By taking a low nitrogen swirl burner as the research object

the effects of the blade angle of tertiary air on the nozzle flow field distribution

temperature distribution and CO and NOx generation characteristics of the burner were studied through experiment and numerical simulation. The experimental results showed that

when the swirl blade angle of tertiary air increased from 20° to 50°

the swirl flow intensity enhanced

the return flow of the burner nozzle increased

and the burner entrainment ability has been strengthened. When the swirl blade angle of tertiary air increased to 60°

on the contrary

the entrainment ability of the burner has been weakened as the air flow diffused around. When the tertiary air blade angle was about 50°

the high temperature flue gas was about 1.4 m from the burner nozzle

which was the shortest. With the increase in swirl blade angle of tertiary air

the CO generation concentration decreased at first and then increased

while the NOx generation concentration increased at first and then decreased. When the tertiary air blade angle was about 50°

the CO generation concentration(volume fraction) reached the minimum and the NOx concentration reached the maximum. It can be inferred that

the optimum swirl blade angle of tertiary air for low load steady combustion of boilers is about 50°. Through field tests on a 660 MW unit boiler

the lowest steady combustion load of the boiler was reduced from 25% rated load to 20% rated load under the same operating conditions after the tertiary air blade angle of the burner been adjusted from 0°～30° to 50°.