Optical Diagnostics of Swirling Flame by Simultaneous Planar Laser-induced Fluorescence and High-speed Chemiluminescence Imaging of OH Radical

Swirl-stabilized flame is commonly used in gas turbine combustor. Under the operation conditions of interests, such flame is in turbulent regime, exhibiting quasi-periodic dynamic characteristics with one or multiple oscillation modes. We have reported a strategy to investigate the dynamics of the flame. The measurement of the swirling flame in a gas turbine model combustor is carried out by simultaneous planar laser-induced fluorescence (PLIF) and high-speed chemiluminescence (CL) imaging of OH radical, as the former technique is capable of providing highly resolved transient structure of the reaction zone of the flame while the latter is a perfect indicator of the dynamic motion of the flame. The proper orthogonal decomposition (POD) method was applied to both sets of data to unveil the main dynamics mode of both observations. The evolution of the OH* CL mode coefficients provided the information of the oscillation frequency and the momentum of the flame when the PLIF image is taken. Furthermore, the connection of the OH PLIF and OH* CL measurements were investigated by extended proper orthogonal decomposition (EPOD) method. The EPOD analysis showed a strong correlation between the reaction zone at the PLIF plane and the total OH* CL of the flame, enabling the reconstruction of the evolution of the reaction zone. By the application of the strategy above, combustor was tested under different equivalent ratio, and the dynamics of the flame were compared.