Flame structure and local extinction of turbulent premixed flames using two-sheet OHPLIF technique

In this study, using two-sheet OH-PLIF technique, we have obtained instantaneous two-dimensional flame images to examine highly turbulent premixed combustion in a cyclone-jet combustor. Since OH plays an important role in the combustion reaction, it has been reported that the flame front can be determined for the discussion of flame extinction. Here, the circumferential flame length and probability of flame existing are evaluated at different turbulence intensity. From vertical and horizontal images, the local flame extinction is confirmed based on 3D flame structure. When the exit velocity (Um) is increased, more cusps appear on the flame front. At φm =0.90, the circumferential flame length is monotonically larger. However, at φm=0.75, the flame length is decreased at Um> 20 m/s. In this condition, the probability of flame existing is decreased. Thus, the reduction of flame length could be explained by the local extinction.