Flame morphology of hydrous ethanol combustion under EGR dilution for port fuel injection and direct injection in a spark ignition optical engine

The increasing popularity of plug -in hybrid vehicles has prompted investigation of options such as range extender units, which may include small engines powered by biofuels. To minimize energy consumption, the best technologies must be chosen, including the use of exhaust gas recirculation (EGR, as a charge dilution technique) and the best alternative for fuel injection systems. Therefore, a combustion evaluation was conducted on an optically accessible engine fueled with hydrous ethanol to determine the effects of different injection modes, such as direct injection (DI) and port fuel injection (PFI), combined with EGR. The study employed high-speed camera imaging to analyze flame morphological characteristics and understand their impact on in-cylinder thermodynamics and engine emissions. The DI mode presented more stability than PFI, although the dilution limit was lower for DI.