Ducted Fuel Injection: Effects of Stand-off Distance and Duct Length on Soot Reduction 2019-01-0545
Ducted fuel injection (DFI) has been shown to be an effective method to significantly reduce soot formation in mixing controlled compression ignition (MCCI) diesel flames. This reduction has been demonstrated in both combustion vessels and in an optical engine. The mechanisms driving the soot reduction are, at this time, not fully understood. There are many geometrical variable options, and optimal configurations are also not immediately evident. The objective of this study is to show the effects of some of these geometric variables, namely stand-off distance (0.1-6mm) for a 2x14mm duct, and duct length (8-14mm) at a given stand-off distance of 0.1mm.
A 137m on-axis single-hole injector operated at 100-250MPa was used in a continuous flow, constant pressure vessel. Results show that the shortest stand-off distance of 0.1mm yields the greatest soot reduction for a 2x14mm duct. Also, at the stand-off distance of 0.1mm, the longer the duct, the greater the soot reduction. Additionally, the performance of a 2x8mm duct placed at a longer stand-off distance is comparable to a longer duct with a short stand-off distance, i.e. the duct exit locations are similar. All results with greater soot reduction also had faster combustion.