Experimental And Numerical Investigation Of Reactivity Controlled Compression Ignition On A Diesel Engine

Clean and efficient combustion mode(such as low-temperature combustion) developed rapidly in order to reduce the emissions of NOx and soot in diesel at the same time. However, disadvantages in terms of combustion control and difficulties to expand to high load have become an obstacle to the development of HCCI; and PCI over-reliance on high EGR rate. RCCI was achieved through dual injection, different fuels with numerous chemical reactivities were injected into the cylinder and different chemical reactivity gradients were formed in it, in this way the control of combustion was achieved.Dual injection bench was set up in the form of the transformation engine intake port system. Systematically studied the effects of different proportions of gasoline, the injection timing of diesel and different premixed fuels(gasoline, ethanol, B20) on the combustion and emission characteristics of RCCI in different conditions. Studies showed that with the change of proportion of gasoline showing a variety of heat release rate under different loads. With the increase in the proportion of gasoline can reduce NOx and soot at the same time; With the injection delay, the engine was more gentle and NOx was further reduced. Ethanol and B20 can achieve a greater range of chemical reactivity gradients in the cylinder, and thus can achieve lower emissions of NOx and soot.Knocking occurred easily at high load and high proportion of gasoline. Experiments proved that reducing the fuel injection timing, replacing gasoline with ethanol and B20 can expand this combustion mode to the high-load conditions.Coupling three-dimensional computational fluid dynamics and detailed kinetic mechanism of chemical reactions to achieve the simulation of RCCI combustion mode. Results show that with this combustion mode,gasoline was ignited by multi-point ignition core formed through multi-point ignition of diesel. Compared with the conventional diesel combustion, the high temperature region was significantly reduced, thereby reducing the NOx emissions. HC was formed mainly around the center of the combustion chamber and the cylinder wall, CO is mainly distributed in the center of the combustion chamber where was the low-temperature region.