Combustion Optimization of a Multi-Cylinder CI Engine Running with a Low RON Gasoline Fuel Considering Different Air Loop and After-Treatment Configurations 2017-01-2264

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOx and particulate emissions when used in compression ignition engines. In this context, low research octane number (RON) gasoline, a refinery stream derived from the atmospheric crude oil distillation process, has been identified as a highly valuable fuel. In addition, thanks to its higher H/C ratio and energy content compared to diesel, CO₂ benefits are also expected when used in such engines.

In previous studies, different cetane number (CN) fuels have been evaluated and a CN 35 fuel has been selected. The assessment and the choice of the required engine hardware adapted to this fuel, such as the compression ratio, bowl pattern and nozzle design have been performed on a single cylinder compression-ignition engine.

The purpose of this paper is to assess different air-path and after treatment system (ATS) definitions to maximize the potential of a low-RON gasoline fuel running on a multi-cylinder compression ignition engine. Low pressure (LP) and high pressure (HP) EGR were evaluated to fulfill Euro 6d standard with and without NOx after-treatment system. The CO₂ benefits were estimated thanks to a specific Design of Experiment (DoE) methodology developed by IFPEN. The results were computed through the combination of 16 hot and cold operating points whereas 0D models were used to generate the ATS efficiencies.

Meet the Euro 6 NOx regulation on WLTC without NOx ATS is possible with a complex LP+HP EGR air-path. Nevertheless, a greater CO₂ potential was identified with HP EGR system combined with SCR. Once put into practice, Euro 6 regulation was met with a reduction of almost 7% of CO₂ on WLTC. Noise levels were comparable to a Euro 5 diesel reference engine.