Thermal analysis of a light-duty CI engine operating with diesel-gasoline dual-fuel combustion mode

Abstract

Reactivity Controlled Compression Ignition (RCCI) is one of the most promising premixed combustion modes, aimed at reducing simultaneously engine emissions and fuel consumption. In this work, the global energy balance (GEB) of a single-cylinder engine operating with dual-fuel and RCCI modes is analysed. The methodology used allows determining the energy degradation from the energy release during the combustion to the final work output, thus evaluating the performance of such combustion mode. The weight of each GEB term is analysed using two references: the injected and the burned fuel energies, thus decoupling the combustion and thermal processes. The analysis is performed by evaluating the effect of some key parameters: low/high reactivity fuel ratio, injection timing and EGR rate. The results show that increasing the low reactivity fuel leads to a better shape of the heat release rate, with a reduction of heat transfer and exhaust losses, thus improving the thermal efficiency about 1% with respect to a conventional Diesel combustion. Injection timing swept shows that a suitable optimization leads to further thermal efficiency increase up to 4%, while EGR has a limited effect. It is also concluded that there is still room for further improvement by reducing incomplete combustion losses.