Effect of Fuel Type and Tip Deposits on End of Injection Spray Characteristics of Gasoline Direct Injection Fuel Injectors

There has been a great effort expended in identifying causes of Hydro-Carbon (HC) and Particulate Matter (PM) emissions resulting from poor spray preparation, leading to characterization of fueling behavior near nozzle. It has been observed that large droplet size is a primary contributor to HC and PM emission. Imaging technologies have been developed to understand the break-up and consistency of fuel spray. However, there appears to be a lack of studies of the spray characteristics at the End of Injection (EOI), near nozzle, in particular, the effect that tip deposits have on the EOI characteristics. Injector tip deposits are of interest due to their effect on not only fuel spray characteristics, but also their unintended effect on engine out emissions. Using a novel imaging technique to extract near nozzle fuel characteristics at EOI, the impact of tip deposits on Gasoline Direct Injection (GDI) fuel injectors at the EOI is being examined in this work. Additionally, the impact of the test fuel used will also be evaluated. This work will present the large influence of fuel type on the average droplet diameter and average total fuel mass at EOI post injector needle closing. Furthermore, it will show that the injectors with deposits exhibited reduced visible fuel mass and reduced drop size regardless of fuel type when compared to clean injectors of the same type. Two multi injector studies were performed to verify the results.