Effects on performances, emissions and particle size distributions of a dual fuel (methane-diesel) light-duty engine varying the compression ratio

A significant impact of the CR variation and injection parameters on the combustion characteristics and emissions is revealed in DF mode (MHC). In particular, benefits on methane unburnt (MHC) and combustion noise can be attained reducing the CR. A global CO2 reduction of about 12%, over the NEDC, can be definitely obtained with an average CH4 substitution rate of about 50% and independently of the CR at the expense of the DF- CO2 equivalent that is higher (22%) compared to D mode. The DF particles concentration in the accumulation mode is generally reduced as well as the estimated particle number on the NEDC. Moreover, within the tested engine class, a CR of 15.5 appears to be the best compromise among the global efficiency and pollutant emissions outputs to operate in DF mode.