Low RON Gasoline Calibration on a Multi-Cylinder Compression Ignition Engine to Fulfill the Euro 6d Regulation 2017-24-0091

Reducing the CO₂ footprint, limiting the pollutant emissions and rebalancing the ongoing shift demand toward middle-distillate fuels are major concerns for vehicle manufacturers and oil refiners. In this context, gasoline-like fuels have been recently identified as good candidates. Straight run naphtha, a refinery stream derived from the atmospheric crude oil distillation process, allows for a reduction of both NOx and particulate emissions when used in compression-ignition engines. CO₂ benefits are also expected thanks to naphtha’s higher H/C ratio and energy content compared to diesel.

In previous studies, wide ranges of Cetane Number (CN) naphtha fuels have been evaluated and CN 35 naphtha 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, nozzle design and air-path technology, have been performed on a light-duty single cylinder compression-ignition engine.

The purpose of this paper is to demonstrate the potential of a recalibrated light-duty multi-cylinder compression-ignition engine running with CN 35 naphtha fuel with the just necessary engine and after-treatment hardware modification. The implementation of a specific global Design of Experiment (DoE) methodology developed by IFPEN was applied in steady-state conditions to calibrate the engine. The behavior of an after-treatment exhaust line (ATS) with DOC, DPF and SCR systems, was evaluated by 0D simulation. To be compliant with the Euro 6d regulation, several DoEs, considering the coolant temperature were performed to fully cover the WLTC cycle range and models representing the engine behavior in a large part of the engine map were then created. The Euro 6 regulation was met with a reduction of almost 7% of CO₂ on WLTC, using a Euro 6 diesel like ATS design. Noise levels were comparable to a Euro 5 diesel reference engine. Different ATS efficiencies were also assessed with a significant impact on the CO₂ potential. Engine calibration and after-treatment are, de facto, strongly linked.