Abstract: The flame velocity is about 60-200 m/s at the nozzle of the high velocity coal combustor.The flame is long and the convective heat exchange ratio between the flame and membrane wall is increased in the furnace,which comes into being a uniform temperature field without local over-heating and slagging by the traditional low velocity pulverized coal burner.Taking 14 MW high-speed pulverized coal burner as the research object,the key factors liked swirl intensity and secondary air temperature on the combustion of pulverized coal in the burner were studied and the structural optimization design was carried out in this article according to the combustion characteristics of pulverized coal in the burner by way of numerical simulation.The study about swirl intensity shows that the shape of recirculation zone changes little when the swirl intensity increases from 2.2 to 3.7.The recirculation zone starts from the jet of primary duct to the swirl vane,and the recirculation zone surrounds the primary duct.The maximum return flow is near the primary air nozzle,and the farther away from the primary air nozzle is,the smaller the return flow is.The swirl intensity has little effect on the maximum recirculation flow ratio which is around0.45 kg/s and the effect of swirl strength on the return flow becomes larger when the distance from the jet is more than somewhere L/H<0.35.It appears that the recirculation flow ratio increases as the swirl intensity gets stronger and the ratio is from 0.17 kg/s to 0.30 kg/s at the end of the recirculation flow zone.The results shows that flame is 150 m/s at the nozzle of the combustor with moderate swirl intensity which is proportional to the swirl intensity of the secondary air at the inlet of the combustor.The swirl intensity at the nozzle is 0.10-0.28.The fuel and oxygen is hierarchical distribution which means the nozzle center is fuel-rich and oxygen-lean.The study shows that the concentration of combustible component at the middle of the nozzle decreases when the swirl intensity increases. Concentration of CO、H2 and coke is deducing from 11% to 10%,1.65% to 1.40% and 0.14% to 0.11%,respectively.The oxygen concentration at the nozzle edge is deducing from 13% to 10%.At the same time,the study shows that it has little difference on the oxygen and combustible gas distribution when the swirl intensity is increased from 3.2 to 3.7,indicating that the effect of swirl strength on combustion is weakened.In order to study the effect on combustion of secondary air temperature,the three different temperatures such as 0,100 and 200 ℃ were set and studied.The result shows that when the temperature of secondary air increases,the carbon conversion in the combustor is increased by 20% to 65%while the reaction time is deduced from 0.15 s to 0.11 s.Central air is arranged when it comes to structural optimal design of the combustor.The swirl condition of the central air and 3 kinds of conditions were studied.The results show that the combustible gas at the middle of the nozzle is dropped within a radius less than 75 mm when central air is added in the combustor.The oxygen concentration is increased when the central air is direct flow as the jet flow is rigid and can get to the middle of the nozzle.The swirl central air has little effect on the oxygen distribution at the nozzle but the effect of reducing the concentration of combustible components is better than that of the DC center wind.