The large-eddy simulation (LES) method was used to compare the premixed combustion characteristics of high and low swirls

and the flame stability mechanism of low swirl was analyzed. Results showed that LES coupling with PaSR combustion model can accurately capture the small structures and flow field distribution of premixed flame. The low swirl flow had a weak recirculation zone (sometimes just a low velocity zone)

while a high swirl flow produced a strong recirculation zone with a low frequency vibration of the precession vortex core (PVC). By analyzing the change of vortex and flame temperature field

it was found that vortices generated from swirl and center jet flow were the main factors of stability mechanism to stabilize flame in the low velocity region

forming alternating W and V flame.