LES Study on the Flow Field and Flame Response of a Stratified Swirling Flame

In this paper, a Large Eddy Simulation (LES) study of stratified swirl premixed flames is carried out based on OpenFOAM toolbox. For the novel stratified swirl burner (BASIS), the LES was performed with incompressible solver ReactingFoam, Partially Stirred Reactor (PaSR) combustion model and linear-distributed temperature boundary conditions at both the unforced and forced conditions. The results show that the time-averaged flame structure obtained under the unforced condition agrees well with the experimental results. Clear vortex structures are displayed by the three-dimensional streamline. Under the forced conditions, the Flame Transfer Function (FTF) of the stratified flame is obtained for the first time. The phase of FTF is found to be linear relationship with forcing frequency, while the gain firstly reaches the minimum at 150 Hz and then climbs to the maximum at 250 Hz, finally decreases rapidly after 400 Hz, showing a characteristic of the low-pass filter.