The bell-type air nozzle is commonly used in large scale circulating fluidized bed(CFB) boilers.However

ash leakage and abrasion occurs on a great number of the bell-type air nozzles during practical operation

and turns worse with the boiler service time

which finally affects safety and stability of the boiler.Analysis for this problem shows the gap between core tube top and the air nozzle clothing is the major reason.The resistance performance of the air nozzle with different gaps was numerically investigated.The results show that

the resistance of the air nozzle dropped by 9.1%

21.8%and 30.8% when the gap was 1mm

3mm and 5mm

respectively

indicating the gap has seriously damaged the resistance of the air nozzle.Besides

the setting mode of the hole at outlet of the bell-type air nozzle also had a bad effect on ash leakage and abrasion.It suggested the hole can be downward declined.