Potential of Naphtha-like Fuel on an Existing Modern Compression Ignition Engine

Recent work has demonstrated the potential of gasoline-like fuels to reduce NO_X and particulates emissions when used in diesel engines. Indeed, fuels highly resistant to auto-ignition provide more time for fuel and air mixing prior to the combustion and therefore a more homogeneous combustion. Nevertheless, major issues still need to be addressed, particularly regarding UHC and CO emissions at low load and particulate/noise combustion trade-off at high load. The purpose of this study is to investigate how an existing modern diesel engine could be operated with low-cetane fuels and define the most appropriate Cetane Number (CN) to reduce engine-out emissions. With this regard, a selection of naphtha and gasoline blends, ranging from CN30/RON 57 to CN35/RON 41 was investigated on a Euro 5, 1.6L four-cylinder engine. Results were compared to the conventional diesel running mode using a minimum NO_X level oriented calibration, both in steady state and transient conditions. Firstly, the results showed that the low-end torque and the maximum power are achievable with a low CN fuel. Secondly, at part load, engine-out NO_X and PM emissions were significantly reduced with low CN fuels while achieving very good efficiency. Dedicated injection strategies were established to properly manage combustion noise and therefore meet the same level as with diesel fuel. UHC and CO emissions are a remaining issue that needs to be addressed. Finally, global assessments were performed on regular driving cycles like WLTC to definitely sort out the potential of each fuel.