Predicting diesel combustion characteristics with Large-Eddy Simulations including tabulated chemical kinetics

Abstract

Tabulated chemical kinetics are applied to Large-Eddy Simulations (LES) of diesel spray combustion. To this purpose, Flamelet Generated Manifolds (FGMs) are constructed using (igniting) counterflow diffusion flames computed with two different reaction mechanisms. The chemistry is parameterized as a function of the mixture fraction and a reaction progress variable. LES of an extensive set of igniting n-heptane liquid sprays are performed and compared with well-documented experiments from the literature (engine combustion network).Main characteristics, spray penetration depth, ignition delay time, and flame lift-off length, are compared to measured values. They correspond very well for variations in ambient oxygen content and ambient temperature. Both of the studied reaction mechanisms give similarly well predictions. Only in the low temperature limit they over-predict the measured ignition delay. The results show that the ignition delay trend is captured with only one igniting laminar flame in the chemistry table.