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Testing scuffing resistance of materials for marine 2-stroke engines: Difficulties with lab scale testing of a complex phenomenon
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Ångström Tribomaterials group)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
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2015 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 340-341, no SI, p. 9-18Article in journal (Refereed) Published
Abstract [en]

Optimising sliding materials of marine two-stroke diesel engine cylinders for reduced risk of scuffing is imperative because of the high costs associated with replacing the cylinder liner. But how can a complex and poorly understood phenomenon such as scuffing be tested? This study investigates the potential of material selection based on lab tests. Experience from ship operation is combined with analysis of lab scale scuffing tests to evaluate the possibilities of gaining applicable knowledge from scuffing testing. Two piston ring materials, a grey cast iron and a plasma sprayed cermet coating, both currently used in engines, were tested. Each of the materials was tested with two surface characters, achieved by run-in in a real engine and by fine grinding respectively. The ranking of the two materials proved to differ between the two surface characters. In the tests, scuffing could only be detected when all oil had become removed from the contact by being adsorbed by agglomerated wear debris and scraped away. This and other critical mechanisms behind scuffing in the tests are thoroughly discussed and compared to possible mechanisms taking place in the engine.

Place, publisher, year, edition, pages
2015. Vol. 340-341, no SI, p. 9-18
Keyword [en]
Cylinder liner; Lubricated wear including scuffing, Marine two-stroke diesel engine, Materials, Piston ring
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Materials Engineering
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
URN: urn:nbn:se:uu:diva-265177DOI: 10.1016/j.wear.2015.06.015ISI: 000362926400003OAI: oai:DiVA.org:uu-265177DiVA, id: diva2:862737
Conference
16th Nordic Symposium on Tribology - NORDTRIB 2014, 10-12 june 2014, Aarhus, Denmark
Funder
EU, FP7, Seventh Framework Programme, 265861
Available from: 2015-10-23 Created: 2015-10-23 Last updated: 2018-01-11Bibliographically approved
In thesis
1. Tribology for Greener Combustion Engines: Scuffing in Marine Engines and a Lubricating Boric Acid Fuel Additive
Open this publication in new window or tab >>Tribology for Greener Combustion Engines: Scuffing in Marine Engines and a Lubricating Boric Acid Fuel Additive
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Tribologi för grönare förbränningsmotorer : Skuffning i fartygsmotorer och ett smörjande borsyrabaserat bränsleadditiv
Abstract [en]

This thesis aims at increased knowledge in two fields of tribological research; both related to making currently used combustion engines greener. The first field regards the possibilities of using a boric acid fuel additive to increase fuel efficiency. The second field is about the severe wear phenomenon scuffing, which can become problematic when cargo ships are operated on low-sulphur fuel to reduce sulphuric emissions.

Tribological tests were developed and performed to simulate the applications. Advanced surface analysis was performed to understand changes occurring on the outermost surface of sliding components, which affect friction and wear. Samples from engines were studied to verify the relation between the lab tests and the applications.

In the case of boric acid, the coefficient of friction was below 0.02 for large parts of the tests, but varied with test parameters. The corresponding reduction in friction was up to 78% compared with tests without the additive. As an attempt to assess if the substantial fuel savings found in field tests with passenger cars (6%) can be explained by friction reduction in boundary and mixed lubricated parts of the piston assembly, assumptions were presented that would lead to fuel savings close to these 6%. Boric acid was detected on surfaces after the tests, and the tribofilm appearance depended on test parameters. The tribofilms were shown to be affected by storage time and test temperature; a finding that is vital for future studies.

In the case of scuffing, mechanisms were studied and accumulation of wear debris had a significant role on scuffing initiation in the lab scale scuffing tests. Regarding the possibility to test materials scuffing resistance, there was a large scatter in the results, and thereby difficult to draw conclusions. Two new piston ring materials were identified to perform somewhat better than the currently used.

In conclusion, findings that could facilitate immediate improvement of fuel efficiency of today’s combustion engine vehicles as well as findings that strengthen available hypotheses on scuffing mechanisms are presented. The latter offers improved understanding of scuffing and thereby give possibilities to counteract the higher risk associated with operation on cleaner fuel.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 97
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1607
Keyword
Friction, wear, lubrication, energy loss, atmospheric emissions, fuel efficiency, transport.
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Other Materials Engineering
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-333430 (URN)978-91-513-0174-7 (ISBN)
Public defence
2018-01-19, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2017-12-21 Created: 2017-11-29 Last updated: 2018-03-08

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Olander, PetraHollman, PatrikJacobson, Staffan

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