Particle size distribution in a transparent CR diesel engine fuelled with RME and GTL by means of multiwavelength spectroscopy

In this paper, broadband UV-NIR flame emission measurements were performed in an optical Common Rail (CR) diesel engine in order to evaluate the formation process of soot particles with high spatial and temporal resolution. The measurements were carried out in a direct injection (DI) CR transparent research diesel engine equipped of a Euro 5 multi cylinder head. Two alternative fuels, chosen as representative of the first generation biofuel, rapeseed methyl ester (RME), and of the second generation biofuel, gas to liquid (GTL), and a commercial diesel were used. A comparison between the soot (particle) size distribution measured into the cylinder by means of a numerical procedure applied to optical data and those at the exhaust by means of an electrical low pressure impactor (ELPI) was performed. The engine condition 1500 rpm x 2 of break mean effective pressure (BMEP) was analyzed because it is characteristic of the New European Driving Cycle (NEDC).