Multi-Zone Predictive Modeling of Common Rail Multi-Injection Diesel Engines

The paper deals with the development of a multi-zone phenomenological model for the combustion process in a common rail multi-injection Diesel engine. The model simulates the fuel jet and its interaction with surrounding gases by dividing the jet core into many parcels in order to describe the thermal gradient and the chemical composition within the combustion chamber. This is mandatory for the simulation of the NO pollutant formation, carried out via the Zeldovich mechanism. The air entrainment into the fuel jet is modeled by means of the momentum balance applied to each zone and to the air zone. The stratification of the chemical composition within the cylinder and the details of the spray and its interaction with the air zone are simulated to estimate the spray penetration and speed, the mass of entrained air and the equivalence ratio in each zone. The combustion model is based on the laminar-and-turbulent characteristic-time approach. The three model parameters have been tuned on one engine cycle and the model validation has been accomplished by comparison against a wide set of measurements on a Fiat 1.9 Common-Rail Multi-Jet engine. The simulation results show a very good agreement between measured and predicted engine cycles and NO emissions.