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The fuel direct injection in SI engines is demonstrating a remarkable potential regarding the reduction of consumption and pollutant emission. Nevertheless, the management of the mixture formation “in-cylinder” - in conditions of a short duration and of a complex fluid dynamic configuration imposes both an accurate modeling and an exact control of the process. The problem gains on complexity when considering the use of alternative fuels which becomes more and more a subject of actuality. The paper presents a comparative analysis of mixture formation process and engine performances, when applying direct injection of gasoline, respectively of ethanol in a four-stroke single cylinder SI engine. The modulation of the injection rate shape is the result of a fuel high pressure wave, generated in a pressure pulse direct injection system.

Many technologies are being developed to solve the trouble of the urban pollution. Among other solutions (improvements in engine control and combustion, electrical propulsion) one of the foreseen ways is the employment of low or zero carbon content fuels, such as hydrogen. In fact a nearly zero emission vehicle may be obtained through the hydrogen propulsion; in this case the only polluting agents are nitrogen oxides if an internal combustion engine is used. Though fuel cells are considered as the most promising solution in the long term, they are still in their prototypical phase and the use of the internal combustion engine use remains until today a relevant topic. It has been evident since the 80s that direct injection is the only method to get a high specific power without pre-ignition and backfire phenomena. However this technique shows a higher difficulty in getting a well-mixed charge.