Hammerton, James Richard;
(2024)
An in situ optical spectroscopy study of lubricant degradation used in internal combustion engines.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Deposit formation in internal combustion engines (ICE) is universally recognised as a major issue due to the negative effects these have on both performance and particularly the longevity. In this work, a base oil, a fully formulated oil containing five additive compounds and monoblends (i.e., base oil + one additive) were decomposed in both air and air mixed with NO2 (760 ppm) to determine the effect that these have on deposit formation. The decomposition behaviour was determined by performing in situ and ex situ measurements. The former being performed under conditions (temperature and gas composition) mimicking an ICE environment. Specifically, in situ transmission FTIR and UV-Vis measurements were performed using a modified Harrick temperature controlled demountable liquid cell. The FTIR data provided details about the functionalisation of the hydrocarbon species being formed and the extent of their oxidation with time. In contrast, the UV-Vis data gave insight into the formation and growth of small unconjugated hydrocarbon species forming larger conjugated polymeric species. Ex situ dynamic light scattering, and gel permeation chromatography measurements provide additional information about the size of the hydrocarbon particle size and distribution and the molecular weight of the precursor species formed respectively during the degradation reaction. The principal findings of these studies are that all oils degraded to form similar conjugated polymeric species, suggesting that additives do not have a significant influence on the degradation mechanism(s) but do influence the rate. The addition of NO2 to the in situ measurements resulted in little difference to the base oil degradation speciation and rate of reaction. However, the formulated oil experienced a twofold rate increase in the formation of the polymeric species, suggesting that NO2 inhibits the additive chemistry. In contrast, ex situ measurements revealed the physicochemical characteristics of the solid particles to be insensitive to the gas composition.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | An in situ optical spectroscopy study of lubricant degradation used in internal combustion engines |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10191471 |
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