Combustion characteristics and emissions formation of a compression ignition engine fueled with C8 biofuels blends

Energy scarcity and pollution problems have prompted researchers to search for renewable and clean energy sources for compression ignition (CI) engines. Two C8 biofuels, i.e., n-octanol and di-n-butylether (DnBE), are both promising to be the diesel fuel candidates because of their good ignition ability. However, their physical and chemical properties are different from each other. Thus, the combustion process of a CI engine could be optimized by manipulating the blending ratio of n-octanol and DnBE. In this work, to investigate the effects of n-octanol and DnBE blends on the combustion characteristics and emissions formation in a CI engine, the numerical investigation was carried out by the coupled KIVA4-CHEMKIN code. A multi-component reaction mechanism was implemented in the code to mimic the combustion of the fuels. Different DnBE/n-octanol blends were designed by varying the DnBE from 10% to 90% with an interval of 10% on an energy basis. Then the CI engine fueled with pure n-octanol, pure DnBE, and their blends was simulated at the engine speeds of 1500 rpm and 2280 rpm, respectively. Results suggest that blending more DnBE in octanol can shorten the ignition delay, increase peak pressure, mitigate pressure rise rate, and prolong the combustion duration. The emitted CO of the n-octanol fueled CI engine is high at both speeds. Blending DnBE in n-octanol can reduce CO emissions but inevitably leads to a rise in NO. More importantly, soot-free combustion can be achieved by fueling either n-octanol or DnBE. Finally, the optimal DnBE blending ratio is selected at 50%, of which IMEP can be improved by 6.12% and 6.9%, and CO can be reduced by 69.91% and 65.98% with acceptable increases in NO at 1500 and 2280 rpm, respectively. This implies that the optimization of CI engines can be achieved by adjusting the blending ratio of n-octanol and DnBE.