Effects of Flash Boiling in Nozzle Flow of GDI Injector on Air/Fuel Mixture

Abstract

The widths of fuel plumes around nozzle outlets expanded due to flash boiling during the nozzle flow. In some sprays, the length (penetration) of the air/fuel mixture increased due to the flash boiling. A cavitation model was incorporated in a simulation of the fuel spray integrating a simulation of the nozzle flow with a simulation of the air/fuel mixture. The simulation was applied to fuel sprays from a gasoline direct-injection injector; six nozzles were placed on an orifice cup in axial symmetry. Expansions of the plumes (in terms of width) around the nozzle outlets due to flash boiling and extension of spray penetration qualitatively agreed with the measured ones. Effects of the expansions of the plumes due to flash boiling on spray-penetration distance were also studied. The result of that study indicated that interactions between the expanded plumes around the nozzle outlets cause the spray shape of the air/fuel mixtures to thin, thereby extending the penetration of the spray.