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In the field of gasoline turbocharged engines, the improvement of combustion efficiency represents a critical point when increased engine torque and reduced fuel consumption are simultaneously expected. Though gasoline port fuel injection is a well known and wide spread technology for fuel delivery in spark-ignition engines, detailed information on the features of the liquid fuel spray and the wall film formation could significantly contribute, in terms of emission control, to the engine development. In this paper, air-fuel mixture formation and smoke emissions of a turbocharged port-fuel-injected gasoline engine have been investigated by using experimental and numerical analysis techniques. The objective of this activity is to properly choose the injection system and strategy aimed to optimize both engine performance and emission levels. 3-D CFD calculations have been performed in order to deeply investigate the complex phenomena occurring before the combustion process starts.

In this paper, an experimental and numerical analysis of combustion process and knock occurrence in a small displacement spark-ignition engine is presented. A wide experimental campaign is preliminarily carried out in order to fully characterize the engine behavior in different operating conditions. In particular, the acquisition of a large number of consecutive pressure cycle is realized to analyze the Cyclic Variability (CV) effects in terms of Indicated Mean Effective Pressure (IMEP) Coefficient of Variation (CoV). The spark advance is also changed up to incipient knocking conditions, basing on a proper definition of a knock index. The latter is estimated through the decomposition and the FFT analysis of the instantaneous pressure cycles. Contemporary, a quasi-dimensional combustion and knock model, included within a whole engine one-dimensional (1D) modeling framework, are developed. Combustion and knock models are extended to include the CV effects, too.

Hydrogen and gasoline can be burned together in internal combustion engines in a wide range of mixtures. In fact, the addition of small hydrogen quantities increases the flame speed at all gasoline equivalence ratios, so the engine operation at very lean air-gasoline mixtures is possible. In this paper, the performance of a spark-ignition engine, fuelled by hydrogen enriched gasoline, has been evaluated by using a numerical model. A hybrid combustion model for a dual fuel, according to two one-step overall reactions, has been implemented in the KIVA-3V code. The indicated mean pressure and the fuel consumption have been evaluated at part load operating points of a S.I. engine designed for gasoline fuelling. In particular, the possibility of operating at wide-open throttle, varying the equivalence ratio of air-gasoline mixture at fixed quantities of the supplemented hydrogen, has been studied.

In this paper, the behavior of a downsized spark-ignition engine firing with alcohol/gasoline blends has been analyzed. In particular, different butanol-gasoline and ethanol-gasoline blends have been examined. All the alcohol fuels here considered are derived from biomasses. In the paper, a numerical approach has been followed. A one dimensional model has been tuned in order to simulate the engine operation when it is fueled by alcohol/gasoline mixtures. Numerous operating points, characterized by two different engine speeds and several low-medium load values, have been analyzed. The objective of the numerical analysis is determining the optimum spark advance for different alcohol percentages in the mixtures at the different engine operating points. Once the best spark timing has been selected, the differences, in terms of both indicated torque and efficiency, arising in the different kinds of fueling have been evaluated.

Spark-ignition engines are characterized by poor levels of thermal efficiency, it is known, especially when running at partial load. Since part-load operating points are the most commonly used in engine average life, achieving a given torque value with small displacement, high mean effective pressure engines, the so-called “downsizing”, permits, in general, to limit some typical engine losses (for instance: pumping and friction losses), improving the fuel consumption in a wide range of engine operating points. Small displacement engines, usually, achieve high toque values thanks to supercharging techniques. In this paper, knock risks for a small displacement turbo-charged spark-ignition engine have been analyzed. A parametric analysis of numerous variable influencing engine performance and knock resistance has been carried out by means of 1-D numerical simulations.