Large-eddy simulation of unstable non-reactive flow in a swirler combustor

A comprehensive study on the influence of the unsteady non-reactive flow characteristics of turbulent flow in a three-stage swirl combustion chamber using power spectral density methods was conducted using large eddy simulations. The results demonstrated that instabilities were observed owing to large-scale vortex structures and periodic oscillations of the non-reactive flow. The boundary of the central recirculation zone (shear layers) enhanced the instability of the Helmholtz mode in the combustor. By considering the power spectral density of different monitoring points, the instability characteristics were accurately determined according to the oscillatory energy obtained in the non-reactive flow field. Large-scale vortex structures and periodic oscillations were the main reasons for the unsteady characteristics of the non-reactive flow field. The large eddy simulation results were compared with the experimental data, and the average absolute relative deviation between the large eddy simulation and experimental velocity components in the combustor were less than 12.04%. The results provide valuable insights into the unstable non-reaction flow characteristics in the combustion chamber.