Onboard Ethanol-Gasoline Separation System for Octane-on-Demand Vehicle

Bioethanol is being used as an alternative fuel throughout the world based on considerations of reduction of CO2 emissions and sustainability. It is widely known that ethanol has an advantage of high anti-knock quality. In order to use the ethanol in ethanol-blended gasoline to control knocking, the research discussed in this paper sought to develop a fuel separation system that would separate ethanol-blended gasoline into a high-octane-number fuel (high-ethanol-concentration fuel) and a low-octane-number fuel (low-ethanol-concentration fuel) in the vehicle. The research developed a small fuel separation system, and employed a layout in which the system was fitted in the fuel tank based on considerations of reducing the effect on cabin space and maintaining safety in the event of a collision. The total volume of the components fitted in the fuel tank is 6.6 liters. It was demonstrated that the onboard fuel separation system possessed sufficient control performance in practical use in actual driving environments. In addition, measurements of fuel separation speed in LA4 driving cycle showed that the system was able to separate the fuel at a speed higher than the speed of consumption of high-octane-number fuel necessary for the engine. The ethanol concentration of the separated fuel was approximately 90%. This figure represents a sufficient octane number to control knocking in high-compression-ratio engines under high-load conditions. The power consumption of the fuel separation system was approximately 350W. Taking the increase in engine fuel efficiency into consideration, it is possible to expect an increase of approximately 15% in fuel efficiency for the vehicle as a whole.