Ducted Fuel Injection vs. Conventional Diesel Combustion: Extending the Load Range in an Optical Engine with a Four-Orifice Fuel Injector

Ducted Fuel Injection (DFI) has been shown to attenuate soot formation across a wide range of operating conditions in direct-injection compression-ignition engines. The concept is to inject fuel through a small tube inside the combustion chamber to reduce equivalence ratios at the autoignition zone relative to conventional diesel combustion (CDC). DFI has been studied at loads as high as 8.5 bar gross indicated mean effective pressure (IMEPg) and as low as 2.5 bar IMEPg using a four-orifice fuel injector. This study expands on the previous work by exploring 1.1 bar IMEPg (idle) conditions and 10 bar IMEPg (higher-load) conditions with the same four-orifice fuel injector. DFI and CDC are directly compared at each point in the study. At the idle condition, the intake dilution was swept to elucidate the soot and NOx performance of DFI in this new load range. This study expands the range of conditions over which DFI has been shown to attenuate soot formation. It also shows that DFI enables low-NOx idle operation that is not achievable with CDC due to excessive soot formation with high levels of dilution.