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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 Relevant published and unpublished work from prior ECN workshops is reviewed.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.

For better understanding of soot formation and oxidation processes in diesel spray flame, the nanostructure of primary soot particles directly sampled in a diesel spray flame was investigated via High-Resolution Transmission Electron Microscopy (HRTEM). A single-shot diesel spray flame was achieved in a constant volume combustion vessel under diesel-like conditions (Ta=1000K, Pa=2.7 MPa) and a micro-grid for HRTEM observation was directly exposed to the spray flame to thermophoretically sample soot particles onto the grid surface. A preliminary nanostructure investigation was conducted for x500k magnification HRTEM images of soot particles directly sampled in diesel spray flames of Fischer-Tropsch Diesel (FTD) fuel seeded with naphthalene as a representative aromatic substance. A MATLAB code for HRTEM image processing and analysis of lattice fringes within primary soot particles was developed and used to characterize the length, tortuosity and separation of lattice fringes.