Direct injection in internal combustion engines is often realised with a multi hole injection regardless of the combustion process. This creates a spray pattern consisting of multiple jets with a small distance between their origin. This leads to an interaction of adjacent spray jets. The spray characteristic is significantly influenced by this interaction, and can considerably change the fuel evaporation and with it the emission behaviour with varying number of holes or hole nozzle geometry.The influence of this interaction is very important to understand. Experimental investigations, especially if a good optical access to a single jet is necessary, often needs to use a comparable injector with a reduced number of holes. To determine the influence of the closing of nozzle holes of a production injector, it is necessary to understand the interaction of adjacent spray jet. In addition to experimental investigation, 3D-CFD simulation models can also use a reduction of spray jet number for a partial consideration of fuel mixture to reduce the computing time. For this use case a determination of the correlation between spray formation and reduced nozzle holes is also important.In this work the spray pattern of a 6-hole gasoline DI-injector (Bosch HDEV 5) is investigated. Afterwards 5 holes are closed the spray formation of the resulting 1-hole injector is compared to the original spray pattern. The fuel mass flow through one hole can change by closing other holes due to a change of hydrodynamic phenomena inside the nozzle. This effect is investigated experimentally and is supported by CFD-calculations of the fluid dynamics inside the nozzle. A correcting factor is determined to reach the same fuel flow through the single hole as through each hole of the standard injector.In addition to the hydrodynamic effects inside the nozzle, the spray jets interact outside of the nozzle. This can lead to a changed spray jet form. Therefore, the change of the penetration depth and of the deformation of the jacket of the fuel jets are investigated comparing standard and single hole injector. The droplet speed, size and spatial distribution are measured for a further characterization of the jets. Additional investigations of the influence of the fuel pressure and fuel temperature are being carried out.

Comparison of Spray Formation of a Multi and a Single Hole Gasoline Direct Injector

Paper Proceedings: https://asmedigitalcollection.asme.org/ICEF/ICEF2021/volume/85512

ASME 2021 Internal Combustion Engine Division Fall Technical Conference (ICEF2021)

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