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Nowadays, the vehicle hybridization and the use of non-conventional fuels for heavy-duty applications brings to a new beginning in the use of spark ignition (SI) engines. For a standard intake system, the premixed fuel/air mixture is controlled by the injection of fuel after the throttle valve. Then, the geometry of the intake system, with the intake duct, the intake valves and the cylinder head shape, influences the characteristics of the flow within the cylinder up to the combustion process. The new technology of fluid-power and electrical actuations gives the opportunity to decouple the intake and exhaust valve actuations with respect to the standard cam shaft distribution. The Variable Valve Actuation (VVA) concept is not new, but its application is now affordable and flexible enough to be applied to partial load conditions.

The partial fuel stratification, by means of direct fuel injection, is one of the most suitable combustion strategies in order to overcome the limits of ignition control and operating range of HCCI engines. In this work, a multidimensional model, coupled with a detailed kinetic mechanism for ethanol oxidation, is used to investigate the performance of a partially stratified charge CI engine fueled by ethanol. The model, which accounts for turbulence effects on combustion, has been validated in a previous work, against experimental results in terms of both HCCI engine performance and emissions. In this work, computations have been carried out by varying the fraction of the fuel stratified charge and the injection timing and by considering different flow structures within the cylinder.

The transition to electric vehicles in the transportation sector still faces multiple technological challenges and large investments as regards both vehicle design and vehicle charging infrastructure. Therefore, internal combustion engines still play a role in such a sector, making the engine improvements, in terms of pollutant emissions and efficiency, essential to mitigate the impact of human activities on the environment. One of the possible approaches to improve the efficiency of internal combustion engines is the recovery of the engine exhaust heat, from both the hot exhaust gases and the engine cooling system. In recent years, among the energy recovery strategies, the use of direct injection of H2O under supercritical and superheated thermodynamic states has been explored. Such a technique uses pressurized water recovered from the exhaust gases, heated to high temperature by using the engine exhaust heat and re-injected into the engine combustion chamber.

The efficiency of ICEs is strongly affected by exhaust gases and engine cooling system heat losses, which account for about 50% of the heat released by combustion. A promising approach is to transfer this exhaust heat to a fluid, like water, and inject it into the combustion chamber under supercritical conditions. In such a way, the recovered energy is partially converted into mechanical work, improving both engine efficiency and performance. A quasi-dimensional model has been implemented to simulate an SI engine with supercritical water injection. Specifically, a spark ignition ICE, four-stroke with Port Fuel Injection (PFI) has been considered. The model accounts for gas species properties, includes valves opening/closing, wall heat transfer, a water injection model and a combustion model. The influence of some injection parameters, i.e.

In this work, an ozone/air/gasoline mixture has been used as an alternative strategy to achieve a stable combustion in a spark ignition (SI) single cylinder PFI research engine. The air intake manifold has been modified to include four cells to produce ozone with different concentrations. In the research engine, various operating parameters have been monitored such as the in-cylinder pressure, temperature and composition of the exhaust gases, pressure and temperature of the mixture in the intake manifold, engine power and torque and specific fuel consumption. Experimental tests have been carried out under stoichiometric mixture conditions to observe the influence of ozone addition on the combustion process. The results show an advance and an increase of the in-cylinder pressure compared to the reference test-case, where a gasoline/air mixture is used. It is worth noting that, especially under stoichiometric condition, ozone concentration induces auto-ignition and knock.