Evaluation of ethanol blends for PHEVs using engine-in-the-loop

The easy availability, lower well-to-wheel emissions, and relative ease of use associated with existing engine technology have made ethanol and ethanol-gasoline blends a viable alternative to gasoline for spark-ignition (SI) engines. The lower energy density of ethanol and ethanol - gasoline blends results in higher volumetric fuel consumption than that associated with gasoline. On one hand, when higher-level ethanol blends are used, the higher latent heat of vaporization can result in cold-start issues. On the other hand, a higher octane number, which indicates resistance to knock and enables optimal combustion phasing, improves engine efficiency, especially at higher loads. This paper compares fuel consumption and emissions for two ethanol blends with gasoline (E50 and E85) for conventional (nonhybrid), and series-type plug-in hybrid vehicles. Each vehicle configuration results in different engine operating regimes and multiple engine ON events. For each vehicle type, the sensitivities of fuel consumption and emissions to the three fuels are assessed. The impacts of ethanol blends on fuel consumption and emissions depend on the engine operating regime. The combined impact on fuel economy that results from low energy density (negative impact) and higher efficiency at high engine loads (positive impact) is assessed for the series PHEV. Changes to the vehicle energy management strategy for the series PHEV are proposed based on the differences in fuel consumption for the different blends. In this study, Argonne's vehicle system simulation and control software AUTONOMIE was used to simulate the engine-in-the-loop process. This paper describes the process in the AUTONOMIE environment.