A quantitative analysis of nozzle surface bound fuel for diesel injectors

Jack Turner, Dan Sykes, Guillaume De Sercey, Viacheslav Stetsyuk, Martin Gold, Richard Pearson, Cyril Crua

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


In a fuel injector at the end of the injection, the needle descent and the rapid pressure drop in the nozzle leads to discharge of large, slow-moving liquid structures. This unwanted discharge is often referred as fuel ‘dribble’ and
results in near-nozzle surface wetting, creating fuel-rich regions that are believed to contribute to unburnt hydrocarbon emissions. Subsequent fluid overspill occurs during the pressure drop in the expansion stroke when
residual fluid inside the nozzle is displaced by the expansion of trapped gases as the pressure through the orifices is equalised, leading to further surface wetting. There have been several recent advancements in the characterisation of these near nozzle fluid processes, yet there is a lack of quantitative data relating the operating conditions and hardware parameters to the quantity of overspill and surface-bound fuel. In this study, methods for quantifying nozzle tip wetting after the end of injection were developed, to gain a better understanding of the
underlying processes and to study the influence of engine operating conditions. A high-speed camera with a longdistance microscope was used to visualise fluid behaviour at the microscopic scale during, and after, the end of injection. In order to measure the nozzle tip temperature, a production injector was used which was instrumented with a type K thermocouple near one of the orifices. Image post-processing techniques were developed to track both the initial fuel coverage area on the nozzle surface, as well as the temporal evolution and spreading rate of surface-bound fluid. The conclusion presents an analysis of the area of fuel coverage and the rate of spreading and how these depend on injection pressure, in-cylinder pressure and in-cylinder temperature. It was observed that for this VCO injector, the rate of spreading correlates with the initial area of fuel coverage measured after the end of injection, suggesting that the main mechanism for nozzle wetting is through the impingement of dribble onto the nozzle. However, occasional observations of the expansion of orifice-trapped gas were made that lead to a significant increase in nozzle wetting.
Original languageEnglish
Title of host publication ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems
Subtitle of host publication 8B EXPERIMENTAL TECHNIQUES 2
Publication statusPublished - 6 Sep 2017
Externally publishedYes
Event28th European Conference on Liquid Atomization and Spray Systems - Universitat Politencia de Valencia, Valencia, Spain
Duration: 6 Sep 20178 Sep 2017
Conference number: 28
https://www.cmt.upv.es/ILASS2017/Default.aspx (Link to Conference Website)


Conference28th European Conference on Liquid Atomization and Spray Systems
Abbreviated titleILASS2017
Internet address


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