Droplet collision in a diesel spray has been studied through the observations of a binary collision system with two equivalent droplets of the same kind. However, DWI (Direct Water Injection) system recently introduced to reduce NOx emission from marine diesels could have the collisions between the droplets of different kind, that is, between water and fuel. Especially, the DWI system with a two-needle type injector may produce considerable collisions between fuel and water because of its near co-axial nozzle layout and its great difference in injection pressure. Conventional CFD codes applied to DWI spray propagation have been not very successful so far, since they only consider the coalescence and the stretching separation of two identical liquid droplets. In this study, the empirical criteria were directly adopted into KIVA3 code. This was divided into bounce, coalescence and separations after the collision of two droplets of any kind. The effective entrainment of water into fuel spray was numerically captured in the DWI system of the two-needle injector. The results were partially confirmed through observation of the actual DWI spray in a constant volume bomb.
Diesel spray simulation in direct water injection considering collision between fuel and water droplets
2009
8 Seiten, 12 Bilder, 2 Tabellen, 8 Quellen
Conference paper
English
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