The influence of primary air velocity and external overfire air blade angle on outlet flow field was simulated by CFX soft ware

taking the single DRB-4Z dual channel swirl burner of a power plant as an example.Results indicate that

properly reducing the primary air speed can enlarge the recirculation zone

but too low the speed will weaken the later stage mixing of primary and secondary air

which goes against the stable ignition of pulverized coal.With an increase in external secondary air blade angle

the flame length increases significantly

postponing the blending of external secondary air and the primary air

decreasing the ignition stability

and causing slagging on the waterwall opposite the burner.As the outer secondary air blade angle decreases

the swirl strength reduces

and the reduction of the highest axial and tangential velocity of the pulverized coal accelerates.Too small angle of the outer secondary air causes the formation of recirculation zone in the center of flame tail

which has adverse effect on the combustion stability and shortens the service life of the burner.