Flamelet generated manifold simulation of highly swirling spray combustion: Adoption of a mixed homogeneous reactor and inclusion of liquid-flame heat transfer

We undertake the modeling of the combustion of highly swirling fuel sprays using the Flamelet-Generated-Manifold (FGM) combustion-chemistry-reduction technique, especially the use of adiabatic tables generated with non-premixed chemical reactors. Preceding investigations indicated that tables thus generated can present uncertainties when used for predicting the finite-rate phenomena and different flame modes, and these are important for better prediction of spray flames in gas turbines. Thus, to address these, we have adopted a mixed-homogeneous chemical reactor that is applicable to both pre-mixed and non-premixed reactions and evaluated this using detailed computations of a constant-pressure mixed reactor. In addition, we have included curated levels of flame-liquid heat gain and loss in the generation of the FGM libraries and analyzed the effects on the major species formation. The methodologies were then incorporated into a Reynolds-averaged-Navier-Stokes model to analyze the data from the reacting ethanol spray flames, and the results were tested against the values of the mixture fraction at axial locations, the burner power output, the flame heat release structure, and the mean of the flame lift-off. The computed burner power output and mean flame lift-off were ∼90.4% and ∼89.6% of the reported experimental data, respectively. Compared with the newest published large-eddy-simulation data, the predictions for the mixture fraction values especially at the center of the flame in the central-recirculation-zone were not underestimated, and the spatial distribution of the flame OH captured the flame height and shape better. The inclusion of mixed homogeneous reactors and flame-liquid heat transfer in FGM can enhance their use in spray-combustion studies.