عنوان مقاله [English]
Recently, RCCI combustion mode has been proposed, and various researches have been done on this kind of combustion. Such combustion mode has improved the emission shortages of diesel engines besides its advantages. Previous studies mostly investigated the performance and emissions of RCCI engines. In this study, RCCI combustion is studied from the viewpoint of production and consumption of important species. In this RCCI engine gasoline injected at the intake port and diesel injected directly into the cylinder. Investigations showed that first, heat release is started by diesel fuel and an initial heat is released; then gasoline fuel energy is released. The appearance of formaldehyde species shows the cool flame combustion and consumption of diesel fuel; then the appearance of hydroxyl radical and the consumption of gasoline happen simultaneously. Also, some portion of formaldehyde is consumed with the appearance of hydroxyl radical. Heat release started by diesel and followed by gasoline has positive effects. First, by this sequential heat release, the in-cylinder temperature does not increase suddenly, so heat losses decreased. Second, due to the low temperature, NOx emissions reduced. Further -64 CA and -74 CA injection timings and 20 and 28 percent diesel mass fractions have been studied. Results show that the start of combustion is not dependent on these two parameters and its occur at a specific crank angle. So the cool flame combustion only dependent on temperature. But the main combustion is dependent on the temperature and equivalence ratio so the injection timing and diesel mass fraction have shown their effect at this section of combustion.