanisms of pressure generation for several eccentricity ratios. The results of the present work indicate that journal bearing textured by a proper texturing zone and dimple depth are characterized by substantial load support levels. However, in the range of high eccentricity ratios, the promotion of texturing and slip can significantly degrade the performance of the load support. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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Open AccessArticle
Modeling the Fatigue Wear of the Cylinder Liner in Internal Combustion Engines during the Break-In Period and Its Impact on Piston Ring Lubrication
Lubricants 2019, 7(10), 89; https://doi.org/10.3390/lubricants7100089 - 11 Oct 2019
Abstract
In internal combustion engines, a significant portion of the total fuel energy is consumed to overcome the mechanical friction between the cylinder liner and the piston rings. The engine work loss through friction gradually reduces during the engine break-in period, as the result [...] Read more.
In internal combustion engines, a significant portion of the total fuel energy is consumed to overcome the mechanical friction between the cylinder liner and the piston rings. The engine work loss through friction gradually reduces during the engine break-in period, as the result of liner surface topography changes caused by wear. This work is the first step toward the development of a physics-based liner wear model to predict the evolution of liner roughness and ring pack lubrication during the break-in period. Two major mechanisms are involved in the wear model: plastic deformation and asperity fatigue. The two mechanisms are simulated through a set of submodels, including elastoplastic asperity contact, crack initiation, and crack propagation within the contact stress field. Compared to experimental measurements, the calculated friction evolution of different liner surface finishes during break-in exhibits the same trend and a comparable magnitude. Moreover, the simulation results indicate that the liner wear rate or duration of break-in depends greatly on the roughness, which may provide guidance for surface roughness design and manufacturing processes. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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Open AccessArticle
Effect of Viscosity and Speed on Oil Cavitation Development in a Single Piston-Ring Lubricant Assembly
Lubricants 2019, 7(10), 88; https://doi.org/10.3390/lubricants7100088 - 09 Oct 2019
Abstract
A high-speed camera has been used to produce unique time-resolved images of high quality to describe the dynamics of the lubricant flow and cavitation characteristics in a sliding optical liner over a fixed single piston-ring lubricant assembly for three lubricants with different viscosities [...] Read more.
A high-speed camera has been used to produce unique time-resolved images of high quality to describe the dynamics of the lubricant flow and cavitation characteristics in a sliding optical liner over a fixed single piston-ring lubricant assembly for three lubricants with different viscosities to establish their impact on cavitation formation and development. The images were obtained at two cranking speeds (or liner sliding velocity) of 300 rpm (0–0.36 m/s) and 600 rpm (0–0.72 m/s), at a lubricant temperature of 70 °C and a supply lubricant rate of 0.05 L/min. A special MATLAB programme has been developed to analyse the cavitation characteristics quantitatively. The dynamic process of cavities initiation was demonstrated by time-resolved images from fern cavity formation to fissure cavities and then their development to the sheet and strings cavities at a liner sliding velocity of around 0.17 m/s. The results for both up- and down-stroke motions showed that the cavities reach their fully developed state downstream of the contact point when the liner velocity reaches its highest velocity and that they start to collapse around TDC and BDC when the liner comes to rest. Within the measured range, viscosity had a great influence on length of cavities so that a decrease in viscosity (from Lubricant A to C) caused a reduction in length of cavities of up to 35% for Lubricant C. On the other hand, an increase in speed, from 300 rpm to 600 rpm, have increased the number of string cavities and also increased the length of cavities due to thicker oil film thickness with the higher speed. Overall, the agreement between the processed data by MATLAB and visualisation measurements were good, but further thresholds refinement is required to improve the accuracy. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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Open AccessArticle
Modelling Transitions in Regimes of Lubrication for Rough Surface Contact
Lubricants 2019, 7(9), 77; https://doi.org/10.3390/lubricants7090077 - 02 Sep 2019
Abstract
Accurately predicting frictional performance of lubrication systems requires mathematical predictive tools with reliable lubricant shear-related input parameters, which might not be easily accessible. Therefore, the study proposes a semi-empirical framework to predict accurately the friction performance of lubricant systems operating across a wide [...] Read more.
Accurately predicting frictional performance of lubrication systems requires mathematical predictive tools with reliable lubricant shear-related input parameters, which might not be easily accessible. Therefore, the study proposes a semi-empirical framework to predict accurately the friction performance of lubricant systems operating across a wide range of lubricant regimes. The semi-analytical framework integrates laboratory-scale experimental measurements from a pin-on-disk tribometer with a unified numerical iterative scheme. The numerical scheme couples the effect of hydrodynamic pressure generated from the lubricant and interacting asperity pressure, essential along the mixed lubrication regime. The lubricant viscosity-pressure coefficient is determined using a free-volume approach, requiring only the lubricant viscosity-temperature relation as the input. The simulated rough surface contact shows transition in lubricant regimes, from the boundary to the elastohydrodynamic lubrication regime with increasing sliding velocity. Through correlation with pin-on-disk frictional measurements, the slope of the limiting shear stress-pressure relation γ and the pressure coefficient of boundary shear strength m for the studied engine lubricants are determined. Thus, the proposed approach presents an effective and robust semi-empirical framework to determine shear properties of fully-formulated engine lubricants. These parameters are essential for application in mathematical tools to predict more accurately the frictional performance of lubrication systems operating across a wide range of lubrication regimes. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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Open AccessArticle
Numerical Study of Power Loss and Lubrication of Connecting Rod Big-End
Lubricants 2019, 7(6), 47; https://doi.org/10.3390/lubricants7060047 - 01 Jun 2019
Abstract
A hydrodynamic lubrication analysis for connecting rod big-end bearing is conducted. The effects of engine speed, operating condition, lubricant viscosity and oil temperature on tribological performance of big-end bearing have been examined. Force equilibrium is solved to define instantaneous eccentricity between journal and [...] Read more.
A hydrodynamic lubrication analysis for connecting rod big-end bearing is conducted. The effects of engine speed, operating condition, lubricant viscosity and oil temperature on tribological performance of big-end bearing have been examined. Force equilibrium is solved to define instantaneous eccentricity between journal and bearing to have accurate estimation of oil film thickness at interface of connecting rod big-end bearing and crankpin. Connecting rod big-end is treated as π film hydrodynamic journal bearing and finite difference scheme is applied to calculate generated hydrodynamic pressure and frictional power loss at each crank angle. Beside the development of analytical formulation, well-known Mobility model introduced by Booker has been employed to be compared with the analytical model. The presented analytical model reduces the complexity and the numerical effort with respect to Mobility method, thus shortening the computation time. The simulation results show good agreement between analytical model, Mobility approach and experimental data. Full article
(This article belongs to the Special Issue Tribology of Powertrain Systems)
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