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Content archived on 2024-06-18

Characterisation of Fuel Additives Effect on Fuel Injector Design

Final Report Summary - FAEFID (Characterisation of Fuel Additives Effect on Fuel Injector Design)

The primary objective of this research fellowship is the characterisation of the effect of Diesel fuel additives on internal nozzle flow and the emerging spray. Understanding of such behaviour will enhance the design of Diesel injector nozzles, as well as, the development of fuel additives, resulting in improved designs that take advantage of the newly developed additives towards a clean internal combustion engine and environmentally friendly operation.
During the initial stage of this research, a wide search in the related available literature was conducted, so that the fellow could familiarize himself with the state of the art additive technology, its effects (if any) on injector operation and with measurement techniques of fuel physical properties. This literature review showed that not only the available material concerning fuel additives were very few, but also chemical composition of additives was not public (as proprietary) and Diesel fuel measurement techniques (with required accuracy) dictated manufacturing of devices that proved expensive and could not be funded. Following this period, a number of decisions were made. Primarily, the most appealing Diesel fuel additive packages were chosen for future work, based on knowledge acquired through the literature review. Secondly, it was decided to ask for a partner’s support on additised fuels supply and characterisation; the fellow has been successful in securing this support and as much of insight as possible on additives technology. Furthermore, the fellow looked for possible collaborators in measuring fuel physical properties in extreme fuel pressure conditions.
In the second stage of the research activity, the fellow started the experimental activity, as well as, the design (where applicable) of future activities. The fellow has managed to successfully measure physical properties of the chosen Diesel fuels at atmospheric pressures and ambient temperatures. Moreover, experiments continued according to the initially proposed plan, however, results were not promising, and proved highly inconclusive. However, all indications pointed towards a strong interaction between additives and cavitation initiation and development. Therefore, a strategic decision was taken to shift the focus of this programme towards fundamental study of cavitation of additised fuels. The latter included the design of a prototype nozzle and the replacement of a task in WP4 with an exotic measurement technique, that of providing density measurements utilising x-rays and computed tomography. At this point it should be highlighted that these actions were not initially described in the proposed WorkProgramme, but the CITY group in collaboration with the scientist in charge from the outgoing host (SBU) believe that these changes are of added value as they have not been conducted before focusing on such application.
During the final year of this programme, the fellow has followed the modified work plan and completed all the associated tasks. Following the successful design of the experimental device certified by the preliminary experiments, the fellow completed high-speed visualisation of internal fuel flow and conducted successfully X-ray computed tomography (CT) measurements providing liquid volume fraction information inside the flow channel at a resolution of ~15μm. In brief, high-speed imaging identified transient features of the flow that are being studied in detail and provide useful information on string cavitation and vortex shedding mechanisms through bubble detachment and collapse. Additionally, density measurements through micro-CT technique provided quantitative information on cavitation vapour volume fraction (or fuel liquid volume fraction) locally that identify differences among various additives and constitute valuable validation data for computational fluid dynamics (CFD) models development. During this last year of the fellowship, certain CFD models have been developed in order to describe accurately the effect of certain additives on fuel flow.
Finally, during this period, the fellow had the opportunity to disseminate the work undertaken, participating in 6 conferences, while also preparing 5 papers for submission in high respected peer-reviewed scientific journals. The collaboration between the fellow and researchers from highly respected Universities and national US laboratories for facilitating a micro-CT experiment on Diesel fuel flows was also a highlight of this period, mainly due to the joint work which was needed for design and safety needs.

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