Evaporation and mixture formation of gasoline–ethanol sprays in spark ignition engines with pre-blended injection and dual injection: a comparative study

Evaporation of sprays and mixture formation as injection of pre-blended gasoline-ethanol mixture and as separate injection of the fuels are investigated by means of numerical simulation. Effects of operating conditions and different configurations of injection systems have been examined. Under the same operating conditions, pure gasoline mostly evaporated during the injection period, while pure ethanol evaporated mainly during the compression process. Charge temperature in the cylinder for pure ethanol is ~60°C lower than that for pure gasoline at the end of the compression process. Independently from injection system, the dual injection results in a higher evaporation rate compared to pre-blended injection. Whether pre-blended injection or dual injection is employed, the evaporation rate is improved for port injection (PI) compared to direct injection (DI). Besides, vapour concentration at the end of the compression process of PI increases with a shift from a single-inlet manifold to double-inlet manifolds. Mixture homogeneity is enhanced with increasing ambience temperature or/and an increasing engine speed with pre-blended injection, while a strong stratified charge mixture is achieved with dual injection using double-inlet manifolds or with DI of ethanol combined with PI of gasoline.