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Boric acid as a lubricating fuel additive - Simplified lab experiments to understand fuel consumption reduction in field test
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.ORCID iD: 0000-0002-4301-8038
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.ORCID iD: 0000-0003-2704-5447
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.ORCID iD: 0000-0002-3955-5746
2017 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376, p. 822-830Article in journal (Refereed) Published
Abstract [en]

In field tests, a boric acid based fuel additive has led to reduced fuel consumption. The reduction was substantial, an average of 6 and 10% in passenger cars and diesel generators respectively. Aiming towards improved understanding of mechanisms behind the fuel saving, three methods to mimic the effect of the additive in the piston-ring/cylinder contact have been evaluated. A reciprocating cylinder/flat configuration with ball bearing steel against grey cast iron was used, and it was lubricated with base oil. The different methods were as following: A) repeated spraying of a small amount of the boric acid solution onto the surfaces, B) predeposition of a boric acid layer on the flat surface and C) a combination of method A) and B). The three methods all showed effects of the additive, spanning from about 20% to 50% reductions (in the latter case, from roughly 0.1 to 0.05 in coefficient of friction averaged over the stroke). The greatest potential of the additive was seen with local coefficient of frictions lower than 0.020 in tests at room temperature with Method C. This means a reduction of around 75% compared to the lowest levels measured for the reference tests run without the additive. The most stable friction test was Method A, where a small amount of boric acid solution was repeatedly sprayed onto the lubricated sliding surfaces. In this type of test, friction reductions of roughly 20% and 40% were found at 100 C and room temperature respectively. The tribological and chemical mechanisms of boric acid in this test configuration are yet not fully understood and more studies are needed. However, the observed poor stability of the tribofilms containing boron and oxygen complicates such activities.

Place, publisher, year, edition, pages
2017. Vol. 376, p. 822-830
Keywords [en]
Boric acid, Lubrication, Friction, Fuel consumption, Fuel additive
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:uu:diva-329131DOI: 10.1016/j.wear.2017.01.105ISI: 000403904000093OAI: oai:DiVA.org:uu-329131DiVA, id: diva2:1148168
Conference
21st International Conference on Wear of Materials (WOM), MAR 26-30, 2017, Long Beach, CA, USA
Funder
VINNOVAAvailable from: 2017-10-10 Created: 2017-10-10 Last updated: 2017-11-29Bibliographically 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
Keywords
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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Larsson, ElinOlander, PetraJacobson, Staffan

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