A Numerical Study on Correlation of Chemiluminescent Species and Heat Release Distributions Using Large Eddy Simulation

A mixed timescale subgrid model of a large eddy simulation was used to simulate the turbulence regime in diesel engine combustion. The combustion model used the direct integration approach with a diesel oil surrogate mechanism (developed at Chalmers University of Technology and consisting of 70 species and 309 reactions). Additional reactions for the generation and consumption of OH∗, CO₂∗, and CH∗ species were added from recent kinetic studies. Collisional quenching and spontaneous emission resulted in de-excitation of the excited state radical. A phenomenological soot formation model (developed at Waseda University) was combined with the LES code. The following important steps were considered in the soot model: particle inception where naphthalene grows irreversibly to form soot, surface growth with the addition of C₂H₂, surface oxidation (induced by OH radicals and O₂ attack), and particle coagulation. Using the aforementioned numerical approach, we investigated the correlation of the excited chemical species (OH∗, CO₂∗, and CH∗) with heat release distributions in the final stages of diesel spray combustion. The excited chemical species models performed well, indicating that heat release regions can be predicted from the concentrations of excited radical species.