Impact of the Second Injection Characteristics and Dilution Effect on Gasoline Partially Premixed Combustion 2014-01-2673
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. This experiment showed that splitting the fuel mass equally between the injections is not the optimal solution. Having more or less fuel in the first injection affects combustion phasing, pollutant emissions and efficiencies
In future work, experiments in an optical engine will provide a physical understanding to build an efficient control strategy.