Comparative study on alcohols-gasoline and gasoline-alcohols dual-fuel spark ignition (DFSI) combustion for high load extension and high fuel efficiency

This paper presents an experimental study of the alcohols-gasoline and gasoline-alcohols dual-fuel spark ignition (DFSI) combustion for knock suppression and higher engine efficiency using a gasoline engine with high compression ratio. Alcohols-gasoline DFSI is organized using a port fuel injection (PFI) of high oxygenated, high latent heat of vaporization, and high octane alcohol fuel to suppress knock and a direct injection (DI) of high energy density and high volatility fuel to extend engine load, while gasoline-alcohols DFSI is organized by gasoline PFI and alcohol DI. Three different alcohols were studied, including methanol, ethanol, and hydro-ethanol. The engine was naturally aspirated and operated at stoichiometric condition. In each test, the percentage of alcohol injection was varied from 0 to 100%. The effects of these two combustion modes on knock-limit extension, fuel economy, and combustion characteristics were investigated. Both alcohols-gasoline DFSI and gasoline-alcohols DFSI are promising approaches of using alternative alcohol fuels in practical gasoline engines with significant improvement in engine efficiency and knock suppression. Gasoline-alcohols DFSI exhibits better anti-knock performance and achieves higher fuel efficiency than alcohols-gasoline DFSI.