Sensitivity to chemical kinetics models in time-evolving turbulent non-premixed flames

To investigate the sensitivity of simulation predictions to chemical kinetics, GRI-Mech 3.0 and an 11-species syngas model, are compared by performing 3D finite-rate kinetics-based direct numerical simulations (DNS) of temporally evolving turbulent non-premixed flames. Dynamic adaptive chemistry and correlated transport techniques are applied for efficient simulation. Significant deviations (86∼100 K difference in the temperature field) indicate high sensitivity to the chemical kinetics. This sensitivity to the chemical kinetics is magnified relative to a 1D steady laminar simulation by the effects of unsteadiness and turbulence (up to 7 times for temperature, up to 12 times for CO, up to 13 times for H₂, up to 7 times for O₂, up to 5 times for CO₂, and up to 13 times for H₂O), with the deviations in species concentrations, temperature, and reaction rates forming a nonlinear positive feedback loop under the considered reacting flow conditions. The deviations between the two models majorly caused by: (a) GRI-Mech 3.0 contains more species and related kinetic pathways than the 11-species model; (b) reaction rate coefficients are different for the same reactions. Both (a) and (b) are sensitive to unsteadiness and other turbulence effects. However, (b) is the dominant part and is more sensitive.