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For several years, the development of combustion and injection systems has been focused on drastically reducing pollutant emissions while preserving the high fuel efficiency which characterizes Diesel engines. In the mean time, the industrial robustness and the customer reliability had to be secured for worldwide applications. Within this working frame, project investigations have shown the importance of injector nozzle characteristics as a potential to greatly improve the fuel spray quality and thereby reduce engine-out emissions. Design parameters like hole diameter, hydro grinding, conicity or inlet hole radius have shown a direct influence on the internal hydraulic flow, allowing a better trade off between high performances and emissions; at the same time, induced cavitation has been identified not only for its well known influence on the discharge coefficient but also for its key role versus coking phenomena which especially appear with small hole diameters.

To provide fuel/air ratio quantitative measurements in an S.I engines, a transparent cylinder engine is investigated with the Fuel-Air Ratio Laser Induced Fluorescence (FARLIF) technique. In a homogeneous mixture, the two dimensional distribution for the fuel/air ratio is calibrated and measured during the compression stroke for different equivalence ratios. After spark ignition, the combustion zone and the flame front are visualized by laser sheet LIF. The direct-injection stratified-charge, new concept for gasoline engines is investigated with FARLIF. In the direct injection gasoline engine where the fuel is directly injected into a cylinder and the flow is highly turbulent, two injection timings are used: -early injection (i.e. during the intake stroke) to promote a homogeneous distribution; -late injection during the compression stroke, to generate a ultra-lean stratified charge.