Pocket formation and behavior in turbulent premixed flames

Pocket formation is an important characteristic of turbulent premixed flames and understanding pocket behavior is key to developing high-fidelity numerical combustion models. In this study, a dual-burner experiment is used to study pockets in single- and dual-flame configurations and synchronized high-speed OH-planar laser-induced fluorescence and stereoscopic-particle image velocimetry imaging techniques are implemented to track flame pockets and the surrounding flow field. Statistical analysis of pocket origin and fate is performed using a novel tracking algorithm incorporating non-rigid image registration. Results show that pocket formation rates increase as a function of increasing inlet turbulence level; reactant pocket formation increases as a function of downstream distance, whereas product pocket formation decreases. Tracking reactant pocket lifetime shows that a majority of these pockets burn out and displacement speeds are characterized. Product pockets usually merge with the main flame surface, which could have an impact on local flame structure and propagation. Results presented in this study show that pocket behavior in turbulent flames can change local flame dynamics and it is important to capture these effects in sub-grid scale combustion models to accurately predict flame behavior.