Influence of Turbulence-Chemistry Interaction in Blow-out Predictions of Bluff-Body Stabilized Flames

Abstract

Large Eddy Simulations (LES) were performed to investigate the effect of turbulence –chemistry interaction on flame instability and flame-vortex interactions in bluff body stabilized premixed flames. A semi-global reduced kinetics mechanism and a skeletal mechanism were developed and implemented with a Laminar Chemistry (LC) model and an Eddy Dissipation Concept (EDC) model to simulate bluff-body stabilized propane-air flames using the experimental conditions of Kiel et al. (2007). Simulations were performed for reactive and non-reactive cases with coarse (0.65 million cells) and fine (2.4 million cells) grids. Simulations with fine grids were able to predict the recirculation zone thickness correctly as observed in the experiments. Simulation results also show that the near-field wake behind the bluff body was dominated by the Von-Karman vortex shedding for the non-reacting case as well as the reacting case with EDC models, while a shear layer generated vortex sheet was observed for reacting flow cases with the LC models. The simulation results demonstrate that turbulence-chemistry interactions play a major role in predicting the blow-out conditions. LES predictions with the EDC model show that the blow-out occurs at 0.6 equivalence ratio as observed experimentally at a DeZubay number of ~10.