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Visualization of single-hole nozzles into quiescent ambient has been used extensively in the literature to characterize spray mixing and combustion. However in-cylinder flow may have some meaningful impact on the spray evolution. In the present work, visualization of direct diesel injection spray under both non-reacting and reacting operating conditions was conducted in an optically accessible two-stroke engine equipped with a single-hole injector. Two different high-speed imaging techniques, Schlieren and UV-Light Absorption, were applied here to quantify vapor penetration for non-reacting spray. Meanwhile, Mie-scattering was used to measure the liquid length. As for reacting conditions, Schlieren and OH* chemiluminescence were simultaneously applied to obtain the spray tip penetration and flame lift-off length under the same TDC density and temperature. Additionally, PIV was used to characterize in-cylinder flow motion.

The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

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.