Effect of the Structure of Flow Deflector on Ignition and Flame shape of the Centrally Staged Combustor

Centrally staged premixed is a practical method to reduce NOx emission in aero-engines. Previous research has demonstrated that the flow inside the combustor has a significant effect on the ignition performance and flame shape. In this paper, the local flow field in a model combustor is changed by mounting a flow deflector at the main stage channel outlet. The effect of the length and central angle of the flow deflector on the ignition performance is investigated experimentally. The time scale of each phase of a successful ignition event is extracted using Otsu’s threshold segmentation method. It is found that the flow deflector significantly improves the ignition performance of the centrally-staged combustor and extends the ignition boundary. Based on this, the shape of the flame at different flow deflector lengths and central angles is also captured by a highspeed camera. The spatial patterns of the flame dynamic are identified using the proper orthogonal decomposition (POD) method. Additionally, the first few order modes, whose energy proportions are relatively larger, dominate the flame dynamics. The results indicate that as the length of the flow deflector increases, the flame primarily presents the vortex shedding mode, while as the central angle of the flow deflector decreases, the circumferential rotation mode dominates. There is a greater fluctuation in the zone where the chemiluminescence of the flame is stronger.