Large eddy simulations of flame extinction in a turbulent line burner

© 2019 Elsevier Ltd Large eddy simulations of flame extinction with N 2 as extinguishing agent are performed focusing on combustion modelling with infinitely fast chemistry. EDM and EDC combustion models, an enthalpy-based flame extinction model based on a locally variable critical flame temperature and WSGGM for radiation are employed in order to predict flame extinction in a turbulent CH 4 line burner. The numerical predictions of mean thermocouple temperatures, combustion efficiencies and radiative fractions with different grid sizes are compared to the experiments by White et al. (2015). Overall, the results from the numerical simulations agree well qualitatively and, to some extent, quantitatively with the experimental data when small grid sizes are employed. The examined centerline and radial profiles at two axial locations of the mean temperatures are reasonably well predicted. The decrease in the combustion efficiencies as the extinction limit is approached is reproduced by the numerical simulations. The decreasing trend in the radiative fractions as the oxidizer stream is diluted with N 2 is also captured by the simulations using a WSGGM model for radiation. Nevertheless, the influence of the combustion model is shown to be substantial towards predicting flame extinction due to differences in the predicted flame temperatures. Equally important is the influence of the simple re-ignition model based on a constant re-ignition temperature.

Jaar van publicatie:2019