Onboard Ethanol-Gasoline Separation System for Octane-on-Demand Vehicle 2020-01-0350
Bio-ethanol is being used worldwide as an alternative fuel because of CO2 emission reduction and energy sustainability.
It is common knowledge that ethanol has an advantage of high anti-knock quality. It is also well known that enhancement of both fuel economy and high load performance for general gasoline engines are limited by knocking.
In order to increase anti-knock performance, a fuel system was developed to separate ethanol blended gasoline fuel into high-octane number fuel (high-concentration ethanol fuel) and low-octane number fuel (low-concentration ethanol fuel) on a vehicle.
The onboard fuel separation system, installed in the fuel tank, mainly consists of a pervaporation membrane module, a fuel supply pump for the membrane, heat exchangers for fuel heating, a condenser for the permeated fuel vapor and a vacuum pump to control the pressure on the permeation side. Vapor that was not condensed at the condenser is supplied to the engine through a canister purge line.
In this study, it was revealed that the onboard fuel separation system has controllability sufficient for use in automobiles by evaluating the stability of fuel temperature and the amount of vapor. The system can separate ethanol blended gasoline without a shortage of high-octane number fuel in LA4 driving cycle. The average ethanol concentration of the permeated fuel was greater than 60%. It has a high enough octane number to suppress knocking at high-load conditions in a high-compression ratio engine.
By applying this onboard fuel separation system to a high-compression ratio engine, knocking can be suppressed by selectively using separated high-ethanol concentration fuel at high-load operating conditions.