Optimizing the Piston/Bore Tribology: The Role of Surface Specifications, Ring Pack, and Lubricant Applied Nano Surfaces

Format:

Book

Conference/Event

Author/Creator:

Zhmud, Boris, author.

Contributor:

Brodmann, Boris

Grabon, Wieslaw

Schorr, Dietmar

Tomanik, Eduardo

Conference Name:

SAE Powertrains, Fuels & Lubricants Meeting (2020-09-22 : Krakow, Poland)

Language:

English

Physical Description:

1 online resource cm

Place of Publication:

Warrendale, PA SAE International 2020

Summary:

The continuing pursuit for better fuel efficiency stands behindmany recent advancements in engine technology. "Downsize andcharge" has become the major development paradigm alongsidebroad acceptance of fuel stratified injection, variable valvetrain,cylinder deactivation, 48V electric auxiliaries, powertrainhybridization, use of low-friction coatings and advanced surfacefinishing methods in component manufacture, etc. The introductionof higher power densities (in excess of 100 kW/L and 200 Nm/L inmodern engines) raises performance requirements for engine oil. Atthe same time, the introduction of high-speed diesel enginesjustifies the move towards lower oil viscosities in order to reduceon-road greenhouse gas (GHG) emissions. Advanced surface finishingmethods, such as self-lubricated hard coatings, mirror-likethermally sprayed bores, mechanochemical surface finishing, helicalslide honing etc. as well as availability of high-sensitivitytesting rigs and "digital twin" simulation tools createnew opportunities for engine tribology optimization. On thelubricant side, there is an increasing use of synthetics due totheir superior performance. New additives types are also coming tothe market to address new performance challenges. In particular,superlubricity additives should be mentioned. However, there existsa certain gap, both in attitude and competence, between universityresearchers and lube industry professionals as their willingness toventure out for new technologies is concerned. A narrow-sightedone-component-at-a-time optimization approach still prevails atmany OEMs due to their internal organizational structure. However,there are many examples proving that the one-component optimizationis often nothing less than misleading, necessitating the need for acomplete system approach. For instance, there is no point inoptimizing the friction of the top ring without taking into accountthe oil control ring, as all rings in the ring pack work together.Also, what is optimal for a high-speed short-stroke engine is notnecessarily optimal for a low-speed long-stroke engine. In thepresent communication, we will demonstrate such a "systemapproach" in action. We will present experimental data andsimulation results demonstrating the role of GD&T, surfacespecifications, ring pack, and lubricant on the piston/boretribology. Friction, wear and combustion chamber sealing will beconsidered and the shortcomings of one-component approachdemonstrated. The importance of in-design "pairing" oflow-viscosity motor oils with the ring pack and the cylinder borecharacteristics in order to achieve maximum reduction in GHGemissions and improvement in fuel economy without sacrificing theendurance will be elucidated. References: E. Tomanik and othersCombined lubricant-surface system approach for potential passengercar CO2 reduction on piston-ring-cylinder bore assembly, in press,Available online 21 December 2018, Tribology International,https://doi.org/10.1016/j.triboint.2018.12.014 B. Zhmud,Low-Friction Powertrains: Current Advances in Lubricants andCoatings, in Proc. Engine Expo 2017, June 20-22, 2017, Stuttgart,Germany. B. Zhmud, In-manufacture Running-in of Engine Componentsby Using the Triboconditioning® Process, in Proc. the 7thInternational Conference on Fracture Fatigue and Wear, July 9-10,2018, Ghent, Belgium, pp. 671-681

Notes:

Vendor supplied data

Publisher Number:

2020-01-2167

Access Restriction:

Restricted for use by site license