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In this work, the first injection of gasoline was maintained at 30 CAD Before TDC and the second one was swept between 10 CAD Before TDC to 5 CAD After TDC, in order to demonstrate the ideal positioning of the second injection. The results showed that when it was placed near TDC, low emissions, acceptable noise and acceptable efficiencies could be obtained. The effect of EGR, simulated by N2 addition, was also studied. As expected, globally the effect of the EGR rate was to delay the combustion phasing and to decrease NOx emissions. The optimal EGR dilution rate was found to be 30% with respect to the cycle-to-cycle variation criterion (< 5%). Increasing the dilution rate increased HC, CO and PM emissions, due to a considerable delay in combustion phasing caused by the reduction in the fuel reaction rate and the in-cylinder lack of oxygen when the EGR rate reached 30%. The impact of the fuel mass distribution between the two injections was also considered.

Recent works have demonstrated the possibility of operating compression ignition engine with high resistance to auto-ignition fuels as gasoline. By using gasoline and dilution by exhaust gas recirculation, compression ignition can reach high efficiencies and low particulate (PM) and NOx emissions. One of the promising strategies to reach this combustion is the Gasoline Partially Premixed Combustion (GPPC) concept. First step of the study was to optimize the run of a single cylinder Diesel engine in GPPC with double injections strategy by change the second injection phasing and EGR level. The optimum in terms of heat release rate and regulated pollutant emissions was obtained for second injection timing around TDC and an EGR level at 30%.