Date

2022-7-27

Author

Kıyıcı, Fırat

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In modern gas turbine combustors, flame stabilization is achieved by use of swirlers which introduce swirl component to the flow field. Swirlers are inherently sensitive to flow and environmental conditions, and even a minor geometrical modification can change the flow field remarkably. One of the critical parameters that affect the performance of the swirler is the channel orientation of the swirler channels. In the literature, the channel orientation has been mostly investigated at constant confinement ratio levels, and results showed that the performance of the co-rotating (CO) and counter-rotating (CR) swirlers are different in a number of aspects. In this study, the sense of the swirler channel rotation is investigated under different confinement ratio levels at a fixed total swirl number of 1.2 by using a 2D2C PIV system in isothermal conditions. The experimental results show that the confinement affects the CO and CR swirlers oppositely. As the confinement ratio increases, the radial expansion of the swirling jet decreases in the CR swirler while it increases in the CO swirler for the confined cases. For all levels of confinement, a higher degree of radial expansion is observed in the CO swirler. In addition, steady-state RANS simulations are performed to support the experimental findings, which are in good agreement with experimental data except for the unconfined condition. On the other hand, Large Eddy Simulations (LES) provide results that are in a better agreement with the experimental data in the unconfined configuration. Furthermore, a spectral proper orthogonal (S-POD) analysis is conducted to understand the effect of the confinement ratio on the dynamics of coherent flow structures. The S-POD results exhibit a single helical structure with a frequency of 1.2 kHz observed for both CO and CR swirlers under all confinement ratio levels. The S-POD mode shapes reveal that the confinement can suppress low-frequency global instability modes or higher frequency mode structures. Finally, changing the number of channels does not change the frequency of the PVC when the swirl number is kept identical.

Subject Keywords

SWIRLER, COMBUSTION CHAMBER, LARGE EDDY SIMULATION, PARTICLE IMAGE VELOCIMETRY

URI

https://hdl.handle.net/11511/98625

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Graduate School of Natural and Applied Sciences, Thesis