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The paper illustrates the interdisciplinary matching of different numerical and experimental techniques, aimed to characterize the performances, emissions and combustion noise radiated from a small-size DI diesel engine. The main objective is the development of proper models to be included within an optimization procedure, able to define an optimal injection strategy for a common-rail engine. The injection strategy is selected to simultaneously reduce the fuel consumption, the pollutant emissions and the combustion noise. The engine considered is a naturally aspirated, four strokes, two valves, single-cylinder engine (505 cm3 displacement), to be equipped with a prototype common-rail fuel injection system. A preliminary experimental investigation is carried out on the above engine, equipped, however, with a standard mechanical injection system (base engine).

Despite the recent efforts devoted to develop alternative technologies, it is likely that the internal combustion engine will remain the dominant propulsion system for the next 30 years and beyond. Also as a consequence of more and more stringent emissions regulations established in the main industrialized countries, strongly demanded are methods and technologies able to enhance the internal combustion engines performance in terms of both efficiency and environmental impact. Present work focuses on the development of a numerical method for the optimization of the control strategy of a diesel engine equipped with a high pressure injection system, a variable geometry turbocharger and an EGR circuit. A preliminary experimental analysis is presented to characterize the considered six-cylinder engine under various speeds, loads and EGR ratios.

Gasoline direct injection (GDI) allows flexible operation of spark ignition engines for reduced fuel consumption and low pollutants emissions. The choice of the best combination of the different parameters that affect the energy conversion process and the environmental impact of a given engine may either resort to experimental characterizations or to computational fluid dynamics (CFD). Under this perspective, present work is aimed at discussing the assessment of a CFD-optimization (CFD-O) procedure for the highest performance of a GDI engine operated lean under both single and double injection strategies realized during compression. An experimental characterization of a 4-stroke 4-cylinder optically accessible engine, working stratified lean under single injection, is first carried out to collect a set of data necessary for the validation of a properly developed 3D engine model.