Numerical Study to Achieve Low Fuel Consumption and Nitrogen Oxides Emissions in a Split-Cycle Engine Adapted from the Conventional Architecture

This work presents a numerical study of the performance and nitrogen oxides (NOₓ) emissions of a conventional ethanol engine converted to work as a flex-fuel nonconventional architecture: the Split-Cycle Engine (SCE). For this study, the conventional engine fueled with hydrous ethanol was modeled and validated with data from experimental tests. Then the model was converted to operate as an SCE with two compressors and two expanders and simulated with a progressive downsizing of the compressors of the SCE. When the swept volume of the compressors was reduced to 87% of that of the expanders, the thermal conversion efficiency increased by 3.3%. Because of this, the downsized SCE was submitted to simulation runs using two different fuels: hydrous ethanol (H100) and an indolene-ethanol blend (H85). The results of the simulations were compared to the experimental results of the conventional engine. The SCE fueled with H100 showed significant losses in volumetric efficiency, brake power, torque, and brake thermal conversion efficiency and showed higher brake-specific fuel consumption, but it also led to a compelling lower absolute fuel consumption compared to the conventional architecture. The SCE fueled with H85 showed even lower fuel consumption, which led to a thermal conversion efficiency comparable to that of the conventional engine. Both fuels generated significantly lower NOₓ emissions in the SCE compared to the conventional engine. These results indicate that the SCE can work as an operating mode of conventional flex-fuel engines for automotive applications when low power and performance are needed, reducing the fuel consumption and NOₓ emissions.