Internal Diesel Injector Deposits

QC 20241111

Abstract

 Heavy-duty transportation is a significant contributor to greenhouse gas emissions. One way to reduce CO2 emissions from this sector is through the use of drop-in fuels, where alternative fuels are used directly or blended with conventional fuels. However, these blends can have solubility issues, leading to precipitation of soft particles, resulting in clogged fuel filters, and disrupt injector performance, thereby reducing engine efficiency and increasing fuel consumption. As advanced fuel systems are introduced and blending proportions of alternative fuels rise to meet stricter environmental regulations, these challenges are likely to become more prevalent. Therefore, research in this area is essential, as the use of drop-in fuels is expected to grow and the associated problems are anticipated to become more common. This thesis investigates the formation of internal diesel injector deposits (IDIDs) from drop-in fuels and proposes mechanisms for their formation. The research involved characterizing deposits from field injectors and developing experimental methods to generate deposits under controlled conditions. Two experimental methods were designed for deposit generation, along with a standardized methodology for characterizing both field and laboratory-generated IDIDs. Insights from field injector analyses guided the design of test fuel blends and experiments using these new methods. The experimental results demonstrate that the composition of IDIDs varies based on the type of fuel used. Deposits from fatty acid methyl ester (FAME) biodiesel blends mainly consist of metal soaps, inorganic salts, and nitrogen compounds, likely from biodiesel degradation. In contrast,paraffinic renewable fuels, such as hydrogenated vegetable oil (HVO), tend to form deposits from fuel additives such as corrosion inhibitors and detergents, likely due to lower solvent power of the fuel. Importantly, deposits formed exclusively within the injectors, highlighting temperature as a critical factor. A laboratory thermal deposit test (TDT) was developed to explore the chemistry of these deposits and the effects of temperature and fuel contaminants. Additionally, a custom-built injector rig was created to reproduce IDIDs under engine-like conditions and test injector performance. Fullengine tests were also conducted to study soft particle formation during operation. A two-layer formation mechanism was proposed, with an inorganic calcium sulfate layer followed by an organic layer of metal soaps and additives, which was successfully reproduced in the injector set up. Engine tests revealed that soft particles form during operation with higher biodiesel blends. This work emphasizes the importance of a robust fuel system capable of handling soft particles and suggests that minimizing contaminants and maintaining high fuel quality can help reduce deposit formation. These findings support the ongoing use of drop-in fuels in advanced fuel systems. Furthermore, the thesis successfully developed specific methods to address internal injector issues and created setups for studying deposit chemistry in the laboratory, including an injector test rig for evaluating injector performance, as well as engine test operations under realworld conditions. 

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