The Injection Rate Shaping consists in a novel injection strategy to control air-fuel mixing quality via a suitable variation of injection timing that affects the injection rate profile. This strategy has already provided to be useful to increase combustion efficiency and reduce pollutant emissions in the modern compression ignition engines fed with fossil Diesel fuel. But nowadays, the ever more rigorous emission targets are enhancing a search for alternative fuels and/or new blends to replace conventional ones, leading, in turn, a change in the air-fuel mixture formation.
In this work, a 1D model of spray injection aims to investigate the combined effects of both Injection Rate Shaping and alternative fuels on the air-fuel mixture formation in a compression ignition engine. In a first step, a ready-made model for conventional injection strategies has been set up for the Injection Rate Shaping. Experimental data collected in an optical single-cylinder compression ignition research engine via the 2D visible and infrared advanced diagnostic techniques have been used to validate the model. Commercial Diesel fuel has been used. Afterward, two parameters suggestive of air-fuel mixing have been evaluated, i.e., the equivalence ratio and the vapor fuel mass variation over time. A comparison between conventional and Injection Rate Shaping strategies is reported. Finally, the model has been implemented to simulate Rapeseed Methyl Ester biodiesel injection. Moreover, the behavior of a blend 50 v/v percentage of Diesel and n-octane and a blend 50 v/v percentage of Diesel and propane has been studied. The different behavior in injection process compared to fossil Diesel fuel is highlighted. The main issues are pointed out.