Numerical Study of Flow Characteristics of a Central-Staged Swirl Combustor

The two-combustion-zone design approach is adopted in order to achieve good idle LBO in a central-staged swirl combustor. The flow characteristics of the combustor are investigated through large eddy simulation (LES). The numerical method is validated by comparing the numerical results of time-average velocity profiles with PIV results at various axial locations. The grid scale is analyzed through Pope’s criterion to guarantee that most turbulent kinetic energy can be resolved by the present mesh. The coherent structures are isolated from turbulence flow by proper orthogonal decomposition (POD) method. Multiple monitor probs are set up in swirling flow and shear layers. The fast Fourier transform (FFT) is used to obtain frequency characteristic of time-domain signal. The difference between time-average velocity field and instantaneous velocity field is first explained. The recirculation zones are sorted by the locations and formation mechanism. The precessing vortex core (PVC) is found to be the crucial coherent structure of central-staged combustor. The spatial structure and temporal evolution of PVC are captured. Both single-helix and double-helix modes are discovered through POD method. By using phase-averaged method, the interaction between PVC and axial velocity field is investigated.