Methanol-gasoline DFSI (dual-fuel spark ignition) combustion with dual-injection for engine knock suppression

This paper presents an experimental study on the M-G DFSI (methanol-gasoline dual-fuel spark ignition) combustion for knock suppression in a gasoline engine with high compression ratio. M-G DFSI is organized using a port-injection of high oxygenated, high latent heat and high octane number fuel to suppress knock and a direct injection of high energy density and high volatility fuel to extend high load. The effects of methanol/gasoline ratio of DFSI (dual-fuel spark ignition) under stoichiometric condition on engine knock suppression were investigated. The comparative analysis of the fuel economy and combustion characteristics of the enriched gasoline combustion and Methanol-Gasoline DFSI were conducted. When the enriched gasoline mixture is at the equivalence air/fuel ratio (lambda) of 0.8, the high load can be extended by 13.6% but the ISEC (indicated specific energy consumption) increases by 23.8%. On the contrary, when using M-G DFSI with 54% methanol, the high load can be extended by 11.7% and the ISEC decreases by 14.1%. Compared with gasoline enriched combustion, the ignition delay of DFSI with 54% methanol is about 1 degrees CA longer, while the peak pressure (P-max) and the maximum pressure rise rate (PRRmax) of the DFSI are 5.0 bar and 0.5 bar/degrees CA higher. In addition, the crank angle of 50% heat release (CA50), the crank angle of P-max and the crank angle of PRRmax are about 3 degrees CA earlier. This also the case as the mass fraction of methanol increases. It can be shown that Methanol-Gasoline DFSI is a potential combustion concept to suppress engine knock and extend the high load limit for high efficient utilization and alternative fuel practical application of gasoline engine. (C) 2014 Elsevier Ltd. All rights reserved.