Numerical investigation on combustion process in a spark-ignited direct-injection alcohol engine via hybrid combustion model

A hybrid combustion model, combining a single-step irreversible combustion reaction with eddy breakup (EBU) model by introducing a delay coefficient of turbulent combustion, is established. Three-dimensional numerical simulation of the combustion process in an alcohol engine, with a new type of spark-ignited direct-injection circularly stratified-charge combustion system, is carried out. The computed pressure and heat release data coincide with the experimental results. The simulation results show that the stratification concentration from rich to lean of air-fuel mixture downstream along the direction of air swirl motion can be formed stably in the alcohol engine. The higher latent heat of evaporation of alcohol fuels results in a lower air-fuel mixture temperature. The premixed and diffusive stages coexist during the combustion process, and the combustion proceeds stably and rapidly.