On-line thermodynamic diagnosis of diesel combustion process with paraffinic fuels in a vehicle tested under NEDC

The increasing interest for using alternative fuels, more environmentally friendly compared to fossil fuels, has motivated this research work. The knowledge of the combustion process with these fuels provides an important tool for increasing performance and for reducing pollutant emissions. This knowledge allows a better calibration of engine parameters configured in the Electronic Control Unit. For this reason, this paper presents the evolution of the main parameters of the combustion process of a light-duty vehicle equipped with a Euro 4 diesel engine, operating with gas to liquid fuel, a hydrotreated vegetable oil fuel, and a commercial diesel fuel (with 5.8% of biodiesel) as reference. Tests were carried out on a chassis dynamometer under controlled ambient conditions following the New European Driving Cycle. One of the engine cylinders was instrumented with a Kistler Kibox device combined with an opened electronic control unit and a system for online thermodynamic combustion diagnosis. Thermodynamic diagnosis parameters have been compared, at different time windows, along the New European Driving Cycle. Results also show that the effect of cetane number of fuels on ignition delay can be appreciated at the beginning of NEDC (1st U) and, more strongly, in the rest of the cycle. It is remarkable that paraffinic fuels show better indicated efficiency because of the more centered combustion (around the Top Dead Center). Diesel fuel shows higher maximum apparent heat release which is indicative of faster combustion process and higher ignition delay.