Insights into the dynamics of full-scale sector combustor isothermal flow field

An experimental investigation in a sector (20 degree) of a full-scale annular gas turbine combustor is performed. The sector combustor is optically accessible for the flow and flame visualization of the primary and exit zones of the combustor. The distinctive feature of the experimental setup is that it preserves the geometrical details of an annular combustor that includes the casing, dome and combustor liner. The combustor design features a series of primary and secondary dilution holes with multiple film cooling strips on the outer and inner liner. In the present study, the time-resolved Particle Image Velocimetry (PIV) experiments are conducted in the central longitudinal plane and two azimuthal planes to gain insight into the dynamics of the sector combustor. Proper Orthogonal Decomposition (POD) is applied to the data to obtain the dominant dynamics of the combustor. The major coherent structures of the swirl flow field, the primary dilution jets flow field, and the dominant interaction of swirl and dilution jets are elucidated here. The azimuthal plane data provides a three-dimensional explanation of dilution jet dynamics. The dynamics of the exit zone if found to be influenced by the secondary dilution jet dynamics. The spectral properties of dynamics are illustrated from the recorded acoustic (p') signal and the time coefficient of the POD eigenmodes. Further, the experiments are performed by blocking the dilution jets (without-DJ). These experimental data help to identify the source of the dominating frequency ( f _d ) within the combustor, which is found to be the swirl flow instabilities. Without-DJ data also showcases the role of dilution jets in convecting the swirl flow generated acoustics to the exit zone. The reconstructed flow field using POD provides physical insights into the dynamics occurring within the sector combustor.