To predict the boundaries of flashback and blow-off

partial premixed combustion model is employed to perform computational fluid dynamics(CFD) simulation of the natural gas premixed swirl burner. The combustion chamber is 60 mm in diameter and 160 mm in length. The simulation conditions include two oxidizers

the air and the 25%O_(2+) 75%N_2(volume fraction). The swirler exit is flash back with axial velocity of 0.6～1.5 m/s and blowoff of 1.5～4.5 m/s. The model is verified by the flashback and blow-off experimental data

and the influence of the structural parameters on the boundaries of flash back and blow-off is analyzed. The Realizable k-ε model and Reynolds stress turbulence model are compared

and it shows the Reynolds stress model has better simulation results. The changes of Da number at the section of swirler exit before and after flashback and blow-off are analyzed. It is found that there is a certain relationship between 1/Da at critical flashback point and mixing fraction

as well as Da at critical blow-off point and mixing fraction at different gas velocities. Keeping the geometric swirl number unchanged

the flow fields before and after the flashback and blow-off and their boundaries for three kinds of swirler inlet structures are compared and analyzed. The results show that

the influence of the structural parameters on flashback intervals is opposite to that on blow-off

and there is an optimal combination of the inlet length and width to maximize the stable combustion region between flashback and blow-off.