Exploring the Effects of the Key Multi-Injection Parameters on Combustion and Emissions in Intelligent Charge Compression Ignition (ICCI) Mode 2020-01-2035

Developing advanced combustion mode has been the active area for high efficiency and ultra-low emissions of the next-generation internal combustion engines. In this paper, a series of experiments were conducted in a modified single-cylinder compression ignition engine for operating a brand-new combustion mode denoted as intelligent charge compression ignition (ICCI) mode. By using two common-rail systems, commercial gasoline and diesel were alternately directly injected into the cylinder through multi-injection strategies in the injection timing range of 50~320 °CA BTDC. Thus, the in-cylinder stratified condition can be flexibly and accurately adjusted in this unique combustion mode. The key injection parameters, such as gasoline injection timing and diesel split ratio, were investigated to explore their effects on engine combustion, emissions, and fuel consumption. The results showed that the diesel split ratio mainly affected combustion phasing, while the gasoline injection timing had significant effects on the peak value of in-cylinder pressure and pressure rising rate. Higher diesel split ratio in early injection caused earlier combustion phasing and higher in-cylinder temperature, leading to higher NOx emissions, but the accumulation mode particle was decreased. Besides, when more gasoline was injected in compression stroke to form more homogeneous cylinder condition, lower NOx emissions of 0.1 g/kWh were reached, meeting EURO VI standard. Furthermore, lower CO emissions and fuel consumption can be obtained simultaneously, while the accumulation mode particle decreased along with nucleation mode increasing. However, peak pressure and peak pressure rising rate were increased because of more concentrated heat release. HC emissions of all the experimental cases had few vary in the experiment.