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Increasingly stringent limits to pollutants released by Internal Combustion Engines pushed the automotive research to develop technologies to reduce fuel consumption and emissions. Higher injection pressures are beneficial to accelerate the atomization phase, reducing the particulate matter and unburned hydrocarbon emissions. However, the spray protrusion inside the combustion chamber is enhanced and, consequently, the generation of a thick wall film, which tends to increase the latter emissions. Thus, multiple-injection strategies might be beneficial for both the atomization rate and the spray penetration, owing to a stratified charge inside the chamber. This paper investigates the effect of the adoption of multiple-injection strategies on the behaviour of a GDI injector operating in high injection pressure conditions. The resulting injected mass is influenced by electrical phenomena on the excitation circuit, which mainly depend on the relative time between the end of the first injection and the start of the following. Hence, the total amount of fuel injected with the multiple-injection pattern will differ from its nominal value. In this work, a specific experimental layout was developed to characterize the behaviour of the injector in different operating conditions and quantify the deviation between actual and nominal injected mass. The impact of the magnetized coils on the overall injected mass has been captured referring to the modification of the shape of the driving current profile with respect to the nominal one. Then, a correlation which considers the electric charge variation on the coils has been implemented to model the phenomenon and, consequently, to counterbalance the electro-magnetic effect on the injected mass. The resulting strategy successfully allowed to reduce the difference between the actual and target fuel mass from up to 30% to almost 5%, owing to its implementation on the injection control system to automatically correct the injection commands and compensate the fuel mass deviations. [ABSTRACT FROM AUTHOR]

The H2-ICE project aims at developing, through numerical simulation, a new generation of hybrid powertrains featuring a hydrogen-fueled Internal Combustion Engine (ICE) suitable for 12 m urban buses in order to provide a reliable and cost-effective solution for the abatement of both CO2 and criteria pollutant emissions. The full exploitation of the potential of such a traction system requires a substantial enhancement of the state of the art since several issues have to be addressed. In particular, the choice of a more suitable fuel injection system and the control of the combustion process are extremely challenging. Firstly, a high-fidelity 3D-CFD model will be exploited to analyze the in-cylinder H2 fuel injection through supersonic flows. Then, after the optimization of the injection and combustion process, a 1D model of the whole engine system will be built and calibrated, allowing the identification of a "sweet spot" in the ultra-lean combustion region, characterized by extremely low NOx emissions and, at the same time, high combustion efficiencies. Moreover, to further enhance the engine efficiency well above 40%, different Waste Heat Recovery (WHR) systems will be carefully scrutinized, including both Organic Rankine Cycle (ORC)-based recovery units as well as electric turbo-compounding. A Selective Catalytic Reduction (SCR) aftertreatment system will be developed to further reduce NOx emissions to near-zero levels. Finally, a dedicated torque-based control strategy for the ICE coupled with the Energy Management Systems (EMSs) of the hybrid powertrain, both optimized by exploiting Vehicle-To-Everything (V2X) connection, allows targeting H2 consumption of 0.1 kg/km. Technologies developed in the H2-ICE project will enhance the know-how necessary to design and build engines and aftertreatment systems for the efficient exploitation of H2 as a fuel, as well as for their integration into hybrid powertrains. [ABSTRACT FROM AUTHOR]