investigation of isothermal flow inside a new combustor with two-stage axial swirler

Experiments and numerical simulations are performed to study the cold flow field characteristics in a two-stage axial swirl combustion chamber. large eddy simulation with dynamic turbulent kinetic energy sub-grid scale model is used to calculate the flow field, and particle image velocimetry is used to measure the turbulent flow field. the calculated results are found to be in a good agreement with the experiment results. due to the shear layers and the density difference between co2 and air flows, the central recirculation zone appears. with the increase of the ratio of flow velocity between inner and outer tubes, the central recirculation zone shrinks gradually, while the length and range of the angular recirculation zone increase continuously. the vortex structure develops in the axial and radial directions, and the vortex breakdown mostly occurs in the upstream regions. however, outside the central recirculation zone, only one shear layer is observed, and its vortex structure is almost extended up to the exit of the combustion chamber. in addition, precession vortex core is not seen in all the conditions.