Numerical simulation of a DISI engine with a reduced chemical kinetic mechanism for gasoline–ethanol blends

The urgent need for decarbonizing the transportation sector and combating global warming has prompted countries to seek effective solutions considering their energy matrices. In Brazil, ethanol plays a crucial role on achieving this goal with the existing flex-fuel vehicles and the well-established infrastructure. In this context, having accurate models for predicting the engine performance and helping understand complex phenomena is very desired for both industry and academy. In this paper, a reduced chemical kinetic mechanism for gasoline/ethanol blends, having 75 chemical species and 343 reactions, was implemented and validated in 0D/1D simulations for laminar flame speed and ignition delay time. Expanding this study to 3D CFD simulations of a direct injection spark ignition engine, the mechanism was validated for fuel blends varying from 22% in volume of ethanol added in gasoline to neat ethanol (named as E22, E27, E50, E85 and E100) under stoichiometric air–fuel mixture and partial load conditions. The numerical in-cylinder pressure, heat release rate and specific NOx emissions agreed reasonably with the engine test data, although for ethanol fuel rich a slightly delay in combustion phase was predicted and for gasoline-rich fuel a propensity to knock was seen in the simulation results when a hot exhaust valve temperature was used. A sweep in exhaust valve wall temperature was carried out from 525 to 450 K and in the latter condition, the knock was eliminated. The investigated mechanism has proven to deliver reasonable results in a relatively short time interval, which can be suitable for industry applications.