Dynamic adjustment of the Eddy Dissipation Concept model for turbulent/combustion interactions in mixed combustion regimes

Abstract

The Eddy Dissipation Concept (EDC) combustion model, in comparison with some other combustion models, has drawn attention, especially for the Moderate or Intense low oxygen Dilution (MILD) combustion. The original formulation of the EDC combustion model is not developed for the MILD combustion regime, and a revision of the model could be considered. In this study, the effect of the characteristic frequency on the EDC combustion model has been investigated, and some parametric studies on the ratios of length and time scales of the fine structures to the Kolmogorov scales have been performed. Results revealed that finding optimum model constants for all combustion field with a wide range of Damköhler numbers seems to be complicated. The variations in scales ratio of fine structure to the Kolmogorov eddies shows different consequence at low and high Damköhler number combustion regions which leads to a conclusion on difficulties for EDC model global optimization. As a solution, a localized modulation method based on some local variables such as the turbulence Reynolds number and Damköhler number has been developed and applied on the Adelaide Jet in Hot Coflow(JHC) and Delft Jet in Hot Coflow (DJHC), and in addition in supplementary material on Sandia/TUD piloted flame and Sydney bluff-body burners. These burners demonstrate combustion regimes with both low and high Damköhler numbers. Results have shown the better performance of the local approach in the simulation of the burners. The improvement is more perceptible at the sections far from the inlet, where Damköhler number is increased, in comparison with the standard (default) EDC model. The average of deviations from the measurements is decreased by more than 10% and even more by a decrement in oxidizer oxygen level.