Study of Flame Dynamics and Flashback Mechanism in a Gas Turbine Combustor Using Simultaneous OH-PLIF and PIV

The present study aims to investigate the effects of burner geometry on flame characteristics, stabilization, and the occurrence of flashback using the Triple Annular Research Swirler (TARS). A premixing tube is placed at the exit of the burner. Simultaneous Planar Laser Induced Fluorescence (PLIF) of OH radicals indicating the reacting zone and Particle Image Velocimetry (PIV) for flow field mapping, were applied to study the flow- and flame-dynamics during transition from flame stabilized in the combustion chamber to flame
flashback in the mixing tube. Particular attention was placed on the flame behavior/dynamics near the lean blow out (LBO). The flow field featured a central recirculation zone (CRZ), and an annular swirling jet with internal and external shears layers. The movement of the flame front relative to the upstream stagnation point of the vortex breakdown at different conditions was studied. Simultaneous planar measurements using laser diagnostics, namely, Planar Laser Induced Fluorescence (PLIF) of OH radicals and Particle Image Velocimetry (PIV), have been carried out. With mixing tube and at lean cases, vortex breakdown and the flame holding occurred close to the tube exit. As the equivalence ratio was increased, the flame entered intermittently into the premixing tube. Increasing further the equivalence ratio, the flame was stabilized inside the premixing tube. Different statistical evaluations were performed on the data to obtain better understanding of the flame stabilization mechanism. They included PDF of the axial velocity, mean velocity field and mean intensity of the OH radical, two-dimensional correlation between PIV and LIF data, POD analysis of the velocity vectors, distribution of OH radical intensity and binary images of density distribution of the seeding particles.