Characterizing the role of fuel injection strategies on performance, combustion, and emissions in intelligent charge compression ignition (ICCI) mode

Abstract

In a novel combustion mode, intelligent charge compression ignition (ICCI), the effects of fuel injection strategies were studied on a modified single-cylinder engine with the given engine load and speed. Commercial gasoline and diesel were used to represent low-reactivity fuel and high-reactivity fuel, respectively. The in-cylinder stratification, fuel–air mixture formation, heat release rate profile and combustion phasing were investigated in detail. Engine thermal efficiency, fuel consumption, gaseous and solid emissions were further studied. In the single-injection strategy and the multiple-injection strategy, different diesel injection timings were configured to find the influence of their changing trends on engine performance, combustion and emissions. In the single injection strategy, the diesel injection of 60 °CA BTDC can lead to the highest indicated thermal efficiency. In contrast, only a specific injection strategy influences the heat release in small-scale split injection. Using multiple injections of high-reactivity fuel and adjusting the combustion phasing decrease the excessive in-cylinder pressure and maximum pressure rise rate in the single injection. Meanwhile, alternate fuel injection to build a stratified environment in the cylinder can maintain the indicated thermal efficiency at a high level. The indicated thermal efficiency is close to 50% when the diesel first injection timing is 60 °CA BTDC, the second injection timing is 38 °CA BTDC or 100 °CA BTDC. The single diesel injection strategy of 60 °CA BTDC reaches the best emissions, in which the NOx emissions are lower than 0.5 g/kWh. The multiple split injection strategies can further reduce carbon monoxide and total hydrocarbon emissions.