Effect of port injected ethanol on combustion characteristics in a dual-fuel light duty diesel engine

Nowadays, alcoholic fuels gain increased interest as alternative transportation biofuel even in compression ignition engines due to the fact that they contain oxygen and can be produced in a sustainable way. Furthermore, due to their lower CN (Cetane Number) they suit better for premixed combustion applications. Experimental research was conducted on a single cylinder engine provided with modern engine architecture modified for DF (Dual-Fuel) purposes. The authors have investigated the use of ethanol in a DF engine in order to exploit its well-known advantages in premixed combustion mode. The DF approach appears to be a promising solution because it permits flexible control of the premixed fuel fraction regardless from the operating conditions. This improves the exploitation of the ethanol potential according the engine working conditions. Recent literature publications have proved the possibility to increase the thermodynamic efficiency at medium and high load in DF configuration compared to a conventional DI (Direct Injection) diesel configuration. However, it is still not clear what the effective working area and right control parameters for light duty engines are for which the DF configuration outperforms the DI diesel configuration. Within this framework, the research was performed to provide additional knowledge on DF in terms of operating range and engine control strategies (e.g. injection parameters). At medium and high load, the results show the potential for ethanol to decrease NOx and soot emissions simultaneously while improving the thermal efficiency. On the contrary, a significant increase of HC (Hydro Carbon) and CO (Carbon Monoxide) emissions were observed for low load and the DI diesel configuration outperformed the DF configuration in terms of emissions and efficiencies.