The dual-fuel combustion mode known as reactivity controlled compression ignition (RCCI) allows an effective control of the combustion process by means of modulating the in-cylinder fuel reactivity depending on the engine operating conditions. This strategy has been found to be able to avoid the NOx-soot trade-off appearing during conventional diesel combustion (CDC), with diesel-like or better thermal efficiency in a great part of the engine map.
The role of the low reactivity fuel properties and engine settings over RCCI combustion has been widely investigated in literature, concluding that the direct-injected fuel injection timing is a key parameter for controlling the in-cylinder fuel stratification. From this, it can be inferred that the physical and chemical characteristics of the direct-injected fuel should have also an important role on the RCCI combustion process.
This experimental work investigates the effects of using direct-injected fuels with different properties on RCCI engine-out emissions and performance. For this purpose, three fuels based on diesel-gasoline mixings at different ratios (D90, D70 and D50), also known as dieseline, have been tested and compared to pure diesel (D100). Gasoline used for mixing was 98 ON, which was also used as low reactivity fuel in all the cases. Methodologically, the direct-injected fuels were compared by means of a series of parametric sweeps varying EGR, gasoline fraction and direct injection timing at same levels.