Under current regulations, gasoline engines are facing lubricity and wear
challenges that need to be met by enhanced gasoline lubricity. Gasoline lubricity
can be enhanced by lubricity improvers such as heavy fatty acid methyl esters.
This thesis presents the ‘High Frequency Reciprocating Rig’ (HFRR) tests
carried out on a standardized tribological test rig as per a modified version of
ASTM D6079, to account for the effects of volatility of gasoline. Testing 5 gasoline
types (gasolines A-E) blended with 2 lubricity improver types (LI1-2) at 2
concentrations, 250 and 500 ppm, provided insights on the changes in lubrication
behavior with different gasoline composition, LI type, and concentration.
The gasoline types with higher aromatic content and average carbon number
(lower volatility) resulted in less wear and better lubricity regardless of LI
concentration. The highly aromatic gasoline “A” performed better with the fatty
acid-based LI1. Gasolines “B-E”, which are less aromatic, resulted in less wear
with the ester-based LI2. The decrease in wear volumes with LI2 was more
pronounced with the highly volatile gasolines B and E. These insights were mainly
challenged by the failure of some tests due to the high volatility of gasoline. To
mitigate this effect and confirm the findings, less volatile gasoline surrogates
were designed to mimic the composition of the gasoline types on functional group basis, and were blended with the same lubricity improvers, and then tested using
the same method. This improved the results and showed that high aromaticity
enhanced the lubricity of the gasoline blends, especially with fatty-acid based LI1,
but degraded it beyond 50% aromatic content. The enhancement of lubricity with
higher average carbon number was also highlighted.
To create deeper understanding of the lubrication mechanisms involved, it is
recommended to study the rheological properties of the blends, analyze the
chemical composition of the deposits on the wear tracks, and repeat the tests with
continuous supply of lubricant to further decrease the effect of gasoline volatility
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/679857 |
| Date | 07 1900 |
| Creators | Al Ashkar, Youssef |
| Contributors | Sarathy, Mani, Physical Science and Engineering (PSE) Division, Roberts, William L., Szekely, Gyorgy |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | 2023-07-25, At the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis will become available to the public after the expiration of the embargo on 2023-07-25. |
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