Lagrangian Analysis of Turbulent Flame Structure in High-Speed Combustor

The current study investigates the structural evolution of a turbulent flame and the effects induced by the flame-vortex dynamics. A bluff-body stabilized, premixed flame in a high-speed combustor is used to analyze the turbulent flame. Simultaneous high-speed CH* chemiluminescence and particle image velocimetry (PIV) are implemented to characterize the flame-flow fields and flame structure. The flame temporal evolution and structural dynamics are ascertained using a Lagrangian tracking and decomposition method. The flame initial position is determined from the CH* data and is convected spatio-temporally with the Lagrangian equations of motion with the PIV velocity data. The flame-vortex dynamics are investigated by decomposing the vorticity transport equation, and considering the individual vorticity mechanisms: vortex stretching, viscous diffusion, baroclinic torque, and dilatation. In doing so, the vorticity mechanisms are tailored to convect the flame spatio-temporally; the Lagrangian tracking results are compared with the CH* data. Comparison of the experimental data with the numerical tracking results allows the influence of each vorticity mechanism on the flame structural dynamics to be categorically determined.