Ducted Fuel Injection: An Experimental Study on Optimal Duct Size

Kenth Svensson; Russell Fitzgerald; Glen Martin

doi:10.4271/2022-01-0450

Ducted fuel injection (DFI), a concept that utilizes fuel injection through ducts, was implemented in a constant pressure High Temperature Pressure Vessel at 60 bar ambient pressure, 800-1000 K ambient temperature, and 21 % oxygen. The ducts were 14 mm long and placed 3-4.7 mm from the orifice exit. The duct diameters ranged from 1.6-3.2 mm and had a rounded inlet and a tapered outlet. Diesel fuel was used in single-orifice fuel injectors operating at 250 MPa rail pressure.

The objective of this work was to study soot reduction for various combinations of orifice and duct diameters. A complete data set was taken using the 150 μm orifice. A smaller data set was acquired for a 219 μm orifice, showing similar trends.

Soot reduction peaked at an optimal duct diameter of 2-2.25 mm, corresponding to an 85-90 % spray area reduction for the 150 μm orifice. Smaller or larger duct diameters were less effective. Duct diameter had a minimal effect on ignition delay.

Ambient temperature had an apparent strong effect on soot reduction. At 800 K, where the reaction rates were slower, DFI reduced soot by more than 94 % via longer lift-off lengths regardless of the duct geometry. At 1000 K, where the lift-off length was much shorter, apparent DFI soot reduction peaked at 42 %. For the larger orifice diameter, duct effectiveness was less sensitive to duct diameter.

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Ducted Fuel Injection: An Experimental Study on Optimal Duct Size 2022-01-0450

SAE MOBILUS