Several swirling CH4/air diffusion flames were investigated in a gas turbine model combustor via the temporal phenomenon of thermos-acoustic and the spatial flame mode transition. In the combustion mode transition

three-dimensional computed tomography of chemiluminescence (3D-CTC) technique was utilized due to the complexity of swirling combustion flow field. The 3D emissions of CH* were measured and taken as qualitative indicators of the heat release rate under three Reynolds number conditions (from 5 000 to 20 000). This 3D measurement method utilized 8 multi-directional CH* images as inputs combined with tomographic algorithms to compute the 3D distribution of CH* intensities. In order to verify the reconstruction fidelity

the two-dimensional visualization of the reconstructed shape was compared with the time-averaged projection under high-speed photography

and the results showed that the reconstruction error was within 5%. In this study

the transitions of heat release area with Reynolds number were analyzed

and the results showed that the heat release rate changed more obviously along the nozzle radical direction than the axis direction

and the largest heat release area moved forward significantly. The thermo-acoustic study was obtained by high speed CH* images

finding that the oscillating frequency of heat release increased with the increase of the Reynolds number.