Impact of fueling methods on the combustion and cyclic variability in a compression ignition engine

This study aims to explore the impacts of the blending, fumigating, and combined fumigating+blending (F + B) methods, compared to the diesel method, on the engine combustion and cyclic variability parameters under five engine loads and speeds. The diesel and blending methods created heterogeneous combustion, while the fumigating and F + B methods created homogeneous+heterogeneous combustion. A fixed fuel composition of diesel-biodiesel-ethanol (D80B5E15, volume %) was used for the blending, fumigating, and F + B methods to maintain the same overall fuel composition for the comparison. It is found that all examined fueling methods have no pre-ignition and a similar trend for cumulative heat release fractions under all tested conditions. The blending method has similar, while the fumigating method has slightly longer overall combustion progression (from ignition delay to 95% of heat release) up to about 3 °CA in contrast to the diesel method. Compared to the diesel method, the blending (47.2 and 43.6%) and fumigating (22.3 and 22.2%) methods have longer premixed combustion phase, however a shorter diffusion combustion phase is achieved only by the blending method (−19.1 and −19.5%) and the fumigating method has no effect (1.7 and −1.3%) on it, according to the average results from five loads and speeds, respectively. Also, the blending (6.6 and 8.8%) and fumigating (26.3 and 53.5%) methods cause increase in COV_IMEP. While, the blending method (9.2 and 6%) causes increase in COV_Max(dP/dθ), and the fumigating method (−2.7 and −2.9%) leads to drop in COV_Max(dP/dθ). The F + B method gets the results in between those of the fumigating and the blending methods.