Investigating the effects of duct length and diameter and fuel-injector orifice diameter in a compression-ignition engine equipped with ducted fuel injection

Abstract Ducted fuel injection (DFI) has been shown to be effective at attenuating soot emissions from mixing-controlled compression-ignition engines. Furthermore, simultaneously low soot and nitrogen oxide (NOx) emissions have been achieved when DFI is combined with simulated exhaust-gas recirculation. Whereas previous studies investigating the effects of duct length and diameter have been conducted in combustion vessels, this is the first such study conducted in an engine. The work presented here quantifies the effects of duct length and diameter using 2- and 3-mm ducts that are 8, 12, and 16 mm long with a four-orifice fuel injector. This study also employs a larger fuel-injector-orifice diameter than has been studied previously. A comparison of 0.110-mm and 0.175-mm fuel-injector-orifice diameters with a single duct geometry is also presented. This study finds that the larger fuel-injector-orifice diameter provides better soot attenuation when it is used with a larger-diameter duct. The purpose of the larger orifice was to achieve a higher load than has been reported in previous DFI studies, namely 13.4 bar gross indicated mean effective pressure.