Lubricants

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4 pages, 157 KiB

Open AccessEditorial

Editorial: Special Issue “Automotive Tribology”

by Adolfo Senatore

Lubricants 2020, 8(4), 48; https://doi.org/10.3390/lubricants8040048 - 17 Apr 2020

Cited by 4 | Viewed by 2746

Abstract

The automotive industry faces new challenges and fast technological changes [...] Full article

(This article belongs to the Special Issue Automotive Tribology)

Research

Jump to: Editorial

12 pages, 2437 KiB

Open AccessArticle

Investigations of the Friction Losses of Different Engine Concepts: Part 3: Friction Reduction Potentials and Risk Assessment at the Sub-Assembly Level

by Christoph Knauder, Hannes Allmaier, David E. Sander and Theodor Sams

Lubricants 2020, 8(4), 39; https://doi.org/10.3390/lubricants8040039 - 31 Mar 2020

Cited by 8 | Viewed by 4392

Abstract

One of the biggest requirements of today’s engine development process for passenger cars is the need to reduce fuel consumption. A very effective and economic approach is the use of low-viscosity lubricants. In this work, sub-assembly resolved friction reduction potentials and risks are [...] Read more.

One of the biggest requirements of today’s engine development process for passenger cars is the need to reduce fuel consumption. A very effective and economic approach is the use of low-viscosity lubricants. In this work, sub-assembly resolved friction reduction potentials and risks are presented for three different engine concepts. By using a developed combined approach, the friction losses of the base engines are separated to the sub-assemblies piston group, crankshaft journal bearings, and valve train over the full operation range of the engines. Unique analyzing of boundary conditions makes it possible for the first time to compare friction reduction potentials and possible risks, not only between diesel and gasoline engines for passenger car applications, but also with particular focus on the power density of the three engines. Firstly, the engines have been specifically chosen regarding their specific power output. Secondly, one identical SAE 5W30 lubricant suitable for all engines is used to neglect influences from different lubricant properties. Thirdly, identical test programs have been conducted at the same thermal boundary conditions at engine media supply temperatures of 70

^{\circ}

C and 90

^{\circ}

C. For the crankshaft journal bearings, high reduction potentials are identified, while risks arising occur at the valve train and the piston group systems. Full article

(This article belongs to the Special Issue Automotive Tribology)

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19 pages, 3990 KiB

Open AccessArticle

Investigations of the Friction Losses of Different Engine Concepts. Part 2: Sub-Assembly Resolved Friction Loss Comparison of Three Engines

by Christoph Knauder, Hannes Allmaier, David E. Sander and Theodor Sams

Lubricants 2019, 7(12), 105; https://doi.org/10.3390/lubricants7120105 - 25 Nov 2019

Cited by 13 | Viewed by 5001

Abstract

In this work, friction loss investigations and comparisons of three different four-cylinder engines for passenger car applications are presented, using a recently developed combined approach. By merging extensive experimental with reliable and predictive journal bearing simulation results, a sub-assembly-resolved friction loss analysis of [...] Read more.

In this work, friction loss investigations and comparisons of three different four-cylinder engines for passenger car applications are presented, using a recently developed combined approach. By merging extensive experimental with reliable and predictive journal bearing simulation results, a sub-assembly-resolved friction loss analysis of the piston group, crankshaft journal bearings and valve train is conducted for all three engines. The engines have been chosen individually based on their specific power output and crank train geometry. The measurement program covers a wide range of corresponding engine operation points (identical speed, load and thermal boundary conditions). In addition, the investigations are carried out for different engine media supply temperatures ranging from 70

^{\circ}

C to 110

^{\circ}

C for a comprehensive consideration of the friction losses at reduced lubricant viscosity. For reasons of comparability, all investigations conducted in this work have been carried out using the same modern SAE 5W30 lubricant. This is done to exclude influences from different lubricant properties which may have significant effects on the tribological behaviour of the engines’ sub-assemblies. While the diesel engine showed a friction reduction potential over the entire engine operation range when increasing the engine media supply temperatures, the gasoline engines showed a different behaviour. For the gasoline engines, disadvantages arise especially at low engine speeds. By using the developed combined approach, it was possible to assign mixed lubrication regimes at the valve train systems and at the piston groups. Full article

(This article belongs to the Special Issue Automotive Tribology)

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35 pages, 14491 KiB

Open AccessArticle

Investigations of the Friction Losses of Different Engine Concepts. Part 1: A Combined Approach for Applying Subassembly-Resolved Friction Loss Analysis on a Modern Passenger-Car Diesel Engine

by Christoph Knauder, Hannes Allmaier, David E. Sander and Theodor Sams

Lubricants 2019, 7(5), 39; https://doi.org/10.3390/lubricants7050039 - 26 Apr 2019

Cited by 34 | Viewed by 9416

Abstract

This work presents the application of a combined approach to investigate the friction losses in a modern four-cylinder passenger-car diesel engine. The approach connects the results from engine friction measurements using the indication method and the results from journal-bearing simulations. The utilization of [...] Read more.

This work presents the application of a combined approach to investigate the friction losses in a modern four-cylinder passenger-car diesel engine. The approach connects the results from engine friction measurements using the indication method and the results from journal-bearing simulations. The utilization of the method enables a subassembly-resolved friction loss analysis that yields the losses of the piston group, crankshaft journal bearings, and valve train (including the timing drive and crankshaft seals). The engine and engine subassembly friction losses are investigated over the full speed and load range, covering more than 120 engine operation points at different engine media supply temperatures ranging from 70 to 110

^{\circ}

C. The subsequently decreasing lubricant viscosity due to higher engine media supply temperatures allow for the identification of friction reduction potentials as well as possible risks due to an onset of mixed lubrication. Furthermore, additional strip-tests have been conducted to determine the friction losses of the crankshaft radial lip seals, the timing drive, and the crankshaft journal bearings, thus enabling a verification of the calculated journal-bearing friction losses with measurement results. For the investigated diesel engine, a friction reduction potential of up to 21% could be determined when increasing the engine media supply temperature from 70 to 110

^{\circ}

C, at engine speeds higher than n = 1500 rpm and part load operating conditions. At low engine speeds and high load operations, the friction loss reduction potential is considerably decreased and below 8%, indicating mixed lubrication regimes at the piston group and valve train. Full article

(This article belongs to the Special Issue Automotive Tribology)

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10 pages, 2403 KiB

Open AccessArticle

Artificial Neural Network-Based Analysis of the Tribological Behavior of Vegetable Oil–Diesel Fuel Mixtures

by Costel Humelnicu, Sorin Ciortan and Valentin Amortila

Lubricants 2019, 7(4), 32; https://doi.org/10.3390/lubricants7040032 - 9 Apr 2019

Cited by 30 | Viewed by 3757

Abstract

The use of fuel mixtures of diesel and vegetable oils in diesel engines is a field of research due to the necessity of reducing pollution. Besides the properties required for the normal operation of diesel engines, other aspects that must be investigated are [...] Read more.

The use of fuel mixtures of diesel and vegetable oils in diesel engines is a field of research due to the necessity of reducing pollution. Besides the properties required for the normal operation of diesel engines, other aspects that must be investigated are linked to the influence of these mixtures on piston ring–cylinder tribosystem behavior. Methods used for reducing the friction and wear on the engine cylinders, such as special surface machining, lubricant driving piston rings, etc., are well known. If the fuel mixture brings some improvement in this area, such as a reduction of the friction coefficient value, this can be a way to reduce the power lost by friction into the engine cylinders. In this paper, a methodology is presented based on artificial neural networks for analyzing the complex relationship between vegetable oil percentages in fuel mixtures, with the goal of finding an optimal proportion of vegetable oil corresponding to a minimum value of the friction coefficient. Regular methods were used for data acquisition, i.e., a pin-on-disk module mounted on a tribometer, and two types of vegetable oils were studied, namely sunflower and rapeseed oils. The obtained results show that for each type of vegetable oil there is an optimal proportion leading to the best tribological behavior. Full article

(This article belongs to the Special Issue Automotive Tribology)

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19 pages, 4491 KiB

Open AccessArticle

Lubrication Analyses of Cam and Flat-Faced Follower

by Hazim U. Jamali, Amjad Al-Hamood, Oday I. Abdullah, Adolfo Senatore and Josef Schlattmann

Lubricants 2019, 7(4), 31; https://doi.org/10.3390/lubricants7040031 - 5 Apr 2019

Cited by 15 | Viewed by 8833

Abstract

The principal factors that affect the characteristics of contact problem between cam and follower vary enormously during the operating cycle of this mechanism. This includes radius of curvature, surface velocities and applied load. It has been found over the last decades that the [...] Read more.

The principal factors that affect the characteristics of contact problem between cam and follower vary enormously during the operating cycle of this mechanism. This includes radius of curvature, surface velocities and applied load. It has been found over the last decades that the mechanism operates under an extremely thin film of lubricant. Any practical improvement in the level of film thickness that separates the contacted surfaces represents an essential step towards a satisfactory design of the system. In this paper a detailed numerical study is presented for the cam and follower (flat-faced) lubrication including the effect of introducing an axial modification (parabolic shape) of the cam depth on the levels of film thickness and pressure distribution. This is achieved based on a point contact model for a cam and flat-faced follower system. The results reveal that the cam form of modification has considerable consequences on the level of predicted film thickness and pressure distribution as well as surface deformation. Full article

(This article belongs to the Special Issue Automotive Tribology)

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17 pages, 6414 KiB

Open AccessArticle

Film Thickness and Shape Evaluation in a Cam-Follower Line Contact with Digital Image Processing

by Enrico Ciulli, Giovanni Pugliese and Francesco Fazzolari

Lubricants 2019, 7(4), 29; https://doi.org/10.3390/lubricants7040029 - 28 Mar 2019

Cited by 12 | Viewed by 4999

Abstract

Film thickness is the most important parameter of a lubricated contact. Its evaluation in a cam-follower contact is not easy due to the continuous variations of speed, load and geometry during the camshaft rotation. In this work, experimental apparatus with a system for [...] Read more.

Film thickness is the most important parameter of a lubricated contact. Its evaluation in a cam-follower contact is not easy due to the continuous variations of speed, load and geometry during the camshaft rotation. In this work, experimental apparatus with a system for film thickness and shape estimation using optical interferometry, is described. The basic principles of the interferometric techniques and the color spaces used to describe the color components of the fringes of the interference images are reported. Programs for calibration and image analysis, previously developed for point contacts, have been improved and specifically modified for line contacts. The essential steps of the calibration procedure are illustrated. Some experimental interference images obtained with both Hertzian and elastohydrodynamic lubricated cam-follower line contacts are analyzed. The results show program is capable of being used in very different conditions. The methodology developed seems to be promising for a quasi-automatic analysis of large numbers of interference images recorded during camshaft rotation. Full article

(This article belongs to the Special Issue Automotive Tribology)

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13 pages, 3101 KiB

Open AccessArticle

Reduction of CO₂ Emissions and Cost Analysis of Ultra-Low Viscosity Engine Oil

by Keita Ishizaki and Masaru Nakano

Lubricants 2018, 6(4), 102; https://doi.org/10.3390/lubricants6040102 - 18 Nov 2018

Cited by 13 | Viewed by 9209

Abstract

This study is focused on the reduction of CO₂ emissions and costs associated with ultra-low viscosity (ULV) engine oils for passenger vehicles. Specifically, the reduction in life cycle CO₂ (LCCO₂) emissions from lower-viscosity engine oil and the oil drain [...] Read more.

This study is focused on the reduction of CO₂ emissions and costs associated with ultra-low viscosity (ULV) engine oils for passenger vehicles. Specifically, the reduction in life cycle CO₂ (LCCO₂) emissions from lower-viscosity engine oil and the oil drain interval (ODI) extension were estimated taking into account both mineral engine oil and synthetic engine oil. Furthermore, the cost-effectiveness of ULV engine oils were investigated by performing base-stock cost analysis. When the volatility limit of the Noack test (American Society for testing and materials (ASTM) D5800) was set to 15 wt %, the results indicated that the lower limit of kinematic viscosity at 100 °C (KV100) for mineral engine oil (with Group-III base-stock) and synthetic engine oil (with polyalphaolefin (PAO) base-stock) were approximately 5.3 and 4.5 mm²/s, respectively. Compared to conventional 0W-16 mineral engine oil (KV100 6.2 mm²/s), the effect of reducing LCCO₂ emissions on ULV mineral engine oil (ULV-Mineral, KV100 5.3 mm²/s) was estimated at 0.6%, considering 1.5–1.8 L gasoline engines in New European Driving Cycles (NEDC) mode. ULV-Mineral, which continues to use a mineral base-stock, is considered highly cost-effective since its cost is similar to the conventional 0W-16 mineral engine oil. On the other hand, compared with ULV-Mineral, the vehicle fuel efficiency improvement from the use of ULV synthetic engine oil (ULV-PAO, KV100 4.5 mm²/s) was estimated to be 0.5%. However, considering CO₂ emissions during engine oil production, the reduction of LCCO₂ emission from ULV-PAO compared with ULV-Mineral was estimated to be only 0.1% or less using 2030 standards (assuming a vehicle fuel efficiency of 66.5 g-CO₂/km) when ODI is set equivalent (7500 km) to mineral engine oil. As a result, ULV-PAO’s cost-effectiveness, considering the cost increase of PAO base-stock, was found to be nominal. Contrariwise, when the characteristics of PAO base-stock with higher oxidation stability are used comparatively with the mineral base-stock while extending the ODI to 15,000 km, the effect of reducing LCCO₂ emissions of ULV-PAO was estimated to be 0.7% in 2030, making ULV-PAO a competitive and cost-effective alternative. In other words, the popularization of synthetic engine oil toward 2030 will require the consideration of both viscosity reduction and ODI extension. Full article

(This article belongs to the Special Issue Automotive Tribology)

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