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The effect of the shape of the bowl on the combustion process and emissions of a Natural Gas - Diesel dual fuel engine is analyzed. The simulation of the dual fuel combustion is performed with a modified version of the KIVA3V code where diesel is treated as the main fuel and a further reacting specie is introduced as methane (CH4). The auto-ignition of the pilot is simulated with a modified version of the Shell model and the first stage of the combustion, related to the pilot burning process, is simulated with the Characteristic Time Combustion model. When the temperature of the mixture reaches a certain threshold, a kernel of combustion is initialized. Until the kernel reaches a nominal radius the combustion of CH4 is prevented. The combustion of CH4 is simulated with a turbulent characteristic time too. Numerical models were chosen as a compromise between accuracy and computational time.

The goal of the investigation is the evaluation of the environmental impact of hybrid and electric mobility in Lecce, a city of about 100,000 inhabitants in southern Italy. The investigation starts from the definition of specific driving cycles for the University campus and Lecce city center under different conditions of traffic and weather. The data acquired in this way are used to evaluate the performance of four typologies of vehicles: a gasoline city car (Smart Fortwo), the corresponding electric version (Smart ED), three range extenders and a plug-in hybrid electric vehicle operating with blended discharge. The simulation of the different power trains is performed with AVL-Cruise and validate through comparison with literature results on the European driving cycle.