Modeling Fuel-Air Mixing, Combustion and Soot Formation with Ducted Fuel Injection Using Tabulated Kinetics
2022-01-0483
03/29/2022
- Event
- Content
- Ducted Fuel Injection (DFI) has the potential to reduce soot emissions in Diesel engines thanks to the enhanced mixing rate resulting from the liquid fuel flow through a small cylindrical pipe located at a certain distance from the nozzle injector hole. A consolidated set of experiments in constant-volume vessel and engine allowed to understand the effects of ambient conditions, duct geometry and shape on fuel-air mixing, combustion and soot formation. However, implementation of this promising technology in compression-ignition engines requires predictive numerical models that can properly support the design of combustion systems in a wide range of operating conditions. This work presents a computational methodology to predict fuel-air mixing and combustion with ducted fuel injection. Attention is mainly focused on turbulence and combustion modelling. The first is mainly responsible for the mixture formation process in presence of large velocity gradients and flow recirculations, while the second must include detailed kinetics and turbulence chemistry-interaction to correctly predict ignition delay and flame structure. Literature experimental data are used for model assessment and validation under different ambient conditions and duct layout in terms of length and distance from the nozzle. Two different RANS turbulence models are tested (k-epsilon and k-omega-SST) to evaluate how they describe the flow in the duct region and the air/fuel mixing occurring downstream. Afterwards, the influence of the combustion model is evaluated considering three different approaches based on tabulated kinetics: well-mixed and tabulated flamelet progress variable. For this last one, flamelet libraries were generated with diffusion flame calculations performed both with tabulated kinetics or direct chemistry integration. A comparison between experimental and computed data of vessel pressure, heat release rate, flame liftoff and soot mass allowed to identify the most suitable combination of turbulence and combustion models. Finally, preliminary results of engine simulations are illustrated.
- Citation
- Lucchini, T., Zhou, Q., D'Errico, G., and Severgnini, D., "Modeling Fuel-Air Mixing, Combustion and Soot Formation with Ducted Fuel Injection Using Tabulated Kinetics," SAE Technical Paper 2022-01-0483, 2022, .