Earlier studies have proven how ducted fuel injection (DFI) substantially reduces
soot for low- and mid-load conditions in heavy-duty engines, without significant
adverse effects on other emissions. Nevertheless, no comprehensive DFI study
exists showing soot reductions at high- and full-load conditions. This study
investigated DFI in a single-cylinder, 1.7-L, optical engine from low- to
full-load conditions with a low-net-carbon fuel consisting of 80% renewable
diesel and 20% biodiesel. Over the tested load range, DFI reduced engine-out
soot by 38.1–63.1% compared to conventional diesel combustion (CDC). This soot
reduction occurred without significant detrimental effects on other emission
types. Thus, DFI reduced the severity of the soot–NOx tradeoff at all
tested conditions. While DFI delivered considerable soot reductions in the
present study, previous DFI studies at low- and mid-load conditions delivered
larger soot reductions (>90%) compared to CDC operation at the same
conditions. Therefore, the DFI configuration used here has been deemed
nonoptimal (in terms of parameters such as the injector-spray and piston
geometries), and several improvements are recommended for future studies with
high-load DFI. These improvements include employing better spray-duct alignment,
a deeper piston bowl with a smaller injector umbrella angle, and a fuel injector
that opens and closes faster. The study also suggests future research to make
DFI ready for commercialization, such as metal-engine tests to ensure desirable
DFI performance over an engine’s complete speed/load map. Overall, this study
supports the continued development and commercialization of DFI to meet upcoming
emissions regulations for heavy-duty vehicles. Specifically, multicylinder
engine experiments and CFD simulations should be utilized to optimize the
performance and clarify the full potential of DFI.