Numerical Simulation of Non-reacting Ducted Fuel Injection by Means of the Diffuse-Interface Σ-Y Atomization Model

Ducted Fuel Injection (DFI) is a new technology recently developed with the aim of reducing soot emission formation in diesel compression ignition engines. DFI concept consists of the injection of fuel spray through a small duct located downstream of the injector nozzle leaving a certain gap, the so-called Stand-off distance. Currently, CFD modelers have investigated its performance using classical spray modeling techniques such as the Discrete Drops Method (DDM). However, as discussed in the literature, this type of technique is inappropriate when applied to dense jets as those occurring in diesel sprays, especially in the near-nozzle region (where the duct is placed). Therefore, considering a more appropriate modeling technique for such a problem is mandatory. In this research work, an Eulerian single-fluid diffuse-interface model called Σ-Y and implemented in the OpenFOAM framework is utilized for the simulation of non-reacting conditions. The model relevance is twofold, as it is particularly suited for the dense spray regions existing in the vicinity of the nozzle exit and inside the duct, and because it includes a coupled drift flux model for dilute spray regions. An analysis of free-jet performance against DFI one is presented considering a single diesel jet injected from a 180 μm orifice in a constant volume vessel. In this regard, a 2 mm internal diameter, 14 mm long duct was studied, while the duct sharp inlet was positioned 2 mm downstream of the nozzle orifice. A deep insight into the mixing process is conducted to take advantage of the valuable Eulerian framework tool and thus, enhancing the understanding of DFI process.