Modifying the constant coefficients of Eddy-dissipation concept model in moderate or intense low-oxygen dilution combustion using inverse problem methodology

摘要

There are many differences between combustion modeling of conventional and moderate or intense low oxygen dilution combustion. Among them, turbulent-chemistry interaction modeling is an open field of study. Studies show that the eddy dissipation concept model is very suitable for modeling of moderate or intense low-oxygen dilution combustion but the constants of eddy dissipation concept should be modified for better prediction.In this work, the inverse problem methodology is applied to predict the optimum volume fraction and time scale constants of eddy dissipation concept in order to enhance the accuracy of the numerical prediction of moderate or intense low-oxygen dilution combustion in a jet-in-hot-coflow burner. For this purpose, computational fluid dynamics modeling approach, considering Reynolds-averaged Navier-Stokes equations and detailed reaction mechanism, is used in the openfoam package. The results show that the values of 0.48 and 1.9 are suitable for time scale and volume fraction constants, respectively, as the values leading to the highest results in comparison to experimental data. After validating the numerical results, the effect of sinusoidal variations in the preheated co-flow temperature on the flame characteristics of Methane-Hydrogen blended fuel, to produce more complete moderate or intense low-oxygen dilution combustion regime, was considered. The results show that in moderate or intense low-oxygen dilution combustion regime, the peak temperature under sinusoidal variations in the preheated co-flow temperature is constant as compared to typically moderate or intense low-oxygen dilution combustion; but the amount of CO2 and H2O species, as well as OH and CH2O intermediate species, are increased and CO emission is reduced.