Effects of Diesel Injection Parameters in a Heavy Duty Iso-Butanol/Diesel Reactivity Controlled Compression Ignition (RCCI) Engine

Due to the higher combustion efficiency and fewer exhaust emissions in comparison with other diesel combustion strategies, RCCI combustion attracted lots of attention. Using two fuels with different reactivities lead to lower fuel consumption and considerably less NOx and PM emissions. An investigation has been carried out in order to examine the simultaneous effects of diesel injection pressure and single injection timing on the emissions formation and engine performance in a heavy duty single-cylinder butanol-diesel reactivity controlled compression ignition (RCCI) diesel engine. A reduced chemical n-heptane-n-butanol-PAH mechanism which consists of 76 species and 349 reactions has been used to simulate the combustion process of the dual-fuel diesel engine. Validation of the applied mechanism has been firstly done by comparing with available RCCI engine experimental data, and then the simulations have been further extended to analyze the combustion characteristics of RCCI combustion modes. Twenty-one different strategies based on two variables (diesel direct injection timing and injection pressure) have been investigated. For injection pressure, in addition to baseline 800 bar injection pressure, 650 and 1000 bar have been considered and, in case of direct fuel injection timing, seven injection timings (60 to 30 CA BTDC in 5 CA steps) for diesel direct injection have been proposed. The results showed that increasing injection pressure leads to enhance the air-fuel mixing process and accompanied with shorter ignition delay that could considerably decrease the amounts of NOx emissions. By injecting diesel fuel at 45 CA BTDC with 1000 bar as injection pressure, ISFC has decreased by 2.5%, IP has increased by 2.3%, and amounts of pollutant emissions have considerably decreased in comparing with baseline operation case.