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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 Relevant published and unpublished work from prior ECN workshops is reviewed.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 hydrogen-diesel dual direct injection (H2DDI) combustion strategy in a compression-ignition engine is investigated numerically, reproducing the configuration of previous experimental investigations. These experiments demonstrated the potential of up to 50% diesel substitution by hydrogen while maintaining high engine efficiency; nevertheless, the emission of NOx increased compared with diesel operation and was strongly dependent on the hydrogen injection timing. This implies the efficiency and NOx emission are closely associated with hydrogen charge stratification; however, the underlying mechanisms are not fully understood. Aiming to highlight the hydrogen injection-timing influence on hydrogen/air mixture stratification and engine performance, the present study numerically investigates the mixture formation and combustion process in the H2DDI engine concept using Converge, a three-dimensional fluid dynamics simulation code.