An Experimental Investigation on Spray Mixing and Combustion Characteristics for Spray C/D Nozzles in a Constant Pressure Vessel 2018-01-1783

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. Results extend the range of variation of previously reported experiments in the literature for such nozzles, showing good agreement with such previous results and enlarging the available database for CFD validation. A systematic shorter lift-off length is observed for Spray C, while ignition delay from broadband luminosity and schlieren visualization show no clear difference between both nozzles. Comparison against literature results from Spray A has also been performed, from which behavior of the larger nozzles is seen to be highly affected by the slower mixing process.