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This paper reports the study of the effects of alternative diesel fuel and the impact for the air-fuel mixture preparation. The injection process characterization has been carried out in a non-evaporative high-density environment in order to measure the fuel injection rate and the spatial and temporal distribution of the fuel. The injection and vaporization processes have been characterized in an optically accessible single cylinder Common Rail diesel engine representing evaporative conditions similar to the real engine. The tests have been performed by means of a Bosch second generation common rail solenoid-driven fuel injection system with a 7-holes nozzle, flow number 440 cc/30s @100bar, 148deg cone opening angle (minisac type). Double injection strategy (pilot+main) has been implemented on the ECUs corresponding to operative running conditions of the commercial EURO 5 diesel engine.

GM Powertrain Europe and Istituto Motori CNR have undergone a research project aimed at studying the effects on engine performance, emissions and fuel consumption of alternative diesel fuels, from both first (FAME) and second (GTL) generation. The present paper reports some of the results achieved studying the impact on injection and spray behavior of rapeseed and soybean methyl-esters, as well as of GTL diesel blends. The test were performed on a Bosch second generation common rail solenoid-driven fuel injection system capable of 1600bar maximum injection pressure, fitted on GM 1.9L Euro4 diesel engine for passenger cars. The characterization of the injection process has been carried out in terms both of fuel injection rate, as well as of spatial and temporal fuel distribution in a quiescent non-evaporative optically accessible chamber.

Spray impingement on walls is an important physical process in modern DI Diesel engines as it greatly influences mixture formation, combustion process and exhaust emissions. The mixture preparation is, in fact, a crucial aspect for the correct operation of the engine as it significantly affects the combustion process. In this paper three models, among the available in literature, have been selected and implemented in the KIVA-3V code. Namely, the models by O'Rourke and Amsden (OA model) [1, 2], by Bai and Gosman (BG model) [3] and by Lee et al. (LR model) [4, 5] are compared in terms of performance and capability of representing the splash phenomenon. The model capabilities are firstly tested comparing the numerical results with four sets of experimental literature data, characterized by low injection pressures. The high injection pressures of modern Diesel engines result in droplets velocities emerging from the nozzle greater than 300 m/s.

Numerical and experimental analyses of hollow cone sprays generated by pressure-swirl injectors for Direct Injection Spark Ignition (DISI) engines have been performed. Spray characteristics have been measured by a gathering and processing system for spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 100 μm). A detailed spatial and temporal characterization of the emerging spray has been carried out showing interesting peculiarities of the jet for different operative conditions. Some results of a work in progress, aiming to select and to validate proper models for the spray development simulation are, also, discussed. Numerical calculations are based on the KIVA 3V code modified in basic spray sub models. Some important physical phenomena are captured in the computations at the backpressure of 0.1 MPa.