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Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore...
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Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology

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

Deadline for manuscript submissions: closed (20 December 2024) | Viewed by 8543

Special Issue Editors

Dr. Boris Zhmud

E-Mail Website
Guest Editor
Tribonex AB, Knivstagatan 12, 753 23 Uppsala, Sweden
Interests: lubricant formulations (engine oils, metalworking emulsions); solubility and lubricity issues; additives and surface chemistry
Special Issues, Collections and Topics in MDPI journals
Dr. Eduardo Tomanik

E-Mail Website
Guest Editor
USP Departamento de Engenharia Mecânica (PME), Universidade de São Paulo, São Paulo, Brazil
Interests: tribology; wear testing; friction; surface engineering; automotive engineering; piston ring

Special Issue Information

Dear Colleagues,

Legislative combustion engine bans marked a major decline in the R&D interest in the internal combustion engine (ICE), and many major OEMs aim to go 100% electric by 2030-2040. At the same time, many experts admit that, due to many objective factors, vehicles powered by ICEs will remain in operation for decades to come. Development of alternative carbon-neutral fuels can bring about a renaissance in ICE development as the practical limitations of the electric-only approach are exposed.

With over 1 billion ICE-powered cars currently in use in the world, improving the fuel efficiency and curbing emissions of the current fleet is crucial. Moreover, many lessons learnt through ICE tribology optimization work lay a useful knowledge foundation for electrical powertrain optimization. One key lesson is that a complete system approach is required in order to balance multiple aspects of vehicle performance, durability, and economy.

Since a significant part of energy losses in ICEs come from friction, engine tribology has been an important research topic over the past two decades and a significant progress in improving the engine efficiency has been achieved. Improving the piston/bore tribology has been one of the chief contributors to this progress. Significant advances have been made in light-weight piston design, the use of low friction coatings for piston skirts and the ring pack, the use of advanced honing methods and spray-coatings for the cylinder bore, etc.

This Special Issue aims to cover the current advances in the piston/bore tribology with contributions from world-leading experts in the field.

Dr. Boris Zhmud
Dr. Eduardo Tomanik
Guest Editors

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

  • internal combustion engine
  • piston/bore tribology
  • emissions
  • piston ring pack
  • cylinder bore honing
  • thermal spray coatings
  • low friction coatings
  • APS
  • PTWA
  • TWAS

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Published Papers (7 papers)

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Research

18 pages, 5307 KiB  
Article
Engine Lubricant Impact in Light-Vehicle Fuel Economy: A Combined Numerical Simulation and Experimental Validation
by Fernando Fusco Rovai, Eduardo Sartori, Jesuel Crepaldi and Scott Rajala
Lubricants 2025, 13(4), 137; https://doi.org/10.3390/lubricants13040137 - 22 Mar 2025
Viewed by 213
Abstract
The optimization of passenger car efficiency is an important contribution to GHG emissions mitigation. This global warming concern is pushing technological solutions to reduce vehicle fuel consumption and consequently CO2 emissions. In this work, the impacts of engine lubricants with lower viscosity [...] Read more.
The optimization of passenger car efficiency is an important contribution to GHG emissions mitigation. This global warming concern is pushing technological solutions to reduce vehicle fuel consumption and consequently CO2 emissions. In this work, the impacts of engine lubricants with lower viscosity and friction modifier additive in a light-vehicle with a spark ignition engine were numerically simulated and experimentally validated. The substitution of a baseline 5W40 lubricant by a lower viscosity 5W20 proposal resulted in 2.9% lower fuel consumption in a combined cycle. This fuel consumption improvement is enhanced to 6.1% with a 0W16 lubricant with friction modifier. A 1D simulation model based on lubricant temperature and viscosity impact on engine friction was developed and presented good experimental correlation in combined cycle for 5W20, showing a 7% lower fuel consumption advantage than the experimental results. The numerical simulation advantage was 38% lower than experimental results for 0W16 that contains friction modifier, as the additive impact was not considered in this mathematical model. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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18 pages, 3930 KiB  
Article
Lubricant Viscosity Impact in Fuel Economy: Experimental Uncertainties Compensation
by Fernando Fusco Rovai and Eduardo Tomanik
Lubricants 2025, 13(2), 49; https://doi.org/10.3390/lubricants13020049 - 24 Jan 2025
Cited by 1 | Viewed by 671
Abstract
Climate constraints impose greenhouse gas emissions mitigation, and passenger cars have considerable contributions to contribute to this. To improve the engine efficiency of vehicles equipped with conventional powertrains, many technologies are available but with limited individual contribution. The experimental assessment of some technology [...] Read more.
Climate constraints impose greenhouse gas emissions mitigation, and passenger cars have considerable contributions to contribute to this. To improve the engine efficiency of vehicles equipped with conventional powertrains, many technologies are available but with limited individual contribution. The experimental assessment of some technology regarding fuel economy measurement results is sometimes lower than test uncertainties. This study proposes a methodology to compensate the fuel economy for two test uncertainties: vehicle speed variations and battery recharging. The proposed method can be applied when investigating the effects of different vehicle design changes, including engine power cell design. In this work, the proposed method is demonstrated on the test of two oils: one 5W40, the other 5W20, both without FM. Applying the proposed methodology to experimental results, the expected higher influence of oil viscosity on urban conditions could be observed, and the experimental results presented a much better correlation with the vehicle numerical simulation. Applying the proposed compensation, fuel savings of using the 5W20 in comparison to the 5W40 oil was 3.5% under urban conditions and 2.0% on highways. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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39 pages, 22737 KiB  
Article
Comparative Research in the Field of the Parametric Effect of Lubricant Cavitation Initiation and Development on Friction and Wear in Piston Ring and Cylinder Liner Assemblies
by Polychronis Dellis
Lubricants 2024, 12(12), 460; https://doi.org/10.3390/lubricants12120460 - 20 Dec 2024
Viewed by 877
Abstract
This research follows closely previous findings in flow characteristics and phenomena that take place in the piston ring and cylinder liner interface during motoring and firing engine operation, and also compares results between different optical engine set-ups. Cavitation visualisation in a simulating lubrication [...] Read more.
This research follows closely previous findings in flow characteristics and phenomena that take place in the piston ring and cylinder liner interface during motoring and firing engine operation, and also compares results between different optical engine set-ups. Cavitation visualisation in a simulating lubrication single-ring test rig and oil transport and cavitation visualisation in custom made cylinder assemblies of optical engines are the tools used to quantify the transport process under the piston ring and cylinder liner. Simplification of the interface is an essential technique that enhances the researcher’s confidence in results interpretation. Engine complexity and severe oil starvation are impeding the analysis of the experimental results. Visualisation experiments constitute an effective way to test various lubricant types and assess their overall performance characteristics, including their properties and cavitation behaviour. The repeatability of the visualisation method establishes the parametric study effects and offers valuable experimental results. As a further step towards the lubricant composition effect, a link between the lubricant formulation and the operating conditions could be established as the oil performance is assessed with a view to its transport behaviour. Image processing is used to quantify the impact of cavitation on piston ring lubrication in conjunction with varied operating and lubricant parameters. The characteristics of the lubricant and the working environment have an impact on these types of cavities. Viscosity, cavitation, oil film thickness (OFT), lubricant shear-thinning characteristics and friction are all linked. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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22 pages, 15270 KiB  
Article
Modeling Inertia-Driven Oil Transport Inside the Three-Piece Oil Control Ring of Internal Combustion Engines
by Tsung-Yu Yang, Mo Li and Tian Tian
Lubricants 2024, 12(11), 394; https://doi.org/10.3390/lubricants12110394 - 16 Nov 2024
Viewed by 845
Abstract
The three-piece oil control ring (TPOCR), traditionally used in light-duty gasoline engines, is becoming a viable option for heavy-duty gas and hydrogen engines due to its ability to control lubricating oil consumption (LOC) under throttled conditions. Understanding the distribution of oil inside the [...] Read more.
The three-piece oil control ring (TPOCR), traditionally used in light-duty gasoline engines, is becoming a viable option for heavy-duty gas and hydrogen engines due to its ability to control lubricating oil consumption (LOC) under throttled conditions. Understanding the distribution of oil inside the TPOCR groove, as well as the effects of rail gap and drain hole positions, is critical for optimizing TPOCR and groove designs. In this work, a one-dimensional oil distribution model was developed to simulate inertia-driven oil transport in the TPOCR groove. A novel approach was proposed by first dividing the TPOCR into units composed of a pair of expander pitches. Then, the relationship between the oil outflow rate of the unit and its oil mass was established with the help of three-dimensional two-phase computational fluid dynamics (CFD) simulations. This relationship was then used to model one-dimensional oil transport along the circumference of the TPOCR groove. Incorporating the boundary conditions at the rail gaps and drain holes, this simple model can complete computations for 10,000 cycles within a few seconds, allowing for quick the evaluation of transient behavior and design iterations. Studies on low-load conditions show that the model, with reasonable adjustment for the boundary conditions, can match the oil distribution patterns observed in visualization experiments. This is the first step toward studying oil transport in the TPOCR groove before involving the effects of gas flows. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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25 pages, 12647 KiB  
Article
Impact of Mid-to-Low-Ash, Low-Viscosity Lubricants on Aftertreatment Systems after 210,000-Kilometer Real-World Road Endurance Trials
by Heng Shao, Hua Hu, Yitao Luo, Lun Hua, Jinchong Pan, Gezhengting Zhu, Yan Jiao, Jingfeng Yan and Guangyuan Wei
Lubricants 2024, 12(7), 240; https://doi.org/10.3390/lubricants12070240 - 3 Jul 2024
Viewed by 1133
Abstract
Engine lubricants globally face the challenge of meeting the demands of new engine technologies while enhancing energy efficiency and reducing emissions. Lubricants must enhance their performance and sustainability, improve reliability in complex and harsh environments, and minimize environmental impact and health risks. This [...] Read more.
Engine lubricants globally face the challenge of meeting the demands of new engine technologies while enhancing energy efficiency and reducing emissions. Lubricants must enhance their performance and sustainability, improve reliability in complex and harsh environments, and minimize environmental impact and health risks. This study explores the influence of two different formulations of low viscosity lubricants, tested through actual road endurance trials, on a hybrid vehicle’s aftertreatment system performance and overall emission levels. The study includes 120,000 km of endurance testing in four different challenging environments in China, as well as 90,000 km of endurance testing in a typical urban and highway driving cycle in a large city. Results indicate that emissions from the test vehicles during the 120,000 km and 210,000 km durable Worldwide harmonized Light vehicle Test Cycles (WLTCs) meet China’s Stage 6 light-duty vehicle emission standards, with the 210,000 km Real Driving Emission test (RDE) results also conforming to these standards. Relative to fresh TWC, the light-off temperature increased by a mere 60 °C, and the oxygen storage capacity declined by around 19% following endurance testing. Additionally, the GPF exhibited satisfactory performance after 210,000 km of endurance testing, showing lower backpressure values compared to the fresh-coated samples, with no notable ash buildup observed in the substrate. Drawing on the outcomes of actual road endurance testing, this study illustrates that employing low-to-mid-ash-content, low-viscosity lubricants is both compatible and reliable for aftertreatment systems in present or advanced hybrid technologies. Premium lubricants facilitate vehicles in sustaining compliant and stable emission performance, even amid harsh environments and complex operating conditions. Furthermore, the tested lubricants effectively inhibit excessive aging of the aftertreatment system over prolonged mileage. Moreover, this study discusses the feasibility of rapid aging evaluation methods for aftertreatment systems based on engine test benches, juxtaposed with actual road endurance testing. These findings and conclusions offer crucial references and guidance for enhancing lubricant performance and sustainability. Subsequent studies can delve deeper into the correlation between lubricant performance and environmental impact, alongside optimization strategies for lubricants across various vehicle models and usage scenarios. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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18 pages, 7684 KiB  
Article
Experimental Investigation of a Free-Form Honed Cylinder Liner for Heavy-Duty Engines
by Frederik Stelljes, Florian Pohlmann-Tasche and Friedrich Dinkelacker
Lubricants 2024, 12(4), 132; https://doi.org/10.3390/lubricants12040132 - 16 Apr 2024
Viewed by 1528
Abstract
For future internal combustion engines, driven by regenerative fuels, efficiency is more important than ever. One approach to reduce the losses inside the piston cylinder unit (PCU) is to improve the alignment of the liner and the piston. Therefore, a cylinder liner with [...] Read more.
For future internal combustion engines, driven by regenerative fuels, efficiency is more important than ever. One approach to reduce the losses inside the piston cylinder unit (PCU) is to improve the alignment of the liner and the piston. Therefore, a cylinder liner with a free form was developed at the Institute of Technical Combustion (ITV) of the Leibniz University Hannover which compensates radial and linear deformations along the stroke. The layout is based on a FEM simulation. The liner was manufactured by the Institute of Production Engineering and Machine Tools (IFW) of Leibniz University of Hannover with a novel turn-milling process. The liner was investigated on the heavy-duty Floating-Liner engine of ITV with a displacement of 1991 ccm and a bore diameter of 130 mm. The experimental results show improvement in the friction losses over the whole engine map in the range of 9% and up to 17.3% compared to a serial liner. Sealing efficiency could be improved up to 28.8%, depending on the operational point. Overall, the investigation aims for lower fuel consumption which would in result fewer emissions. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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18 pages, 13365 KiB  
Article
Sources and Destinations of Oil Leakage through TPOCR Based on 2D-LIF Observation and Modeling Analysis
by Mo Li and Tian Tian
Lubricants 2023, 11(12), 522; https://doi.org/10.3390/lubricants11120522 - 9 Dec 2023
Viewed by 1999
Abstract
The Three-Piece Oil Control Ring (TPOCR) is becoming a viable option for heavy duty gas and hydrogen engines due to the low particle concentration in these engines. Although direct oil leakage from the gap is not likely to happen with the misalignment of [...] Read more.
The Three-Piece Oil Control Ring (TPOCR) is becoming a viable option for heavy duty gas and hydrogen engines due to the low particle concentration in these engines. Although direct oil leakage from the gap is not likely to happen with the misalignment of the upper and lower rail gaps, there exist other less-apparent oil leaking mechanisms through the TPOCR. This work is targeted at understanding the oil leakage’s source and destination through the rail and liner interfaces across the whole cycle. The 2D Laser Induced Fluorescence technique was applied on an optical engine to study the oil transport behavior. Combined with a TPOCR model for dynamics and lubrication, the mechanisms that cause rail twist and oil scraping by the upper rail were analyzed. It was found that the symmetrical rail can scrape the oil up in the up-strokes. The scraped oil first accumulates in the clearance between the upper rail and groove, as well as at the upper corner of the rail Outer Diameter before being transferred to both the third land and liner when the piston changes direction at Top Dead Center. Rails with an asymmetrical profile can reduce or enhance these effects depending the orientation of the rails. This study provides findings that could help design the engine to better control Lubricate Oil Consumption and properly lubricate the Top Dead Center’s dry region at the same time. Full article
(This article belongs to the Special Issue Tackling Emissions from the Internal Combustion Engine: Advances in Piston/Bore Tribology)
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