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The Engine Combustion Network (ECN) is a coordinate effort from research partners from all over the world which aims at creating a large experimental database to validate CFD calculations. Two injectors from ECN, namely Spray C and D, have been compared in a constant pressure flow vessel, which enables a field of view of more than 100 mm. Both nozzles have been designed with similar flow metrics, with Spray D having a convergent hole shape and Spray C a cylindrical one, the latter being therefore more prone to cavitation. Although the focus of the study is on reacting conditions, some inert cases have also been measured. High speed schlieren imaging, OH* chemiluminescence visualization and head-on broadband luminosity have been used as combustion diagnostics to evaluate ignition delay, lift off length and reacting tip penetration. Parametric variations include ambient temperature, oxygen content and injection pressure variations.

A radiation-based 2-color method (2C) and light extinction imaging (LEI) have been performed simultaneously to obtain two-dimensional soot distribution information within a diesel spray flame. All the measurements were conducted in an optically accessible two-stroke engine equipped with a single-hole injector. The fuel used here is a blend of 30% Decane and 70% Hexadecane (in mass). According to previous research, operating conditions with three different flame soot amounts were investigated. The main purpose of this work is to evaluate the two soot diagnostics techniques, after proper conversion of soot-related values from both methods. All the KL extinction values are lower than the saturation limit. As expected, both techniques show sensitivity with the parametric variation. The soot amount increases with higher ambient gas temperature and lower injection pressure. However, the LEI technique presents more sensitivity to the soot quantity.